How does the thermoplastic low-smoke halogen-free flame retardant cable material perform in terms of ozone resistance?
Release Time : 2025-12-01
As a core component of environmentally friendly cable sheaths and insulation layers, thermoplastic low-smoke halogen-free flame-retardant cable material's ozone resistance is a key indicator of its long-term outdoor stability. This type of material uses thermoplastic polyolefins (such as polyethylene and ethylene-vinyl acetate copolymers) as a matrix, and adds inorganic flame retardants (such as aluminum hydroxide and magnesium hydroxide), antioxidants, and UV absorbers to achieve characteristics such as zero hydrogen halide release, low smoke density, and low toxicity during combustion. Its excellent ozone resistance mainly stems from the synergistic effect of the material's inherent chemical structure and formulation design.
Thermoplastic polyolefin molecules do not contain unsaturated double bonds or aromatic ring structures. This saturated hydrocarbon chain structure gives it a natural resistance to ozone attack. Ozone, as a strong oxidant, mainly initiates chain oxidation reactions through addition reactions with unsaturated bonds or by abstracting hydrogen atoms at the allylic position. The saturated structure of polyolefins reduces reaction sites at the source, thereby lowering the risk of ozone corrosion. For example, polyethylene molecular chains consist only of carbon-carbon single bonds and carbon-hydrogen bonds, making them less prone to breakage or cross-linking in ozone environments, thus maintaining the material's physical integrity.
Antioxidant systems in the formulation design further enhance the material's ozone resistance. Antioxidants block the propagation of oxidation chain reactions by capturing free radicals or peroxides generated from ozone decomposition. For example, hindered phenolic antioxidants (such as antioxidant 1010) preferentially react with free radicals to generate stable phenoxy radicals, thereby terminating the oxidation process; phosphite antioxidants (such as antioxidant 168) prevent further decomposition into free radicals by decomposing peroxides. This synergistic effect of multiple antioxidant mechanisms significantly improves the material's stability in ozone environments.
While the addition of inorganic flame retardants may potentially affect ozone resistance, their negative impact can be minimized through appropriate surface modification. Flame retardant particles such as aluminum hydroxide and magnesium hydroxide have weak interfacial bonding with the matrix resin, easily forming micropores or stress concentration points, providing channels for ozone penetration. To address this, the industry employs silane coupling agents to surface-treat flame retardants, enabling them to form chemical bonds with polyolefin molecular chains, enhancing interfacial bonding, and reducing microporous defects. This modification not only improves the flame retardant properties of the material but also indirectly optimizes its ozone resistance.
The addition of ultraviolet (UV) absorbers provides an additional protective barrier for the material. Ozone readily decomposes under UV light, producing singlet oxygen and other reactive oxygen species, accelerating material aging. UV absorbers (such as benzotriazoles and benzophenones) absorb UV energy and convert it into heat, reducing the generation of reactive oxygen species and thus mitigating the synergistic damage caused by ozone and UV radiation. This "dual-resistance" design provides the material with more comprehensive protection in outdoor environments.
In practical applications, thermoplastic low-smoke halogen-free flame retardant cable material must undergo rigorous ozone aging tests to verify its performance. These tests are typically conducted at an ozone concentration of 50 pphm and a temperature of 40℃ ± 2℃, observing for surface cracks or fissures. Under these conditions, high-quality materials can maintain a smooth surface and prevent crack propagation for a long time, indicating that their ozone resistance meets industry standards. This superior performance makes them widely used in scenarios with extremely high safety requirements, such as urban rail transit, high-rise buildings, and new energy facilities.
Compared with other cable materials, thermoplastic low-smoke halogen-free flame retardant cable material has a significant advantage in ozone resistance. Traditional halogen-containing flame retardant materials (such as PVC) contain chlorine, which produces corrosive gases when burning, and their unsaturated structure is more susceptible to ozone attack; while thermoplastic elastomers (TPEs) have a certain degree of ozone resistance, but require the addition of special additives to achieve the same level. Thermoplastic low-smoke halogen-free materials, with their natural chemical stability and optimized formulation design, achieve a balance between ozone resistance, environmental friendliness, and safety, making them the preferred material in the modern cable industry.