PVC wire does indeed exhibit performance degradation under prolonged exposure to strong ultraviolet (UV) radiation. This process involves physicochemical changes in the material's molecular structure, accompanied by a significant decline in appearance, mechanical properties, and electrical properties. The degradation mechanism can be analyzed from four aspects: the principle of UV action, the material degradation process, environmental synergistic effects, and practical application examples.
UV damage to PVC wire begins with a photo-oxidation reaction. The carbon-carbon and carbon-hydrogen bonds in the PVC molecular chain absorb light energy under UV radiation (wavelength 200-400nm). When the photon energy exceeds the chemical bond energy, the molecular chain breaks, generating free radicals. These free radicals combine with oxygen in the air to form peroxides, which further decompose into polar substances such as aldehydes and ketones, leading to a decrease in the material's internal insulation performance. For example, the PVC insulation layer, originally used for current isolation, may form conductive channels due to the accumulation of polar substances, increasing the risk of leakage. Furthermore, UV radiation accelerates the migration and oxidation of plasticizers in PVC, causing the wire surface to gradually harden and become brittle, losing its original flexibility.
The material degradation process is accompanied by significant changes in appearance. PVC wire exposed to strong ultraviolet (UV) radiation for extended periods will gradually fade, turning from its initial color to yellow or white. This is due to the absorption of light in the visible light region caused by the conjugated double bonds formed by molecular chain breakage. As the reaction intensifies, cracking or powdering may occur on the wire surface, with crack depths reaching millimeters. The powdery flaking material consists of degraded polymer fragments. These changes not only affect aesthetics but also directly weaken the wire's mechanical strength. For example, the originally flexible PVC sheath may become brittle and break upon slight bending, exposing the internal conductors and posing a safety hazard.
Environmental factors exacerbate the destructive effects of UV radiation. High temperatures accelerate the thermal degradation process of PVC, increasing the rate of molecular chain breakage several times over. Humidity further decomposes the polymer structure through hydrolysis, causing the wire to absorb water and swell, reducing its insulation resistance. In coastal or industrially polluted areas, salt spray and chemical gases in the air can synergistically enhance UV radiation, accelerating the corrosion and aging of the PVC surface. For example, a coastal photovoltaic project using ordinary PVC conduits experienced pipe cracking after three years, leading to water ingress and short circuits in the cables. This forced the entire array to shut down for repairs, resulting in losses exceeding ten million yuan. This case vividly illustrates the challenges environmental factors pose to the weather resistance of PVC wires.
In practical applications, the degradation of PVC wires can trigger a chain reaction. Deterioration in insulation performance can lead to leakage, short circuits, and even fires; reduced mechanical strength can cause the wires to break under vibration or external force, interrupting circuit connections; and cosmetic damage can affect the overall sealing of equipment and accelerate the aging of internal components. For instance, in outdoor lighting systems, PVC wires exposed to prolonged sunlight may develop cracked insulation, allowing rainwater to infiltrate and causing frequent lamp malfunctions. In industrial automated production lines, brittle PVC sheaths may crack due to mechanical friction, exposing wires that could become entangled in moving parts, causing equipment downtime.
To slow down the UV degradation of PVC wires, the industry typically employs multiple protective measures. In terms of material modification, adding UV-resistant additives (such as hindered amine light stabilizers) can absorb or shield ultraviolet rays, reducing their damage to molecular chains. Surface treatment technologies (such as fluorocarbon coatings) can form a dense protective film, blocking the contact between ultraviolet rays and oxygen. Optimized structural design (such as increasing wire wall thickness) can reduce the amount of light energy absorbed per unit area. In addition, rationally planning the wire layout (such as avoiding direct sunlight), using sunshades, or selecting alternative materials with stronger weather resistance (such as cross-linked polyethylene) are also effective methods.
The performance degradation of PVC wire under long-term exposure to strong ultraviolet radiation is the result of the combined effects of material properties and environmental factors. From photo-oxidation reactions at the molecular level to mechanical failure at the macroscopic level, this process not only shortens the lifespan of the wire but may also cause safety hazards. Therefore, in outdoor or high-UV environments, measures such as material modification, protective design, and regular testing are necessary to ensure the long-term stable operation of PVC wire.
