Effect of a chain extender on the rheological and mechanical properties of biodegradable poly(lactic acid)/poly[(butylene succinate)-co-adipate] blends

Biodegradable polymer blends based on poly(lactic acid) (PLA) and poly[(butylene succinate)-co-adipate] (PBSA) were prepared with a laboratory internal mixer. An epoxy-based, multifunctional chain extender was used to enhance the melt strength of the blends. The morphology of the blends was observed with field emission scanning electron microscopy. The elongational viscosities of the blends, with and without chain extender, were measured with a Sentmanat extensional rheometer universal testing platform. The blends with chain extender exhibited strong strain-hardening behavior, whereas the blends without chain extender exhibited only weak strain-hardening behavior. Measurements of the linear viscoelastic properties of the melts suggested that the chain extender promoted the development of chain branching. The results show that PBSA contributed to significant improvements in the ductility of the PLA/PBSA blends, whereas the chain extender did not have a significant effect on the elastic modulus and strain at break of the blends. The combined blending of PLA with PBSA and the incorporation of the chain extender imparted both ductility and melt strength to the system. Thus, such an approach yields a system with enhanced performance and processability. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013