Effect of poly(lactic acid) molecular weight and composition on the morphology and crystallization behavior of polyhydroxybutyrate/poly(lactic acid) blends

Abstract

AbstractThis study investigates the effects of molecular weight and crystallinity of polylactic acid (PLA) on the morphology and crystallization behavior of polyhydroxybutyrate (PHB)/PLA blends. Utilizing a solution casting method, we discovered that the molecular characteristics of PLA significantly influence the thermal and structural properties of the blends. The lower molecular weight and amorphous PLA notably broadened the temperature range for PHB's banded spherulite formation, indicating enhanced miscibility. In contrast, semicrystalline PLA variants produced smaller spherulites within large PHB matrices. The high molecular weight PLA had an unusual, relatively low melting point which led to a competition between the molecular weight effect and the supercooling effect regarding the isothermal crystallization kinetics. The blend morphology was observed in thin films in which the usual crystal formation of PHB was severely hindered in the presence of crystalline PLA but could form thin lamellae when the PLA was amorphous. At ultra‐thin thickness, where crystallization is impossible, the amorphous co‐continuous structure of the blends was revealed by melting the film. Our research contributes to the development of advanced biodegradable materials for environmental sustainability, emphasizing the intricate interplay between polymer blend components that can be tuned for specific applications.Highlights The study explores the blend morphology and crystallization of PLA/PHB. The temperature range for PHB's spherulite formation broadens with PLA. PLA's partial miscibility with PHB shifted Tg and caused delayed Tm of PHB. Usual PHB crystal formation is hindered with crystalline PLA. Thin PHB lamellae formed within amorphous PLA and observed via AFM.