Biopolymer toughening with chain extenders

Polylactic acid (PLA) is one of the most popular biodegradable polymers today. However, it has its drawbacks, such as poor melt strength and narrow processing window. In this study, PLA 2003D was compounded with chain extenders (CE) at weight percentages of 0.2%, 0.5%, 0.75% and 1.0%, using two co-rotating screws. Two types of multifunctional epoxy extenders were used, Joncryl® ADR-4300 and Joncryl® ADR-4370F. The thermal, mechanical, chemical and rheological properties of the PLA blends were investigated. The DSC results showed that there was a lower crystallinity with increasing concentrations of CE, suggesting that the blends increased in ductility. The results showed that the mechanical (i.e. impact resistance, ductility) and rheological (i.e. melt strength) properties improved with increasing concentrations of CE. The impact resistance and ductility of the blends increased with increasing concentrations of CE. When compared to pure PLA, the PLA blends exhibit enhanced melt strength and strain-hardening behaviour. These results are supported by results of the FTIR and GPC, which indicated that the PLA blends had an increase in molecular weight. The change in molecular weight and molecular architecture due to the chain extender plays an important role in the enhancement of the properties. Lastly, a blown film application was used to demonstrate the improvements in melt strength and processing window. This experiment allows for future research to explore other possible applications of PLA blends or other polymer blends.Bachelor of Engineering (Materials Engineering