Investigation of kinetic triplets for thermal degradation of thermally cured vinyl ester resin systems and lifetime predictions

The thermal degradation of thermally cured vinyl ester resin systems is studied for different heating rates. The kinetic triplets, the activation energy, pre-exponential factor and the reaction model f(alpha) for the different reaction extent of conversions (alpha) are estimated using advanced isoconversional methods. Although the thermal degradation curves show the degradation occurs as a single stage, the kinetic parameters suggest the otherwise. The activation energy remains constant for alpha = 0.3-0.575 but varies during the initial and final stages of conversion. Similarly, the pre-exponential factor shows considerable variation between the lower and higher reaction extent (alpha) values. This shows the complexity in the reaction. The probable reaction mechanism that the degradation follows has been explained. The complexity of the thermal degradation and the changes in reaction model f(alpha) over different reaction extent has been related. The appropriate working temperature for different thermal lifetime of the cured vinyl ester resin system for the failure of conversion alpha = 0.2 has been predicted under the nitrogen atmosphere.