Addition liquid silicone rubber is usually composed of vinyl silicone oil, hydrogen containing silicone oil, platinum catalysts and fillers. Fillers include white carbon black, carbon black, metal oxide, calcium carbonate or silicon carbide, etc., while MQ silicone resin is commonly used as filler for transparent LSR. Vinyl silicone oil is the basic polymer of LSR. The vinyl content, molar mass and distribution of vinyl silicone oil directly affect the properties of silicone rubber.

Low vinyl content, low crosslinking density, low hardness and low tear strength of silicone rubber; If the vinyl content is too high, the hardness of the vulcanizate becomes larger and brittle, and the aging resistance decreases. Experiments show that the vinyl mole fraction is generally controlled at 0.12% ~ 0.5%, and higher or lower than this ratio will prolong the vulcanization time of silicone rubber.

Vinyl silicone oil with small molar mass can reduce the viscosity of the compound, improve the fluidity, improve the crosslinking density of silicone rubber to a certain extent, and make it have certain tensile strength and hardness; Vinyl silicone oil with high molar mass can improve the elasticity and elongation at break of silicone rubber; Silicone rubber with excellent properties can be obtained by using vinyl silicone oil with wide molar mass distribution. Therefore, the combination of low viscosity vinyl silicone oil and high viscosity vinyl silicone oil to prepare liquid silicone rubber can achieve good results. Xu Zhijun et al. Studied the role of vinyl silicone oil in vinyl silicone rubber and found that adding some vinyl silicone oil can improve the properties of vulcanizate.

J. E. mark believes that in the vulcanization system, the vinyl of some vinyl silicone oil is relatively concentrated, which can produce plastic micro areas with high strength, which is very helpful to the physical and mechanical properties of vulcanizates; However, if two vinyl groups are adjacent or the spacing is small, the complete addition is only equivalent to one crosslinking point, which has little effect on the elasticity and strength of silicone rubber.