Nucleation and plasticization dual functions of multi-branched poly(L-lactic acid) (PLLA) for PLA

Abstract

Poly(lactic acid) (PLA) is the most reliable biodegradable polymer due to the industrial scale production and the variety of the products in the market. However, PLA performs extremely slow crystallization in comparison to other commercial petroleum-based polymers such as polypropylene (PP), polyethylene (PE), 1/70 times of high density polyethylene (HDPE) and shows the glass transition temperature (Tg,) above room temperature (58 ºC). This leads to brittleness and low impact resistance. For the past several years, the improvement of PLA by enhancing crystallization as well as plasticization via adding nucleating agents such as starch and talc, and blending with flexible polymer such as poly(butylene succinate) (PBS), poly(butylene adipate-co-terephthalate) (PBAT), etc. have been reported. However, the phase separation is still the main problem. Here, we propose multi-branched polymers as a dual functions additive, i.e. nucleating agent and plasticizer evidenced from the significantly accelerated crystallization and the lowering of Tg without phase separation.