Curing kinetics of Benzoxazine-epoxy copolymer investigated by non-isothermal differential scanning calorimetry

Abstract

The reaction of epoxy novolac resin cured with benzoxazine resin (BA-a) was investigated under non-isothermal DSC at different heating rates. The kinetic parameters and the kinetic models of the curing processes of the benzoxazine-epoxy novolac mixtures were examined utilizing isoconversional methods, Flynn-Wall-Ozawa and Friedman methods. The benzoxazine-epoxy novolac mixture exhibits two dominant curing processes. The reaction 1 at lower temperature is attributed to the reaction among the benzoxazine monomers, while the reaction 2 corresponds to the formation of an etherification between hydroxyl group of polybenzoxazine and epoxide group or homopolymerization reaction of epoxide group at high temperature. The average activation energies of the reaction 1 and reaction 2 were determined to be 81 kJ mol-1 and 118 kJ mol-1, respectively. The autocatalytic kinetic model was found to be the best description of the investigated curing reactions. In addition, the predicted curves from our kinetic models fit well with the non-isothermal DSC thermogram. © 2010 Elsevier Ltd. All rights reserved.