Kinetic study of the novolac resin curing process using model fitting and model-free methods

The curing behavior of novolac type phenolic resin was studied through differential scanning calorimetry (DSC) using model fitting and model-free (isoconversion) kinetic methods. For the model fitting kinetic study, a piecewise fitting approach was developed to describe the dependence of cure reaction rate on temperature and curing degree. The piecewise model displayed excellent modeling ability. In the model-free kinetic study, Friedman, and Kissinger-Akahira-Sunose methods were used to calculate the curing activation energy. The dependence curve of activation energy on conversion and the piecewise model fitting results both displayed a change in the kinetic reaction mechanism from the autocatalytic to n-order regime. According to the isothermal prediction results, the model-free kinetic methods show much better prediction ability, compared with the model fitting methods. Also, Friedman and Kissinger-Akahira-Sunose methods were found to show similar results in predicting the isothermal curing behavior of this novolac resin.