Abstract
The thermotropic liquid crystal copolyester P-BPA2.5 and P-BPAF2.5 with low melting temperature and high glass transition temperature were obtained by introducing 2.5mol% bisphenol A (BPA), bisphenol AF (BPAF) and terephthalic acid (TA) receptively into the molecular chain of poly (oxybenzoate-co-oxynaphthoate). The isothermal and nonisothermal degradation behavior of the two copolyesters P-BPA2.5 and P-BPAF2.5 were studied by thermo-gravimetry analysis (TGA) under nitrogen atmosphere. The degradation kinetics of the copolyesters under dynamic and isothermal heating conditions was evaluated byKissinger-Akahira-Sunose (KAS) and iso-conversional methodrespectively. Results showed that the activation energy (E) values followed the order P-BPAF2.5>P-BPA2.5 under dynamic heating atmosphere. However, the P-BPA2.5 showed a better thermal stability as compared with P-BPAF2.5 under isothermal heating conditions. The differences of degradation mechanism between the two copolyesters may be a reason for this phenomenon, which was discussed in detail in the text.
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