Performances of hydrophobic cycloaliphatic epoxies exposed to acidic fog under DC stress

Hydrophobic cycloaliphatic epoxy (HCEP) has been used as outdoor insulation material to maintain good electrical performances under multiple stresses, in which acidic attack to this kind of materials has been causing concern in recent years. To study the performances of HCEPs under acid rain, a new acid fog test method has been established and an acid fog chamber was constructed. During the 1000 h acidic rain test, contact angles of the HCEPs decreased and the less hydrophobic samples had higher leakage currents. Increase of the surface roughness and diameters of the micro holes have been observed by AFM and SEM, and oxidation of surface groups was analyzed by FTIR. Resistance to tracking and erosion remained good after the 1000 h test. The results showed that HCEPs exhibited good outdoor insulation performances in acidic fog under DC stress.