Application Of Hydrophobic Fumed Silica in RTV Silicone Rubber

Room temperature vulcanized silicone rubber (RTV) sealant is widely used in the home and industrial fields, outstanding performance, from spacecraft seals and connectors, new energy vehicle gaskets, to bathroom tile bonding, door and window glass sealing, it plays an important role. In practical applications, RTV sealant has obvious advantages, good rheology and physical properties, environmental friendliness, elasticity, high and low temperature resistance (60-250 ℃), excellent weather resistance, easy to use and molding is not limited by the mold, simple assembly process, low material cost, but also has seismic damping effect. The excellent performance of RTV sealant is closely related to silicone rubber, silicone rubber crosslinking agent system and reinforcing agent fumed silica. Among them, fumed silica is divided into untreated type and treated type, that is, hydrophilic fumed silica and hydrophobic fumed silica, and hydrophilic fumed silica will affect the silicone RTV system because of different specific surface area and the change of addition amount. So what effect does treated hydrophobic fumed silica have on it? HB-151 is a hydrophobic fumed silica with a specific surface area of 150㎡/g treated with dimethyldichlorosilane (DDS). HB-139 is a hydrophobic fumed silica with a specific surface area of 200㎡/g treated by polydimethylsiloxane (PDMS). HB-612 is a kind of hydrophobic fumed silica with a specific surface area of 150 m2/g modified by Hexamethyldisilazane (HMDS). HB-132 is a hydrophobic fumed silica with a specific surface area of 200㎡/g after deep treatment with Hexamethyldisilazane (HMDS). HB-151 and HB-612 are the same hydrophilic fumed silica treatment, but the treatment agent is different, so is HB-132 and HB-139. The technical staff of Huifyou Nano tested the influence of hydrophobic fumed silica on the consistency of silicone RTV system. The technical staff found that hydrophobic fumed silica can effectively enhance the viscosity and consistency of RTV system, and the thickening effect is more obvious with the increase of the addition amount, while the thickening performance of hydrophobic products prepared by different treatment agents is different. The contribution of the product to consistency after advanced treatment is weak. In the tensile strength test, Huifong Nano technicians found that hydrophobic fumed silica can effectively enhance the tensile strength of RTV system, and the strengthening effect is better with the increase of the addition amount. The strengthening trend of products treated with different treatment agents is similar, but the efficiency is different. In the test of elongation at break, technicians found that the addition of hydrophobic fumed silica below 10% demonstrated a good growth trend of elongation at break. After the addition amount reached 12.5%, the elongation at break of HB-151 showed a downward trend, similarly, the growth of HB-612 slowed down. In the silicone RTV system, the hydrophobic fumed silica can effectively help to enhance its physical and mechanical properties, increase its viscosity, and play a reinforcing role, but the appropriate addition amount and appropriate specific surface area should be determined according to the specific testing of the product system.