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Biodegradable Plastics and Composites

Biodegradable polymers such as polylactic acid (PLA) can be derived from renewable plant resources such as corn, sugar beets, etc. Compared with common petroleum-based polymers such as polypropylene (PP), advantages of PLA include high strength and high modulus, in addition to being a biodegradable renewable resource. Disadvantages of PLA include low resistance to conditions of high heat and humidity, low heat distortion temperature (HDT), low flexibility, and long mold cycle time.

PLA possesses higher strength than PP, but inferior heat resistance and impact strength.

A main focus of our research is to improve the properties of PLA, especially durability, to enable its use in automotive and other severe applications. A primary cause of low durability of PLA is hydrolysis under high humidity conditions. As shown below, water molecules attack the ester linkages in PLA, causing breakdown of the material. This process is self-catalyzed by protons on the carboxyl (COOH) end groups. Durability may be significantly improved by modifying the material to retard or prevent this process. Of course, the tendency to hydrolyze is what gives PLA its desired biodegradability. Thus, improving durability while maintaining biodegradability is a considerable challenge.

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Degradation of PLA occurs through hydrolysis and breakdown of the ester linkage.

© 2008 YTC America Inc.