After adding a reinforcing filler, the strength of silicone rubber can be increased by about 40 times, the specific performance is that the tensile strength of vulcanized rubber is increased from 0.35MPa of pure silicone rubber to 14Mpa.This reinforcing effect is significantly better than that of other rubber materials (usually the reinforcing rate is 1.4-10 times), reflecting the decisive role of reinforcing fillers in the properties of silicone rubber.


Mechanism of action and reasons for performance improvement of reinforcing fillers
Increase in physical crosslinking points：
Reinforcing fillers (such as nano-silica) form a microcrystalline region with silica as the nucleus in silicone rubber, which increases the physical crosslinking point and makes crystallization more likely to occur, thereby improving the mechanical strength.
Filler and polymer interaction：
A cross-linking network is formed between the filler and the silicone rubber molecular chain through covalent bonds, hydrogen bonds and Van der Waals forces. At the same time, the network structure between the filler particles increases the effective volume of reinforcement and further enhances the modulus of the elastomer.
Influence of filler type and structure：
Fumed silica: large specific surface area (200-380 m2/g), significant reinforcement effect, can increase the tensile strength of silicone rubber by about 10 times.
Nano-silica: The rigid chain structure serves as the reinforcing skeleton, and its hardness increases linearly with the increase of the specific surface area. The tear strength is the largest at 250 m2/g specific surface area, and the tensile strength is optimal at 200 m2/G.
Comprehensive effect of reinforcing filler on the performance of silicone rubber
Improved mechanical properties：
After reinforcement, the tensile strength, hardness, wear resistance and tear resistance of silicone rubber have been significantly improved, while the compressive properties, compression deformation rate and elastic recovery have been improved.
Enhanced thermal stability：
The reinforcing filler can increase the initial decomposition temperature of silicone rubber and improve thermal stability.For example, when 40 parts of silica are added, the initial decomposition temperature (T5) and semi-decomposition temperature (T50) of silicone rubber reach 495.4℃ and 632.6℃, respectively.
Improved flame retardant properties：
Reinforcing fillers (such as silica) have non-combustible properties, which can reduce the content of combustibles in silicone rubber and increase the oxygen index.When 50 parts of silica were added, the oxygen index of silicone rubber increased from 19.4% to 25.0%.