Improved dielectric and mechanical properties of aramid fiber reinforced epoxy resin composites by polyethyleneimine grafting

In this paper, aramid fiber surface is modified by polyethylenimine (PEI) grafting with abundant -NH2 active groups after plasma surface activation treatment. Various aramid fiber reinforced epoxy resin composites (AFRC) are prepared. The effects of PEI grafting on the dielectric and mechanical properties of AFRC are studied. Obtained results show that PEI is successfully grafted onto aramid fiber surface as evidenced by x-ray photoelectron spectroscopy results, and effectively improves the interfacial properties between aramid fiber and epoxy resin. The dielectric properties, including DC conductivity, dielectric constant, and integration charge Q(t) of the composites are improved after optimized modification parameters, and the breakdown strength is increased by up to 23%. These are attributed to the decrease in interfacial polarization and the increase in interfacial bonding strength. Furthermore, the interfacial shear strength of AFRC is increased from 29.5 MPa to 63.7 MPa, which further verifies the improvement of interfacial performance. This paper provides a way to improve the dielectric and mechanical properties of AFRC, which is of great significance for its application in high voltage power equipment.