Effect of the segmental mobility restriction on the thermoset chemical kinetics

The cure kinetics of an epoxy-amine commercial thermoset system have been investigated with the isothermal differential scanning calorimetry technique. In particular, a kinetic study has been performed in the glass-transition zone, in which diffusion phenomena compete with the chemical transformations and the overall reaction rate is partially slowed by the reduced segmental chain mobility. A generalized form of the Vorgel equation has been formulated to account for the effect of the increasing glass-transition temperature on the chain mobility and, therefore, on the overall reaction rate. The kinetic model has been expressed with two factors representing the chemical reaction rate and the segmental mobility reduction. As the main result, the activation energy relative to the diffusion phenomena has been found to be very low, having a value of 42.5 K ? 0.356 kJ/mol, which is compatible only with the small-angle rotation of the reactive unit.