Polydopamine-Enabled Surface Modification to Improve the Dielectric Property of Aramid Fiber/Epoxy Composites for Insulation Rod

Abstract

The poor interfacial adhesion between aramid fiber and epoxy resin is the main issue affecting the dielectric properties of the aramid fiber-reinforced composite (AFRC). In this paper, the bioinspired polydopamine (PDA) coating method is used to modify the aramid fiber surface, which is already activated by plasma treatment. Various aramid fiber/epoxy composite samples are prepared, and the effects of the PDA concentration on the dielectric properties are studied. It is indicated that the interfacial bonding strength between the fiber and epoxy resin could be improved, thus contributing to higher mechanical strength and enhanced dielectric properties. Results show that the DC conductivity, dielectric constant and integration charge Q(t) of the modified composites are significantly reduced, while the dielectric breakdown strength is increased. Under an optimized dopamine concentration of 2 g/L, the breakdown strength is enhanced by 25.1%, while the charge accumulation rate is decreased by 46.5%. Meanwhile, the interfacial shear strength of the composite is increased from 29.5 to 65.2 MPa, showing great application potential in high voltage power equipment.