Preparation of biodegradable PLA/PBAT blends with balanced toughness and strength by dynamic vulcanization process

Abstract

Polylactic acid (PLA) has received significant attention in recent years as a commercially available biodegradable resin. However, its brittleness limits its broader adoption. Blending PLA with another biodegradable resin poly(butylene adipate-co-terephthalate) (PBAT) is a simple strategy to toughen PLA, however, the effect is limited and the tensile strength is generally harmed. In this work, PBAT, initiator BIBP and cross-linker TAIC were initially mixed and then extruded into pre-crosslinked PBAT pellets. Subsequently, the pre-crosslinked PBAT and PLA were melt-blended to create PLA/micro-crosslinked PBAT composites. The effects of different TAIC contents on the degree of PBAT gelation, properties and morphological structure of composites were explored. The results showed that TAIC could effectively improve the mechanical properties of PLA/PBAT, particularly the notched impact strength. When the TAIC content was 0.3 wt% of PBAT, the notched impact strength and elongation at break of PLA/PBAT (7/3) reached 42.26 kJ/m2 and 264.26 %, respectively, which are both far higher than those of the blend without cross-linking (9.37 kJ/m2 and 21.29 %). The composites still exhibited excellent tensile strength (46.23 MPa) and tensile modulus (1676.84 MPa), surpassing those of PLA/un-crosslinked PBAT composites. This enhanced toughening and tensile strength maintaining effect is attributed to the network structure in PBAT and the increased compatibility between PLA and PBAT caused by cross-linking within PBAT and at PLA/PBAT interface. The dynamic vulcanization strategy using an extruder provides a possibility for the large-scale preparation of stiff-tough PLA. Of course, further work, including pilot or industrial trials, is necessary to validate scalability.