Crystallization Kinetics and Multiple Melting Behavior of Biodegradable Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)

Abstract

Abstract The crystallization and melting behavior of biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] with 11 % 4HB content was investigated by differential scanning calorimetry (DSC), small and wide angle X-ray scattering (SAXS and WAXS). The Avrami analysis was performed to obtain the kinetic parameters of crystallization. The results showed that the Avrami equation was suitable for describing the isothermal and nonisothermal crystallization processes of P(3HB-co-4HB). Based on the values of the equilibrium melting temperature and the half-time of crystallization, its nucleation constant of crystal growth kinetics was obtained by using the Lauritzen-Hoffman model, which was found to be 1.92 × 105 K2, lower than that for pure PHB. During the subsequent heating process, quite different multiple melting behaviors were observed for P(3HB-co-4HB) crystallized isothermally or nonisothermally. The origins of the multiple melting behaviors were discussed based on either the presence of dual lamellar thicknesses or the melt-recrystallization mechanism. In general, the crystallization and melting behaviors were elucidated by this work.