Morphology and properties of biodegradable and biosourced polylactide blends with poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate)

Biodegradable polymer blends based on biosourced polymers, namely polylactide (PLA) and poly(3‐hydroxybutyrate‐ co ‐4‐hydroxybutyrate) (P(3HB‐ co ‐4HB)), were prepared by melt compounding. The effects of P(3HB‐ co ‐4HB) on the miscibility, phase morphology, thermal behavior, mechanical properties, and biodegradability of PLA/P(3HB‐ co ‐4HB) blends were investigated. The blend was an immiscible system with the P(3HB‐ co ‐4HB) domains evenly dispersed in the PLA matrix. However, the T g of P(3HB‐ co ‐4HB) component in the blends decreased compared with neat P(3HB‐ co ‐4HB), which might be attributed to that the presence of the phase interface between PLA and P(3HB‐ co ‐4HB) resulted in enhanced chain mobility near interface. The addition of P(3HB‐ co ‐4HB) enhanced the cold crystallization of PLA in the blends due to the nucleation enhancement of PLA caused by the enhanced chain mobility near the phase interface between PLA and P(3HB‐ co ‐4HB) in the immiscible blends. With the increase in P(3HB‐ co ‐4HB) content, the blends showed decreased tensile strength and modulus; however, the elongation at beak was increased significantly, indicating that the inherent brittlement of PLA was improved by adding P(3HB‐ co ‐4HB). The interesting aspect was that the biodegradability of PLA is significantly enhanced after blends preparation. POLYM. COMPOS., 2012.