Effect of Triphenylphosphine on the Cure Reaction and Thermal Stability of Diglycidyl Ether of Bisphenol A-based Epoxy Resin

AsulPhone-nitrogen containing heterocyclic ring, tetraphenylthiophene diamine (TPTDA) was prepared and used as curing agent together with triphenylphosphine (PPh3) to cure diglycidyl ether of a bisphenol A-based epoxy resin (DGEBA). Activation energies (Ea ) for curing DGEBAITPTDA and DGEBA/ TPTDAlPPh3 systems by using DSC data and Kissinger equation are 66.6 kJ/mol and 76.6 kJ/mol, respectively. The increase in Ea can be due to polymerization of DGEBA by PPh3 and formation of larger molecules with reduced mobility before curing with TPTDA to start. Ea of thermal degradation of cured DGEBAITPTDA and DGEBAlTPTDAlPPh3 systems by using TGA data and Horowitz-Metzger equation are 56.0 kJ/mol and 128.0 kJ/mol, respectively. The onset decomposition temperature and the char yield have increased from 230°C to 320°C and from 21.4% to 32.5% for the above systems, respectively. The addition of PPh3 to the curing mixture enhanced char formation and improved thermal stability of the resin.