Enhancement in crystallization kinetics of the bacterially synthesized poly(β-hydroxybutyrate) by poly(butylene succinate)

Poly(β-hydroxybutyrate), PHB, is a bio-based and biodegradable material. However processing and application of the PHB are disturbed by its low crystallization rate. In this manuscript the crystallization behavior of the PHB was improved via incorporation of another biodegradable polymer, i.e. poly(butylene succinate), PBS. The two polymers show phase separation in the blends. PBS varies from a dispersed phase to a continuous phase with increasing its content from 20 to 70 wt% and a co-continuous morphology is observed at PBS 50 wt%. Although the spherulitic radial growth rate of the PHB is retarded to a certain extent by the PBS, the non-isothermal crystallization temperature is increased by around 30 °C while the half-life crystallization time is reduced significantly, indicating an increased overall crystallization rate of the PHB. The increased crystallization rate of PHB is attributed to a modified multi-nucleation mechanism, i.e. homogeneous nucleation, heterogeneous nucleation and self-enhanced nucleation.