Effect of the segmental mobility restriction on the thermoset chemical kinetics

Cure kinetic of an epoxy-amine commercial thermoset system has been investigated by the isothermal differential scanning calorimetric technique. In particular, the kinetic study has been performed in the glassy transition zone where diffusion phenomena become competing with the chemical transformations and the overall reaction rate is partially slowed down by the reduced segmental chain mobility. A generalized form of the Vogel equation has been formulated to account for the effect of the glassy transition temperature increasing on the chain mobility and, hence, on the overall reaction rate. The kinetic model has been expressed by means of two factors representing the chemical reaction rate and the segmental mobility reduction respectively. As main result, the activation energy Es relative to the diffusion phenomena has been found very low showing the value of 42.5 K„l0.356 kJ/mol, which is compatible only with small-angle rotation of the reactive unit.