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 i i 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 - i i i 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) . i v 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 . v 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 vi i 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 i x 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 2.4Reference Abella, L., S. Nanbu, et al. (2007). 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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 25 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 properties of sulfone-containing epoxy resin cured with anhydride." Polymer DegradationandStability 86(3): 515-520. Parrish, D. J. and J. H. Fike (2005). "The Biology and Agronomy of Switchgrass for Biofuels."Critical Reviews inPlant Sciences 24(5-6): 423-459. Perlack, R. D., L. L. Wright, et al. (2005). Biomass as feedstock for a bioenergy and bioproducts industry: the technical feasibility of a billion-ton annual supply, DTIC Document. Peter, M. (2002). "Energy production from biomass (part 1): overview of biomass." BioresourceTechnology83(1): 37-46. 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 crop."BioresourceTechnology56(1): 83-93. 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 different sources for use in phenol?formaldehyde resin synthesis." Bioresource Technology98(8): 1655-1663. 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 silicone-containing epoxy resin."Polymer 41(16): 6113-6122. Xie,T.andF.G. Chen (2005). "Fast liquefaction ofbagasse in ethylene carbonate and preparation of epoxy resin from the liquefied product." Journal of Applied Polymer Science 98(5): 1961-1968. Yamada, T. and H. Ono (1999). "Rapid liquefaction of lignocellulosic waste by using ethylenecarbonate."BioresourceTechnology70(1): 61-67. Yamada, T. and H. Ono (2001). "Characterization of the products resulting from ethyleneglycol liquefaction ofcellulose."Journal ofWoodScience 47(6): 458-464. Zeng, X., Y. Ma, et al. (2007). "Utilization of straw in biomass energy in China." Renewable andSustainable Energy Reviews 11(5): 976-987. Zhao, B. Y., G. Chen, et al. (2001). "Synthesis of lignin base epoxy resin and its characterization."Journal ofMaterials Science Letters 20(9): 859-862. 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. 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(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. 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