Used for reinforcement of silicone compounds and organic polymers, Cabot fumed silica strengthens rubber, allowing it to be stretched and deformed without breaking. Cabot offers a range of untreated and treated fumed silicas for optimum performance in silicone applications including:  

• Room Temperature Vulcanizing (RTV) silicones
• High Temperature Vulcanizing (HTV) silicones
• Liquid Silicone Rubbers (LSR)
• Silicone Defoamers

Fumed silica provides thixotropy and reinforcement for RTV sealants, while its shear-thinning property provides thickening and sag resistance at rest or low shear and thinning at high shear for easy application.

 In HTVs and LSRs, fumed silica strengthens the cured rubber, increasing hardness, modulus, tensile strength and tear strength. Unlike other reinforcing fillers, fumed silicas can be used in transparent or clear applications.

In general, as the surface area of fumed silica increases, so does thickening and reinforcement. However, high surface area fumed silicas require high shear dispersion equipment to achieve optimal performance.

 In moisture curing RTVs, treated fumed silicas have less adsorbed moisture -- offering better shelf-life and compound stability. Their hydrophobic surface treatments are more compatible with silicones, making it easier to wet-in and incorporate and greatly reducing compounding time. Some Cabot treated silicas do not require additional in-situ treatment or processing aids -- which are required for all untreated fumed silicas in HTVs and LSRs to prevent crepe hardening or structuring.