Design and characterization of bio-based polymer blends and composites

Abstract

Synthetic polymers derived from renewable resources offer opportunities to improve sustainability. Compared to their fossil fuel based counterparts, bio-based polymers may be designed to meet the same physical property requirements while reducing primary energy requirements and greenhouse gas emissions. Polymer blending and reinforcement by fibers in composites are established techniques to enhance physical properties. These techniques may be used to develop unique materials systems that broaden the application range of bio-based polymers. This thesis presents an evaluation of structure-property relationships in several blend systems incorporating commercially successful bio-based polymers of particular interest, then introduces a novel bio-based thermoset resin and evaluates its suitability for use in fiber reinforced composites. Miscibility is proved in blends of polyamide-4,10 and polyamide-6,10, enabling the ability to fine tune physical properties according to relative compositions using simple melt-mixing techniques. Quaternary blends of poly(L-lactide), poly(D-lactide), isotactic poly(methyl methacrylate), and syndiotactic methyl (methyl methacrylate) exhibit simultaneous stereocomplex crystallization and homopolymer crystallization within a single amorphous phase, and the presence of poly(methyl methacrylate) promotes stereocomplex formation in poly(lactide). To develop a bio-based thermoset resin, poly(lactide) is simultaneously cleaved into oligomers and functionalized with vinyl end-groups so that it may act as a cross-linking agent in a free-radical polymerization with methyl methacrylate. The low viscosity resin exhibits outstanding physical properties when cured and reinforced with unidirectional glass fiber composites.