Crystallization behaviors of chain extended poly (lactic acid) modified with ST-NAB3 and its improved mechanical and thermal properties

Abstract

The widespread use of traditional petroleum-based plastics is causing significant environmental pollution for example microplastics issues, due to its non-biodegradability. Poly (lactic acid) (PLA) as a representative biodegradable polymer is a promising candidate to replace petroleum-based plastics in some fields of disposable packaging materials and tableware. In this work, in order to improve the poor crystallization, mechanical and heat resistance performances of PLA, styrene-acrylonitrile-glycidyl methacrylate (SAG) as a chain extender and octamethylenedicarboxylic dibenzoylhydrazide (ST-NAB3) as a heterogeneous nucleating agent (HNA) were added simultaneously into PLA matrix. The chain-extended PLA (CPLA) with branch structures had smaller crystal sizes and higher crystal density, compared with those of pure PLA. In addition, thanks to the nucleation effect of ST-NAB3 and the development of “shish-kebab”, this tendency became more pronounced in CPLA/HNA systems. It was worth mentioning that, CPLA with the ST-NAB3 content of 1 wt.% (CPLA-1) possessed the highest crystallinity of 43.6%. Meanwhile, CPLA-1 had the best impact strength and heat deformation temperature of 38.9 kJ/m2 and 91.3°C respectively, which had increased by 11.3 kJ/m2 and 32.4°C contrast to pure PLA. On the whole, this study proposed a simple and effective method, which provided a new possibility for PLA modification research.