In situ grafting approach for preparing PLA/PHBV degradable blends with improved mechanical properties

A one-step reactive extrusion process has been demonstrated to toughen the poly(lactic acid) (PLA) blend without sacrificing its mechanical strength and degradability. Specifically, poly(lactic acid) (PLA), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and the peroxide initiator were first introduced into the mixer and then heated at the elevated temperatures for triggering the grafting reaction during the extrusion. During this process, the thermal decomposition of PHBV results in the unsaturated bonds that can directly grafted onto the PLA backbones by free radical reactions. From this study, we found that PLA/PHBV blend with a mass ratio of 80/20 (PLA/PHBV) and 0.3 wt% 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (DBPH) is an optimized condition, leading to an improved elongation at break of 15.95%, which is 3.1 times of the PLA and 1.5 times of the PLA/PHBV blend without the initiator, while tensile strength exhibited very limited decreased compared to PLA. Overall, this work presents an environmentally friendly and industrial feasible approach to prepare bio-based toughened PLA for improving the elongation at break, while retaining the tensile strength and degradability.