Curing of diglycidyl ether of bisphenol A by aromatic diamines and thermalbehaviour of cured resins

The curing of diglycidyl ether of bisphenol A (DGEBA) with N,N'-bis-(4-amin ophenyl)-1,4-benzoquinone diimine (Q) was investigated as a function of dia mine concentration. The glass transition temperature (T-g) of the cured res in was determined by DSC. The maximum value of T-g (170"C) was obtained whe n a stoichiometric amount of Q was used. At low phr of diamine T-g was very low. This may be due to incomplete curing of DGEBA. The activation energy of curing as determined by multiple heating rates was found to be 102 kJ mo l(-1). The curing of DGEBA with mixed diamines, i. e. Q and 4,4'-diaminodip henylsulfone (DDS) (stoichiometric amount), was also investigated. A decrea se in the onset temperature of curing and a broadening of the exotherm were observed when mixed diamines were used. The cured resins were stable up to 330 degrees C and decomposed in a single step. The char yield at 800 degre es C of DGEBA cured with Q was high (29%).