Biodegradable poly (lactic acid) blends toughened with in situ formed core-shell structure by reactive processing

Abstract

Biodegradable poly (lactic acid) (PLA) blends toughened with a core-shell structure were successfully prepared by melt-blending PLA with poly (butylene adipate-co-terephthalate) (PBAT) and poly (ether-block-amide) (PEBA). Scanning electron microscopy (SEM) and atomic force microscopy-infrared (AFM-IR) analyses confirmed the presence of core-shell structure in the PLA matrix, in which the core and the shell are PBAT and PEBA, respectively. To enhance the interfacial compatibility between PLA and PEBA, glycidyl methacrylate (GMA) was grafted onto PEBA, yielding the PEBA-GMA copolymer. The epoxy groups in PEBA-GMA reacted with the end groups (-OH, –COOH) of PBAT and PLA, which enhanced the interfacial compatibility of PLA/PEBA and PEBA/PBAT, thereby facilitating the formation of a smaller dispersed phase with core-shell structure. Consequently, a super-toughened PLA/PEBA-GMA/PBAT blend was prepared. The PLA/PEBA-GMA5/PBAT (70/15/15) blends achieved a notched Izod impact strength of 72.9 kJ/m². Moreover, with a fixed PLA matrix content of 80 wt%, the upper limit of core PBAT content in PLA/PEBA-GMA3/PBAT blends was 18 wt%, while the minimum shell PEBA-GMA3 content was 2 wt% to ensure that the blends were ductile fracture. The composite of this blend had a lower stiffness loss, i.e., 26 %, demonstrating a well-balanced toughness and stiffness. Furthermore, the PLA/PEBA-GMA3/PBAT (70/25/5) blend exhibited excellent toughness at low temperatures, achieving a notched Izod impact strength of 47.1 kJ/m² at −20 °C. Enzyme degradation experiments confirmed that the PLA blends retained the biodegradability of PLA, PBAT, and PEBA, ensuring that the blends were environmentally friendly.