In an earlier work the author had studied the degradation kinetics of polyethylene terephthalate (PET), polytrimethylene\r\nterephthalate (PTT), and polybutylene terephthalate (PBT) under nonisothermal conditions in air and N2 at heating rates of\r\n5, 10, 15, and 20?C/min. In this paper the kinetic degradation parameters of PET, PTT, and PBT were estimated using the Coats-\r\nRedfern method for two different weight loss regions ranging from 2ââ?¬â??8% (Zone I) and 8ââ?¬â??40% (Zone II). A comparative analysis\r\nof the enthalpy-entropy compensation effect for these polyesters in air and N2 is presented. A linear relationship was found to exist\r\nbetween entropy and enthalpy values. The following criteria were applied to establish an enthalpy-entropy compensation effect and\r\nto check the presence of an isokinetic temperature: (a) Exnerââ?¬â?¢s plot of log k3T1 versus log k3T2 , and (b) Krug et al. linear regression\r\nof ?H versus ?G. By the use of the latter two methods, varying isokinetic temperatures were obtained. These temperatures were\r\nnot in the range of the experimental work conducted, indicating that these systems do not display compensation phenomena.
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