Curing Behavior and Heat Resistance of Epoxy Resin Cured by Diamine with Heterocyclic Ring

Benzobisoxazole-containing diamine, 2, 6-Di(p-aminophenyl)benzo [1.2.5.4] bisoxazole (DIABO), was derived from diaminodihydroxybenzene dihydrochloride (DADHB·2HCl) and p-aminobenzoic acid (PABA) via condensation reaction. The structure of DIABO was confirmed through FTIR, ¹ H NMR, x-ray diffraction (XRD) and UV-Vis spectra, etc. The curing behavior of diglycidyl ether of bisphenol A (DGEBA) and DIABO as curing agent was investigated using differential scanning calorimetry (DSC). Dynamic kinetic parameters were calculated by using Kissinger's and Ozawa's methods, respectively. The glass transition temperatures of cured system, DGEBA/DIABO, DGEBA/DIABO/DDS (cured with mixtures of DIABO and diaminodiphenyl sulfone (DDS)) and DGEBA/DDS, were 213°C, 193°C and 175°C, respectively, based on torsional braid analysis (TBA). The integral procedure decomposition temperatures (IPDT) were 885°C, 734°C and 604°C, respectively. Char yields at 572°C were 39.82%, 24.66% and 21.57%, respectively. Hydrothermal ageing of cured resins was also discussed. All results showed that DIABO as curing agent can remarkably improve the thermal and hydrothermal resistance of the cured epoxy resins.