Modi f i c ati on and c haract e ri z a t i on of l i q u e f i e d bi oma s s - base d e poxyr e s i n
by
Na n We i
A t he s i s s ubmi t t e d t o t he Gr a duat e F a c ul t y o fAuburn Univer s i t y
i n par t i a l f ulf i l l m e nt of t her e quir e m e nts f or t he De gre e o f
Ma s t e r o f Enginee r i ng
Auburn, Al a bam aAugust 3,2013
Ke ywords: biom a s s , l i quef a c t i o n, s wi t c hgra s s , e poxyr e s i n
C opyr i ght 2013b y Na n We i
Approved by
Yi f e n Wa ng, C o-c hai r , As s oci a t e P r ofe s s or of Bi o s yst e m s Enginee r i ngBr i a n K. Vi a , C o-c hai r , As s oci a t e P r ofe s s or of F ore s t r y a nd Wi l dli f e S c i e nce s
Ma r i a L . Auad, As s oci a t e P r ofe s s or of P olym e r a nd F i ber Enginee r i ngTi m o t hy P Mc Donal d, As s oci a t e P r ofe s s or o f Bi o s yst e m s Enginee r i ng
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Abst r a c t
Wi t h t he i ncr e a s i ng r e quir e m e nt o f biom a s s c om posi t e s , people have pai d m ore a t t e nti on t o
t he i ncr e a s i ng use o f s ynthet i c a dhe s i ves , whic h r e quir e pet r ole um - bas e d r e s ourc e s . Ta l k i ng
a boutpet r ole um - bas e d r e s ourc e s , t he i ncr e a s e d dem a nds f or e ner gy a nd c onc e r ns a bout e ner gy
s e c uri t y a nd c l i m a t e c ha ngehave c r e a t e d m ore a nd m ore a t t e nti on on t he a l t e r nat i ve a nd
r e newa ble e ne r gy whic h w i l l gra dual l y s ha r e m ore port i o n of providing e ner gy a nd t hen r e pla c e
t he s i gnif i c a nt r ole of pet r ole um - bas e d r e s ourc e s . S ynthet i c gl ues ( ur e a f orm a l dehyde/ phe nol
f orm a l dehyde a dhe s i ves a r e t he m ost wi d e l y ut i l i z e d binder s us e d i n t he wood c om posi t e s
i ndust r y) us e d i n m ost biom a s s c om posi t e s oft e n c onta i n f orm a l dehyde, whic h i s a t oxic
c hem i c a l organic s ubst a nce . Ther e f ore , we pla nned t o deve l o p a novel a dhes i ve wi t hout
f orm a l dehyde. The novel a dhes i ve w i l l be obta i ned by diglyci d yl e t her of biphenol A ( E P ON
828)r e a c t e d wi t h bio-oil whic h wa s produc e d by t he l i quef a c t i o n of biom a s s .
I n t his s t udy,t wo kinds of biom a s s i ncl uding s wi t c hgra s s a nd s out her n pine wood we r e
c onver t e d t o bio-oil t hrougha l i quef a c t i o n proce s s , a nd t he n bio-oil wa s ut i l i z e d a s a f e e dst ock
f or e poxy r e s i n s ynthes i s . The a i m of t his s t udywa s t o produce a nd c har a c t e r i z e t he l i quef i e d
biom a s s bas e d e poxy r e s i n. This s t udy c onta i ned t wo m a i n par t s , one i s usi ng s outh pine wood a s
r a w m a t e r i a l f or l i quef a c t i o n a nd t he other one i s us i ng s wi t c hgra s s a s r a w m a t e r i a l f or
l i quef a c t i o n. And i n e a c h par t , t he proce dure wa s c om pose d of t hre e s t e ps, ( 1) l i quef a c t i o n, ( 2)
e poxidat i on a nd c ur i ng, a nd ( 3) c har a c t e r i z a t i o n. Thre e dif f e r e nt r a t i o s of diglyci d yl e t her o f
biphenol A ( EP ON 828)t o bio-oil ( 1:1, 1:2, 1:3 a nd 1:4) we r e i nves t i gat e d. F our i e r t r a nsf orm -
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i nfr a r e d s pec t r osc opy( F T - I R) a na l ysi s proved t hat e poxy f unct i o nal i t y wa s s ucc e s s f ull y
i ntr oduce d i nto t he l i quef a c t i o n oil . To det e r m i ne t he c ure proper t i e s a nd t her m a l s t a bil i t y of t
a dhes i ve/ c e l l ulo s e c om posi t e , t her m a l a nal ysi s usi ng t he dif f e r e nti a l s c a nning c a l ori m e t r y ( DS C ) ,
e xtr a c t i on t e s t s a nd t her m o gra vim e t r i c a na l ysi s ( T GA) , whic h we r e c onduct e d.
I n t he f i r s t par t , t hrought he hydroxylnum b e r t e s t s a nd a nal yze d t he r e s i d ue c ont e nts , t he opti m a l
t e m per a t ure a nd t i m e f or l i q uef a c t i on we r e 220o C a nd 2hrs . The opti m a l r a t i o o f Epon 828a nd
s outher n pine woodbas e d bio-oil wa s 1:1 whic h e xhib i t e d t he hi ghes t proper t i e s i n t he t e s t s of
dif f e r e nti a l s c a nning c a l ori m e t r y ( DS C ) , e xtr a c t i on t e s t s , Dynam i c Me c hanic a l a nal yze r ( DMA)
a nd t her m o gra vim e t r i c a nal ysi s ( TGA) . C om par e d t o t he e xper i m e nt whic h wa s done b y Thoma s
J . Robinson, he us e d bio-oil whic h us e d t he s a m e s outher n pine wood a s r a w m a t e r i a l but
t hrought he pyrolysi s proce dure , t he gla s s t r a nsi t i o n t e m per a t ure wa s l owe r a nd t he e xtr a c t i on
r e s ult s we r e a l s o l owe r bec a use t he c r oss l i nk bet we e n t he Epon 828a nd bio-oil i n t his r e s e a r c h
wa s l owe r t han t hey did.
I n t he s e c ondpar t , t hrought he hydroxylnumber t e s t s a nd a na l yze d t he r e s i d ue c onte nts , t he
opti m a l t e m per a t ure a nd t i m e f or l i quef a c t i o n we r e 250o C a nd 2hr s . The opti m a l r a t i o o f Epon
828a nd s wi t c hgra s s bas e d bio-oil wa s 1:1 whic h s howe d t he hi ghes t proper t i e s i n t he t e s t s of
dif f e r e nti a l s c a nning c a l ori m e t r y ( DS C ) , e xtr a c t i on t e s t s , Dynam i c Me c hanic a l a nal yze r ( DMA)
a nd t her m o gra vim e t r i c a nal ysi s ( TGA) .
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Ac knowl e dgme nts
F i r s t l y, I would l i ke e xpre s s m y s i nce r e gr a t i t ude t o Dr . Yi f e n Wa ng ( Ma j or Advis or) f or
his pat i e nce a nd guidance o n t his r e s e a r c h work duri ng t he pas t t wo yea r s . T hi s work would be
i m poss i ble t o a c hi e ve wi t houth i s s upport . I would l i ke t o e xpre s s a ppre c i a t i o n t o Dr . Br i a n K.
Vi a ( C o-Advis or) f or hi s s upport a nd c ons t r uct i ve c r i t i c i s m s . Hi s e nthusi a s t i c a nd profe s s i onal
a pproac h t o r e s e a r c h has t a ughtm e a gre a t val uable t ool f or t he f uture . F i nal l y, I wa nt t o t hank
Dr . Ma r i a L . Auad, a nd Dr . Ti m o t hy P. Mc Donal d f or bei ng m y c om m i t t e e m e m ber s a nd f or
t hei r t i m e o n r e vie wi ng m y t hes i s . On t he other ha nd, I nee d t o m a ke m y hones t t ha nksgo t o t he
m e m ber s o f our r e s e a r c h gr oup ( We i J i a ng, S huhuiWa ng, Ba ngping Wa ng, T . J Robinson,
C e l i kbag Yusuf a nd Ac quah Gi f t y) f or t hei r a s s i s t a nce i n m y dat a c oll e c t i o n a nd a nal ysi s . I a m
a l s o i ndebte d t o t he S ha nghai Oc e a n Univer s i t y , I would n ? t ha ve m a de i t t his f a r wi t houtwhose
f i nanci a l s ponsors hip . La s t l y, I would l i ke t o t hank m y par e nts a nd f a m i l y f or a l l t hei r
e ncoura gem e nt a nd s upport t hroughoutm y e nti r e a c a dem i c c a r e e r . At t he e nd but not t he l e a s t , I
would l i ke t o give m y e nthusi a s t i c a ppre c i a t i o n t o m y boyf r i e nd L i Li ng a nd s pec i a l f r i e nd
Xi a ofe i Wa ng who ga ve m e t he m ost s upport a nd e ncoura gem e nt .
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Ta ble of C ont e nts
Abst r a c t .........................................................................................................................................i i
Ac knowl e dgme nts ........................................................................................................................i v
Li s t of Ta ble s ................................................................................................................................i x
Li s t of F i gure s ..............................................................................................................................xi
Li s t of Abbre via t i o ns..................................................................................................................xvi
C ha pte r 1 I nt r oduct i on...................................................................................................................1
C ha pte r 2 Li t e r a t ure Re vie w ........................................................................................................4
2.1 Ener gy Bi o m a s s ..................................................................................................................4
2.1.1P ote nti a l of e ner gy biom a s s ..........................................................................................4
2.1.2Li gnin ...........................................................................................................................5
2.1.3C e l l ulo s e .......................................................................................................................8
2.1.4He m i c e l l use ..................................................................................................................9
2.1.5S wi t c hgra s s .................................................................................................................10
2.1.6S out her n pine wood ...................................................................................................12
2.2 Li q uef a c t i on of biom a s s ....................................................................................................13
2.3 Epoxyr e s i n .......................................................................................................................16
2.3.1Wood-bas e d e poxy r e s i n ............................................................................................17
2.3.2Te s t Me t hodso f Adhes i ve..........................................................................................19
2.3.2.1Dynam i c Di f f e r e nti a l S c a nning C a l ori m e t r y ( DS C ) ............................................20
vi
2.3.2.2Ther m o Gr a vim e t r i c Anal yze r ( TGA) ..................................................................21
2.3.2.3Dynam i c Me c hanic a l Ana l yze r ( DMA ) ...............................................................22
2.3.2.4F our i e r Tr a nsf orm I nf r a r e d S pec t r osc opyMa c hine ( F T - I R) ...............................22
2.4 Re f e r e nce .............................................................................................................................23
C ha pte r 3 Modif i c a t i o n a nd c har a c t e r i z a t i o n of l i quef i e d s out her n pine woodbas e d e poxyr e s i n .......................................................................................................27
3.1 I ntr oduct i o n .......................................................................................................................27
3.2 Ma t e r i a l s a nd Me t hods......................................................................................................31
3.2.1.Bi o m a s s ( s outher n pine wood)P r e par a t i on...............................................................32
3.2.2Li q uef a c t i on of s outh pine wood................................................................................32
3.2.2.1De t e r m i nat i o n of r e s i due c onte nt........................................................................33
3.2.2.2Hydroxylgroup num b e r t e s t ................................................................................34
3.2.2.3P H val ue e xam i nat i o n ..........................................................................................35
3.2.2.4I nte r a c t i o n i n l i quef a c t i o n usi ng F T- I R ...............................................................36
3.2.3P r e par a t i on of s outher n pine woodbas e d e poxy r e s i n ...............................................36
3.2.4Anal yti c a l m e t hods .....................................................................................................37
3.2.4.1.Me a s ure m e nt of gla s s t r a nsi t i o n t e m per a t ure s .....................................................37
3.2.4.2Me a s ure m e nt of Ther m a l De gra dat i on..................................................................37
3.2.4.3I nte r a c t i o n bet we e n Epon828a nd s outher n pine wood bas e d o i l usi ng F T- I R ....38
3.2.4.4C r oss l i nk degre e us i ng S oxhle t e xt r a c t i on t e s t s ....................................................38
3.2.5Da t a Anal ysi s ..............................................................................................................39
3.3 Re s ult s a nd Di s c uss i o n ......................................................................................................39
3.3.1Re s i due c ont e nt o f l i quef i e d s outher n pine wood......................................................39
3.3.2Hydroxylnumber a nd pH va l ue of l i quef i e d s out her n pine wood.............................41
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3.3.3Di f f e r e nti a l S c a nning C a l ori m e t e r ( DS C ) .................................................................45
3.3.4Ther m o Gr a vim e t r i c Anal yze r ( TGA) .......................................................................49
3.3.5Extr a c t i on t e s t s ...........................................................................................................51
3.3.6F T- I R s pec t r osc opy....................................................................................................54
3.4 C onc l usi ons.........................................................................................................................58
3.5 Re f e r e nce .............................................................................................................................60
C ha pte r 4 Modif i c a t i o n a nd c har a c t e r i z a t i o n of l i quef i e d s wi t c hgra s s - bas e d e poxyr e s i n ....... 62
4 .1 I ntr oduct i o n .......................................................................................................................62
4 .2 Ma t e r i a l s a nd Me t hods......................................................................................................66
4 .2.1.Bi o m a s s ( s outher n pine wood)P r e par a t i on...............................................................67
4 .2.2Li q uef a c t i on of s outh pine wood................................................................................68
4 .2.2.1De t e r m i nat i o n of r e s i due c onte nt........................................................................68
4 .2.2.2Hydroxylgroup num b e r t e s t ................................................................................68
4 .2.2.3P H val ue e xam i nat i o n ..........................................................................................69
4 .2.2.4I nte r a c t i o n i n l i quef a c t i o n usi ng F T- I R ...............................................................69
4 .2.3P r e par a t i on of s outher n pine woodbas e d e poxy r e s i n ...............................................69
4 .2.4Anal yti c a l m e t hods .....................................................................................................69
4 .2.4.1.Me a s ure m e nt of gla s s t r a nsi t i o n t e m per a t ure s .....................................................69
4 .2.4.2Me a s ure m e nt of Ther m a l De gra dat i on..................................................................69
4 .2.4.3I nte r a c t i o n bet we e n Epon828a nd s outher n pine wood bas e d o i l usi ng F T- I R ....69
4.2.4.4Me a s ure m e nt of Ther m a l De gra dat i on..................................................................69
4.2.4.5F T- I R c har a c t e r i z a t i o n of I nte r a c t i o n bet we e n Epon 828a nd bio-s wi t c hgra s s - bas e do i l us i ng F T- I R ......................................................................................................69
4.2.4.6C r oss l i nk s t a bil i t y us i ng S oxhle t Extr a c t i on t e s t s .................................................69
v i i i
4 .2.5Da t a Anal ysi s ..............................................................................................................69
4 .3 Re s ult s a nd Di s c uss i o n ......................................................................................................69
4 .3.1Re s i due c ont e nt o f l i quef i e d s outher n pine wood......................................................69
4 .3.2Hydroxylnumber a nd pH va l ue of l i quef i e d s out her n pine wood.............................71
4 .3.3Di f f e r e nti a l S c a nning C a l ori m e t e r ( DS C ) .................................................................76
4 .3.4Ther m o Gr a vim e t r i c Anal yze r ( TGA) .......................................................................81
4.3.5DMA r e s ult s ...............................................................................................................83
4 .3.6 Extr a c t i on t e s t s ...........................................................................................................85
4 .3.7 F T- I R s pec t r osc opy....................................................................................................88
4 .4 C onc l usi ons.........................................................................................................................92
4 .5 Re f e r e nce .............................................................................................................................94
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Li s t o f Ta ble s
Ta ble 2.1 C e l l ulo s e / l i gnin c ont e nt/ hem i c e l l ulo s e s of s e l e c t e d biom a s s ( w t %) ( P e t e r 2002)........7
Ta ble 2 .2 C om posi t i on ( % dry bas i s ) of dif f e r e nt s wi t c hgra s s var i e t i e s f r om NREL ? s biom a s sf e e dst ock c om posi t i o n a nd proper t i e s dat a bas e ( Ke s hwa ni a nd C he ng 2009)...........12
Ta ble 2.3 Di f f e r e nt m e t hods of t he biom a s s l i q uef a c t i on ..........................................................1 4
Ta ble 3.1 S pec i f i c DS C r e s ult s of dif f e r e nt s a m ple a t dif f e r e nt l i quef a c t i o n t e m per a t ure s a ndr a t i o s o f Epon 828t o s outher n pine woodbas e d bio-oil .............................................46
Ta ble 3.2 S pec i f i c DS C r e s ult s of dif f e r e nt s a m ple a t dif f e r e nt l i quef a c t i o n t i m e s a nd r a t i o o fEpon 828t o s outher n pine woodbas e d bio-oil . ..........................................................4 8
Ta ble 3.3 The Ac e t one S oxhle t e xtr a c t i on t e s t s of s outher n pine woodbas e d e poxy r e s i n i ndif f e r e nt l i quef a c t i o n t e m per a t ure . ..............................................................................52
Ta ble 3.4 The Ac e t one S oxhle t e xtr a c t i on t e s t s of s outher n pine woodbas e d e poxy r e s i n i ndif f e r e nt l i quef a c t i o n t i m e ..........................................................................................53
Ta ble 3.5 E xper i m e nta l r e s ult I ..................................................................................................58
Ta ble 3.6 E xper i m e nta l r e s ult I I .................................................................................................59
Ta ble 4.1 The a ver a ge c om posi t i o n a nd t he s t a ndar d devia t i on of t he det e r m i nat i on of s i xdif f e r e nt s a m ple s .........................................................................................................64
Ta ble 4.2 S pec i f i c DS C r e s ult s of dif f e r e nt s a m ple a t dif f e r e nt l i quef a c t i o n t e m per a t ure s a ndr a t i o s o f Epon 828t o s wi t c hgra s s bas e d bio-oil .........................................................78
Ta ble 4 .3 S pec i f i c DS C r e s ult s of dif f e r e nt s a m ple a t dif f e r e nt l i quef a c t i o n t i m e a nd r a t i o ofEpon 828t o s wi t c hgra s s bas e d bio-oil .......................................................................80
Ta ble 4.4 The Ac e t one S oxhle t e xtr a c t i on t e s t s of s wi t c hgra s s bas e d e poxyr e s i n a t dif f e r e ntl i quef a c t i o n t e m per a t ure s ...........................................................................................86
Ta ble 4.5 The Ac e t one S oxhle t e xtr a c t i on t e s t s of s wi t c hgra s s bas e d e poxyr e s i n a t dif f e r e ntl i quef a c t i o n t i m e s ........................................................................................................87
x
Ta ble 4.6 E xper i m e nta l r e s ult I ...................................................................................................92
Ta ble 4.7 E xper i m e nta l r e s ult I I ..................................................................................................93
xi
Li s t of F i gure s
F i g ure 2.1 ( a ) S c hem a t i c r e pre s e nta t i on of t he s t r uct ura l unit s of l i gnin, a nd ( b) s t r uct ura ls e gm e nt of l i gnin propose d b y Adle r ( 1977)( Adle r 1977).........................................6
F i gure 2.2 Li gnin pre c urs ors f or pla nts .........................................................................................7
F i gure 2.3 C he m i c a l s t r uct ure of c e l l ulo s e ....................................................................................8
F i g ure 2.4 S ugar c om ponent of hem i c e l l ulo s e s ( J OHAN VE R ENDE L , C hurc h e t a l . 2011).... 10
F i gure 2.5 ( a ) S t r uct ure of bis phenol- A diglyci d yl e t her e poxyr e s i n
( b) S t r uct ure of TE TA...............................................................................................17
F i g ure 2.6 ( a ) Di f f e r e nti a l S c a nning C olori m e t e r s Q2000TA I nst r um e nts C ompany
( b) Re f r i ger a t e d c ooli ng s ys t e m 90 TA I nst r um e nts C ompany
( c ) Tz e r o s a m ple pre s s a nd pans T a I ns t r um e nts C om pany ......................................21
F i g ure 3.1 ( a ) S c hem a t i c r e pre s e nta t i on of t he s t r uct ura l unit s of l i gnin, a nd
( b) S t r uct ura l s e gm e nt of l i gnin propose d by Adle r ( 1977)( Adle r 1977).................28
F i gure 3.2 I dea l i z e d net work f orm a t i on dur i ng c ur i ng r e a c t i o n of e poxy-l i gnin s yst e m ( AbdulKha l i l , Ma r l i a na e t a l . 2011).....................................................................................30
F i gure 3.3 S c he m a t i c of t he E- P s yst hes i s r e a c t i on ( Ma r i a L . Auad, Zhao e t a l ., 2007) ...........30
F i gure 3.4 F l ow c ha r t o f opti m i z i ng t he l i quef a c t i o n t e m per a t ure when t he l i quef a c t i o n t i m e wa sf i xed a t 2hrs ...............................................................................................................31
F i gure 3.5 F l ow c ha r t o f opti m i z i ng t he l i quef a c t i o n t i m e when t he l i quef a c t i o n t e m per a t ure wa sf i xed a t 220
o C ...........................................................................................................32
F i gure 3.6 The S oxhle t e xt r a c t or devic e ......................................................................................39
F i gure 3.7 ( a ) Re l a t i o nship bet we e n t he l i quef a c t i o n t e m per a t ure a nd r e s i d ue per c e nta ge........40
xi i
F i gure 3.7 ( b) Re l a t i o nship bet we e n t he l i quef a c t i o n t i m e a nd r e s i d ue per c e nta ge....................41
F i gure 3.8 ( a ) Re l a t i o nship bet we e n t he l i quef a c t i o n t e m per a t ure a nd t he hydroxylgroupnumber .............................................................................................................42
F i gure 3.8 ( b) Re l a t i o nship bet we e n t he l i quef a c t i o n t i m e s a nd t he hydroxylgr oup num b e r .... 43
F i gure 3.9 ( a ) Re l a t i o nship bet we e n t he l i quef a c t i o n t e m per a t ure a nd pH va l ue.......................44
F i gure 3.9 ( b) Re l a t i o nship bet we e n t he l i quef a c t i o n t i m e a nd pH va l ue...................................44
F i gure 3.10DS C r e s ult s o f dif f e r e nt s a m ple i n dif f e r e nt l i quef a c t i o n t e m per a t ure a nd r a t i o ofEpon 828t o s outher n pine woodbas e d bio-oil .......................................................46
F i gure 3.11 S pec i f i c DS C r e s ult s of dif f e r e nt s a m ple i n dif f e r e nt l i quef a c t i o n t e m per a t ure a ndr a t i o of Epon828t o s outher n pine wood bas e d bio-oil ...........................................47
F i gure 3.12 DS C r e s ult s o f dif f e r e nt s a m ple s i n dif f e r e nt l i quef a c t i o n t i m e a nd r a t i o of Epon828t o s outher n pine wood bas e d bio-oil ........................................................................48
F i gure 3.13 S pec i f i c DS C r e s ult s of dif f e r e nt s a m ple s i n dif f e r e nt l i q uef a c t i on t i m e a nd r a t i o ofEpon 828t o s outher n pine woodbas e d bio-oil .......................................................49
F i gure 3.14Ther m o gra vim e t r i c ( T G) c urves f or s out her n pine wood bas e d e poxyr e s i ns whenl i quef a c t i o n t i m e wa s f i xed a t 2 hours a nd l i quef a c t i o n t e m per a t ure wa s c hanged
f r om 180o C t o 240o C...............................................................................................50
F i gure 3.15 Ther m o gra vim e t r i c ( T G) c urves f or s out her n pine wood bas e d e poxyr e s i ns whenl i quef a c t i o n t e m per a t ure wa s f i xed a t 220
o C a nd l i quef a c t i o n t i m e wa s c ha nged f r om
1 hourt o 3 hours ......................................................................................................51
F i gure 3.16 The a c e t oneS oxhle t e xtr a c t i on t e s t s of s outher n pine woodbas e d e poxy r e s i n a tdif f e r e nt l i quef a c t i o n t e m per a t ure ...........................................................................52
F i gure 3.17 The a c e t oneS oxhle t e xtr a c t i on t e s t s of s outher n pine woodbas e d e poxy r e s i n a tdif f e r e nt l i quef a c t i o n t i m e .......................................................................................53
F i gure 3.18 F T- I R gr a ph of Absorbance ve r s us Wa venumber f or Epon828,Bi o - oil ( Li q uef a c t i ont i m e wa s 2h, t e m per a t ure wa s 220
o C ) a nd bio-oil bas e d e poxyr e s i n. ...................55
F i gure 3.19 F T- I R gr a ph of Absorbance ve r s us Wa venumbe f or s outher n pine wood bas e d e poxyr e s i ns when l i quef a c t i o n t i m e wa s f i xed a t 2 hours a nd l i quef a c t i o n t e m per a t ure wa s
c hanged f r om 180o C t o 240o C.................................................................................56
x i i i
F i gure 3.20 F T- I R gr a ph of Absorbance ve r s us Wa venumbe f or s outher n pine wood bas e d e poxyr e s i ns when l i quef a c t i o n t e m per a t ure wa s f i xed a t 220
o C a nd l i quef a c t i o n t i m e wa s
c hanged f r om 1 hourt o 3 hours ...............................................................................57
F i gure 4.1 I dea l i z e d net work f orm a t i on dur i ng c ur i ng r e a c t i o n of e poxy-l i gnin s yst e m ( AbdulKha l i l , Ma r l i a na e t a l . 2011).....................................................................................65
F i gure 4.2 S c he m a t i c of t he E- P s yst hes i s r e a c t i on ( Ma r i a L . Auad, Zhao e t a l ., 2007)...........66
F i gure 4.3 F l ow c ha r t o f opti m i z i ng t he l i quef a c t i o n t e m per a t ure when t he l i quef a c t i o n t i m e wa sf i xed a t 2hrs ...............................................................................................................67
F i gure 4.4 ( a ) Re l a t i o nship bet we e n t he l i quef a c t i o n t e m per a t ure a nd r e s i d ue per c e nta ge........70
F i gure 4.4 ( b) Re l a t i o nship bet we e n t he l i quef a c t i o n t i m e a nd r e s i d ue per c e nta ge....................71
F i gure 4.5 ( a ) Re l a t i o nship bet we e n t he l i quef a c t i o n t e m per a t ure a nd t he hydroxylgroupnumber .............................................................................................................74
F i gure 4.5 ( b) Re l a t i o nship bet we e n t he l i quef a c t i o n t i m e a nd t he hydroxylgroup num b e r ......74
F i gure 4.6 ( a ) Re l a t i o nship bet we e n t he l i quef a c t i o n t i m e , l i quef a c t i o n t i m e a nd pH va l ue......75
F i gure 4.6 ( b) Re l a t i o nship bet we e n t he l i quef a c t i o n t i m e , l i quef a c t i o n t i m e a nd pH val ue......76
F i gure 4.7 DS C r e s ult s o f dif f e r e nt s a m ple a t dif f e r e nt l i quef a c t i o n t e m per a t ure s a nd r a t i o s o fEpon 828t o s wi t c hgra s s bas e d bio-oil ......................................................................78
F i gure 4.8 S pec i f i c DS C r e s ult s of dif f e r e nt s a m ple a t dif f e r e nt l i quef a c t i o n t e m per a t ure s a ndr a t i o s o f Epon 828t o s wi t c hgra s s bas e d bio-oil ........................................................79
F i gure 4.9 DS C r e s ult s o f dif f e r e nt s a m ple a t dif f e r e nt l i quef a c t i o n t i m e s a nd r a t i o s of Epon 828t o s wi t c hgra s s bas e d bio-oil .......................................................................................80
F i gure 4.10 S pec i f i c DS C r e s ult s of dif f e r e nt s a m ple i n dif f e r e nt l i quef a c t i o n t i m e s a nd r a t i o s ofEpon 828t o s wi t c hgra s s bas e d bio-oil ....................................................................81
F i gure 4.11 Ther m o gra vim e t r i c ( T G) c urves f or s wi t c hgra s s bas e d e poxy r e s i ns whenl i quef a c t i o n t i m e wa s f i xed a t 2 hours a nd l i quef a c t i o n t e m per a t ure wa s c hanged
f r om 200o C t o 260o C...............................................................................................82
F i gure 4.12 Ther m o gra vim e t r i c ( T G) c urves f or s wi t c hgra s s bas e d e poxy r e s i ns whenl i quef a c t i o n t e m per a t ure wa s f i xed a t 250
o C a nd l i quef a c t i o n t i m e wa s c ha nged f r om
1 hourt o 3 hours ......................................................................................................83
F i gure 4.13 S t ora ge m odulus ( E ? ) f or s wi t c hgra s s bas e d e poxyr e s i n s yst e m s ...........................85
xiv
F i gure 4.14 The a c e t oneS oxhle t e xtr a c t i on t e s t s of s wi t c hgra s s bas e d e poxyr e s i n i n dif f e r e ntl i quef a c t i o n t e m per a t ur e ..........................................................................................86
F i gure 4.15 The a c e t oneS oxhle t e xtr a c t i on t e s t s of s wi t c hgra s s bas e d e poxyr e s i n i n dif f e r e ntl i quef a c t i o n t i m e ......................................................................................................87
F i g ure 4.16 F T- I R gr a ph of Absorbance ve r s us Wa venumbe f or Epon 828,Bi o - oil a nd bio-oilbas e d e poxyr e s i n ...................................................................................................89
F i gure 4.17 F T- I R gr a ph of Absorbance ve r s us Wa venumbe f or s wi t c hgra s s bas e d e poxyr e s i nswhen l i quef a c t i o n t i m e wa s f i xed a t 2 hours a nd l i quef a c t i o n t e m per a t ure wa s
c hanged f r om 200o C t o 260o C.................................................................................90
F i gure 4.18 F T- I R gr a ph of Absorbance ve r s us Wa venumbe f or s wi t c hgra s s bas e d e poxyr e s i nswhen l i quef a c t i o n t e m per a t ure wa s f i xed a t 250
o C a nd l i quef a c t i o n t i m e wa s
c hanged f r om 1 hourt o 3 hours ...............................................................................91
xv
Li s t o f Abbre via t i o ns
DS C Di f f e r e nti a l S c a nning C a l ori m e t r y
DMA Dynam i c Me c hanic a l a nal yze r
TGA Ther m o Gr a vim e t r i c Anal ysi s
Epon 828 Di glyci dyl Et her of Bi p henol A
P F P he nol f orm a l dehyde
UF ure a f orm a l dehyde
1
Chapter1Introduction
Renewable plant biomass resources, which include lignin,cellulose,
hemicellulose and other polysaccharides, are showing significance asasuitable
replacement for fossil-fuel resources.Currently,biomass from industrial residues is
noteffectively used, but is receiving increasingattention bysociety.
Inthe study ofJasiukaityt?et al.,biomass suchas woodandgrass are themost
important renewable natural products (Jasiukaityt?,Kunaver et al.,2010).
Liquefaction ofbiomass can beachieved using polyhydric orphenol alcohols under
specific acidas thecatalyst conditions (Yamada and Ono,2001; Rezzoug and Capart,
2002;Pan,Shupe et al.,2007;Jasiukaityt?,Kunaver etal.,2009).Phenols area
common andefficient solvent.Despite their high efficiency during liquefaction, those
phenols which arenot removed from thereaction wastestream could result in high
pollution and higher recovery costs (Jasiukaityt?,Kunaver etal.,2010).Thus, many
researchersaretrying tofind alternative solvents which include other multifunctional
alcohols,such asglycerol, and(poly) ethylene glycol and diethyleneglycol (Yamada
andOno,2001;Kobayashi, Asanoet al.,2004;MaandZhao,2008; Kunaver,Medved
et al.,2010).
Common adhesives usedfor binding all kindsof materials in thecomposites
industryinclude melamine urea-formaldehyde (MUF), diphenylmethane diisocyanate
(MDI), phenol formaldehyde (PF) and ureaformaldehyde (UF).PFis most widely
2
usedbecause ofits ideal mechanical properties,as well asmoisture resistance,but
using high volumes of these adhesives resultsin adepletion ofpetroleum-based
resources.Furthermore, these synthetic adhesives contain high levels oftoxins which
canbeharmful tohumans. Human consumption oftheseorganic substanceshas
become problematic, andthus ways toreduce orremove formaldehyde emissions are
beneficial. Consequently, oneaspect ofthis research is to develop anovel type of
adhesive without formaldehyde.
One replacement forurea formaldehyde would beepoxyresins,but it is
expensive inits natural form. However,if biomass based epoxy resin (this research is
using biomass through liquefactionprocedure to obtain liquid biomass ) could beused
asasubstitute during adhesive production, theresin could become more cost
competitive with urea/phenolformaldehyde andreduce the possibility of dangerous
formaldehyde emissions. Various biomass materials such asswitchgrass, wheat straw,
maize strawand woodcan beutilized tomake adhesives.The biomass is converted
into liquid bio oil throughaliquefaction procedure inmost research procedures.
Liquefaction ofbiomass provides achemical mixture whichcontains alot of
highly aliphatic hydroxyl groups.Also reactive aromatic groups can beusedas
reactionsites inthe preparation offoams, adhesives,or other moldings; exploring a
newapplication field inthe utilization ofwaste woodmaterials. Theuse ofliquid
wood in the preparationof newpolymers results inhigher efficiency inthe utilization
ofrenewable resources,and actas asubstitute for materials produced from crudeoil.
The main objectives ofthis project were asfollows:
3
Produceanoil/epoxy basedthermoset which will replace thehardener part ofa
typical epoxy-amine type ofepoxybymodification and characterizationofliquefied
biomass (switchgrass andsouthern pinewood)-basedepoxy resin.
1.Obtain the optimal OHnumber for improved reactivitybyvarying liquefaction
time and temperature.
2.Produceanoil/epoxy basedthermoset and characterize theliquefied biomass
(switchgrass andsouthernpine wood)-basedepoxyresin for different Epon 828to
bio-oil ratios.
3.Determine the optimal ratio of Epon828andsouthern pine wood basedepoxy
resin for different Epon 828tobio-oil ratios.
To achieve theseobjectives, the following subobjectives were carried out:
1. Producebio oil through liquefaction using switchgrass andsouthernpine
wood.
2. Producehigh-quality resins using different ratios of bio oil reactedwith
Epon 828.Determine the optimal ratio ofEpon andbio oil for the following chemical,
mechanical, and thermal properties ofthe curedadhesive: solvent extraction, DMA
(Dynamic Mechanical Analyzer), DSC(Differential Scanning Calorimeter), and TGA
(Thermo Gravimetric Analysis).
4
Chapter2Literature Review
2.1Energy Biomass
2.1.1 Potentialof biomassfor energy
Inrecent years, more andmore attention hasbeenplaced onCO2 emissions and
the consequentcorrelation withglobal warming. Biomass is awidely available
feedstock,andutilization of biomass for bioproducts canplay asignificant rolein
CO2 reduction during manufacturing while providing asafealternative for the
environment. Hoogwijk and Faaij (et al.2003) explored therange inbiomass for
energyona global scale.Theyargue that,inabout 50years, theglobal utilization
potential rangeof theglobal potential of primary biomass will beverybroadly
quantizedat 33?1135EJ yr?1.Basedonthe studies whichwere accomplished in
different countries and areas, thelargest potential contribution,0?988EJ yr?1,results
from the energycrops harvestedfrom surplus agricultural land.Given thebroad
availability ofbiomass, this feedstockfor energyis anticipatedto actas alarge scale
substitutein thenear future,whichcould result in adepressionin petroleum use. As
previously reported, renewable energysources (RES) suchas biomass, hydropower,
geothermal, solar,wind andmarine energies supply 14%ofthe total world energy
demand. Biomass already provided 62%ofthe total renewable energy sources in
1995(Ayhan,2005).Arecent study indicatedthat the rangeof geographical potential
5
biomass can betransformed into transportation fuels orelectricity andfuel, whichis
equal toseveral times the present oil consumption (Hoogwijk, Faaij etal.,2005).
Another study clarified the possibility ofusing strawused as biomass energy in China.
China has some of themost abundant strawresources inthe world andproduced more
than 620million tonsof strawin 2002(Zeng,Maet al.,2007). These studiesillustrate
that this energy biomass hasgreat potential to actas asubstitutefor petroleum based
fuel. Inother previous studies, it was found that different fermentation processes, such
asethanol andmethane production, could occur with acceptable wastewater
purification levels (Claassen,vanLier etal.,1999).It was discussedthat different
fermentation processes enable amore diverse utilization ofbiomass for gaseous and
liquid biofuel applications.
2.1.2Lignin
Lignin is anaromatic polymer which is generated by anoxidative combination
bythe coupling of4-hydroxyphenylpropanoids (Vanholme, Demedts et al.,2010).
Lignin can beisolated from extractive-free wood asaninsoluble residue after the
hydrolytic removal ofpolysaccharides. Alternatively, lignin can behydrolyzed and
extracted from wood,or converted toasoluble derivative. The termklason lignin is
usedwhen polysaccharides are extractedfrom the woodvia hydrolysis with72%
sulfuric acid(Sj?str?m ,1993).Lignins arecomplex polymers that consistof
phenylpropane units.Figure 1shows that Lignin is constitutedbyenzymatic
polymerisation ofthree monomers, which areconiferyl alcohol, synapyl alcohol,and
p-coumaryl alcohol that lead,respectively, toguaiacyl (G), syringyl(S) and
6
p-hydroxyphenyl propane (p-H)-typeunits (Fig. 2.1a).The structure of lignin is a
complicated macromolecule (Fig.2.1b) withagreat variety ofdifferent kinds of
functional groupsandover 10different types oflinkages(Tejado, Pe?aet al.,2007).
Fig.2.1(a) Schematic representationof thestructural units oflignin, and (b)structural
segment of lignin proposed byAdler (1977) (Adler,1977).
Figure 2.2shows thelignin precursorsfor plants.Thereare three basic lignin
monomers found inlignins. Grasses and straws contain all three lignin monomers .
Hardwoods contain bothconiferyl alcohol (20-75%)and sinapyl alcohol (25-50%).
But,softwoods contain only coniferyl alcohol. This could beused toexplain the
different characteristics ofsouthern pine woodbased epoxy resin and switchgrass
basedepoxyresin.
7
OH
OH
OH
R1 OH
OH
R1 R1OH
Figure 2.2Lignin precursors for plants.
Here R1 means the?OCH3 group.
The various hydroxyl groupsexperience decomposition reactions such as
gasification and liquefactionthat result inanincreased availability ofreactive groups
for further applications.The biomass usedin this research was switchgrass and
southernpine wood.Table 1shows theproportions ofhemicelluloses/lignin/cellulose
ofsoftwoods andhardwoods and,at the same time, wheat,straw,and switchgrass for
comparison (Peter,2002).
Table 2.1
Cellulose/lignin content/hemicelluloses ofselected biomass (wt %)(Peter 2002)
Biomass Lignin (%) Cellulose(%) Hemi-cellulose (%)
Softwood 27?30 35?40 25?30
Hardwood 20?25 45?50 20?25
Wheatstraw 15?20 33?40 20-25
Switchgrass 5?20 30?50 10?40
Hardwoods &
Softwood
Conlferylalcohol
Grasses
P-coumaryl
alcohol
Hardwoods
Sinapyl alcohol
8
2.1.3 Cellulose
Celluloseis the most abundant natural polymer in woodandplants and can be
extracted from industrial wastes invarious forms and modifications (Abella, Nanbuet
al.,2007).Approximately 45-50%of thedry substance inmost wood species is
comprised ofcellulose withthe majority ofthe volume locatedpredominantly in the
secondary cell wall (Mohan, Pittman etal.,2006).Some forms oflignocellulosic
materials may havemore cellulose than wood.Cellulose is aremarkably pure organic
polymer with units ofanhydroglocoseheld togetherin alongstraight chain molecule.
The chemical structure ofcellulose is a homopolysaccharide through thelinking of(1
?4)?glycosidic bondswhichare composed by?-D-glucopyranoseunits (Fig 2.3).
Twoglucose anhydride units comp osethe basicrepeating unit ofthe cellulose
polymer whichis calledacellobiose unit (Balat,Balat et al.,2009).
Fig.2.3Chemical structure ofcellulose
Bundlesof cellulose molecules are aggregatedtogether inthe form of
microfibrils, in whichhighly ordered (crystalline) regions alternate with less ordered
(amorphous) regions. Microfibrils build upinto fibrils whichfurther build up into
cellulose fibersresulting in anatural composite matrix within theS-layer of thecell
wall. Asa consequenceof its fibrous structure andstronghydrogen bonds, cellulose
9
hasahigh tensile strengthwhen primarily loaded axially and is insoluble inmost
solvents(Sj?str?m ,1993).
2.1.4 HemicelluloseHHH
Incontrast tocellulose,whichis ahomopolysaccharide ,hemicelluloses are
heteropolysaccharides.And like cellulose, most hemicelluloses functionto connect
cellulosic to lignin type polymers resulting in adequatestress transfer upon loading
andconsequently are important in thestructural support ofthe cell wall (Sj?str?m ,
1993).The amount ofhemicelluloses per dryweight ofwoodis usually between 20
and30%whichis the secondmajor wood chemical constituent inwood chemical
composition. Here is thespecific data fordifferent kinds ofwood.Avarietyof
hemicelluloses usually account for 28%insoftwoods and35% inhardwoods (Rowell,
1984).Hemicellulose is amixture of various polymerized monosaccharides suchas
mannose, galactose,arabinose, xylose,glucose 4-O-methyl, glucuronic acid, and
galacturonic acid residues.Hemicelluloses (arabinoglycuronoxylanand
galactoglucomammans) arerelated toplant gums, andexist in much shorter molecule
chains thancellulose.Also, hemicelluloses exhibit lower molecular weightsthan
cellulose. Thehemicelluloses arerepresented inbroadleavedwoods as pentosans and
inconiferous woods asmostly hexosanes.Thesepolymers that consist of thesesugar
units are typically easily brokendown inhigh thermal environments. Hemicelluloses
arederived mainly from chains ofpentose sugars andact asthe adhesive material
whichhold the cellulose micells andfibers together (Demirbas ,2008).Formulas of
the sugar component of hemicelluloses arelisted inFig 2.4(JohanVerendel, Church et
10
al.,2011).
Fig.2.4Sugar component ofhemicelluloses (Johan Verendel,Churchet al.,2011)
2.1.5Switchgrass
Thereare many kinds ofbiomass which could be transformed into therenewable
bioenergy toreplace thenon-renewable energy suchasnatural gas,fuels anddiesel
etc. which arebeing consumed inincreasing quantities.Inthe last 20years,
switchgrass utilizationfor non-foragepurposes has increased, especially inthe field of
bioenergy (Parrish and Fike,2005).In theresearch ofthe avid J.Parrish and John H.
Fike,they discussedthe biology and agronomy ofswitchgrass for biofuels and
confirmed it asapotential renewable fuel source(Parrish andFike,2005).
Switchgrass(Panicum virgatum L.) is aperennial and warm-season (C4) species
grown inmultiple divergent populations throughout NorthAmerica. In another study,
Sanderson, M.A.(etal 1996)further supported that switchgrasshas thepotential to
beasustainable herbaceous energy cropparticularly for transportationfuel and/or
biomass-generated electric power (Sanderson, Reed etal.,1996).Lemus, R.et al
(2004) explored theeffect ofgrinding performance onthephysical properties of
11
wheat andbarley straws, corn stover,and switchgrass(Mani, Tabil et al.,2004). They
foundthat switchgrass hadthe highest specific energyconsumption (27.6kW?ht-1)
among the four materials. After comparing the physical properties of grinds suchas
moisture content, geometric mean diameter ofgrind particles, particle size distribution,
andbulk and particle densities were determined. They contendedthat switchgrass had
the highest calorific value and thelowest ashcontent among the biomass species
testedwhichmay berelated tothe variationin chemical constituents.Recently,
Keshwani andCheng agreedthat switchgrass is apromising feedstockfor
value-addedapplicationsdue toits potentially low processing requirements and high
productivity, for agricultural inputs and positive environmental impacts (Keshwani
andCheng,2009).They pointed outthat other value-added uses ofswitchgrass
includinggasification andliquefaction for bio-oil productionandfurther upgrading
into biobased composites, polymers andadhesives arepossible.
The chemical composition and energyassessment of theswitchgrass are
important in determining its potential useas bothafuel andvalue addedproducts
suchas adhesives. Table 2.2gives asummary ofthe amount ofcellulose,
hemicelluloses andlignin present invarious types ofswitchgrass. This data originated
from the National Renewable EnergyLaboratory?s biomass feedstockproperties and
composition database (Keshwani and Cheng,2009).
12
Table 2.2
Composition (%dry basis) ofdifferent switchgrass varieties from NREL?s biomass
feedstockcomposition andproperties database (Keshwani and Cheng,2009)
Switchgrassvariety Cellulose Hemicellulose Lignin
Alamo-whole plant 33.48 26.10 17.35
Alamo ?leaves 28.24 23.67 15.46
Alamo?stems 36.04 27.34 17.26
Blackwell?whole plant 33.65 26.29 17.77
Cave-in-Rock?whole plant 32.85 26.32 18.36
Cave-in-Rock ?whole plant (high yield) 32.11 26.96 17.47
Cave-in-Rock ?leaves 29.71 24.40 15.97
Cave-in-Rock ?stems 35.86 26.83 17.62
Kanlow-leaves 31.66 25.04 17.29
Kanolw-stems 37.01 26.31 18.11
Trailblazer 32.06 26.24 18.14
2.1.6Southernpinewood
The biomass used for bio-oil productionin this researchwas southernpine wood
whichis awidely available biomass inthe southern part oftheUS. According to the
Billion-Ton Annual Report (Perlack,Wright etal.,2005),368million dry tons/yearof
sustainable andremovable biomass could beproducedonexisting forestlands.They
estimate dthat nearly 1/4 ofthe entire annual biomass population could beusedfrom
forest andagricultural resources tosupply bioenergy and bioproduct processes
(Perlack,Wright etal.,2005).
13
2.2 Liquefactionofbiomass
Accordingto XianyangZeng (2007), technologies which have beenpolularized
andcommercialized in China suchas direct biogas, combustion, strawgasification,
andstrawbriquetting havethe potential for being environmentally friendly while
providing anadequate supply ofrural energy. But other technologies, including straw
carbonization,liquefactionand bio-coal, havebeenunderutilized. Despite their low
cost and technical feasibility, theyare currently being developed slowly (Zeng, Maet
al.,2007).Liquefaction is anticipatedto playa significant role inthe global energy
sector dueto thesimplicity of thereagent andoperation,aswell asenvironmentally
friendly process.According to Rezzoug and Capart(2002), the processof wood
liquefactionoccurs in two steps: a)ethylene-glycol orother pure orrecycledsolvents
areused asawood solvent andb)high pressuresare utilized toprovide catalytic
hydrogenationandsolvolysis toproducea liquid product. Inthe first step of their
experiment, theyused ethylene glycol andsulphuric acidwith a4:1and0.01:1 ratio to
the biomass, respectively, obtain the bio-oilsuccessfully. The temperature ofthe
reactorwas raisedat arate of3?/min and thenkept ata plateau of250?.From these
results,weknowthat thechemical composition of liquefied cellulosestrongly
dependsonthe liquefying conditionssuch astime and temperature. Forcellulose, the
rate ofdepolymerization has beenfoundto bealimiting factor which drives thetime
toliquefaction (Kobayashi, Asanoet al.,2004).Furthermore, theysuggested that the
condensationreaction was attributable tothe mutual reaction between degraded
aromatic derivatives from lignin and depolymerized cellulose,orbecause ofthe
14
nucleophilic displacement reaction ofcellulose byphenoxide ion.Others have
characterizedthe residuesafter liquefaction using wet chemical analyses, fourier
transform infrared (FTIR) spectroscopy, x-raydiffraction (XRD),andscanning
electronmicroscopy (SEM)(Pan, Shupe et al.,2007). Three different ratiosof
phenol towood byweight were explored andranged from 1/1to 3/1.These3ratios
were complimented bythree otherexperimental variables including liquefaction
temperature, phenol/wood ratio,andcooking method. It was found that eachfactor
played asignificant role in thecomposition of the residues. Table 2.3represents a
compr ehensive reviewof thedifferent parameters that could beusedduring
liquefactionto generate bio-oil.
Table 2.3Different methods of thebiomass liquefaction
Liquefaction
materials
Reagent Ratio(bas
edon
biomass)
(w/w)
Tempera
ture (?)
Time Resource
Pinewood
chips
Ethylene glycol
Sulphuric acid
4/1
0.01/1
250 Changing (Rezzoug
andCapart,
2002)
Commercial
cellulose,
Lignocellulosi
cs
(Sawdust of
white birch)
EG
97%sulfuric
acid
5/1
0.15/1
150?C Changing (Yamada
andOno,
2001)
White birch,
Cellulose
powder, Alkali
lignin,
Steamed lignin
Glycerol
Polyethylene
glycol
Sulfuric acid
0.3/1
1.5/1
0.15/1
150?C Changing (Kobayashi,
Asano et al.,
2004)
Woodpowder Phenol
Oxalic acid
1/1-3/1
0.05/1-
150?C
180?C
3hrs (Pan, Shupe
et al.,2007)
15
0.15/1
Lignocellulosi
cwaste
(sawdusts of
white birch,
Japanese
cedar,
andJapanese
cypress)
EC,PC
97%sulfuric
acid
5/1
0.15/1
150?C Changing (Yamada
andOno,
1999)
Cellulose EC
PTSA
MSA
5/1
changing
changing
Changin
g
Changing (Sung Phil
Mun,2001)
Bagasse EC - 140?170
?C
0-18mins (Xie and
Chen,2005)
Cornstover
Wheat straw
Ricestraw
EG
EC`
Polyethylene
glycol+
glycerol(9/1)
EC+ EG(8/2)
97%sulfuric
acid
10/3
10/3
10/3
10/3
10/3
160?C Changing (lingyun
liang,2006)
Spruceandfir
sawdust
Glycerol+
DEG(4/1, w/w)
PTSA
3/1
0.09/1
150?C 4hrs (Jasiukaityt?
,Kunaver et
al.,2010)
Meals
(poplar, oak,
spruce and
beech)
Glycerol+DG
(4/1 w/w)
p-toluenesulfon
ic
acid
3/1
0.09/1
180?C 3hrs (Kunaver,
Medved et
al.,2010)
16
Where ethylene carbonate (EC)
Propylene carbonat (PC)
Ethylene glycol (EG)
Methanesulforic acid(MSA)
Diethyleneglycol (DEG)
P-toluenesulphonic acid(PTSA)
2.3Basicintroductionof generalEpoxy resin
Epoxy resin is apolymer whichis formed from twodifferent chemicals. The
basic chemistry ofthe adhesive system involves a diepoxide and apolyfunctional
amine, whichwill lead toacrosslinked system upon curing.The diepoxide is usually
derived from BisphenolAand epichlorohydrin.Asimple diglycidyl derivative of
BisphenolAoroligomeric compounds with epoxideendgroups could then be
producedthrough tightly controlled reactionconditions. The hardener consistsof
polyamine monomers suchas triethylenetetramine (TETA).When these compounds
aremixed together,the amine groupswill react with theepoxide groups toform a
covalent bond.WheneachNHgroup canreact with one epoxidegroup,theresulting
polymer is heavily crosslinked andthus has highrigidity and strength.The most
common andsignificant typeofepoxy resins is formed from reacting epichlorhydrin
withbisphenol Ato producebisphenol Adiglycidyl ethers.The simplest resin ofthis
type is formed from reacting twomoles of epichlorhydrin withonemole of bisphenol
17
Atoproduce thebisphenolAdiglycidyl ether.Figure 2.5(a) shows thebasic structure
ofbisphenol-Adiglycidyl ether epoxyresin. Curing may beachieved byreacting an
epoxywith itself (homopolymeri zation) or byforming acopolymer with
polyfunctional curatives orhardeners. In principle, any molecule containing reactive
hydrogenmay react withthe epoxide groups of the epoxyresin. Common classesof
hardeners for epoxy resins include amines, acids, acidanhydrides,phenols, alcohols,
andthiols. Figure2.5(b) shows the structure ofTETAwhichis atypical hardener.The
amine (NH2) groupsreact with theepoxide groups ofthe resin during polymerization.
Figure 2.5(a)Structure ofbisphenol-Adiglycidyl ether epoxy resin
(b) StructureofTETA
2.3.1Wood-basedepoxyresin
Inrecent years, researchers havepaid great attention tothe optimization ofepoxy
resin mechanical andthermal properties. It hasbeenfoundthat an epoxy resin canbe
toughened using synthesized polyurethaneprepolymer based onhydroxyl-terminated
polyesters (Harani, Fellahi et al.,1998).They addedeither arigid phase orarubbery
phaseto improve epoxyresin toughness.Hajeme Kimura et al.(1998) investigatedthe
epoxyresin cured bybisphenol-Abasedbenzoxazine. This alternative epoxyresin
system was found toexhibit good water resistance,electrical insulation, heat
resistance,andmechanical properties. W.J.Wang et al.(2000) furtherinvestigated the
characterizationandproperties of newsilicone-containing epoxy resin andfoundthat
they could synthesize anewepoxy monomer, triglycidyloxy phenylsilane (TGPS)
18
withcompetitive properties. This newepoxy system exhibited ahigh limiting oxygen
index which resultedin superior flame resistance;making it available forharsh
temperature environments. Thesestudies all demonstrate that the system canbe
engineeredthrough various reaction mechanisms and reactants toresult inawide
array ofapplicationswhich make it asuitable system for newproduct development.
Thereappears to befuture opportunitieswhichinvolve exploring newmethodologies
suchas addingfiller, injecting newcomponents such assubstitutes forpetroleum,
reinforcing elements ,plasticizer,anddialing in the final performance ofthe epoxy
resin system throughchanges insynthesis reactants and processing procedures.
Todate,most biobased epoxysystems havefocused onthe substitutionof lignin,
whichis across-linkedphenylpropanoid polymer; whereas literatureonpyrolysis or
liquefactioninto bio-oil (as asubstitute)has beenmore limited. Lignin and bio-oil
type systems should respond similarly in themechanism of reactionsince bio-oil has
similar polyphenolic typestructures. But therate andmagnitude ofreaction may
differ since bio-oil has smaller sized molecules resulting inmore available OHsites.
Hence, thenext sectionof this review will focus more onlignin-based epoxy resin
whichhasbeen extensivelystudied and has beenshown to maintain orimprove
adhesive thermal and mechanical properties.It is also more friendlyto the
environment and often cheaper sincelignin can beobtainedfrom pulp and paperor
bioenergy waste streams. Inthe researchofDelmas et al.,wheat strawBiolignin?
was usedas asubstitute ofbisphenol-Ain epoxyresin. Synthesis was carried out in
alkaline aqueous media using polyethyleneglycol diglycidyl ether (PEGDGE) as
19
epoxide agent (Delmas, Benjelloun-Mlayah etal. 2013).In thestudy ofKishi etal.,
wood-basedepoxyresins were synthesizedfrom resorcinol-liquefied wood(Kishi,
Fujitaet al.2006).
Hirose, Setal. investigated thesynthesis andthermal properties ofepoxy resins
from ester-carboxylic acidderivative of alcoholysis lignin (Hirose, Hatakeyama et al.,
2003).Hajime Kishi et al.(2006) discussedthe synthesis of wood-basedepoxyresins
andtheir mechanical andadhesive properties. In their study, woodwas first liquefied
inthe presence ofresorcinol both withorwithout asulfuric acid catalyst, and ata
hightemperature. Theyfound that thewood-based epoxy resins would bewell suited
for thematrix component ofnatural plant-fiber reinforced composites.
2.3.2TestMethods ofAdhesive
Thereare many methods which areused toevaluatethe properties ofthe
adhesive.Agreat number ofstudieshave focusedonhowtocharacterize epoxy resin
properties.Forexample, Deng, Hu etal. (1999),investigated thecuring reaction and
physical properties of DGEBA/DETAepoxy resin blendedwith propyl ester
phosphazene.They used DSC(Differential Scanning Calorimeter), SEM,DMA
(Dynamic MechanicalAnalyzer),TGA(Thermo Gravimetric Analyzer) and tensile
testing toinvestigatethe thermal and strengthperformance of theepoxyprepolymer.
Furthermore, inmost studies, most thermal andmechanical properties could be
measured with dynamic differential scanningcalorimetry (DSC), thermogravimetric
analysis (TGA),andDynamic Mechanical Analyzer (DMA) (Park and Jin,2004).
From theaboveresearches, it is evident that DSC,SEM, DMA,tensile testing,and
20
TGAarethe common approaches toevaluate theproperties of epoxy resin.
2.3.2.1DynamicDifferentialScanningCalorimetry (DSC)
The objective of calorimetry is to measure the heat ofthe reaction during curing
andconsequent crosslinking. Inorder to measure heat, the heat needs tobeexchanged.
The exchangedheat canbeused asameasure of theheat exchangedwhichis affected
byatemperature change inasystem ,orthe heat flow created inthe heatexchange
process, leading totemperature differences, could beameasure indicator oftheheat
flowalong its path. Caloric measurements havebeen carried out since the middle of
the 18thcentury. Now,the modern Differential Scanning Colorimeter (DSC)is widely
usedtoday (H?hne, Hemminger et al.,2003). Several studies havebeenconducted to
determine theenthalpy ofpyrolysis for abiomass sample.
DSCis amethod which could beused todetermine the heat required totrigger a
reactionwhich resultsin crosslinking ofthe polymer. As the cross-linkednetwork
develops, it either releases orabsorbs heat depending of thenature ofthe reaction.
This heat flowwith changein temperature canthen beplottedto understand the
crosslinking behavior.More specifically, theshape oftheDSC curveis: theY-axis is
the endothermic or exothermic rate ofthe sample. Inother words,it is theheat flow
rate (dH /dt) (unitsmillijoules /sec) in which thetemperature (T) forms the X-axis.
This analytical toolcan thusbebeneficial in the characterization ofpolymer
thermodynamic andkinetic parameters. Forexample, specific heat capacity,heat of
reaction,the heat oftransition,the phasediagram, reactionrate, rate of crystallization,
the degreeofcrystallinity ofpolymers, and sample puritycan all becalculated or
21
estimated from the enthalpybehavior ofthe system. In this research,the main purpose
ofthe DSCis todetermine the glass transitiontemperature of different bio-based
epoxyresins.Several studies have beenconducted todetermine the endothermic and
exothermic performance ofdifferent material samples. TaoXie et al. employed DSC
todetermine the thermal properties ofepoxyresin from the liquefied product which is
liquefied withthe bagasse inethylenecarbonate(Xie and Chen,2005).They found
that the resin presented higher adhesive shear strengthandbetter thermal stability than
acommercial epoxy resin. Inthe studyof Hui Panetal., theymeasured thecure
kinetic mechanisms oftheLWPFresins with dynamic and isothermal differential
scanning calorimetry (Pan, Shupe etal.,2008).They foundthat the isothermal DSC
data indicatedthat the curereactions ofboth resins followed anautocatalytic
mechanism. Theactivation energies oftheliquefied wood resins were close to that of
areportedlignin?phenol?formaldehyde resin but were higher thanthat ofa typical
phenol formaldehyde resin. In this research,Differential Scanning Colorimeter Q2000
was usedto measure theheat ofthe reaction during curing andconsequent
crosslinking. Refrigerated cooling system, 90andTzero sample press, and pansare all
from TAInstruments Company.
2.3.2.2Thermo GravimetricGGG Analyzer(TGA)GGG
Thermo gravimetric analysis is atechnique usedto determine theweight loss of
amaterial when it is subjectedto high temperatures atacontrolled rate in anitrogen
orair environment .The machine usedfor this techniqueis aThermo Gravimetric
Analyzer (TGA).Inthis study,Thermo Gravimetric Analyzer (TGA) Q500from TA
22
Instruments Company was employed toexam inethe degradationtemperature.
2.3.2.3DynamicMechanicalAnalyzer(DMA)
Dynamic MechanicalAnalyzer is atechnique usedto studyand characterize
materials. The most useful function is to study the viscoelastic behavior ofpolymers.
Asinusoidal stress is applied giving rise tostrain inthe measure .The strain is
measured andmonitored to assist in thecomplex calculation ofmodulus. The
temperature of thesample orthefrequency of thestress is often varied, resulting in a
changein themodulus. This technique can helpdetermine the glass transition
temperature of thematerial and can identify transitionsattributed tomolecular
motions. In theresearch ofJooRan Kim et al. (2012),the thermal experiments were
conducted using the dynamic mechanical analyzer (DMA) todetermine the extent of
the resin conversions andtheir thermal transitions into athermoset matrix.
2.3.2.4FourierTransform InfraredSpectroscopyMachine (FT-IR)
Fourier transform infrared (FT-IR) spectroscopy is arapid, noninvasive
techniquewith considerable potential to rapidly identify the presenceor
disappearance ofkeyfunctional groupsas aresult of different reactionsor treatments
(Ellis, Broadhurst etal.,2002).Inthe researchof Panetal. (2008),they employed
FT-IRto determine thepresence of keyfunctional groupsassociated withliquefied
wood. In thestudies ofHui Panet al.(2007);T.Yamada etal. (1999);JooRan Kim et
al. (2011),FT-IRwas usedto monitor specific peaks oftheresidue after various
liquefactiontreatments (Yamada andOno,1999;Pan,Shupe et al.,2007; Kim and
Sharma ,2012).
23
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reactions yielding aldehydes andaketone inbiomass."
Adler, E. (1977). "Lignin chemistry ?past, present and future." Wood Science and
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Ayhan, D. (2005). "Potential applications of renewable energy sources, biomass
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Balat, M., M. Balat, et al. (2009). "Main routes for the thermo-conversion of biomass
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Ellis, D. I., D. Broadhurst, et al. (2002). "Rapid and Quantitative Detection of the
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Hoogwijk, M., A. Faaij, et al. (2005). "Potential of biomass energy out to 2100, for
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Hoogwijk, M., A. Faaij, et al. (2003). "Exploration of the ranges of the global
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JOHAN VERENDEL, J., T. L. Church, et al. (2011). "Catalytic One-Pot Production
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Keshwani, D. R. and J. J. Cheng (2009). "Switchgrass for bioethanol and other
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the dynamic mechanical properties of epoxy resin composites." Composites Part A:
Applied ScienceandManufacturing 30(8): 997-1002.
Kim, J.R. and S.Sharma (2012). "The development and comparison of bio-thermoset
plastics from epoxidizedplant oils."Industrial Cropsand Products 36(1): 485-499.
Kimura, H., A. Matsumoto, et al. (1998). "Epoxy resin cured by bisphenol A based
benzoxazine."Journal ofApplied Polymer Science 68(12): 1903-1910.
Kishi, H., A. Fujita, et al. (2006). "Synthesis of wood-based epoxy resins and their
mechanical and adhesive properties." Journal of Applied Polymer Science 102(3):
2285-2292.
Kobayashi, M., T.Asano, et al. (2004). "Analysis on residue formation during wood
liquefactionwith polyhydric alcohol."Journal ofWoodScience50(5): 407-414.
Kunaver, M., S. Medved, et al. (2010). "Application of liquefied wood as a new
particle boardadhesive system." BioresourceTechnology 101(4): 1361-1368.
lingyun liang, Z. M.(2006). "liquefactionof cropresidues for polyol production."
Mani, S.,L. G. Tabil, et al. (2004). "Grinding performance and physical properties of
wheat and barley straws, corn stover and switchgrass." Biomass and Bioenergy 27(4):
339-352.
Melvin G.R, C. (2003). "Carbon sequestration and biomass energy offset: theoretical,
potential and achievable capacities globally, in Europe and the UK." Biomass and
Bioenergy24(2): 97-116.
Mohan, D., C. U. Pittman, et al. (2006). "Pyrolysis of Wood/Biomass for Bio-oil:? A
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Critical Review."Energy & Fuels 20(3): 848-889.
Pan, H., T. F.Shupe, et al. (2007). "Characterization of liquefied wood residues from
different liquefaction conditions." Journal of Applied Polymer Science 105(6):
3740-3746.
Pan, H., T. F. Shupe, et al. (2008). "Synthesis and cure kinetics of liquefied
wood/phenol/formaldehyde resins." Journal of Applied Polymer Science 108(3):
1837-1844.
Park, S.-J. and F.-L. Jin (2004). "Thermal stabilities and dynamic mechanical
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Peter, M. (2002). "Energy production from biomass (part 1): overview of biomass."
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Rezzoug, S.-A. and R. Capart (2002). "Liquefaction of wood in two successive steps:
solvolysis in ethylene-glycol and catalytic hydrotreatment." Applied Energy 72(3?4):
631-644.
Rowell, R. M.(1984).The chemistry of solid wood,ACSPublications.
Sanderson, M. A., R. L. Reed, et al. (1996). "Switchgrass as a sustainable bioenergy
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Sj?str?m, E. (1993).Woodchemistry: fundamentals and applications,Academic Pr.
Sung Phil Mun, E.-B. M. H., Tae Ho Yoon (2001). "evaluation of organic sulfonic
acids as catalyst during cellulose liquefaction using ethylene carbonate." Industrial
Engeering Chemistry 7: 430-434.
Tejado,A., C. Pe?a, et al. (2007). "Physico-chemical characterization of lignins from
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Vanholme, R., B. Demedts, et al. (2010). "Lignin Biosynthesis and Structure." Plant
26
Physiology153(3): 895-905.
Wang, W. J., L. H. Perng, et al. (2000). "Characterization and properties of new
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ethylenecarbonate."BioresourceTechnology70(1): 61-67.
Yamada, T. and H. Ono (2001). "Characterization of the products resulting from
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27
Chapter3
Modification and characterization ofliquefiedsouthern pinewood basedepoxy
resin
3.1Introduction
It is essential thatindustrial systems consider factorsthat may becontributing to
global-warming andthe eventual depletion offossil fuels. Utilizationofplant biomass
for bioenergyandbioproducts is one wayto offset carbon emissions becauseit
recyclescarbon insteadof supplementing carbonfrom fossil fuels (Kishi, Fujita etal.,
2006).Because carboncanbesequestered at thesame rate asit is releasedduring
manufacturing, it canbeclassified asarenewable resourcewhichwill ensure a
sustainable but functional andtechnological planet forgenerations to come. Therefore,
people have investedmuch effort into finding ways touse biomass asa renewable
feedstockduring polymer andchemical processing.
Woodis one ofthemost significant natural resources. Woodis anorthotropic
material dueto it complex organization ofwoodchemistry, fiber morphology, and
macro characteristicssuch asearlywood and latewoodformation (Jasiukaityt?,
Kunaver et al.,2009).Lignin, cellulose andhemicelluloses are thethree main
components in woodchemical structure. During liquefaction, hemicellulose and
cellulose areremoved while lignin whichhas asmaller molecular weight is retained.
This is the principalreaction component in the liquefaction process, and it generates
28
anaromatic polymer whichis generatedbyanoxidative combination bythecoupling
of4-hydroxyphenylpropanoids (Vanholme, Demedts etal.,2010).Lignin can be
isolated from extractive-freewood asaninsoluble residue after hydrolytic removal of
the polysaccharides.Alternatively,lignin can behydrolyzed and extracted from wood
orconvertedto asoluble derivative. Figure 3.1(a) and (b)showthe basic structure of
lignin.
Fig.3.1(a) Schematic representationof thestructural units oflignin, and (b)Structural
segment of lignin proposed byAdler (1977)(Adler,1977).
Inthis research, theprincipal material togeneratebio-oil is southern pinewood.
It will beusedasrawmaterials toproduce bio-oil via liquefaction. However, in
additionto thenatural unzipping oflignocellulosic polymers during high temperature
exposure (Via et al.,2013) thedepolymerization ofthe macromolecular structure
29
during liquefactionresults inthe interactionandreaction ofspecific organic reagents
andspecific catalyststothe biomass substrate. The resulting phenolic rich but diverse
bio-oil can thenbe usedas anewfeedstock for polymer production (Yamada and Ono,
2001;Rezzoug andCapart,2002; Kobayashi,Asano et al.,2004).The
depolymerization ofwood components canbeobtained with polyhydric or phenol
alcohols under acid-catalyzedconditions. Liquefied wood hasahigh reactivity due to
the largeamount of phenolic OHgroupsandalcoholic OHgroups (Jasiukaityt?,
Kunaver et al.,2009; Jasiukaityt?,Kunaver et al.,2010; Kunaver,Medved etal.,
2010).Using thesefunctional groups, liquefied woodcanbe converted to
polyurethaneforms and phenolic resins (Tan,1996; Nonaka andTomita etal.,1997;
Zhao, Chen etal.,2001).Liquefiedwood has further potential and may beused asa
resourcefor other valuable biomass-based materials. The epoxy-resin family hasgood
mechanical and adhesive performance, and is widely usedin various fieldssuch as
adhesives,coatings,and matrix resins ofcomposites. The first objective ofthis study
is tosynthesize southern pinewood basedepoxyresins usingliquefied southernpine
wood astheprecursor forresin production. Thesecond objective is to evaluate the
mechanical, thermal, and adhesive properties ofthe wood-basedepoxyresins in order
toclarify its potential for asuiteof applications. Inthe researchofH.P.SAbdul Khalil
et al.(2011),they generated theuse ofEFB-lignin asacuring agent inepoxy resin, as
shown inthe reactionscheme in Figure3.2
30
CH 3
CH 3
O
O
O
O
OH R1R2
OH
O
O CH3
CH 3
O
OH
O
R1 OH
R2
+
n n n n
R1=OMe, R2=H: coniferyl alcohol/guaiacylR1=R2=OMe: sinapyl alcohol/syringyl
R1=R2=H: p-Coumaryl alcohol
Triphenylphosphine
Fig.3.2Idealized network formation during curing reactionof epoxy-lignin system
(Abdul Khalil, Marliana et al.,2011)
Inthe study ofMaria L.Auad etal. (2011),theymainly focusedonthe development
andoptimization ofthe processing methodology toproduce epoxy modified phenolic
foams. They alsoanalyzedthe relationship between thecomposition andthe structure
aswell asthe mechanical and flammability performance ofepoxy-phenolic
(E-P)-basedfoams ,as shown inreaction scheme in Figure 3.3(Maria L.Auad, Zhao
et al.,2007).The epoxythey used was Epon 826and thehydroxyl groupsupplier was
Novolacwhichwere Epon 828andsouthernpine woodbased bio-oil.They have
similar reaction theory toproduce epoxy resin.
Fig.3.3Schematic ofthe E-Psysthesis reaction (Maria L.Auad, Zhao etal., 2007)
Lignin
DGEB-A
31
Whenall ofthe results were analyzed, wefound that theoptimal liquefaction
temperature was 220?when thetime was fixed at2h.Then wefixed the liquefaction
temperature at 220?,andchangedthe liquefactiontime asto1h,2h,and 3h.We
foundthe optimal liquefactiontime byvarious tests including residue content
collectionofliquefaction residue,hydroxyl number test, pHvalue ofbio-oil, andthe
thermal properties testsof southern pinewood basedepoxyresin.
3.2Materials and Methods
The following are flowcharts Figure 3.4ofhowtooptimize the liquefaction
temperature when liquefactiontime was fixed at2hrs and Figure 3.5ofhowto
optimize theliquefaction time when liquefactiontemperature was fixed at220oC.
Fig.3.4Flowchart of optimizing theliquefaction temperature when theliquefaction
time was fixed at 2hrs.
32
Figure 3.5Flowchart ofoptimizing the liquefactiontime whenthe liquefaction
temperature was fixed at 220oC.
3.2.1.Biomass(southern pine wood) Preparation
Ahammer mill (NewHolland grinder model 358,NewHolland, PA.)with
3.175-mm (1/8 in.) sieve sizewas used for particle size reduction. Particles from
southernpine wood(Panicum virgatum) were collected andoven-dried at105?for
12hrs and keptin adesiccator atroom temperature before use.The dried material was
groundto passthrough a20mesh sieve before placing it inthe oven. Diethylene
glycol (99%, from AlfaAesar chemical company) was used asthereagent solvent
during liquefaction.All other chemicals for liquefaction ofsouthernpine woodand
modification ofwood-basedepoxyresins were ofreagent grade and were used
without furtherpurification.
3.2.2Liquefactionofsouthern pinewood
The liquefactionprocedure of southern pinewood was basedonthe general
method describedbyTaoXie (Xie andChen,2005),and thensubsequently modified
33
byMatja?Kunaver (Kunaver,Medved etal.,2010).The liquefactionofsouthern pine
was carriedout free ofpressurein a1000ml three neck glass reactor equipped witha
mechanical stirrer (500rpm) and reflux condenser device.The reactorwas charged
with100gof woodand400gof diethyleneglycol andthen was heated tothe desired
temperature for liquefaction. One gof98% sulfuric acidwas addedandthe mixture
was heated for various times (1h,2hand3h) atvarious temperature (200?,220?,
240?,250?and260?)while beingconstantly stirred.
3.2.2.1Determinationof residuecontent
The residue content evaluation method usedin this work wasa modification of the
method describedbyHui Panet al.(Pan, Shupe etal.,2008)andHajime Kishi et al
(Kishi, Fujitaet al.,2006).The liquefied mixture was dilutedwith 500mL of acetone
andvacuum-filtered withWhattman #1filter paper three times to separatethe
dissolvedsouthern pine wood particle residue and thesolved portion.The insoluble
residueswas put into oven tobedried at 105??2?for 24hrs and storedin a
desiccator.The residue content ofthe liquefied woodwas calculated byeq.(1):
Residue Content (%) =WR/WO ?100 (1)
WhereWR is the oven-dried weight of thesolid southernpine wood residue after the
filtration andWO is the weight ofthe original southern pinewood particles (Pan,
Shupe et al.,2007).The residuecontent was defined asthe percent dryweight ofthe
acetone insoluble substance ofthe total biomass charged. Usually, it is usedas an
index for the extent ofliquefaction.
34
3.2.2.2HydroxylHHH groupnumbertest
The hydroxyl group number ofthe liquefactionproduct is defined asthe mass of
KOHequivalent to that ofthe phthalic anhydride consumed inthe phthalificationof 1
gofthe sample. The hydroxyl number was measured according toASTM D4274-11.
Fresh and dry pyridine andstandard 0.5Nand0.1Nsodium hydroxide solutions,
were usedfor all reactions. First,111to116g ofphthalic anhydride was weighed ina
1000mL brownbottle. Then,700mL ofpyridine was added,which hadbeendistilled
from phthalic anhydride, and thebottle was shaken vigorouslyuntil it was dissolved.
The reagent was stored must stand overnight at room temperature before use. The
samples were addedtothe pressurebottles.Then, 25mL ofthe phthalic anhydride
reagent was then accurately pipetted into eachof thebottles. The following formula (2)
was usedto determine theamount ofsample neededfor thehydroxyl reaction:
Sample size =561/estimated hydroxyl number (2)
The bottles were cappedand the samples were placed closely together withthe
caponthe bottles.The samples and blankswere kept asclose together aspossible in a
waterbath whichwas maintained at 98?2?for 2h.Then thebottles were
removed andallowed tocool toroom temperature. Once cooled, 50mL of redistilled
pyridine and0.5mL ofthe phenolphthalein indicator solutionwere added and then
titratedwith standard 0.5NNaOHsolutions toa pinkendpoint that persists for at
least 15s. Dueto thedark colorationof theliquefied oil, apHdetermination for future
sample titration was made from blanks reacted in triplicate.The following equation(3)
was usedto calculatethe hydroxyl groupnumber from the resultsof titrationvalues.
35
Hydroxyl number =[(B-A) N?56.1]/W +acid number, mg KOH/g (3)
Where,Ais the volume ofthe0.5M sodium hydroxide solutionrequired for the
titration ofthesample (mL); B is the volume ofthe sodium hydroxide solution
requiredfor thetitration ofthe blank solution(mL); N is themolarity of thesodium
hydroxide solution; and Wis the amount ofthe sample (g) tobeanalyzed.
If thesample contains significant acidity oralkalinity, theresult must be
corrected.Anamount ofsample equalto that taken previously for thehydroxyl
determination was weighedinto a400mL Erlenmeyer flask.Then, 75mL of
redistilled pyridine,75mL ofdistilled water,and 0.5mL of phenolphthalein indicator
solution wasadded tothe flask.Thesamples were thentitrated withstandard0.1N
sodium hydroxide solution toapink end point thatpersisted for at least 15s.Because
ofthe darkcoloration ofthe liquefied oil, apHdetermination for futuresample during
titration was made from blanks andreactedin triplicate.The following equation (4)
was usedto calculateacid number.
Acid correction (mg KOH/g) =[(C-B) N?56.1]/W (4)
Here,Cis the titration volume ofthepotassium hydroxide solution (mL); B is the
titration volume oftheblank solution (mL); Nis the normality ofthe sodium
hydroxide solution; and Wis the weight of sample used.
3.2.2.3PHHHH value examination
AFisher Scientific AR20pH/Conductivity Meter was employed for determining
the Phvalue ofthe bio-oil.
36
3.2.2.4Interactionin liquefaction usingFT-IR
The method todetermine the interactionbetween Epon828andbio-oil inthe
liquefactionmethod used inthis work was amodification ofthe method describedby
Kimura Hajime etal. (Kimura, Matsumoto et al.,1998).The Fourier Transform
Infrared(FT-IR) analysis of the liquefied wood residues was performed byan
attenuated total reflectanceATR FT-IRspectrometer (PerkinElmer, model Spectrum
400).Asmall amount ofresiduewas applieddirectly onthe diamond crystal anda
constant force andtime duration (?X) betweensamples was applied. Data was
acquiredusing theFT-IRsoftware Spectrum from 500cm -1 to 4000cm -1.
3.2.3Preparationof southernpinewood basedepoxyresin
Epon 828and liquefied woodEpon 828were mixed until fully homogenized at
ratios of1:1to 1:4at one part increments. Triphenylphosphine was addedinto the
mixture as3%of theamount of Epon828as acatalyst.Tetrahydrofuran was added
into themixture to reducethe viscosity ofthe bio-based epoxy resin whichmakes the
mixture easier tomix until homogeneous .The samples forthe following tests were
prepared bypouring theEpon 828andbio-oil mixture intoaluminum weighing dishes
(10cm diameter ).The curing temperature ramp is 30mins at80?,30mins at 105?,
2hat 150?,1h at180?,and1hat 200?.After thecuring process, the samples
were left in theovento cooldown slowly inorder toremove the bubbles inthe
samples.
37
3.2.4Analyticalmethods
3.2.4.1.Measurement ofglasstransition temperatures
The results ofDifferential Scanning Calorimetry (DSC) andDynamic
MechanicalAnalyzer(DMA) helped tooptimize the ratio of EPON828to bio-oilby
measuring theglass transition temperature for eachratio during polymer crosslinking.
Measurements of theglass-transition temperature andthe curereaction ofthe wood
basedepoxyresin were performed onaTADifferential Scanning Calorimetry (DSC)
Q2000calorimeter. In order tomeasure the glass-transition temperature, about 4-10
mg of southern pinewood basedepoxyresin wasplaced into analuminum sample
panandsealed with alid byTzero sample press.Anempty pan and alid ofthe same
type were used asareference. Thetemperature ofDSCwas programmed first from
the room temperature to-20?and increased from -20?to 300?at20?/min to
eliminate the effect ofwater that might exist inthe sample (Pan,Shupe et al.,2007).
The sample was then heatedto 250?atthe same rate. Dynamic Mechanical
Analyzer (DMA) measured theglass-transition temperature ofvarious southernpine
wood basedsamples byemploying theDynamic MechanicalAnalyzer (DMA)
Instrument RSA3,TAInstruments.
3.2.4.2Measurement ofThermalDegradation
Athermal gravimetric analyzer (TAInstruments TGAQ500)was employed to
measure the thermal degradationof the wood basedepoxyresin after polymerization.
About 7-10mg ofresin powder was placed into asample pan,andthe degradation
reactionwas conductedwithin anitrogenatmosphere where the temperature was
38
increasedfrom ambient temperature to 800?ata heating rate of10.00 oC/min.
3.2.4.3ATRFT-IRcharacterization ofEpon tobio-oilinteraction FT-IR
The Fourier Transform Infrared(FT-IR) analysis ofthe liquefied southern pine
wood residues was performed byan FT-IRspectrometer (PerkinElmer, model
Spectrum 400).Asmall amount ofbiobased epoxyresin was applieddirectly onthe
diamond crystal.Aconstant force and time duration(?X)between samples was
applied.Datawas acquiredusing FT-IRsoftware spectrum.
3.2.4.4Crosslinkcharacterizationperformedby Soxhletextractiontests
As thedegree ofcrosslinking decreases, weight loss of the polymer uponsolvent
exposure should increase and is thusasensitive measure todetermine the optimum
ratio of Eponto bio-oil.The southernpine woodbased epoxy resin was milled to20
meshes .Afterward, thesamples were placed into anoven at105?and left overnight
toremove the moisture, weight the weight ofthecellulose tube wr,andthe total
weight ofcellulose tubeplus sample weight which was wo.Then the ground sample
was placed intothe extraction device which asshown inthe figure3.6,150mL of
acetone was thenaddedinto the extraction tubeThe soxhlet andacetone was refluxed
andthe extraction test was ranfor 4hrs.After 4hrs, theobtainedthe sample was
removed from the extraction tube andplaced into afume hood where theflow rate
was 224,where theacetone was evaporatedoff.The sample and cellulose thimble
were then placedinto avacuum ovento remove the rest ofacetone at 40?for 24hrs.
The sample plus cellulose tubewas weighedandrecorded as wd.The equationto
calculate theextractive content is as follows:
39
Non-extractive content (%) =(wo -wd)/ (wo -wr) ?100
Fig.3.6The Soxhlet extraction system
3.2.5DataAnalysis
All analysis ofdata sets andplotting ofgraphs were performed using Origin 8.0
software (Version8.0,OriginLab Corporation,Microcal Software).
3.3Results and Discussion
3.3.1Residuecontent ofliquefiedsouthernpine wood
Figure 3.7(a)and (b)showthe residue contents ofliquefied southernpine wood
withvarying temperature sandtime s.With theincreasing ofthe temperature, the
residueofthe liquefactionof southern pinewood hadthe tendencyto decrease.The
minimum residuecontent was obtainedat 220oC.However,theresidue content tended
toincrease whenthe temperature reached 240oC.The resultsindicate that temperature
hasagreat influence ontheliquefaction efficiency.It seems that enhancing the
temperature promotes thedegradation ofsouthernpine wood fibers ata relatively low
40
temperature, andit showed the recondensation ofdegraded fragments atahigh
temperature. However,afurther increasein thetemperature could promote the
recondensation ofthe reactionintermediate ,sothe residuecontent tended toincrease.
Inthe researchofXie and Chen,they reportedthe similar tendency that the residue
content decreasedasthe temperature increased atthe lowtemperature. However,the
residuecontent increased asthe temperature increasedat high temperature (Xie and
Chen 2005).Through theFigure 3.7(a) and(b) indicatethat alonger liquefaction
time was not better because theliquefaction time that was 2hhadthe lowestresidue
content.
180 200 220 2400
10
20
30
40
50
60
70
80  Liquefaction time = 2 h
Temperature (oC)
R e s
i d u
e  p e
r c e n
t age
 ( %)
R e s
i d u
e  p e
r c e n
t age
 ( %)
R e s
i d u
e  p e
r c e n
t age
 ( %)
R e s
i d u
e  p e
r c e n
t age
 ( %)
Fig.3.7(a) Relationship betweenthe liquefactiontemperature and residue percentage.
41
1.0 1.5 2.0 2.5 3.00
10
20
30
40
50
60
70
80  Liquefaction temperature = 220oC 
R e s
i d u
e  p e
r c e n
t age
 ( %)
R e s
i d u
e  p e
r c e n
t age
 ( %)
R e s
i d u
e  p e
r c e n
t age
 ( %)
R e s
i d u
e  p e
r c e n
t age
 ( %)
Time (h)
Fig.3.7(b) Relationship betweenthe liquefactiontime and residue percentage.
3.3.2HydroxylHHH numberandpHHHH valueofliquefiedsouthernpine wood
The hydroxyl group content is one ofthe most important factors ofrelevance
when calculating reactant ratios incondensation reactions (Kurimoto, Doi et al.,1999).
As shown in Figure 3.8(a) and (b),the OHgroupnumber for eachsample was taken
at different liquefaction time andtemperatures. As thetemperature increased,the
hydroxyl groupnumber decreased ina nonlinear fashion.This decrease in hydroxyl
groups,alongwith increased temperature ,may beattributedto thedehydration and
thermal oxidationof thediethylene glycols aswell asthe condensationreactions
betweenthe glycols andmain wood components suchas cellulose, hemicelluloses ,
andespecially lignin (Kunaver,Medved etal.,2010).Inthe researchofYaoetal.
(1996), theysubjected glycols aloneto thesame liquefaction conditionsand measured
the hydroxyl group number. They found that the hydroxyl groupnumbers of the
42
glycols did not changesignificantly whichindicated that the main decrease in
hydroxyl groupnumbers ofthe reaction mixture was dueto thereactions betweenthe
main wood components suchaslignin, cellulose and hemicelluloses and the glycols
that were present.
180 190 200 210 220 230 240700
750
800
850
900
950
1000
1050
1100
1150  Liquefaction time = 2 h
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
Temperature (oC)
Fig.3.8(a) Relationship betweenthe liquefactiontemperature and thehydroxyl group
number.
43
1.0 1.5 2.0 2.5 3.0700
720
740
760
780
800
820
840
860
880
900  Liquefaction temperature = 220 oC
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
Time (h)
Fig.3.8(b) Relationship betweenthe liquefactiontime and thehydroxyl group
number.
Therewas nospecific pHvalue tendency when the liquefactiontemperature was
changedfrom 180oCto 240oC,and thehighest pHvalue occurred whenthe
liquefactiontemperature was 200oC.Whenthe liquefactiontime was changed from 1h
to3h,the lowest pHvalue was observed at2h.
44
180 200 220 2402.0
2.2
2.4
2.6
2.8
3.0
3.2  Liquefaction time = 2 h
p H  val
u e
p H  val
u e
p H  val
u e
p H  val
u e
Temperature (oC)
Fig.3.9(a) Relationship betweenthe liquefactiontemperature and pHvalue.
1.0 1.5 2.0 2.5 3.0
2.4
2.6
2.8
3.0
3.2
3.4  Liquefaction temperature = 220 oC
p H  val
u e
p H  val
u e
p H  val
u e
p H  val
u e
Time (h)
Fig.3.9(b) Relationship betweenthe liquefactiontime and pHvalue.
45
3.3.3DifferentialScanning Calorimeter(DSC)
Adifferentialscanning calorimeter was usedin studying theglass transition
temperature of thewood basedepoxyresins.The nature, liquefaction conditionsand
ratios ofEpon 828tosouthernpine woodbased bio-oil before running samples
through theDSChad aneffect ontheresults. The resultsfrom the DSCrun are
presentedin Figure3.10and Figure3.11.Table 3.1shows thespecific glass transition
temperature of eachsample. The different synthesis conditions showendothermic
curepeaks similar to eachother.The sample with220oCas aliquefactiontemperature
and1:1 assynthesis ratio ofEpon 828topine woodbased epoxyresin hadthe highest
glass transitiontemperature. This indicatesthat thedegree ofcrosslinking in this
sample was the highest.And theratio 1:1 (Epon828:wood basedbio-oil) was the
optimal ratio for theproductions epoxyresin. The liquefactiontemperature at220oC
was theoptimal temperature for liquefaction.
46
-20 0 20 40 60 80 100-6
-5
-4
-3
-2
-1
0
1
2
H e at  
F l ow
 ( W/
g)
H e at  
F l ow
 ( W/
g)
H e at  
F l ow
 ( W/
g)
H e at  
F l ow
 ( W/
g)
Temperature (oC)
 180 oC 2hrs 1:1
 200 oC 2hrs 1:2
 200 oC 2hrs 1:3
 220 oC 2hrs 1:1
 240 oC 2hrs 1:1
Fig.3.10DSCresults of different sample indifferent liquefactiontemperature and
ratio of Epon828to southern pinewood basedbio-oil.
Table3.1Specific DSCresults ofdifferent sample indifferent liquefaction
temperature andratio ofEpon 828tosouthernpine wood basedbio-oil.
?-?means the statusof thetest samples were too rubberyto betested.
Temperature Massratio Epon 828:Bio-oil1:1 1:2 1:3 1:4
180 52.44 - - -
200 - 40.84 30.91 -
220 59.73 - - -
240 55.06 - - -
220oC2h 1:1
47
1:1 1:2 1:30
10
20
30
40
50
60
70
80
Ratio of epon 828 to switchgrass based bio-oil
T g T g T g T g 
( ( ( (o o o o C C C C
) ) ) )
 180 oC
 200 oC
 220 oC
 240 oC
Figure 3.11Specific DSCresultsof different sample indifferent liquefaction
temperature andratio ofEpon 828tosouthernpine wood basedbio-oil.
The following Figure 3.12,Figure 3.13andTable 3.2indicatethat the optimal
liquefactiontime was 2h and theoptimal ratio ofsouthern pine woodbased bio-oil
was 1:1because it had thehighest glass transitiontemperatu re, 59.73oC.This
indicatesthat thedegree ofcrosslinking in this sample was the highest.
48
-20 0 20 40 60 80 100
-5
-4
-3
-2
-1
0
1
2
H e at  
F l ow
 ( W/
g)
H e at  
F l ow
 ( W/
g)
H e at  
F l ow
 ( W/
g)
H e at  
F l ow
 ( W/
g)
Temperature (oC)
 220 oC 1hr   1:1
 220 oC 2hrs 1:1
 220 oC 3hrs 1:1
Fig.3.12DSCresults of different samples indifferent liquefaction time andratio of
Epon 828tosouthernpine woodbased bio-oil.
Table3.2Specific DSCresults ofdifferent sample indifferent liquefaction time and
ratio of Epon828to southern pinewood basedbio-oil.
?-?means the statusof thetest samples were toorubbery to betested.
Time (h) Massratio Epon 828: Bio-oil1:1 1:2 1:3 1:4
1 57.18 - - -
2 59.73 - - -
3 - 38.52 - -
220oC2h 1:1
49
1:1 1:2 1:3 1:40
20
40
60
80
100
Ratio of epon 828 to switchgrass based bio-oil
T g T g T g T g 
( ( ( (o o o o C C C C
) ) ) )
 1 h 2 h
 3 h
Figure 3.13Specific DSCresults ofdifferent sample s indifferent liquefactiontime
andratio of Epon828to southernpine woodbased bio-oil.
3.3.4Thermo GravimetricGGG Analyzer(TGA)GGG
Inthe TGA figures, twodifferent decomposition temperatures 380oCand 540oC
were observed torepresent theprimary peaks associatedwith woodbased epoxy resin
degradationin Figure 3.14and Figure 3.15.This is similar toChen et al.(2008) who
observed three overlapping peaks at245`C,418oCand545oCinthe DTG(Derivative
Thermogravimetric) curvesfor acommercial resol PFadhesive.The first temperature
peakin this researchwas 380oCwhich was attributedtothe stage where methylene
bridges decompose orare brokeninto methyl groups.The degradationof phenols
occurs inthe secondstage whichis 540oC.In first stage, 220oCwas the liquefaction
temperature and2hwas the liquefactiontime and themass ratio ofEpon 828to
southernpine woodbased bio-oil was 1:1.Consequently,the first stage had the
50
highest degradation temperature. The secondtemperature peakinthis research was
530oCaccording toliterature, andin this researchwas 540oC.The results obtained
from theTGAthermograms inthe seconddegradation stage showedthat when the
liquefactiontemperature was 240oC,fixed liquefaction time was 2h,andthe mass
was 1:1,the highest degradation temperature was attained.
0 100 200 300 400 500 600 700 800-20
0
20
40
60
80
100
Temperature (oC)
w e i
gh t
 p e r
c e n
t age
( %)
w e i
gh t
 p e r
c e n
t age
( %)
w e i
gh t
 p e r
c e n
t age
( %)
w e i
gh t
 p e r
c e n
t age
( %)
 180oC 1:1  2h
 200oC 1:2  2h
 200oC 1:3  2h
 220oC 1:1  2h
 240oC 1:1  2h
Fig.3.14Thermogravimetric (TG) curves for southern pinewood basedepoxy resins
when liquefactiontime was fixed at 2h and liquefactiontemperature was changed
from 180oCto240oC.
From Figure3.15,when the liquefactiontemperature was 220oC,andfixed
liquefactiontime was 2h, and themass ratio ofEpon 828tosouthernpine wood
basedepoxyresin was1:1, theepoxy resin had thehighest degradationtemperature in
the first degradation stage which indicates thehigher thermal stabilitiesof the
southernpine woodbased epoxy resin. When theliquefaction temperature was 220oC
220oC2h 1:1
51
andliquefactiontime was 1h, and themass ratio ofEpon 828tosouthernpine wood
basedepoxyresin was1:1, theepoxy resin had thehighest degradationtemperature.
The results ofTGA alsoproved that theoptimal liquefaction temperature was 220oC
andoptimal liquefactiontime was 2h.
0 100 200 300 400 500 600 700 800-20
0
20
40
60
80
100
Temperature (oC)
w e i
gh t
 p e r
c e n
t age
( %)
w e i
gh t
 p e r
c e n
t age
( %)
w e i
gh t
 p e r
c e n
t age
( %)
w e i
gh t
 p e r
c e n
t age
( %)
 220oC 1:1  1hr
 220oC 1:1  2hrs
 220oC 1:2  3hrs
Fig.3.15Thermogravimetric (TG) curves for southern pinewood basedepoxy resins
when liquefactiontemperature was fixed at 220oCand liquefactiontime waschanged
from 1hto 3h.
3.3.5Extraction tests
Inorder todetermine the solubility,which in turn can give an indication ofthe
crosslinking volume of the wood basedepoxyresin,extraction tests inacetone were
run.The optimal ratio ofEpon 828to Bio-oil, whichwas more stable,hasa higher
percentageof crosslinking within thenetwork structures.After 4h ofextraction, the
minimum ratio was1:4 which is illustratedinTable 3.3andFigure 3.16.
52
Table3.3TheAcetoneSoxhlet extraction tests ofsouthernpine woodbased epoxy
resin at different liquefaction temperature.
?-?means the statusof thetest samples were too rubberyto betested.
1:1 1:2 1:3 1:40
10
20
30
40
50
w e i
g h t
 l o s
s
w e i
g h t
 l o s
s
w e i
g h t
 l o s
s
w e i
g h t
 l o s
s  ( %)  ( %)  ( %)  ( %)
Ratio of epon 828 to Bio-oil
 180 oC
 200 oC
 220 oC
 240 oC
Figure 3.16The acetone Soxhlet extraction testsof southern pinewood basedepoxy
resin at different liquefaction temperature.
The results oftheacetoneSoxhlet extraction tests ofwood basedepoxyresin in
different liquefactiontemperatures arepresented inTable3.4andFigure 3.16.The
changein themass loss ofdifferent samples ,which usedchanging temperature in the
Temperature
(oC)
Massratio ofEpon 828 to Bio-oil
1:1 1:2 1:3 1:4
Avg(%) SD Avg(%) SD Avg(%) SD Avg(%) SD
180 23.10 0.26 - - - - - -
200 - - 45.93 0.83 - - - -
220 18.64 0.42 - - - - - -
240 37.81 0.76 - - - - - -
53
liquefactionprocesses and thechanging ratios ofEpon 828toBio-oil in epoxidation
reaction,give anindication ofthe optimal ratio of Epon828to Bio-oil whichis 1:1,
andthe weight loss ofthis sample was lowestat 18.64.This showed that the degreeof
crosslinkingin theepoxyresin sample was highest forthe 1:1ratio.
Table3.4TheAcetoneSoxhlet extraction tests ofsouthernpine woodbased epoxy
resin at different liquefaction time.
?-?means the statusof thetest samples were too rubberyto betested.
Time (h)
Massratio ofEpon 828to Bio-oil
1:1 1:2 1:3 1:4
Avg(%) SD Avg(%) SD Avg(%) SD Avg(%) SD
1 72.33 0.42 - - - - - -
2 18.64 0.42 - - - - - -
3 - - 41.09 0.50 - - - -
1:1 1:2 1:3 1:4
20
30
40
50
60
70
80
Ratio of epon 828 to Bio-oil
w e i
gh t
 l os
s
w e i
gh t
 l os
s
w e i
gh t
 l os
s
w e i
gh t
 l os
s   ( %)   ( %)   ( %)   ( %)
 1 h 2 h
 3 h
Figure 3.17The acetone Soxhlet extraction testsof southern pinewood basedepoxy
resin at different liquefaction time.
From theTable3.4andFigure 3.17,the lowest mass loss was resulted from the
54
same sample in which thereaction conditionsincluded ratio ofEpon 828toBio-oil
was 1:1,liquefaction time was 2hrs, and theliquefaction temperature was fixed at
220oC.
3.3.6FT-IRspectroscopy
The composition ofpolymeric materials canbedetermined bymeasuring their
infrared spectra using aFourier transform infrared (FT-IR) spectrometer and then
comparing the results withacommercially available orspecifically prepared spectral
data base.FT-IRidentifies types ofchemical bonds (functional groups) present in
bio-oil orbio-basedepoxyresin. The absorbance oflight atagiven wavenumber is a
functionof theunderlying chemical bondswithin the system. By interpreting the
infrared absorptionspectrum, thepresence of achemical bondin amolecule can be
determined; likewise, theconsumption efficiency ofreactants can beusedto
determine theoptimal ratio. FT-IRwas usedto examine possible interactions between
pine wood,Epon 828,and bio-oil.
From Figure3.18,a broadabsorptionband at3354cm -1was assigned toaromatic
andaliphatic OHgroups (Abdul Khalil, Marliana etal. 2011)which disappearedin
the FT-IRcurve ofsouthernpine woodbased epoxy resin.This means that we
successfully produced Hydroxyl groups and theOHgroup reacted withEpon 828to
generatethe newtype ofsouthernpine woodbased epoxy resin. The characteristic
stretching vibration ofthe peroxide moieties at914cm -1 (C-O-C),completely
disappearedafter curing (Abdul Khalil, Marliana etal. 2011).
55
4000 3500 3000 2500 2000 1500 1000 5000
10
20
30
40
50
60
70
80
90
100
Wavenumber (cm-1)
A b s
o r b
a n c
e ( %
)
A b s
o r b
a n c
e ( %
)
A b s
o r b
a n c
e ( %
)
A b s
o r b
a n c
e ( %
)
 Epon 828
 Bio-oil 220oC 2hrs
 Epoxy resin 220oC 2hrs 1:1
Figure 3.18FT-IRgraph ofAbsorbance versusWavenumber for Epon828,Bio-oil
(Liquefactiontime was 2h,temperature was 220oC)and bio-oil basedepoxyresin.
From theFigure 3.19,when theliquefaction temperature was 220oCand
liquefactiontime was 2h, themass ratio ofEpon 828tobio-oil southern pinewood
was 1:1.This indicatesthat biobased epoxyshould bemanufactured at a1:1ratio.In
other words, the1:1 ratio exhibited thehighest OHconsumption whichsupported a
highly crosslinked structure.
3354cm -1
(C-OHstretch) 914cm -1
(epoxidering)
56
4000 3500 3000 2500 2000 1500 1000 5000
10
20
30
40
50
60
70
80
90
100
Wavenumber (cm-1)
A b s
or b
an c
e ( %)
A b s
or b
an c
e ( %)
A b s
or b
an c
e ( %)
A b s
or b
an c
e ( %)  180oC 1:1  2hrs
 200oC 1:2  2hrs
 200oC 1:3  2hrs
 220oC 1:1  2hrs
 240oC 1:1  2hrs
Fig.3.19FT-IRgraphofAbsorbanceversus Wavenumber for southernpine wood
basedepoxyresins whenliquefaction time was fixed at 2h and liquefaction
temperature was changed from 180oCto 240oC.
From Figure3.20,when the liquefactiontemperature was 220oCandliquefaction
time was 2h,the mass ratio ofEpon 828to southern pinewood basedepoxyresin of
1:1had the lowest OHgroupwhichindicates that it hadthe highest cross linking
structure.
220oC2h1:1
57
4000 3500 3000 2500 2000 1500 1000 5000
10
20
30
40
50
60
70
80
90
100
Wavenumber (cm-1)
A b s
or b
an c
e ( %)
A b s
or b
an c
e ( %)
A b s
or b
an c
e ( %)
A b s
or b
an c
e ( %)
 220oC 1hr  1:1
 220oC 2hrs 1:1  
 220oC 3hrs 1:2 
Fig.3.20FT-IRgraphofAbsorbanceversus Wavenumber for southernpine wood
basedepoxyresins whenliquefaction temperature was fixed at 220oCand liquefaction
time was changed from 1h to3h.
220oC2h1:1
58
3.4Conclusions
The following are experimental results (Table 3.5andTable 3.6)for thewhole
experiment.
Table3.5Experimental Result I
Ratio(Epon:bio-oil)\Temp 180?200?220?240?
Residue Percentage(%) 61.2 54.3 21.6 28.1
Hydroxylnumber (KOH/g) 1078.72?
23.33
892.52?
2.14
750.60?
7.36
790.10?
7.10
pHvalue 2.09 3.07 2.46 2.38
1:1 Tg(?) 52.44 - 59.73 55.06
Weightloss(%) 23.10?
0.26
- 18.65?
0.42
37.82?
0.76
Decomposition temp (?) 444.31 - 449.77 449.77
1:2 Tg(?) - 40.84 - -
Weightloss(%) - 45.93?0.83 - -
Decomposition temp (?) - 446.19 434.53 -
1:3 Tg(?) - 30.91 - -
Weightloss(%) - - - -
Decomposition temp (?) - 426.46 - -
1:4 Tg(?) - - - -
Weightloss(%) - - - -
Decomposition temp (?) -
The conditions above arebased onthereaction time whichis 2h.
59
Table3.6Experimental Result II
Ratio(Epon:bio-oil) 1h 2h 3h
Residue Percentage(%) 52.78 21.6 46.3
Hydroxylnumber (KOH/g) 831.59?
1.64
750.60?
7.36
848.80?
4.67
pHvalue 2.98 2.46 2.27
1:1 Tg(?) 57.18 59.73 -
Weightloss(%) 72.33?0.43 18.65?0.42 -
Decomposition temp (?) 447.08 - -
1:2 Tg(?) - - 38.52
Weightloss(%) - - 41.09?0.50
Decomposition temp (?) - - 443.78
1:3 Tg(?) - - -
Weightloss(%) - - -
Decomposition temp (?) - - -
1:4 Tg(?) - - -
Weightloss(%) - - -
Decomposition temp (?) - - -
The conditions above arebased onthereaction temperature whichis 220oC.
?-?means the statusof thetest samples were too rubberyto betested.
The liquefactionof southern pinewood producedwood basedbio-oil whichwas
utilized tomanufactur eanewtype ofepoxyresin. The southern pinewood based
bio-oil was successfully reacted withthe Epon 828using TPPascatalyst.
The optimal liquefactiontemperature and time was 220oCand 2h,respectively.
The optimal mass ratio ofEpon to southern pinewood basedbio-oil was 1:1,which
hadthe highest crosslinking density.
60
3.5Reference
Abdul Khalil, H. P.S.,M.M.Marliana, etal. (2011)."Exploring isolated lignin
material from oil palm biomass waste ingreen composites." Materials & Design 32(5):
2604-2610.
Adler,E. (1977)."Lignin chemistry ?past, present and future."WoodScience and
Technology11(3): 169-218.
Auad, M.L., L.Zhao, et al.(2007). "Flammability properties and mechanical
performance ofepoxymodified phenolic foams." Journal ofApplied Polymer Science
104(3): 1399-1407.
Jasiukaityt?,E.,M. Kunaver,etal. (2010). "Lignin behaviour during wood
liquefaction?Characterization byquantitative 31P,13CNMRand size-exclusion
chromatography." Catalysis Today156(1?2): 23-30.
Jasiukaityt?,E.,M. Kunaver,etal. (2009). "Cellulose liquefactionin acidified
ethyleneglycol." Cellulose16(3): 393-405.
Kimura, H.,A.Matsumoto, et al.(1998). "Epoxyresin cured bybisphenolAbased
benzoxazine."Journal ofApplied Polymer Science 68(12): 1903-1910.
Kishi, H.,A. Fujita,et al.(2006). "Synthesis ofwood-basedepoxy resins and their
mechanical and adhesive properties."Journal ofAppliedPolymer Science102(3):
2285-2292.
Kobayashi, M.,T.Asano, etal. (2004). "Analysis onresidueformation during wood
liquefactionwith polyhydric alcohol."Journal ofWoodScience50(5): 407-414.
Kunaver,M., S.Medved, et al.(2010). "Application ofliquefied wood asanew
particle boardadhesive system." BioresourceTechnology 101(4): 1361-1368.
Kurimoto, Y.,S.Doi, et al.(1999). Species Effects onWood-Liquefaction in
PolyhydricAlcohols. Holzforschung.53:617.
Nonaka,Y., B.Tomita, et al.(1997). "Synthesis oflignin/epoxy resins in aqueous
systems and their properties." Holzforschung 51(2): 183-187.
Pan,H.,T.F.Shupe,et al. (2007)."Characterizationof liquefied woodresidues from
different liquefactionconditions."Journal ofAppliedPolymer Science105(6):
3740-3746.
Pan,H.,T.F.Shupe,et al. (2008)."Synthesis andcure kineticsof liquefied
61
wood/phenol/formaldehyde resins."Journal ofApplied Polymer Science 108(3):
1837-1844.
Rezzoug, S.-A.and R.Capart (2002). "Liquefactionofwood intwosuccessive steps:
solvolysis inethylene-glycol andcatalytic hydrotreatment." AppliedEnergy 72(3?4):
631-644.
Tan,T.T.M. (1996)."Cardanol-lignin-based epoxy resins: Synthesis and
characterization."Journal ofPolymer Materials 13(3): 195-199.
Vanholme, R., B.Demedts, et al.(2010). "Lignin Biosynthesis and Structure."Plant
Physiology153(3): 895-905.
Xie,T.andF.G. Chen(2005). "Fast liquefaction ofbagasse inethylenecarbonate and
preparation ofepoxyresin from the liquefied product."Journal ofAppliedPolymer
Science 98(5): 1961-1968.
Yamada, T.andH. Ono(2001). "Characterizationofthe products resulting from
ethyleneglycol liquefaction ofcellulose."Journal ofWoodScience 47(6): 458-464.
Yao,Y., M.Yoshioka,et al.(1996). "Water-absorbingpolyurethane foams from
liquefied starch."Journal ofApplied Polymer Science 60(11):1939-1949.
Zhao, B.Y.,G. Chen, etal. (2001)."Synthesis of lignin baseepoxy resin and its
characterization."Journal ofMaterials Science Letters 20(9): 859-862.
62
Chapter4
Modificationand characterization ofliquefiedswitchgrass-basedepoxyresin
4.1Introduction
The increaseddemands for energyalong withconcerns about energy securityand
climate changehave attracted attention toalternative and renewable energy (Kumar
andGupta,2009).Among various available renewable energyoptions, biomass is the
onlyrenewable energysource whichhas thecapability of producing petroleum
compatible products.Climate changeis also one ofthe most serious environmental
concerns. Concentrations ofcarbon dioxide in the atmosphere will continue rising
unless there aremajor changesmade inthe way that fossil fuels are usedto provide
energy.Globally, biomass feedstock will beaprimary sourceof energy during the
next century.It is recommended that modern bioenergy systems beanimportant
contributor in future sustainable energysystems and sustainable development of
industrialized anddeveloping countries (Berndes, Hoogwijk etal.,2003).Biomass is
abiological material, which includes bothanimals andplants.Biomass resources
include wood and woodwaste, animal manure, agricultural crops and cropwaste,
aquatic plants,andenergy crops.Milling activities createhugequantities ofmixed
biomass such aswood, cookingwastes, sewage sludge, and manure. Plant biomass is
typically composed oflignin, cellulose, hemicelluloses and various other minor
compositions depending onplant species.Cellulose and lignin are two most abundant
biopolymers inplant materials, bothof which sequestercarbon during tissue
63
development. Lignin is anamorphous phenolic polymer, whichconsists of
p-hydroxyphenylpropane, guaiacylpropane,and syringylpropane monomers.
Celluloseis alinear polymer ofglucopyranose with molecular weights more than
100,000.Mannose, xylose,andglucose polymerize to form hemicelluloses.
Inthe liquefactionof biomass, using asolvent reagent andanacid catalyst has
beenstudiedas anovel technique toutilize biomass as analternative to
petroleum-based products during chemicals production. Likewise,phenol is one ofthe
most commonly used reagent solventsfor wood liquefaction.Woodliquefaction with
phenol can bedeveloped intonovolac orresol type phenolic resins.Avariety of
general studieshave beencarriedout onwoodliquefaction withphenol,but recently
its usehas beenquestionedbecause it comes from apetroleum basedprocess andcan
bedangerous tohuman exposure. In this research,the principal material to generate
biooil through liquefactionis switchgrass. It is aperennial warm season bunchgrass
native to NorthAmerica, where it occurs naturally from 55?Nlatitude inCanada
southwards into theUnited States andMexico. Switchgrassis oneofthe dominant
species ofthe central NorthAmerican tall grassprairie andcanbe found inremnant
prairies, innative grass pastures, and naturalized along roadsides. The average
composition andthe standard deviationof thechemical ratios arelisted inTable4.1
results expressed as%w/wofdry lignocellulose(Mei Zhen,Da Chun etal.,2010).
64
Table4.1
The average composition and thestandard deviationofthe determination ofsix
different samples (Mei Zhen, Da Chun etal.,2010)
Fraction Average Stddev
Ash 6.8 0.08
Hotwater
Extractives(100?) 5.5 0.07Klasonlignin 18.7 0.43
Glucan 40.6 0.38
Xylan 22.8 0.55
Glacan 3.6 0.03
Others 2.4 0.04
Massbalance 100.4 0.12
Forthe last ?decade,epoxyresins have beencommercialized for major
industrial applications suchasadhesives,coatings, moldings, and soon(WuandLee,
2010).Use is especially important where technical superioritywarrants their higher
costs when compared toother thermosets. In studyof Liu etal. (1997), thelow
shrinkageoncure, characteristicsof toughness, high adhesion tomany substrates,
moisture resistance,goodalkali, and versatility informulation make epoxyresins
widely used inadhesive, laminating, coating, and casting applications (Liu, Hsiue et
al.,1997).Inthis research, epoxy resin was mixed withliquefied bio-oil from
switchgrass feedstock. The final mixture ofthese twochemical substanceswith an
optimal ratio formed anewbio-basedtype adhesive. Thereare many studies about the
propertiesof conventional epoxy resin. In theresearch ofJustin D. Littell et al. (2008),
the epoxy specimens were tested intension,compression ,andtensional loadings
undervarious strain rates ranging from 10?5 to 10?1s?1 and temperatures rangingfrom
65
room temperature to 80?C(Littell, Ruggeri etal.,2008).To test the specimens at high
temperatures, aspecialized clear temperature chamber was used. Theyfound that the
test procedure developed could accurately andquickly categorize the material
response characteristicsof anepoxy resin. Inaddition, theresults displayedclear
strain rateand temperature dependencies in thematerial response toloading. In
another study, theyuseddestructive and non-destructive tests totest the mechanical
properties ofepoxyresins and random fiber epoxy systems (Prassianakis,Kytopoulos
et al.,2006).In theresearch ofH.P.SAbdul Khalil et al.(2011), they generated the
useof EFB-lignin ascuring agentin epoxyresin (Abdul Khalil, Marliana et al.,2011).
Basedontheir theory, the deduction ofthis research is shown in reactionFigure 4.1.
CH 3
CH 3
O
O
O
O
OH R1R2
OH
O
O CH3
CH 3
O
OH
O
R1 OH
R2
+
n n n n
R1=OMe, R2=H: coniferyl alcohol/guaiacylR1=R2=OMe: sinapyl alcohol/syringyl
R1=R2=H: p-Coumaryl alcohol
Triphenylphosphine
Fig.4.1Idealized networkformation during curing reaction ofepoxy-lignin system.
Inthe study ofMaria L.Auad etal. (2007),they mainly focused onthe
development and optimization oftheprocessing methodology to produceepoxy
modified phenolic foams ,andthey analyzedthe relation betweenthe composition and
the structureas well as themechanical andflammability performance of
epoxy-phenolic (E-P)-based foams ,asshown in reactionscheme in Figure4.2(Maria
L.Auad, Zhaoet al.,2007). Theepoxythey usedwas Epon 826andthe hydroxyl
Lignin
DGEB-A
66
groupsupplier was Novolac,whichwere Epon 828and southernpine woodbased
bio-oil.They havesimilar reactiontheory to produceepoxyresin.
Fig.4.2Schematic ofthe E-Psysthesis reaction (Maria L.Auad, Zhao etal., 2007)
4.2Materials and Methods
The following is flowchart (Figure 4.3)of this experiment that showtooptimize
the liquefaction temperature when the liquefaction time was fixed at 2hinthe
researchproject.The flow chart is similar withChapter 3Figure 3.4and Figure3.5
except changing rawmaterial from southern pine woodto switchgrass andthe
liquefactiontemperatures are 200oC,220oC,240oC,250oCand 260oC.
67
Fig.4.3Flowchart of optimizing theliquefaction temperature when theliquefaction
time was fixed at 2h.
Prior tothis study,preliminary studieswere carried forth todetermine the basic
parameters necessaryfor liquefactionand epoxy polymer synthesis. Itwas found that
250?was thebest liquefaction temperature while 2h appearedto besufficient to
yield goodbio-oil visually.Wethendeveloped anexperimental design aroundthe
basetemperature byvarying thetime to1,2and3h.The response variables for this
experimental design included: liquefactionresidue,hydroxyl number test,pHvalue of
bio-oil, and thethermal properties tests ofswitchgrass basedepoxyresin.
4.2.1.Biomass(switchgrass)Preparation
Ahammer mill (NewHolland grinder model 358,NewHolland, PA.)with
3.175-mm (1/8 in.) sieve sizewas used for particle size reduction. Particles from the
switchgrass (Panicum virgatum) was collectedandoven-dried at105?for 12hrs and
kept in adesiccatoratroom temperature beforeuse. Thedried material was ground to
pass througha20mesh sieve before put into oven.Diethylene glycol (99%,from Alfa
Aesar chemical company) was usedas the reagent solvent in theliquefaction.All
68
other main chemicals forliquefaction ofswitchgrass and synthesis ofwood-based
epoxyresins includetriphenylphosphate,98%sulfuric,phthalic anhydride and
pyridine.They were all reagent grade, and used without furtherpurification.
4.2.2Liquefactionofswitchgrass
The liquefactionprocedure of switchgrass was based onthe general method
describedbyTaoXie(Xie andChen,2005),and thensubsequently modified byMatja?
Kunaver (Kunaver,Medvedet al.,2010).The liquefaction ofswitchgrass was carried
outin a1000ml three neckglass reactorequipped with amechanical stirrer (500rpm)
andreflux condenser device. Thereactor was chargedwith 100gofwoodand 400gof
diethylene glycol whenthe flask was heated tothe desired temperature for
liquefaction.1gof 98%sulfuric acid wasadded.The mixture was heated for various
times (1h, 2hand3h)andat various temperatures (180?,200?,220?and240?)
while beingconstantly stirred.
4.2.2.1Determinationof residuecontent
The residue content evaluation method usedin this work wassame with Chapter
3butchanged determination object from southern pinewood liquefactionresidue to
switchgrass liquefactionresidue.Specific equation refers to Chapter 3equation(1).
4.2.2.2HydroxylHHH groupnumbertest
The hydroxyl number was measured according toASTM D4274-11,whichwas
same withChapter 3however changeddetection objectsfrom southernpine wood
basedbio oil toswitchgrass basedbio oil.
69
4.2.2.3PHHHH value examination
Fisher ScientificAR 20pH/Conductivity Meter was employed for determining
the Phvalue ofvarious switchgrass based bio-oil.
4.2.2.4FT-IRcharacterizationofbio-oiland biobasedepoxyreactions
The Fourier Transform Infrared(FT-IR) analysis ofthe liquefied switchgrass
residueswas performed byanFT-IRspectrometer (PerkinElmer, model Spectrum
400),whichwas same method anddevice withChapter 3but changed examine object
from southernpine woodbased biooil toswitchgrass based biooil.
4.2.3Preparationof switchgrass-basedepoxyresin
The method ofpreparation ofswichgrass basedepoxyresin refers tothe method
usedin Chapter3except using switchgrassbased biooil as reactants.
4.2.4Analyticalmethods
Analytical methods usedin this work were same asChapter 3which were used
tocharacter the liquefiedbiomass basedepoxyresin, butthe southern pinewood
basedepoxyresin waschanged toswitchgrass basedepoxyresin.
4.2.5DataAnalysis
All analysis ofdata sets andplotting ofgraphs were performed using Origin 8.0
software (Version8.0,OriginLab Corporation,Microcal Software).
4.3Results and Discussion
4.3.1Residuecontent ofliquefiedswitchgrass
Figure 4.5(a)and (b)showthe residue content ofliquefied switchgrass
processedat different time and temperatures. With increasing temperature, theresidue
70
decreasedina linear fashion.This was different thanwood whichsawaleveling off
ofresidueafter 220oC.Figure4.4(a) and(b) indicate that the longer liquefactiontime
was not better becausewhen the liquefaction time was 2hours thelowest residue
content was observed.The residuecontent ofliquefied switchgrassand southern pine
wood had similar results which provedthe general tendency inthe analysis of
liquefactionresidues.
200 210 220 230 240 250 260
50
60
70
80
90
Temperature (oC)
R e s
i d u
e  p e
r c e n
t age
 ( %)
R e s
i d u
e  p e
r c e n
t age
 ( %)
R e s
i d u
e  p e
r c e n
t age
 ( %)
R e s
i d u
e  p e
r c e n
t age
 ( %)
 Liquefaction time = 2 h
Fig.4.4(a) Relationship betweenthe liquefactiontemperature and residue percentage
71
1.0 1.5 2.0 2.5 3.050
55
60
65
70
75
80
85
90
95
100  Liquefaction temperature = 250 oC
R e s
i d u
e  p e
r c e n
t age
 ( %)
R e s
i d u
e  p e
r c e n
t age
 ( %)
R e s
i d u
e  p e
r c e n
t age
 ( %)
R e s
i d u
e  p e
r c e n
t age
 ( %)
Time (h)
Fig.4.5(b) Relationship betweenthe liquefactiontime and residue percentage.
4.3.2HydroxylHHH numberandpHHHH valueofliquefiedswitchgrass
During the synthesis ofepoxy phenolic resins,there is assumed to beareaction
betweenthe OHgroupsof thenovolac phenolic resin to theepoxy:epon structure
(Auad etal. 2006).This reactionmechanism forms a3dimensional crosslinked
structure andthe density ofthat structure should dependonthe molar ratio ofphenolic
suppliedOHgroups toepoxygroups. Forthis study, thebio-oil from liquefaction is
more complex thansimply measuring theamount of phenolic groups.It is instead
probably similar to pyrolysis oil in which many compounds are present other than
phenols and thus OHseparationandquantification may bedifficult
(Thangalazhy-Gopakumar etal. 2010).Characterization ofthe origin ofthe OH
groups can bechallenging although Ben andRagauskas (2011)have recently
developed apNMRtechniquethat partitions out the hydroxyl group amount for
72
aliphatic OH,phenolic OH,guaiacyl phenolic OH,catechol type OH,
p-hydroxy-phenylOH, and acidOH.But pNMRis acomplex techniqueandnot
alwayswidely available and thusfor this study, thetotal OHnumber was measured
through titrationmethods.
The total hydroxyl number decreased steadily till 250?Candthen risessharply at
260 ?CinFigure 4.5(a).The decrease in hydroxyl group at temperatures below250?C
agreed withWang and Chen (2007) who pursued therapid liquefaction ofwheat straw.
Inthat study, atlower temperatures therewas asteeper dropin OHnumber thanat
higher temperatures. However,our studyoperated athigher temperatures thanthat
study and thehydroxyl groupnumber reverseddirection at 260oCinFigure 4.5(b).
Similar increases inhydroxyl groups,using the absorbance inthe infraredregion asan
indicator,were observed at 280 oCwhen hot compressed water wasused toliquefy
paulownia (Sun etal. 2011).They attributed this increase in OHtocondensation
reactions. Perhapsthat same rational canbeassumed for Fig. 2bin whichthe OH
number increaseddramatically from 2to 3hours.This suggests that theseverity
treatment can beused tomanipulate the OHnumber during liquefaction.
It was alsoobserved that the overall bio-oil OHnumber was higher thanmany
other studies.Zheng et al.(2011)used phenol based solvents andfoundhydroxyl
groups between 280and 622mg KOH/gand this was dependent onthe whetherthe
heating source was microwave orheat bath.Panet al.(2012) suggest that the solvent
and/or catalyst playanimportant rolein OHnumber. Inthat study, when sulfuric acid
was used,numbers similar toother studieswere observed(Zheng etal. 2011)but
73
when phosphoric acidwas used, OHnumbers ashigh as700mg KOH/gcan be
reached (Panet al.2012).For ourstudy, a1:4wood todiethylene glycol ratio was
usedto liquefy the switchgrass.The high level of diethyleneglycol may help to
explain the higherOHnumbers ofthe liquefactionoil. Forexample, Nasar etal.
(2010) found that asthe amount ofethyleneglycol amount increased, thehydroxyl
number inthe liquefactionoil increased.This suggests that diethylene glycol notonly
acts asasolvent but supplements theoverall contributionin OHnumber for the
liquefied biomass. This may beanimportant benefit if themanufacturer would like to
control the overall OHgroup number bycontrolling thesolvent volume during
liquefaction.In theresearch ofYaoet al.(1996),when theglycols were subjectedto
the same liquefaction conditions,it was found that the OHgroups plateauedwith
temperature .This indicatedthat the main decrease inOHnumber in thereaction
mixture was due tothe reactionbetween the main wood components andthe glycols
that were present.
74
200 210 220 230 240 250 260
860
880
900
920
940
960
980
1000  Liquefaction time = 2 h
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
Temperature (oC)
Fig.4.5(a) Relationship betweenthe liquefactiontemperature and thehydroxyl group
number.
1.0 1.5 2.0 2.5 3.0860
880
900
920
940
960
980  Liquefaction temperature = 250 oC
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
H yd r
oxyl
 gr ou
p  n
u m
b e r
 ( m
g K O H / g)
Time (h)
Fig.4.5(b) Relationship betweenthe liquefactiontime and hydroxyl group number.
75
As theliquefaction temperature was increasedfrom 200oCto 260oC,thepH
value tendedto increase.Additionally the highest pHvalue was observed at250oC.
Whenthe liquefactiontime waschanged from 1hto3h,the 2h runhadthe lowest pH
value which was similar towood inchapter 3.
200 210 220 230 240 250 260
3.5
4.0
4.5
5.0
p H  val
u e
p H  val
u e
p H  val
u e
p H  val
u e
Temperature (oC)
 Liquefaction time = 2 h
Fig.4.6(a) Relationship betweenthe liquefactiontemperature and pHvalue.
76
1.0 1.5 2.0 2.5 3.05.1
5.2
5.3
5.4
5.5
5.6
5.7
p H  val
u e
p H  val
u e
p H  val
u e
p H  val
u e
Time (h)
 Liquefaction temperature = 250 oC
Fig.4.6(b) Relationship betweenthe liquefactiontime and pHvalue.
4.3.3DifferentialScanning Calorimeter(DSC)
The DSCwas usedto assess theglass transition temperature ofthe bio-based
epoxyresin. The liquefactionconditions and ratios(Epon 828:bio-oil) were
investigated asexperimental factors for DSCanalysis. From Figure 4.7andFigure 4.8,
it canbeobserved that thethermograms consist of one endothermic peakwhich
rangedfrom 30oCto 65oCinvarious samples. Table 4.2showsthespecific glass
transitiontemperature foreach sample. The differentmodification conditions showed
endothermic curepeaks similar to eachother.The sample with250oCas aliquefaction
temperature anda 1:1ratio hadthe highest glass transition temperature. This was
probably anindication that thecrosslinking density was highest at this ratio. Thus, the
ratio 1:1 (Epon 828:swithcgrass basedbio-oil) was the optimal ratio for theepoxy
resin productions.The liquefaction temperature at 250oCwas optimal temperature for
77
liquefaction.
The Tgof 64?Cwas 20?Clower thanasimilar studythat utilized polyethylene
glycol, glycerol, andsulfuric acid for liquefactionofwood (Wu and Lee 2011).That
study exhibitedasimilar decrease inTg withthe additionofliquefaction oil which
was anindication ofdecreasedcrosslinking. The Tg observedin this study waslower
than otherbio-oil basedepoxy systems (Xie and Chen 2005)and evenlower thanthe
Tg ofasimilar feedstock (lignin) whichnormally exhibitsaTg range of150to165?C
(Mansouri etal. 2011).The lowerTg observed inthis study may be attributable to the
large volume ofdiethylene glycol solvent which actedasaplasticizer and loweredthe
Tg ofthe composite matrix (Lourdin et al.1997).Vanin et al. (2005)found diethylene
glycol toprovide the largest plasticizer effect resulting inthe lowest Tgin films when
compared toother common plasticizers such asglycerol, propylene glycol, and
ethyleneglycol. Plasticizers generally function tomodify the interchain interactions
resulting ina rubberyresponse dueto enhancedflexibility.The lowTgin this study
may thus beattributable to theplasticizing influenceof diethyleneglycol which
apparentlyis retained after liquefactionas further evidenced bythe high OHnumber
within thebio-oil feedstockin Figure 4.5.Toour knowledge,there are noother
studiesthat have found this effect onTg for epoxy-bio-oil based polymers.
78
-20 0 20 40 60 80 100
-3
-2
-1
0
1
2
H e at  
F l ow
 ( W/
g)
H e at  
F l ow
 ( W/
g)
H e at  
F l ow
 ( W/
g)
H e at  
F l ow
 ( W/
g)
Temperature (oC)
 200oC 2hrs 1:2
 200oC 2hrs 1:3
 220oC 2hrs 1:2
 200oC 2hrs 1:3
 240oC 2hrs 1:1
 240oC 2hrs 1:2
 240oC 2hrs 1:3
 250oC 2hrs 1:1
 250oC 2hrs 1:2
 250oC 2hrs 1:3
 250oC 2hrs 1:4
Fig.4.7DSCresults of different samples atdifferent liquefaction temperature sand
ratios ofEpon 828toswitchgrass basedbio-oil.
Table4.2Specific DSCresults ofdifferent samples at different liquefaction
temperature s and ratiosof Epon828to switchgrassbased bio-oil.
?-?means the statusof thetest samples were too rubberyto betested.
Temperature (?) Ratio ofEpon 828 to Bio-oil
1:1 1:2 1:3 1:4
200 - 40.47 37.15 -
220 38.44 48.76 42.41 -
240 42.93 42.68 35.65 -
250 62.84 48.69 35.86 28.25
250oC2h 1:1
79
1:1 1:2 1:3 1:40
10
20
30
40
50
60
70
80
T g  T g  T g  T g  
( ( ( (o o o o C C C C
) ) ) )
Ratio of epon 828 to switchgrass based bio-oil
 200 oC
 220 oC
 240 oC
 250 oC
Figure 4.8Specific DSCresults ofdifferent samples indifferent liquefaction
temperatures and ratios of Epon828to switchgrassbased bio-oil.
Figures4.9and4.10aswell asTable4.3indicatesthe optimal liquefactiontime
was 2h and theoptimal ratio ofswitchgrass basedbio-oil was 1:1?the ratio which
hadthe highest glass transitiontemperature 62.8oC.This indicates that the degree of
crosslinking for this treatment combination was the highest.
80
-20 0 20 40 60 80 100
-6
-5
-4
-3
-2
-1
0
1
2
Temperature (oC)
H e at  
F l ow
 ( W/
g)
H e at  
F l ow
 ( W/
g)
H e at  
F l ow
 ( W/
g)
H e at  
F l ow
 ( W/
g)
 250oC 2hrs 1:1
 250oC 1hrs 1:2
 250oC 1hrs 1:3
 250oC 1hrs 1:4
 250oC 3hrs 1:1
 250oC 3hrs 1:2
 250oC 3hrs 1:3
 250oC 3hrs 1:4
Fig.4.9DSCresults of different sample atdifferent liquefactiontime sandratios of
Epon 828toswitchgrass basedbio-oil.
Table4.3Specific DSCresults ofdifferent sample at different liquefaction time sand
ratios ofEpon 828toswitchgrass basedbio-oil.
?-?means the statusof thetest samples were too rubberyto betested.
Ratio ofEpon 828 to Bio-oil
Time (h) 1:1 1:2 1:3 1:4
1 - 40.16 26.81 31.02
2 62.84 48.69 35.86 28.25
3 62.23 45.64 40.44 35.61
250oC2h 1:1
81
1:1 1:2 1:3 1:40
10
20
30
40
50
60
70
80
T g T g T g T g 
( ( ( (o o o o C C C C
) ) ) )
Ratio of epon 828 to switchgrass based bio-oil
 1 h 2 h
 3 h
Figure 4.10Specific DSCresults ofdifferent sample at different liquefactiontime s
andratios ofEpon 828toswitchgrass basedbio-oil.
4.3.4Thermo GravimetricGGG Analyzer(TGA)GGG
Inthe TGA figures, twodifferent decomposition temperatures ,390oCand 550oC,
were observed torepresent theprimary peaks associatedwith switchgrassbased
epoxyresin degradation.This is similar toChen et al.(2008), whoobserved three
overlappingpeaks at245oC,418oC,and545oCinthe DTG(Derivative
Thermogravimetric) curvesfor acommercial resol PFadhesive.The first temperature
peakin this researchwas 390oC,which was attributedtothe stage where methylene
bridges decompose orare brokeninto methyl groups.The degradationof phenols
occurs inthe secondstage, whichoccurs at550oC.In thefirst stage, with250oCasthe
liquefactiontemperature, 2h asthe liquefactiontime, and 1:1asthe mass ratio of
Epon 828toswitchgrass basedbio-oil,thehighest degradationtemperature was
82
observed.The second temperature peakin this researchwas the degradationof
phenols which temperature was 530oC,according toliterature, andin this research
was 550oC.The results obtainedfrom the TGA thermograms inthe second
degradationstage also showed that when theliquefaction temperature was 250oC,
fixed liquefactiontime was 2h, and themass ratio ofEpon 828toswitchgrass based
epoxyresin 1:1 had thehighest degradation temperature.
0 100 200 300 400 500 600 700 8000
20
40
60
80
100
Temperature (oC)
w e i
gh t
 p e r
c e n
t age
( %)
w e i
gh t
 p e r
c e n
t age
( %)
w e i
gh t
 p e r
c e n
t age
( %)
w e i
gh t
 p e r
c e n
t age
( %)
 200oC 2hr 1:2
 200oC 2hr 1:3
 220oC 2hr 1:2
 220oC 2hr 1:3
 240oC 2hr 1:1
 240oC 2hr 1:2
 240oC 2hr 1:3
 250oC 2hr 1:1
 250oC 2hr 1:2
 250oC 2hr 1:3
 250oC 2hr 1:4
Fig.4.11Thermogravimetric (TG) curves for switchgrass basedepoxyresins when
liquefactiontime was fixed at2handliquefaction temperature was changedfrom
200oCto260oC.
From Figure4.12,when the liquefactiontemperature was 250oCandthe fixed
liquefactiontime was 2h, themass ratio ofEpon 828toswitchgrass basedepoxy
resin of1:1 had thehighest degradationtemperature during the first degradationstage.
250oC2h1:1
83
Whenthe liquefactiontemperature was250oC,the liquefactiontime was 3h, and the
mass ratio of Epon828to switchgrassbased epoxyresin of1:1 had the highest
degradationtemperature.
0 100 200 300 400 500 600 700 8000
20
40
60
80
100
Temperature (oC)
w e i
gh t
 p e r
c e n
t age
( %)
w e i
gh t
 p e r
c e n
t age
( %)
w e i
gh t
 p e r
c e n
t age
( %)
w e i
gh t
 p e r
c e n
t age
( %)
 250oC 2hr 1:1
 250oC 1hr 1:2
 250oC 3hr 1:1
 250oC 3hr 1:2
 250oC 3hr 1:3
Fig.4.12Thermogravimetric (TG) curves for switchgrassbased epoxy resins when
liquefactiontemperature was fixed at250oCandliquefactiontime was changedfrom
1hourto 3h.
4.3.5DMAresults
Figure 4.14shows theDynamic viscoelastic properties oftheswitchgrass based
epoxyresins.The cured switchgrass based epoxy resins showed high stiffness at room
temperature andrubbery plateauafter Tg.The storagemodulus of elasticityof the
different samples at 25oCwas closeto eachother.Additionally the rubberyplateau
indicates that acrosslink networkstructure was surely formed. The highest Tg
occurred inthe sample formed when the liquefactiontemperature was 250oC,the
250oC2h1:1
84
liquefactiontime was 2h,and mass ratio ofEpon 828to bio-oil was 1:3. However,
the orange curve which is when liquefactiontemperature was 250oC,the liquefaction
time was 2h,andmass ratio ofEpon 828tobio-oil was 1:1has thehighest value.
This indicates that the orangecurve sample has the highest percentage ofcrosslinking.
As can beobserved, once theTg is reached,a rubberyplateau wasachieved for
most treatments. Liquefactionat 250oCand anepoxy:oil ratio of1:1 providedthe
highest storagemodulus whentheTg was exceeded. Onthe other hand, thestorage
modulus at lower temperatures and/or at1:2 or1:3ratios were superiorat
temperatures belowTg. This suggests that more flexibility in recipe may bepossible
for lowtemperature product applications.
One oftheadvantages ofthecurrent system is that up to50% ofthe weight ofthe
polymer consists ofbio-oil andthis was competitive orbetterthan similar studies.
Forexample, Nonaka et al.(1997) was ableto achieve maximum storage modulus
when 50%industrial kraft lignin (byweight) was usedto synthesize epoxy-lignin
resins.They foundconsiderable differences inthe E? totemperature trends for
different loadings oflignin. Unlikethis study, theywere ableto achieve higherTg
values (around 140oC)fora similar bio-derived substitutionrate andthe Tg seemed to
approach that typical ofpure lignin (Mansouri etal. 2011).But forour study,despite
bio-oil beingsimilar tolignin in basic composition, thelower Tgmay have been
attributable tothe plasticizing effect ofdiethylene glycol within the epoxyto oil
cross-linkedmatrix.
85
40 60 80 100 1205
6
7
8
9
10
E '  (
G P a)
E '  (
G P a)
E '  (
G P a)
E '  (
G P a)
Temperature (oC)
 200 oC 1:2
 220 oC 1:2
 220 oC 1:3
 240 oC 1:1
 240 oC 1:2
 250 oC 1:1
 250 oC 1:2
Fig.4.13Storage modulus (E?)for switchgrassbased epoxy resin systems.
4.3.6Extraction tests
Inorder todetermine the solubilitywhich should bedirectly related tocrosslink
density,extraction testewere performed. The more stable epoxyresin was foundby
analyzing whichratio ofEpon 828toBio-oil had thehigher percentageof crosslinked
structure.After 4hoursextraction, the minimum Epon 828:switchgrass bio-oil ratio
was 1:4whichwas illustrated inTable 4.4and Figure 4.14
86
Table4.4TheAcetoneSoxhlet extraction tests ofswitchgrass basedepoxyresin at
different liquefactiontemperature s.
?-?means the statusof thetest samples were too rubberyto betested.
Temp
eratur
e(?)
Massratio Epon 828:Bio-oil
1:1 1:2 1:3 1:4
Avg(%) SD Avg(%) SD Avg(%) SD Avg(%) SD
200 - - 61.96 0.43 60.94 0.86 - -
220 - - 46.48 0.34 57.30 0.67 62.00 0.41
240 79.59 0.63 65.18 0.58 71.46 0.80 67.70 0.67
250 41.89 0.78 50.64 0.53 67.60 0.40 61.40 0.42
1:1 1:2 1:3 1:40
10
20
30
40
50
60
70
80
90
100
Ratio of epon 828 to Bio-oil
w e i
g h t
 l o s
s
w e i
g h t
 l o s
s
w e i
g h t
 l o s
s
w e i
g h t
 l o s
s  ( %)  ( %)  ( %)  ( %)
 200 oC
 220 oC
 240 oC
 250 oC
Fig.4.14The acetone Soxhlet extraction tests ofswitchgrass basedepoxy resin at
different liquefactiontemperature s.
The results oftheAcetone Soxhlet extraction testsare presentedinTable 4.4and
Figure 4.14.The change inmass loss for different ratios andtemperatures is
illustrated. The lowest response in weight loss was 41.9andwas aresult ofthe epoxy
resin formed with a1:1ratio and aliquefactiontemperature of250OOOO C.This was much
87
higher thanliquefied wood basedepoxyresins (Chapter 3)andsuggeststhat wood
basedepoxyresins exhibit ahigher degree ofcross linking.
Table4.5TheAcetoneSoxhlet extraction tests ofswitchgrass basedepoxyresin at
different liquefactiontime s.
?-?means the statusof thetest samples were too rubberyto betested.
Time (h)
Massratio Epon 828:Bio-oil
1:1 1:2 1:3 1:4
Avg(%) SD Avg(%) SD Avg(%) SD Avg(%) SD
1 - - 59.19 0.69 53.30 0.16 63.47 0.29
2 41.89 0.78 50.64 0.53 67.60 0.40 61.40 0.42
3 54.97 0.61 50.97 0.72 54.46 0.90 54.64 0.36
1:1 1:2 1:3 1:40
10
20
30
40
50
60
70
80
90
100
w e i
gh t
 l os
s
w e i
gh t
 l os
s
w e i
gh t
 l os
s
w e i
gh t
 l os
s  ( %
)
 ( %
)
 ( %
)
 ( %
)
Ratio of epon 828 to Bio-oil
 1 h 2 h
 3 h
Fig.4.15The acetone Soxhlet extraction tests ofswitchgrass basedepoxy resin at
different liquefactiontime s.
From theTable4.5andFigure 4.15,it is observedthat the lowest mass loss
occurred inthe same sample where the ratio ofEpon 828to Bio-oil was 1:1andthe
liquefactiontime was 2h,and theliquefaction temperature was fixed at250oC.
88
4.3.7FT-IRspectroscopy
The composition ofthe polymeric materials can bedetermined bymeasuring the
response ininfrared spectrawith achangein liquefactionconditions orEpon to
bio-oil ratio.AFT-IRspectrometer was usedandthe peakswere compared to
commercially available spectral data bases. FT-IRidentifies thetypes ofchemical
bonds(functional groups) present in thesolid orliquid sample. The wavelength of
light absorbed is characteristic ofthe chemical bond. Byinterpreting theinfrared
absorption spectrum, the chemical bonds inamolecule canbedetermined. FT-IRwas
usedto examine possible interactions betweenthe switchgrass basedEpon 828and
liquefied bio-oil.
Figure 4.16showsthat hydroxyl groups in the bio-oil had beenconsumed. And
also anEpoxidering inthe Epon 828disappearedwhen thenewswitchgrass based
epoxyresin formed whichmeans that the crosslink was built inthe new epoxy resins.
The characteristic stretching vibration ofthe peroxide moieties at 914cm -1 (C-O-C)
completely disappearedafter curing (Abdul Khalil, Marliana etal. 2011).The peakat
1116cm -1 for the bio-oil was further removed whenblended andcured witheponand
canbeattributed tobandsobserved with variationin lignin (Zhanget al. 2012).A
small peaknear1722cm -1was also observed within the bio-oil which was consumed
after blending andcure. Zhang etal. (2012) attribute this tothe carbonyl groupsthat
must haveparticipated inthe cross-linking reaction.Abroadabsorption band at
3336cm -1was assigned toaromatic andaliphatic OHgroups (Abdul Khalil, Marliana
et al.2011)which disappearedin theFT-IRcurveof switchgrassbased epoxy resin.
89
This means that we producedHydroxyl groupsuccessfully andthe OHgroupreacted
withEpon 828to generate thenewtype ofswitchgrass basedepoxyresin.
4000 3500 3000 2500 2000 1500 1000 5000
10
20
30
40
50
60
70
80
90
100
110
A b s
or b
an c
e ( %)
A b s
or b
an c
e ( %)
A b s
or b
an c
e ( %)
A b s
or b
an c
e ( %)
Wavenumber(cm-1)
 Epon 828
 Bio-oil (liquefaction temperature: 250oC; time: 2hrs) Bio-based epoxy resin
Fig.4.16FT-IRgraphofAbsorbanceversus Wavenumber for Epon 828,Bio-oil and
bio-oil basedepoxyresin.
Figure 4.17shows that whenliquefaction temperature was 250oCand
liquefactiontime was 2h, themass ratio ofEpon 828toswitchgrass basedepoxyresin
1:1had the lowest OHgroupwhichindicates that it hasthe highest cross linking
structure.
3336cm -1
OHstretch 914 cm -1
(epoxide ring)
90
4000 3500 3000 2500 2000 1500 1000 5000
10
20
30
40
50
60
70
80
90
100
A b
s or
b an
c e (
%)
A b
s or
b an
c e (
%)
A b
s or
b an
c e (
%)
A b
s or
b an
c e (
%)
Wavenumber (cm-1)
 200oC 2hrs 1:2
 200oC 2hrs 1:3
 220oC 2hrs 1:2
 220oC 2hrs 1:3
 240oC 2hrs 1:1
 240oC 2hrs 1:2
 240oC 2hrs 1:3
 250oC 2hrs 1:1
 250oC 2hrs 1:2
 250oC 2hrs 1:3
 250oC 2hrs 1:4
Fig.4.17FT-IRgraphofAbsorbanceversus Wavenumbe for switchgrass basedepoxy
resins when liquefactiontime was fixed at2handliquefaction temperature was
changedfrom 200oCto 260oC.
Figure 4.19shows that whenthe liquefactiontemperature was 250oCand
liquefactiontime was 2h, themass ratio ofEpon 828toswitchgrass basedepoxyresin
1:1had the lowest OHgroupwhichindicates that it hasthe highest cross linking
structure.
250oC2h1:1
91
4000 3500 3000 2500 2000 1500 1000 5000
10
20
30
40
50
60
70
80
90
100
Wavenumber (cm-1)
A b s
or b
an c
e ( %)
A b s
or b
an c
e ( %)
A b s
or b
an c
e ( %)
A b s
or b
an c
e ( %)
 250oC 2h 1:1
 250oC 1h 1:2
 250oC 1h 1:3
 250oC 1h 1:4
 250oC 3h 1:1
 250oC 3h 1:2
 250oC 3h 1:3
 250oC 3h 1:4
Fig.4.18FT-IRgraphofAbsorbanceversus Wavenumbe r for switchgrass based
epoxyresins when liquefactiontemperature was fixed at250oCandliquefaction time
was changedfrom 1hour to3hours.
250oC2h1:1
92
4.4Conclusions
The following are experimental results (Table 4.6andTable 4.7)for thewhole
experiment.
Table4.6Experimental Result I
Ratio(Epon:bio-oil)\Temp 200?220?240?250?260?
Residue Percentage(%) 85.48 68.87 57.3 54.2 50.14
Hydroxylnumber (KOH/g) 951.75?
6.423.94
941.29?
5.41
898.11?
3.02
875.32?
6.42
947.82?
8.77
pHvalue 3.51 3.81 4.50 5.18 4.83
1:1 Tg(?) - 38.44 42.93 62.84 -
Weightloss(%) - - 79.59?
0.63
41.89?
0.78
-
Decomposition temp (?) - - 447.08 439.91 -
1:2 Tg(?) 40.47 48.76 42.68 48.69 -
Weightloss(%) 61.96?
0.43
46.48?0.34 65.18?
0.58
50.63?
0.53
-
Decomposition temp (?) 442.60 452.46 446.19 444.56 -
1:3 Tg(?) 37.15 42.41 35.65 35.86 -
Weightloss(%) 60.94?
0.86
57.30?0.67 71.46?
0.81
67.60?
0.40
-
Decomposition temp (?) 416.59 447.98 450.67 428.25 -
1:4 Tg(?) - - - 28.25 -
Weightloss(%) - 62.00?0.41 67.70?
0.67
61.40?
0.42
-
Decomposition temp (?) - - - 409.42 -
The conditions above arebased onthereaction time whichis 2h.
93
Table4.7Experimental Result II
Ratio(Epon:bio-oil) 1h 2h 3h
Residue Percentage(%) 82 54.2 72.4
Hydroxylnumber (KOH/g) 956.48?11.70 875.32?6.42 953.10?10.58
pHvalue 5.47 5.19 5.64
1:1 Tg(?) - 62.84 62.23
Weightloss(%) - 41.89?0.78 54.97?0.61
Decomposition temp (?) - - 450.67
1:2 Tg(?) 40.16 48.69 45.64
Weightloss(%) 59.19?0.69 50.63?0.53 50.97?0.72
Decomposition temp (?) 447.08 - 439.91
1:3 Tg(?) 26.81 35.86 40.44
Weightloss(%) 53.30?0.16 67.60?0.40 54.46?0.90
Decomposition temp (?) - - 441.70
1:4 Tg(?) 31.02 28.25 35.61
Weightloss(%) 63.47?0.30 61.40?0.42 54.64?0.36
Decomposition temp (?) - - -
The conditions above arebased onthereaction temperature whichis 220oC.
?-?means the statusof thetest samples were too rubberyto betested.
The switchgrassbased bio-oil contains anumber ofhydroxyl groups which could
beusedin thereaction tomanufacture anewtype ofepoxyresin. The switchgrass
basedbio-oil was successfully reactedwith theEpon 828using theTPPascatalyst.
The optimal liquefactiontemperature was250oCandthe optimal liquefaction
time was 2h.The optimal mass ratio ofEpon to switchgrassbased bio-oil was 1:1
because it had high performance inall kinds oftests including DSC,TGA, Soxhlet
extraction andFT-IR.
94
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