Thermal decomposition kinetics of thermotropic copolyesters made from trans-p-hydroxycinnamic acid and p-hydroxybenzoic acid

摘要

A series of thermotropic copolyesters were synthesized by direct thermal melt polycondensation of p-acetoxybenzoic acid (PHB) with trans-p-acetoxycinnamic acid (PHC). The dynamic thermogravimetric kinetics of the copolyesters in nitrogen were analyzed by four single heating-rate techniques and three multiple heating-rate techniques. The effects of the heating rate, copolyester composition, degradation stage, and the calculating techniques on the thermostability and degradation kinetic parameters of the copolyesters are systematically discussed. The four single heating-rate techniques used in this work include Friedman, Freeman-Carroll, Chang, and the second Kissinger techniques, whereas the three multiple heating-rate techniques are the first Kissinger, Kim-Park, and Flynn-Wall techniques. The decomposition temperature of the copolyesters increases monotonically with increasing PHB content from 40 to 60 mol %, whereas their activation energy exhibits a maximal value at the PHB content of 50 mol %. The decomposition temperature, activation energy, the order, and the frequency factor of the degradation reaction for the thermotropic copolyester with PHB/PHC feed ratio of 50/50 mol % were determined to be 374degreesC, 408 kJ/mol, 7.2, and 1.25 X 10(29) min(-1), respectively. (C) 2003 Wiley Periodicals, Inc. I Appl Polym Sci 91: 445-454, 2004. [References: 20]