Nonisothermal bulk crystallization and subsequent melting behavior of syndiotactic polypropylenes: Crystallization from the melt state

摘要

Various macrokinetic models, namely, the Avrami, the Tobin, and the Ozawa models, were applied to describe the crystallization process of syndiotactic polypropylene (s-PP) under nonisothermal conditions. Both Avrami and Tobin models were shown to provide a fair description of the experimental data. The Avrami exponent n(a) was found to range from 2.4 to 5.3, while the Tobin exponent; n(t) was found to range from 3.1 to 6.7. The Ozawa model was found to describe the nonisothermal crystallization kinetics of s-PP very well. The Ziabicki's kinetic crystallizability, suggesting the crystallization ability of polymers from the melt when cooled at a unit cooling rate, was also evaluated and was found to range from 0.93 to 1.40 degrees C s(-1). The energy barrier for nonisothermal crystallization, based on the Augis-Bennett method, was found to range from -78.6 to -108.1 kJ mol(-1). (C) 2000 John Wiley & Sons, Inc. [References: 36]