Poly(l-lactide-b-butylene succinate-b-l-lactide) triblock copolymer: A multi-functional additive for PLA/PBS blend with a key performance on film clarity

Abstract

Blending of poly(butylene succinate) (PBS) with poly(lactic acid) (PLA) is an effective way to fine tune PLA brittleness. However, the immiscibility between these two polymers leads to product defects in terms of strength and clarity. The present work proposes a simple triblock copolymer, i.e. poly(l-lactide-b-butylene succinate-b-l-lactide) (PLLA-b-PBS-b-PLLA), as a multi-functional additive, i.e. compatibilizer, plasticizer, and nucleating agent for improving the PLA/PBS blend. Based on a critical content of PLA/PBS (at 80/20 wt%) which gives the opaque film, an addition of PLLA-b-PBS-b-PLLA induces drastic changes in crystallization behavior and mechanical properties. The ratio between PLLA and PBS block length, and the amount are the factors to fine tune the PLA/PBS blend. The PLLA40-b-PBS28-b-PLLA40 at 3 phr is an optimal condition to tune the blends with the decreases in glass transition temperature (Tg) (from ∼50 °C to ∼20 °C) as well as an increase in the elongation at break (for two-fold). At that time, the rapid co-crystallization of PBS and PLA in the blend as seen from the small and homogeneously dispersed spherulite results in a key performance to enhance the clarity of the blend film. The present work demonstrates how the block copolymer of PLA and PBS performs its multi-function for miscibility, toughness, and clarity of PLA/PBS blends.