How can the insulation layer structure of PVC insulated wire be improved to enhance its resistance to corona aging?
Release Time : 2026-03-03
PVC insulated wire is widely used in the electrical field due to its excellent insulation properties and cost-effectiveness. However, during long-term operation, the PVC insulation layer is susceptible to corona discharge, leading to surface deterioration, decreased insulation performance, and even breakdown failures. Therefore, improving the insulation layer structure of PVC insulated wire to enhance its resistance to corona aging is crucial for ensuring the long-term stable operation of the wire.
Corona aging is the result of the combined physical and chemical effects of partial surface discharge in insulating materials under a strong electric field. For PVC insulated wire, corona discharge causes electrolytic pits and cracks on the insulation layer surface, while also inducing oxidative degradation, making the material brittle and reducing its mechanical strength. Furthermore, the ozone and nitrogen oxides generated by corona discharge further accelerate material aging, creating a vicious cycle. Therefore, improving the corona aging resistance of PVC insulation requires a multi-dimensional approach, including material modification, structural design, and process optimization.
Material modification is fundamental to improving the corona resistance of PVC insulation. The corona resistance of PVC can be significantly improved by adding inorganic nanofillers, such as silica, alumina, or montmorillonite. Nanofillers possess high specific surface area and high activity, enabling them to disperse electric field intensity and suppress partial discharge development. Simultaneously, the interfacial interaction between the filler and the PVC matrix forms a dense structure, hindering the penetration of oxygen and ozone and slowing oxidative degradation. Furthermore, the introduction of a complex system of hindered phenolic antioxidants and phosphite-based auxiliary antioxidants can synergistically capture free radicals, terminate the oxidation chain reaction, and extend the material's service life.
In terms of structural design, employing a multilayer composite insulation structure is an effective way to enhance corona resistance. For example, extruding a layer of material with excellent corona resistance, such as cross-linked polyethylene or silicone rubber, onto the PVC insulation layer creates a gradient structure that is "soft inside and hard outside." The outer layer can withstand most of the electric field stress, reducing partial discharge in the PVC layer; the inner PVC layer provides good flexibility and processing performance. In addition, embedding a semi-conductive shielding layer within the insulation layer can uniformly distribute the electric field, preventing corona discharge caused by concentrated electric field, thereby improving overall corona resistance.
Process optimization is equally crucial for improving the corona resistance of PVC insulation layers. During extrusion, strict control of temperature and screw speed is essential to prevent overheating and decomposition of the material, which produces low-molecular-weight substances that reduce the corona resistance of the insulation layer. Simultaneously, optimizing the cooling process ensures rapid and uniform curing of the insulation layer, reducing internal stress and preventing corona discharge caused by stress cracking. Furthermore, employing radiation crosslinking or chemical crosslinking techniques can increase the crosslinking degree of the PVC insulation layer, forming a three-dimensional network structure and enhancing the material's resistance to electrical tracking and mechanical strength.
Surface treatment is a complementary method for improving the corona resistance of PVC insulation layers. Introducing hydrophobic groups or inorganic nanoparticles onto the insulation surface through plasma treatment or chemical coating techniques can reduce surface energy, decreasing the adhesion of water droplets and dirt, thereby inhibiting wet corona discharge. Simultaneously, the surface coating can form a physical barrier, blocking the erosion of oxygen and ozone, and delaying material aging. For example, using a fluoropolymer coating can significantly improve the corona resistance and weather resistance of the PVC insulation layer.
Long-term operating environment management is also a vital aspect of ensuring the corona resistance of PVC insulated wire. Avoiding prolonged operation of electrical wires in high-temperature, high-humidity, or strong electric field environments can effectively slow down corona aging. Simultaneously, regularly inspecting the insulation resistance and partial discharge of wires to promptly detect and address potential faults can extend their lifespan. For wires already showing signs of corona aging, maintenance can be performed by repairing the coating or replacing the insulation layer to restore their corona resistance.