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.