Toughening of polylactide by blending with a novel random aliphatic-aromatic copolyester

Polylactide (PLA) was toughened by blending with a novel biodegradable aliphatic-aromatic copolyester - random poly(butylene succinate-co-glutarate-co-adipate-co-terephthalate) (PBSGAT), with low crystallinity, synthesized from respective dimethyl esters of terephthalic acid, succinic acid, glutaric acid, adipic acid, and 1,4-butanediol. PLA blends with PBSGAT were prepared by melt blending and their structure as well as properties were studied. The copolyester formed particles in the blends and exhibited a separate glass transition. 20-fold increase of the ultimate strain and 2.5 fold increase of the tensile impact strength with respect to neat PLA was achieved in the blends with 25-35 wt.% of PBSGAT. TEM and SEM studies of drawn specimens evidenced that the main mechanism of the toughening was cavitation inside the copolyester particles, which promoted shear yielding and further plastic deformation of PLA matrix. (C) 2014 Elsevier Ltd. All rights reserved.