How to Improve the Weather Resistance of Silicone Rubber?
Silicone rubber is widely used in many fields due to its unique properties. However, in the long-term natural environment, its performance may decline due to factors such as light, temperature and humidity. The weather resistance of silicone rubber can be improved from the aspects of raw material selection, additive use, preparation process improvement and surface treatment. The details are as follows:

Raw Material Selection

• Selection of Basic Polymer: Selecting high-purity and molecular structure-stable basic silicone rubber polymer is the key. Vinyl silicone rubber has good thermal stability and aging resistance, and performs excellently in weather-resistant applications. Phenyl silicone rubber, especially those with high phenyl content, has good resistance to ultraviolet light and can effectively improve the weather resistance of silicone rubber in the light environment.
• Control of Raw Material Impurities: Impurities in raw materials may become the starting point of silicone rubber aging and accelerate the aging process. Therefore, it is crucial to strictly control the impurity content in the basic polymer and other additives. Through fine purification processes, reducing the presence of metal ions, small molecule impurities, etc., can significantly improve the weather resistance of silicone rubber.

Additive Use

• Adding Light Stabilizers: Light stabilizers can absorb or quench ultraviolet energy and prevent ultraviolet light from damaging the silicone rubber molecular chain. Commonly used light stabilizers include ultraviolet absorbers and hindered amine light stabilizers (HALS). Ultraviolet absorbers such as benzophenones and benzotriazoles can effectively absorb ultraviolet light and convert it into heat energy for release, reducing the damage of ultraviolet light to silicone rubber. HALS inhibits the photooxidation reaction by capturing free radicals and decomposing peroxides, further improving the light aging resistance of silicone rubber.
• Adding Antioxidants: Oxygen will react with silicone rubber under high temperature, light and other conditions, resulting in molecular chain scission and performance degradation. Antioxidants can react with free radicals to terminate the chain transfer of the oxidation reaction. Common antioxidants include phenols and amines. Phenolic antioxidants such as 2,6 - di - tert - butyl - 4 - methylphenol (BHT) can provide active hydrogen atoms and combine with free radicals to protect the silicone rubber molecular chain. Amine antioxidants have stronger antioxidant capacity, but may have problems such as discoloration. It is necessary to select the appropriate type and addition amount of antioxidants according to the specific application scenarios.
• Adding Heat Stabilizers: In high temperature environments, silicone rubber may undergo thermal degradation reactions. Heat stabilizers can improve the thermal stability of silicone rubber and reduce the impact of thermal aging. For example, certain metal oxides such as zinc oxide and magnesium oxide can absorb the acidic substances produced by the thermal decomposition of silicone rubber and inhibit the thermal degradation reaction.

Preparation Process Improvement

• Optimization of Vulcanization Process: A suitable vulcanization process can enable silicone rubber to form a uniform and stable cross-linked structure, improving its physical properties and weather resistance. By precisely controlling parameters such as vulcanization temperature, time and pressure, ensure that the cross-linking reaction is fully carried out to form an appropriate cross-linking density. Excessive cross-linking density may cause the silicone rubber to become hard and brittle, while too low cross-linking density will reduce the strength and aging resistance of the silicone rubber.
• Blending Modification: Blending silicone rubbers with different properties or other polymers with silicone rubber can integrate the advantages of each component and improve the weather resistance of silicone rubber. For example, blending fluororubber with silicone rubber, the high chemical corrosion resistance and weather resistance of fluororubber can endow silicone rubber with better comprehensive properties. During the blending process, it is necessary to pay attention to selecting the appropriate blending ratio and process to ensure good compatibility between each component.

Surface Treatment

• Coating Protective Coatings: Coating a protective coating on the surface of silicone rubber is an effective method to improve weather resistance. The protective coating can block the erosion of ultraviolet light, oxygen and moisture on the silicone rubber. For example, organic fluorine coatings have excellent weather resistance, water resistance and chemical corrosion resistance, and can provide good protection for silicone rubber. In addition, some nano-coatings also have good ultraviolet resistance and self-cleaning properties, which can improve the weather resistance of the silicone rubber surface.
• Surface Modification: The surface properties of silicone rubber can be changed by physical or chemical methods to improve its weather resistance. For example, plasma treatment can introduce polar groups on the surface of silicone rubber, enhance surface hydrophilicity or hydrophobicity, improve its adhesion to protective coatings, and also improve surface anti-pollution performance.

Low compression set precipitated silicone rubber