Non-isothermal cure and decomposition kinetics of epoxy-imidazole systems

Non-isothermal curing kinetics of a tetra functional epoxy resin with imidazole-based curing agents was investigated by differential scanning calorimetry (DSC), and decomposition of the cured compounds was studied by thermogravimetric analysis. N,N,N',N'-tetraglycidyl-4, 4'diaminodiphenylmethane (TGDDM) was cured with three types of tertiary amine curing agents including 1-methyl imidazole (MI), 2-methyl imidazole (2MI) and 2-ethyl 4-methyl imidazole (EMI). These systems exhibited cure initiation at around 70-90 A degrees C by DSC. 2-methyl imidazole and 2-ethyl 4-methyl imidazole showed two cure initiation profiles, while the 1-substituted counterpart, MI, showed a single cure initiation profile by DSC. The Kissinger equation was applied to calculate the apparent activation energy for epoxy-imidazole cure reactions. The rate constants and the pre-exponential factor were also determined. The activation energy varied from 59 to 65 kJ mol(-1) for the systems. The Flynn-Wall-Ozawa iso-conversional approach was used to elucidate the activation energies at different extents of conversion during the cure reactions. The cured systems are found thermally stable up to 250 A degrees C. Decomposition kinetics of cured networks was studied using Kissinger equation and Flynn-Wall-Ozawa iso-conversional approach. The cured resins were analyzed for the glass transition temperature and compared with that of a conventional amine-cured system.