Nonisothermal crystallization kinetics of polytetrafluoroethylene

Abstract

An analysis of the crystallization kinetics of polytetrafluoroethylene (PTFE) under nonisothermal conditions is presented. A simple method is proposed to remove the limits of the Ozawa theory. The Avramic exponent, n, can be reasonably well determined from the nonisothermal crystallization exotherm. An n value of similar to 1.49 was obtained for PTFE, which indicates the formation of one-dimensional crystallites (fibrillar type) after thermal nucleation or two-dimensional crystallites (discs) after athermal nucleation. Both these morphologies were experimentally observed. For PTFE crystallization from the melt, activation energy was obtained as 34 kcal/mol. This is much smaller than those of PEEK and PET, indicating a very fast crystallization of PTFE.