Enhanced the melt strength, toughness and stiffness balance of the reactive PB-g-SAG core–shell particles modified polylactide blends with the aid of a multifunctional epoxy-based chain extender

Abstract

A reactive core–shell modifier with the polybutadiene (PB) as core and styrene/acrylonitrile/glycidyl methacrylate terpolymer as shell (PB-g-SAG) was prepared to toughen the polylactide (PLA). Simultaneously, the epoxy-based multifunctional chain extender (CE) was used to further improve the modification ability of PB-g-SAG on the PLA properties. For the PLA/PB-g-SAG/CE blends, the compatibilization reaction between PLA and PB-g-SAG formed the PLA-g-SAG-g-PB copolymer, which improved the interfacial strength between the PLA and PB-g-SAG. At the same time, the branching reaction among the chain extender and the PLA formed the long chain branching structure which enhanced the molecular weight and entanglement density of the PLA. The aid of the epoxy-based chain extender further increased the melt strength, toughness and stiffness of PB-g-SAG toughened PLA blends. When PB-g-SAG content was 20 wt%, 0.5 wt% CE induced the melt strength, impact strength and Young’s modulus of PLA/PB-g-SAG blend increase from 9.2 × 104 Pa·s, 428 J/m and 1634 MPa to 1.27 × 105 Pa·s, 530 J/m and 1845 MPa for the PLA/PB-g-SAG/CE blend. Compared with the pure PLA, the melt strength and impact strength were increased by 1150% and 1666%. Deformation results indicated the massive shearing yielding of the PLA matrix, the cavitation of the polybutadiene and interfacial debonding between the PB-g-SAG and the PLA were the major toughening mechanisms. This research provided a simple and practical strategy to overcome the shortcomings of the PLA and could promote its application in the industrial fields.