Silicone rubber is odorless and non-toxic, not afraid of high temperature and resistant to severe cold. It has good strength and elasticity at 300 degrees Celsius and minus 90 degrees Celsius. Silicone rubber also has good electrical insulation, oxygen resistance, aging resistance, light resistance and aging resistance, mildew resistance, chemical stability, etc. Since the advent of high-temperature vulcanized dimethyl silicone rubber, the rapid development of silicone rubber has made silicone rubber widely used.

Structural characteristics and excellent properties of silicone rubber
1. High molecular bond energy:

The C-C bond energy is 348 KJ/mol; the Si-O bond energy is as high as 444 KJ/mol; and the ultraviolet (300 nm) energy is only 400 KJ/mol. The molecular chain is helical, the bond angle of siloxane is larger (130°-160°), and the intermolecular force is small.

2. The unique properties of silicone rubber:

(1) Excellent weather resistance, UV resistance, O2, O3, salt spray, etc.;

(2) Low surface energy, excellent hydrophobicity and hydrophobic migration;

(3) Excellent insulating properties, stable dielectric properties in a wide range of temperature and frequency. Arc resistance and leakage resistance are very good;

(4) It has good high temperature resistance and can be used continuously at 180-200℃. Although the strength of silicone rubber at room temperature is only half of that of natural rubber or some synthetic rubbers, it can still maintain a certain degree of flexibility, resilience and surface hardness in a high temperature environment above 200°C, with no obvious mechanical properties. Variety;

(5) Good elasticity, good low temperature flexibility, can be used at -50 ℃. The glass transition temperature of silicone rubber is generally -70~-50℃, and the special formula can reach -100℃, indicating its excellent low temperature performance. This is of great significance to the lines used in the aviation and aerospace industries.

(6) Good flame retardant performance, almost no toxic and harmful gases are released when burning;

(7) It can be made into transparent products, and defects such as bubbles or impurities can be easily detected by visual inspection.

Compared with general-purpose rubber, silicone rubber has relatively simple compounding components for all three types of silicone rubber, as is thermal vulcanization type. In addition to raw rubber, the compounding agents mainly include reinforcing agents, vulcanizing agents and some special auxiliaries. Generally, only 5 to 6 components are needed to form a practical formula.

Silicone rubber formulation design should consider the following points:
(1) Silicone rubber is a raw rubber with high saturation, and usually cannot be vulcanized with sulfur, but hot vulcanized. Thermal vulcanization uses organic peroxide as vulcanizing agent, so the compound must not contain active substances that can interact with peroxide decomposition products, otherwise it will affect vulcanization.

(2) Silicone rubber products are generally used at high temperatures, and their compounding agents should be stable at high temperatures. For this reason, inorganic oxides are usually used as reinforcing agents.

(3) Silicone rubber can easily cause the cleavage and rearrangement of siloxane bonds under the action of a small amount of polar chemical reagents such as acids or bases, resulting in a reduction in the heat resistance of silicone rubber. Therefore, they must be considered when selecting compounding agents. The acidity and alkalinity of the vulcanizate should also be considered, so as not to affect the performance of the vulcanizate.