Degradation Behavior and Aging Mechanism of Decay-like Fractured GRP Rod in Composite Insulator

Decay-like fracture is a new type of fracture of composite insulator that is different from normal fracture and brittle fracture. The fracture surface of the glass fiber reinforced polymer (GRP) rod in the decay-like fracture is like rotten wood. There are punctures on the silicone rubber housing and abnormal temperature rise is detected on the composite insulator before fracture. However, the cause and aging mechanism of the decay-like fractured composite insulator is still unknown. In this paper, the degradation behavior of the corroded GRP rod in a composite insulator with abnormal temperature rise was studied. The basic features of the GRP rod were obtained by optical microscope, SEM and TGA. Eroded gap and dendritic shadow in parallel light were found on the GRP rod. Degradation of the epoxy resin, fracture of the glass fiber and failure of the resin-fiber interface leads to the formation of an eroded gap and decreases the GRP-rod transmittance. Chemical reactions in the corroded GRP rod were studied by XPS and FTIR. The reactions of ionic exchange and hydrolysis in the area of the dendritic shadow was weaker, but the oxidation under partial discharge was much stronger. The source of water is discussed and the aging mechanism of the GRP rod is revealed and divided into four stages; namely, deterioration of end fitting, hydrolysis and ionic exchange, oxidation of the epoxy resin, and rapid development. The speed of degradation of GRP rod increases stage by stage and the mechanical properties decreases sharply, which eventually leads to decay-like fracture of composite insulator.