Abstract

Economic and environmental concerns motivate the development of new polymers from renewable resources. In this research, new elastomers and elastic nanocomposites were synthesized from plant oils. These new materials are suitable for elastomer processing and have properties comparable to conventional synthetic rubbers. In addition, they have the potential to be biodegradable and noncytotoxic.

Acrylated oleic methyl ester (AOME), synthesized from high oleic triglycerides, can readily undergo free radical polymerization and form a linear polymer. To achieve the elastic properties, different methods were developed to generate an elastic network and easily control the crosslink density. Ethylene glycol dimethacrylate (EGDMA) was used to crosslink the polymer in situ during bulk polymerization. The mechanical and thermal properties were further improved by adding methyl methacrylate (MMA) to modify the molecular structure of the rubber chain. MMA facilitated the crosslinking and enhanced the glass transition temperature. The effects of initiator type, initiator ratio, cure temperature, EGDMA ratio and MMA ratio on the elastomer properties were explored. In addition to the in situ crosslinking method, a high molecular weight linear polymer was obtained through miniemulsion polymerization and was then mixed with a curing agent to generate a crosslinked network. The saturated polymer structure made crosslinking difficult. Thiadiazole and dicumyl peroxide were used to cure poly(AOME) and the cure mechanism and kinetics were compared. Processing conditions were selected to obtain a homogeneous compound in a banbury mixing approach. Cure kinetics were studied using a moving die rheometer and it was found that the crosslink density changes with the formulations and curing conditions. More homogeneous mixtures were obtained by the solvent dispersion method, in which the poly(AOME) and the cure agent were dissolved together in a solvent. Compared with the samples from in situ crosslinking by bulk polymerization, the samples from miniemulsion polymerization give better network structure, as determined by percolation theory calculation. The poly(AOME) elastomers have a tensile strength in the range of 0.06MPa to 0.57MPa and an elongation in the range of 80--220%. Poly(AOME) elastomers were also found to be biodegradable and noncytotoxic. (Abstract shortened by UMI.)