Mechanism and kinetics of epoxy-amine cure studied by differential scanning calorimetry

The isoconversional kinetic analysis has been applied to nonisothermal DSC data on the cure of an epoxynovolac resin. The process reveals a dependence of the activation energy (E(alpha)) on conversion (alpha). The shape of the dependence has been interpreted in the terms of the reaction mechanisms. It has been found that the model d alpha/dt = (k(1) + alpha(m)k(2))(1 - alpha)(n) used for the kinetically controlled cure gives rise to the dependence of E(alpha) on alpha similar to the experimentally found one. To completely describe the diffusion-controlled cure, the effect of both T and alpha on the change in diffusivity has been taken into account. The equation for the specific rate constant of diffusion, k(D)(T,alpha) = D-o exp(-E(D)/RT + K alpha), has been induced. Its use allows us to obtain a model dependence of E(alpha) on alpha closely matching the experimental one. A technique of predicting isothermal cure from the sole dependence of E(alpha) on alpha has been considered.