Curing Degree Dependence of Dielectric Properties of Bisphenol-A-Based Epoxy Resin Cured With Methyl Hexahydrophthalic Anhydride

The dielectric properties of epoxy resin mainly depend on its microstructures, especially the curing degree. In this article, the reaction process of diglycidyl ether of bisphenol A (DGEBA)/methyl hexahydrophthalic anhydride (MHHPA) system is studied by differential scanning calorimetry, and samples with different curing degrees are prepared by regulating the curing temperature and time. The evolution of microstructure during epoxy resin crosslinking is simulated by molecular dynamics simulation. It is found that the effect of the curing degree on dielectric properties can be attributed to the distribution of polar groups and the mobility of chain segments, while the contribution of free volume is insignificant. With the increase of the curing degree, the epoxy group at the chain end is transformed into an ester group with weaker polarity, as well as the epoxy molecular segments are combined more closely and the mobility of molecules decreases, resulting in an improvement in the dielectric properties of the epoxy resin.