XYSIL® fumed silica for silicone rubber

XYSIL® fumed silica is an efficient reinforcement and rheology control additives for silicone rubber.

Benefit from the unique particle characteristics, XYSIL® fumed silica delivers superior reinforcement while having a relatively minor impact on transparency. The silicone rubber performance are impacted by primary particle size, aggregate size and surface chemistry.


Xunyu offers a range of untreated fumed silica for optimum performance in silicone applications including:

  • Room Temperature Vulcanizing (RTV) Silicone Sealant
  • High Temperature Vulcanizing (HTV) Silicone Rubber
  • Liquid Silicone Rubber (LSR)

In RTV silicone sealant

XYSIL® fumed silica provides thixotropy and reinforcement for RTV silicone 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 HTV silicone rubber and LSR

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

As the surface area of fumed silica increases, so does thickening and reinforcement. However, high surface area XYSIL® fumed silica require high shear dispersion equipment to achieve optimal performance. In general, XYSIL® 150 is used in RTV silicone sealant; XYSIL®200 and XYSIL®300 are used in HTV silicone rubber and LSR.

Fumed Silica XYSIL® for Silicone Rubber

Sytem XYSIL® Grade Concentration in wt.% Effect
RTV-1 Silicone Sealant XYSIL®150 3.0-30 Reinforcement, Thixotropy
RTV-molding compound(2 components) XYSIL®200 3-30 Reinforcement, Thixotropy
HTV Silicone Rubber XYSIL®200 5.0-35 Reinforcement, sag resistance, dispersability, surface quality, life duration
Liquid Silicone Rubber XYSIL®200


5-30 Rheology control, sag resistance, reinforcement, anti-settling