Improved High-Temperature Dielectric Properties of DGEBA/MHHPA/DMP-30 System With Optimizing Postcuring Process

Anhydride-cured bisphenol-A epoxy resin is widely used in the support, insulation, and packaging components of electrical and electronic devices due to its excellent comprehensive performance. The dielectric properties of anhydride-cured epoxy resin depend on its crosslinking structure, which is not only related to the epoxy resin matrix, curing agent, and additives but also greatly affected by the conditions of the curing process. In this study, the high-temperature dielectric properties of diglycidyl ether of bisphenol A (DGEBA)/methyl hexahydrophthalic anhydride (MHHPA)/Tris(dimethylaminomethyl) phenol (DMP-30) system were investigated with respect to the postcuring time. The precuring process was set as 80 and 123 min at 100 °C to reach 80% and 90% curing degree of the system, respectively. On this basis, the postcuring process at 140 °C with the duration of 1, 2, 4, and 8 h was performed to compare the influences of postcuring time on high-temperature insulation performance. The results show that the high-temperature dielectric properties of epoxy resins with 90% precuring degree were generally better than those of 80% precuring degree, while the promotion effect of postcuring time on the high-temperature dielectric properties has a saturation trend. The dc conductivity, dielectric loss, and ac breakdown strength were evaluated comprehensively, and the optimal curing regime was finally selected as 123 min at 100 °C + 4 h at 140 °C.