Modified method for obtaining the critical cooling rate for vitrification of polymers

Abstract

Due to the relevance of the critical cooling rate, Rc, for glasses, Barandiarán and Colmenero (BC) developed a method for calculating Rc as a function of the crystallization temperature on cooling obtained from thermal analysis. The critical cooling rate is obtained by the extrapolation method to conditions of infinity undercooling. However, for polymers, there is a strong reason for modifying the original BC method. In this case, the extrapolation must be extended only to the undercooling associated to the glass transition temperature, Tg, because no crystallization can occur below this temperature. Following this modified method (MBC) proposed by the present authors, the critical cooling rate for PP, PEEK, P10MS and PET were determined. The results showed that the new values are much lower than those obtained by the original BC method.