Gelation and isoconversional kinetic analysis of lignin–phenol–formaldehyde resol resins cure

The curing process of a commercial phenolic (PF) and a lignin–phenolic (LPF) resol resins was studied by thermal mechanical analysis (TMA) and differential scanning calorimetry (DSC) techniques. The main conclusion that we wish to point out is that the gelation can be associated with an isoconversional principle. Thus, the curing kinetics analysis was performed applying non-isothermal DSC data to the isoconversional methods: Ozawa, Kissinger–Akahira–Sunose, and Friedman. These isoconversional methods allowed the determination of the dependence of activation energy and pre-exponential factor on the degree of curing for both resins. Friedman's method presents different results in relation to other methods, but both resins exhibit a similar tendency for kinetic parameters.