The kinetic study of the curing reaction of mono- and di-epoxides obtained during the reaction of divinylbenzene and hydrogen peroxide with acid anhydrides

In this paper, the non-isothermal differential scanning calorimetry (DSC) was employed to investigate the cure process and to determine the kinetic parameters of the curing reactions of mono- and di-epoxides with maleic and glutaric anhydrides. The epoxides were obtained during the epoxidation process of commercially available divinylbenzene by using 60% hydrogen peroxide as the oxidant in the presence of organic solvents and magnesium oxide as the catalyst. It was found that the cure process of epoxides with maleic anhydride was described through higher values of enthalpy of polymerization (ΔHR) and lower temperatures of the cure initiation (Tonset), the peak maximum temperature (Tmax) and the final cure temperature (Tend). It can be considered to accelerate the rate of reaction and lead to an excellent network structure when maleic anhydride was used as curing agent. The kinetic analysis was firstly computed using a model free-estimation of the activation energy (Friedman, Ozawa-Flynn-Wall methods) and then the multivariate non-linear regression with a 6th degree Runge-Kutta process in a modified Marquardt procedure was employed to calculate the corresponding kinetic parameters (Ei, ni, Ai) using the nth-order reaction f(α). The unbranched three-step process of the nth-order reaction f(α) for each step was the best to describe the cure process of mono- and di-epoxide with acid anhydrides. The determined values of the activation energies were in the range 64.7-105.2 kJ/mol for epoxides/glutaric anhydride system and 64.7-82.7 kJ/mol when maleic anhydride was used as hardening agent.