Cold-crystallization kinetics of syndiotactic polystyrene

摘要

The kinetics of the isothermal and nonisothermal cold crystallization of syndiotactic polystyrene (s-PS) were characterized with differential scanning calorimetry. A Johnson-Mehl-Avrami analysis of the isothermal experiments indicated that the cold crystallization of s-PS at a constant temperature followed a diffusion-controlled growth mode with a decreasing nucleation rate. Furthermore, the slow nucleation rate was the controlling step of the entire kinetic process. For nonisothermal cold-crystallization kinetics, we used a simple model based on a combination of the well-known Avrami and Ozawa models. The analysis revealed that, unlike for melt crystallization, the Avrami and Ozawa exponents were not equal. The activation energies for the isothermal and nonisothermal cold crystallizations of s-PS were 792.0 and 148.62 kJ mol(-1), respectively, indicating that the smaller motion units in cold crystallization had a weaker temperature dependence than those in melt crystallization. (C) 2003 Wiley Periodicals, Inc. [References: 41]