Highly-toughened PLLA/PVA biodegradable blends: Graft copolymer tailored crystallization and phase morphology

Poly(l-lactic acid) (PLLA), recognized as a promising substitute for petroleum-based polymers, has garnered significant attention for its various advantages. However, the practical application of PLLA is limited by its poor toughness. This study introduces a novel approach, using a graft copolymer, poly(vinyl alcohol)-graft-poly(l-lactic acid) (PVA-g-PLLA), synthesized through a "grafting to" method to enhance the compatibility of PLLA/PVA blends. It is demonstrated that even though the graft copolymer promotes crystallization, the resultant ternary blends, especially with a mass ratio of 7:3:1, exhibited an 88.7 % elongation at break, representing a 1642 % improvement over pure PLLA and a 576 % increase over binary PLLA/PVA blends. In addition, incorporating PVA-g-PLLA significantly enhanced the toughness of the PLLA/PVA blends without sacrificing strength, thermal stability, or transparency. Remarkably, the Vicat softening temperature of the blends with a 7/3/1.5 ratio increased to about 94.4 °C, substantially higher than the 59.9 °C observed in PLLA/PVA blends. These findings suggest that the newly developed copolymer and the ternary blends hold substantial promise for creating biodegradable materials that do not compromise performance. It suggests a promising future for these materials in various applications where enhanced durability, thermal stability, and environmental sustainability are crucial.