PPR pure plastic pipe, widely used in modern construction, is directly affected by changes in its physical properties after aging, impacting the safety and lifespan of the piping system. Aging is a process of irreversible physicochemical changes in materials under environmental influences. The aging of PPR pure plastic pipe primarily stems from the combined effects of ultraviolet radiation, temperature fluctuations, chemical corrosion, and mechanical stress. These factors damage its molecular structure, leading to a significant decline in performance.
Ultraviolet radiation is one of the core factors inducing the aging of PPR pure plastic pipe. The energy of ultraviolet rays in sunlight is sufficient to break the chemical bonds in the PPR molecular chain, causing the originally stable long-chain polymer to break into shorter chain fragments. This process initially manifests as "powdering" on the pipe surface—after the surface molecular chains break, small molecules lose their binding force and detach, forming a visible powdery substance. As exposure time increases, the molecular chain breakage extends inward, leading to a deterioration in the overall physical properties of the pipe. For example, the originally tough pipe gradually becomes brittle, its pressure resistance is significantly reduced, and problems such as surface cracking and leakage may even occur.
Temperature fluctuations also have a significant impact on the aging of PPR pure plastic pipe. While PPR material possesses a certain degree of temperature resistance, prolonged exposure to low-temperature environments (such as outdoor conditions in northern winters) or frequent freeze-thaw cycles can cause stress within the pipe due to the expansion of water upon freezing, leading to damage to the molecular chain structure. Even if the pipe's appearance remains unchanged after freeze-thaw cycles, irreversible damage has occurred to its internal microstructure, manifesting as reduced toughness and increased brittleness. Furthermore, if the pipe continuously transports hot water exceeding 70°C, the high temperature accelerates the thermal motion of the molecular chains, gradually softening the material and reducing ring stress (the pipe's ability to withstand internal pressure), ultimately leading to deformation or cracking.
Chemical corrosion is another significant cause of aging in PPR pure plastic pipes. If corrosive substances (such as waste gases from chemical plants, acidic or alkaline substances in the soil) are present around the pipe, these media can diffuse to the pipe surface and react chemically with the PPR molecules. For example, strong oxidizing substances may trigger oxidative degradation of the molecular chains, resulting in a rough, discolored, and even porous pipe surface; while certain solvents may cause the pipe to swell, altering its dimensional stability and affecting the sealing of connections.
Mechanical stress accelerates the aging process of PPR pure plastic pipes. During installation or use, pipes may be subjected to external forces such as bending, compression, and vibration. If the stress exceeds the material's tolerance limit, it can cause molecular chain breakage or lattice distortion. For example, if exposed pipes are not securely fixed, long-term vibration may lead to loosening at joints or cracks in the pipe body; while if concealed pipes are buried too shallowly, heavy objects on the ground may cause deformation, making areas of internal stress concentration more prone to aging.
Aging PPR pure plastic pipes exhibit multi-dimensional deterioration in physical properties. Visually, the pipe may change from smooth and uniform to rough, bubbly, or cracked; mechanically, tensile strength, flexural strength, and hardness decrease significantly, and pipes that could previously withstand high pressure may break under slight external forces; furthermore, the air and water permeability of aging pipes may change, increasing the risk of water contamination.
To slow down the aging of PPR pure plastic pipes, a comprehensive approach is needed, addressing material selection, installation standards, and proper use and maintenance. When purchasing, prioritize high-quality pipes with added antioxidants, light stabilizers, and other additives, as these components can effectively absorb ultraviolet rays or inhibit oxidation reactions. Avoid exposed installation; if exposed installation is necessary, wrap the pipes with an insulation layer or reflective film to reduce the impact of direct ultraviolet radiation and temperature fluctuations. During use, regularly check the condition of the pipes, paying particular attention to joints and bends, and replace them promptly if signs of aging are found.
