How can the aging resistance of thermoplastic low-smoke halogen-free flame retardant cable material be improved?
Release Time : 2025-11-03
Thermoplastic low-smoke halogen-free flame retardant cable material is widely used in rail transit, new energy, and high-rise buildings due to its environmental friendliness and safety. However, its aging resistance is affected by factors such as the large amount of inorganic flame retardants and poor material compatibility, often facing challenges such as thermal aging, photoaging, and mechanical stress aging. Improving its aging resistance requires a comprehensive approach from multiple dimensions, including material formulation optimization, additive synergy, process improvement, and structural reinforcement.
Formulation optimization is fundamental to improving aging resistance. Traditional thermoplastic low-smoke halogen-free flame retardant cable material uses polyethylene or ethylene-vinyl acetate copolymer as the base material, filled with large amounts of inorganic flame retardants such as aluminum hydroxide and magnesium hydroxide. However, these flame retardants are prone to phase separation from the base material, leading to increased internal defects and accelerated aging. By introducing compatibilizers, such as maleic anhydride-grafted polyethylene (PE-G-MAH), the interfacial bonding between the flame retardant and the base material can be significantly improved, reducing microcracks caused by phase separation, thereby enhancing the material's thermal stability and anti-aging performance. Furthermore, the synergistic flame-retardant technology of nano-magnesium hydroxide and red phosphorus can reduce the amount of flame retardant filler, minimizing negative impacts on the material's mechanical properties. Simultaneously, the size and surface effects of nanoparticles enhance the material's UV resistance.
Synergistic additives are key to improving aging resistance. The addition of UV absorbers (such as UV-531) and titanium dioxide effectively shields against UV rays, reducing the damage to the material's molecular chains caused by photoaging. Titanium dioxide lowers the material's surface temperature by reflecting sunlight, further slowing down the thermal aging process. Optimizing the antioxidant ratio is equally important. The combined use of primary antioxidants (such as hindered phenols) and secondary antioxidants (such as phosphites) can synergistically inhibit oxidation chain reactions, extending the material's service life. For example, increasing the content of antioxidants and crosslinking aids can inhibit chain initiation and chain propagation reactions during aging, ensuring that the change in tensile strength and elongation at break after aging at 100℃ for 168 hours is controlled within ±30%.
Process improvement is an important means of enhancing aging resistance. Irradiation crosslinking technology uses high-energy rays to form a three-dimensional network crosslinking structure in the material's molecular structure, significantly improving the material's heat resistance and mechanical strength. Companies like Lesso, using irradiation crosslinking technology to produce low-smoke halogen-free cables, achieve temperature resistance ratings of 105℃-125℃, far exceeding the 70℃ of ordinary cables, meeting the requirements of harsh environments such as high temperatures and extreme cold. Furthermore, optimizing the mixing process to ensure uniform dispersion of flame retardants and avoid material degradation caused by localized overheating is also key to improving aging resistance. High-pressure, low-temperature extrusion processes can reduce the thermal history of materials during processing, lowering the risk of molecular chain breakage and further improving material performance.
Structural reinforcement is an effective supplement to improving aging resistance. Addressing the poor heat deformation resistance of thermoplastic low-smoke halogen-free flame retardant cable material, the material formulation can be adjusted, such as reducing the proportion of high-VA content EVA or introducing POE grafted compatibilizers and toughening agents, to improve the material's heat deformation resistance and crack resistance. For outdoor cables, the addition of weather-resistant antioxidants and UV-resistant additives can significantly improve the material's stability at extreme temperatures (e.g., -40℃ to 125℃), preventing cracking caused by thermal expansion and contraction. Furthermore, a multi-layered sheath design, such as an inner flame-retardant layer combined with an outer mechanical protective layer, can form a flame-retardant barrier, slowing the combustion rate and reducing the aging and corrosion of the material by the external environment.
Improving the aging resistance of thermoplastic low-smoke halogen-free flame retardant cable material requires synergistic optimization of formulation, additives, processes, and structure. By introducing compatibilizers, nano-flame retardants, and high-efficiency additives, combined with advanced processes such as radiation crosslinking and low-temperature extrusion, and supplemented by a multi-layered structural design, the material's resistance to thermal aging, photoaging, and mechanical stress aging can be significantly improved, thus meeting the stringent requirements for long-term stability of cable materials in high-end applications.