Effect of Large Linking Groups on the Electrical and Thermal Properties of Aniline Cured Epoxy Resins

Epoxy resin (EP) is one of the most important types of polymers used in electronic and electrical equipment, assuming the role of support and insulation. However, with the increasing voltage levels and loads for power equipment and power systems, the center temperature of critical equipment rises, and failure of insulating materials under the dual action of electric and thermal fields becomes an important challenge. In this paper, the benzene ring structure was introduced into the EP by three aniline curing agents, which made the EP chain segments have a rigid structure to enhance its thermal stability. Additionally, the large linking functional groups were introduced in the middle of the two benzene rings to explore their effects on the electrical and thermal properties of the epoxy. The introduction of the benzene ring resulted in the glass transition temperature (Tg) of the EPs all reaching above 150°C. In addition, the introduction of cyclohexane resulted in the highest Tg of 192.3 for the 1,1-bis (4-aminophenyl) cyclohexane (11CHA) cured EP. For 11CHA cured EP and 4,4'-(propane-2,2-diyl) dianiline (44DAM) cured EP, the incorporation of cyclohexane and isopropyl group resulted in the enhancement of both DC resistivity and DC breakdown strength of the EP materials compared to 4,4'- diaminodiphenylmethane (44DDM) cured EP. The reason for this was explored using molecular dynamics simulations. This is due to the fact that the large linked functional groups increased the chain spacing by hindering the stacking effect of benzene rings and inhibit the transfer of π electrons between benzene rings. This work contributes to the development of high Tg, high resistance and high breakdown strength EP materials for electrical applications.