Poly(lactic acid) with Improved Melt Strength and Gardner Impact Strength

摘要

Poly(lactic acid) or PLA is a commercial biopolyrner made from lactic acid derived from sugar fermentation. "Green-based" [1] PLA is desired as a biodegradable film, sheet and food packaging alternative to oil-based polymers. PLA has a T_m melting point range of 150-162°C [2]. Unfortunately, PLA has poor melt strength and impact strength. High melt strength and impact strength are important properties when manufacturing sheet, film, fibers and molded goods. In this paper we explored several ideas to improve the performance of PLA while maintaining its "green" characteristics. We found that an acrylic based core-shell polymer used at a low concentration significantly increased the Gardner impact strength of 15mil extruded sheet. Also, a high molecular weight acrylic copolymer used at low levels doubled the PLA melt strength. Lastly, reacting PLA with organic peroxides increased the shear modulus, molecular weight and melt strength based on rheometer, multi-angle light scattering and Rheotens analysis.