Due to its unique molecular structure and processing properties, TPE elastomers are widely used in outdoor cables, automotive seals, and sports equipment. However, the unsaturated bonds in their molecular chains are susceptible to UV damage, leading to surface chalking, discoloration, and decreased mechanical properties. Through the scientific combination of UV absorbers, light stabilizers, inorganic pigments, and blending and modification techniques, TPE elastomers' UV resistance can be significantly enhanced, extending their outdoor service life.
UV absorbers are a core component of TPE anti-aging systems. Their mechanism of action is to selectively capture high-energy UV rays and convert them into harmless heat. Benzophenones and benzotriazoles are commonly used. Benzophenones dissipate UV energy through intramolecular hydrogen bond transfer, while benzotriazoles utilize their conjugated structure to absorb a wide range of UV light. Adding 0.5%-2% of benzotriazole absorbers to TPE formulations effectively blocks direct UV damage to the molecular chain, delaying yellowing and embrittlement. These absorbers offer excellent compatibility with the TPE matrix and do not affect the material's transparency or physical properties, making them particularly suitable for outdoor products requiring a high level of aesthetic appeal.
Hindered amine light stabilizers (HALS) complement UV absorbers by capturing free radicals generated during photooxidation, blocking the aging chain reaction. The nitroxide radicals in HALS molecules are recyclable, providing continuous stabilization, making them particularly suitable for long-term outdoor exposure. Adding 0.3%-1.5% HALS to a TPE formulation significantly extends the material's service life in strong UV environments. For example, TPE specifically designed for outdoor waterproof connectors uses SEBS as a base material and is formulated with a specialized UV absorber and HALS. Accelerated aging tests have shown that it can withstand strong outdoor UV conditions for over five years without cracking, discoloration, or elastic degradation.
Inorganic pigments such as titanium dioxide and carbon black create a physical protective barrier. Titanium dioxide scatters and reflects UV light, reducing its penetration; carbon black absorbs UV light and converts it into heat, lowering the material's internal temperature. These pigments work synergistically with organic additives to form a multi-layered anti-aging system. For example, adding 5%-10% titanium dioxide to TPE used in automotive door and window seals can extend the material's service life in high-UV regions. Furthermore, the addition of carbon black enhances TPE's weather resistance, preventing oxidative degradation caused by the combined effects of UV and oxygen.
Polyolefin polymer blending can improve TPE's light resistance. Materials like polyethylene (PE) and polypropylene (PP) have stable molecular structures and excellent UV resistance. By blending TPE with weather-resistant polyolefins, the polyolefin's stable molecular structure can be leveraged to enhance the overall material's light resistance. For example, blending TPE for outdoor furniture with PP ensures stable performance under the combined effects of moisture and UV, preventing rapid aging caused by the synergistic effects of hydrolysis and photooxidation.
Surface coating technology provides a direct UV-blocking solution for TPE. Acrylate and silicone coatings form a dense protective film on the surface of the TPE substrate, preventing UV rays from contacting the substrate. Coextrusion, on the other hand, achieves structured protection by incorporating a layer of UV-resistant material. For example, TPE for garden tool handles is co-extruded with a polyolefin layer containing a UV shielding agent. This ensures stable performance for over five years in outdoor environments while reducing the risk of coating detachment.
The choice of base polymer has a crucial impact on the UV resistance of TPE. TPE based on SEBS (hydrogenated styrene-butadiene-styrene block copolymer) exhibits significantly better ozone and UV aging resistance than TPE based on SBS (styrene-butadiene-styrene block copolymer) due to the absence of unsaturated double bonds in its molecular chain. The double bonds in SBS molecules are easily oxidized and broken by UV rays, leading to hardening and cracking. However, hydrogenation of SEBS increases the molecular chain saturation, fundamentally reducing the potential for photooxidation.
Through additive combinations and process optimization, the UV resistance of TPE elastomers has been significantly improved. The synergistic effect of UV absorbers and HALS, the physical protection provided by inorganic pigments, the structural reinforcement of polyolefin blends, and the direct barrier provided by surface coatings create a multi-layered anti-aging system. SEBS-based weather-resistant TPE can maintain stable performance for more than five years in outdoor environments. It is widely used in scenarios with strict weather resistance requirements and provides a reliable solution for the outdoor application of TPE elastomer.
