Miscibility and crystallization kinetics of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/poly(methyl methacrylate) blends

The miscibility and crystallization kinetics of the blends of random poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(HB-co-HV)] copolymer and poly(methyl methacrylate) (PMMA) were investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). It was found that P(HB-co-HV)/PMMA blends were miscible in the melt. Thus the single glass-transition temperature (T-g) of the blends within the whole composition range suggests that P(HB-co-HV) and PMMA were totally miscible for the miscible blends. The equilibrium melting point (T(m)degrees) of P(HB-co-HV) in the P(HB-co-HV)/PMMA blends decreased with increasing PMMA. The T(m)degrees depression supports the miscibility of the blends. With respect to the results of crystallization kinetics, it was found that both the spherulitic growth rate and the overall crystallization rate decreased with the addition of PMMA. The kinetics retardation was attributed to the decrease in P(HB-co-HV) molecular mobility and dilution of P(HB-co-HV) concentration resulting from the addition of PMMA, which has a higher T-g. According to secondary nucleation theory, the kinetics of spherulitic crystallization of P(HB-co-HV) in the blends was analyzed in the studied temperature range. The crystallizations of P(HB-co-HV) in P(HB-co-HV)/PMMA blends were assigned to n = 4, regime III growth process. (C) 2004 Wiley Periodicals, Inc.