Toughening of Semicrystalline and Amorphous Polylactide with Atactic Polyhydroxybutyrate

ABSTRACT

Biodegradable and biocompatible blends of polylactide with atactic poly([R,S]-3-hydroxybutyrate) were studied. Cold-crystallized blends exhibit lamellar–spherulitic morphology. Lamellae thickness and crystallinity, controlled by conditions of annealing, surprisingly do not depend on blend composition. In contrast, due to partial miscibility, the glass transition, cold crystallization, and melting temperatures depend on composition. Mechanical performance of polylactide, including drawability and toughness, is improved in both amorphous and semicrystalline blends. The main toughening mechanism identified was cavitation of atactic poly([R,S]-3-hydroxybutyrate), initiating multiple crazing of polylactide. A limited shear yielding was also observed. Activity of all these mechanisms brings brittle-to-ductile transformation in blends, above 10 wt% of atactic poly([R,S]-3-hydroxybutyrate).

GRAPHICAL ABSTRACT

KEYWORDS:

• Cavitation
• crazing
• damage mechanism
• polylactide
• polymer blends and alloys
• toughening