Non-isothermal crystallization kinetics of poly(3-hydroxybutyrate) in copoly(ester-urethane) nanocomposites based on poly(3-hydroxybutyrate) and cloisite 30B

摘要

The non-isothermal melt crystallization kinetics of PHB segment in copoly(ester-urethane)s based on poly(3-hydroxybutyrate) and poly(butylene adipate) and their nanocomposites with cloisite 30B (C30B) were investigated at different cooling rates (5, 10, 15, and 20 degrees C min(-1)) using DSC. Ozawa, Avrami, and the combined Avrami-Ozawa (Mo) methods were used for analyzing the non-isothermal crystallization behavior. The results showed that Avrami and Ozawa models provide a fair description of the non-isothermal crystallization process while Mo model was successful in describing it. The results indicated that C30B not only served as heterogeneous nucleating agents for PHB crystallization, at lower content (5 wt%), but also restricted the mobility and diffusion of PHB chains at higher content (10 wt%). Polarized optical microscope (POM) showed that the nucleation density of PHB segment was increased significantly in the case of nanocomposites. The isoconversional method of Friedman was used to determine the effective activation energy of crystallization of the PUs and the Lauritzen-Hoffman parameters (K-g and U*) were calculated by applying the Vyazovkin method. (C) 2015 Elsevier B.V. All rights reserved.