Thermosetting Polymers from Renewable Resources
Type of DegreePhD Dissertation
Polymer and Fiber Engineering
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Polymer science was born as an answer to the need to produce and to understand materials such as plastics, rubber, adhesives, fibers, and paints. It has been recognize as an interdisciplinary field, combining theoretical and experimental knowledge from areas such as chemistry, physics, biology, materials and chemical engineering, etc. It has also been an industry of high levels of innovation, leading the major investments in research and development programs. The continued use of finite fossil fuel resources has shifted thinking towards the future energy scenario of the world, and the polymer science has not escaped to the impact of this trend. The interest in renewable resources is constantly increasing, backed up by new environmental regulations and economic considerations. Biomass is abundant, and polymeric materials based on renewable biomass feedstocks represent a viable alternative to fossil resources. The present work aims to synthesize new, potentially bio-based thermosetting materials from biomass-derived compounds, use them to prepare bio-based thermosetting resins, and investigate the structure-property relations of the resulting polymers. In the first Chapter, background information is provided about the current status of industrial biomass, emphasizing on numbers as well as on new governmental regulations aiming to impulse the use and study of biomass as an alternative chemical feedstock. In the next Chapter, the cationic copolymerization of tung oil, employing limonene and myrcene as comonomers, is presented and discussed. Characterization revealed that the resulting materials behave as elastomeric materials, with the glass-rubber transition occurring at room temperature, and modulus values in the order of MPa. Chapter III investigates the chemical modification of two different functional groups of biomass derived materials; the carbon-carbon double bonds of triglycerides, and the hydroxyl groups of phenolic compounds. These chemical modifications were addressed to introduce more reactive functional groups able to polymerize and to produce materials with a better thermo-mechanical performance. Testing revealed the deep impact that the chemical modification brings up to the thermo-mechanical performance of these materials, generating resins with properties similar to those shown by commercial resins. Chapter IV considers the preparation of interpenetrating polymer networks or IPNs, a particular class of hybrid polymer consisting of two (or more) crosslinked polymers. These multicomponent polymer systems seek to combine the best properties of two or more different polymer networks in order to achieve a material with better properties compared to their not-interpenetrated counterparts. Materials with high toughenability were produced and vastly study. Finally, in certain thermo-mechanically demanding applications, aromatic raw materials are needed to impart the required properties to the thermoset. The most available source of phenolics in nature lies in lignocellulosic. Molecular aromatics can be obtained on a large scale by means of new and arising biorefinery technologies. Chapter V evaluates the viability of synthesizing a high performance bio-based epoxy polymer using fast pyrolysis bio-oil (containing lignin fragments) as a source of phenolic compound.