Thermodynamic aspects of degradation with particular reference to unsaturated polyester resins

Abstract

Like the concept of ceiling temperature, which allows the prediction of when a depolymerisation reaction can occur from the thermodynamic point of view, it is pointed out that degradation reactions other than depolymerisation can be treated in an analogous manner. Since, in many cases, the required thermodynamic data are not available, approximate values can be obtained by calculation from increments, which is valid for gas phase reactions. Likewise, an approximate correction for physical states other than gaseous can be introduced. Calculations on the basis of increments are particularly useful because the increments of parts of the molecule which are not involved in the reaction process do not occur explicitly in the calculation. Thus, for certain types of reaction, typical thermodynamic data can be obtained. In this paper thermodynamic data of some typical reactions which are of importance in the field of the thermal degradation of unsaturated polyester resins are calculated. The results are compared with experimental results obtained from previously published research in the field of polyesters.