Reaction kinetics with diffusion control mechanisms are investigated to model the later-stage cure progressing in a co-cured epoxy network that was formed by blending and heating bisphenol-A polycarbonate (PC) with tetraglycidyl-4,4’-diaminodiphenylmethane (TGDDM), which together were cured with an aromatic amine hardener. Our earlier studies have demonstrated that the epoxy reacts not only with the amine hardener but also with the PC polymer to eventually form a homogeneous network, and that the initial polymerization and cure for this system can be described by an n-th order kinetics. Using the free volume theory, the effect of diffusion control on the kinetics in the gel/vitrified regimes has been modeled successfully, and a more precise kinetic description for the PC/TGDDM/DDS network systems in the full cure range is resulted.