Due to the very poor physical and mechanical properties of pure liquid silicone rubber, it is generally needed to be strengthened and modified to meet the needs of practical application, among which adding reinforcing filler is undoubtedly the most simple and convenient method. The commonly used nano fillers include nano silica, nano calcium carbonate, organic montmorillonite, carbon nanotubes and graphene, nano zinc oxide, nano titanium dioxide, silicon carbide, alumina and nano silver wire, etc.

1, nano silicon dioxide

The synthesis methods of nano-silica are mainly gas phase method and precipitation method. The nano-silica prepared by gas phase method has less hydroxyl group on the surface, uniform particle size and good dispersion. Zhu Zhimin et al. found that the physical and mechanical properties of liquid silicone rubber were significantly improved after adding 10 parts of silica, and the hardness, tensile strength and shear strength of Shoer A could reach 40, 1.6MPa and 1.4MPa, respectively. There is no significant change in shear strength after aging.

Due to the high cost of gas phase silica, the lower cost of precipitation silica has attracted much attention. Precipitated silica moisture content is higher, the surface hydroxyl number is much higher than that of silicon dioxide gas phase method, makes the high surface activity of precipitated silica, easily happened together, is not conducive to disperse in rubber matrix, so in order to solve this problem usually by physical or chemical method for surface modification, prevent the phenomenon of reunion, improve its dispersion.

2. Nano calcium carbonate

Nanometer calcium carbonate with small particle size, high specific surface area, high surface activity, a large quantity and filling processing advantages, such as, the low cost not only as rubber reinforcing filler, and show a good enhanced toughening, sterilization effect, therefore, nano calcium carbonate as a kind of common reinforcing filler is widely used in liquid silicone rubber.

Nanometer calcium carbonate as liquid silicone rubber reinforcing filler, the results show that when the adding amount of nanometer calcium carbonate is 100, the tensile strength of the silicone rubber increased 4.4 times, compared with strengthened silicone rubber elongation at failure for three times, at the same time but also in the hot oxygen aging resistance, oil resistance, highlight the enhancement effect of nanometer calcium carbonate are proved.

3. Organic Montmorillonite (OMMT)

Montmorillonite (MMT) is a typical layered silicate, which is a common reinforcing filler in the rubber industry. In order to improve the compatibility between MMT and silicone rubber, OMMT was prepared by organic modification. It is found that OMMT can be well dispersed in the silicone rubber matrix, which greatly improves the physical and mechanical properties of the silicone rubber.

OMMT/ liquid silicone rubber composites were prepared by solution intercalation method. It was found that the physical and mechanical properties of OMMT/ liquid silicone rubber composites were much better than those of gas phase silica/liquid silicone rubber composites. The structure analysis shows that OMMT has a peeling structure in the rubber matrix.