Dielectric Behavior and Molecular Dynamics Simulation of Multifunctional Epoxy Resin Blends: Structure–Property Relationship

In this paper, the effects of functionality on the dielectric behaviors of various epoxy resin blends are studied and compared. With the increase of functionality, more crosslinking points are introduced, which leads to the increase of β-relaxation strength of epoxy resin. However, interaction among molecules is also enhanced and the cross-linked network becomes more compact, resulting in the suppression in α-relaxation strength and charge migration process. Therefore, incorporating appropriate amounts of multifunctional modifier into the traditional diglycidyl ether of bisphenol A (DGEBA) could improve the dielectric properties at higher temperatures. The epoxy resin modified by tri-functional p-aminophenol triglycidyl ether (TGAP) with 5% content (S-305) shows the lowest dielectric loss. Compared with the DGEBA, tanδ is reduced by 21.57%, 28.21%, and 26.52% for the S-305 at room temperature, 60 and 120 °C, respectively. Molecular dynamics simulation is carried out to clarify the structure-property relationship. The increased crosslinking points decrease fractional free volume (FFV) of the cross-linked network and mean square displacement (MSD) of the molecular chains, which contribute to the improvement of dielectric polarization behavior, especially at higher temperatures.