Aging Failure Mechanism of Graft Modified Polypropylene Cable Insulation

The performance of polypropylene (PP) insulation material used in high-voltage power cables is crucial for ensuring the safe and reliable operation of the cables. To deeply understand the aging and failure mechanisms of graft-modified PP cable insulation, accelerated aging experiments were conducted on the cable insulation layer. The ac breakdown field strength and elongation at break were tested, the density functional theory calculations were performed on the graft-modified PP molecular chains, and further analyses of the physicochemical properties, such as the microstructure and molecular structure changes of the insulation material, were conducted. The results show that when the insulation material reaches the aging failure point, the breakdown performance significantly decreases, the perfection of the crystalline region structure of PP deteriorates with aging time, the content of C=O carbonyl groups significantly increases with aging time, and thermal-oxidative aging accelerates the destruction of PP spherulites. The appearance of oxidation products, structure loosening, and decreased crystallinity during the aging process are the main reasons for the reduction in mechanical performance and breakdown strength. This study provides new insights into the research on the aging mechanism, structure, and performance relationship of PP cable insulation and has important guiding significance for the design of PP insulation materials.