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International Journal of Chemical Engineering
Volume 2012 (2012), Article ID 782346, 8 pages
http://dx.doi.org/10.1155/2012/782346
Research Article

Enthalpy-Entropy Compensation in Polyester Degradation Reactions

Chemical Engineering Department, Kuwait University, P.O. Box 5969, 13060 Safat, Kuwait

Received 22 May 2012; Accepted 28 July 2012

Academic Editor: Adrian Schumpe

Copyright © 2012 Adam Al-Mulla. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In an earlier work the author had studied the degradation kinetics of polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and polybutylene terephthalate (PBT) under nonisothermal conditions in air and N2 at heating rates of 5, 10, 15, and 20°C/min. In this paper the kinetic degradation parameters of PET, PTT, and PBT were estimated using the Coats-Redfern method for two different weight loss regions ranging from 2–8% (Zone I) and 8–40% (Zone II). A comparative analysis of the enthalpy-entropy compensation effect for these polyesters in air and N2 is presented. A linear relationship was found to exist between entropy and enthalpy values. The following criteria were applied to establish an enthalpy-entropy compensation effect and to check the presence of an isokinetic temperature: (a) Exner’s plot of log versus log , and (b) Krug et al. linear regression of ΔH versus ΔG. By the use of the latter two methods, varying isokinetic temperatures were obtained. These temperatures were not in the range of the experimental work conducted, indicating that these systems do not display compensation phenomena.