Studies of cure kinetics and chemical resistance of the cured products of DGEBA with aromatic diamines

An investigation is conducted into the non-isothermal kinetics of the curing reaction of diglycidyl ether of bisphenol A (DGEBA) epoxy resin with two novel aromatic diamines, 4,4'-diaminostilbene (DAS) and 4,4'-diaminoazobenzene (DAAB), as curing agents. Kinetics analysis of the curing reaction of DGEBA with two different concentrations (29 wt% =0.13 mol% and 19 wt%=0.09 mol%) of the curing agents was studied using non-isothermal differential scanning calorimetry (DSC) technique. Two methods (Ozawa and Kissinger) for analysis of the scanning DSC data were applied to calculate the kinetic parameters and compared with kinetic parameters obtained from isothermal DSC tests using Kamal method. Activation energies in the range of 52.5-59.5 kJ/mol were obtained for both DGEBA/curing agent systems. The water absorption and resistance of the cured products against solutions of H2SO4 and NaOH were also studied. Water uptake curves for both systems are similar. Weight loss for the cured products of DGEBA/DAS and DGEBA/DAAB systems in 50% solution of NaOH reached the equilibrium values of 0.2% and 0.5%, respectively after about 80 h and weight gain of the cured products of both systems in 30% solution of sulphuric acid reached the equilibrium value of about 0.3% after about 40 h. The cured products from DGEBA/DAS system showed less weight loss during thermal degradation at 250 degrees C but their water uptake was much higher.