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Why do Insulators use Silicone Rubber?

Pulished on Nov. 19, 2020

Beginning in the second half of the nineteenth century, when erecting transmission lines, the only insulating materials suitable for high voltages were ceramics and glass. In the 1940s, due to the advent of polymer materials, ceramics and glass were no longer the preferred insulator materials. European and American countries began to study polymer insulators. Afterward, the physical properties, electrical properties, long-term reliability, and optimal shape of electrical insulators were studied, and the productivity was continuously improved.

Among the polymer materials that can replace ceramics and glass, silicone rubber has had practical performance since the 1960s and has stood out among several polymers. Silicone rubber insulators have more advantages than ceramic insulators. First of all, it is light in weight, easy to operate, and safe; in addition, ceramic insulators often suffer from cracking, and it will be damaged by an impact. Silicone rubber insulators can resist mechanical shocks such as vehicles colliding with telephone poles.

Although other polymer materials also have the advantages described above, only silicone rubber will not cause too much pollution to the environment. The polymer insulator is waterproof, so there will be no leakage and surface arc phenomenon caused by the falling of water droplets. The water-resistance of China silicon rubber insulator recover faster than other polymer insulators, and it is a durable material that can be used for a long time in harsh environments.

Composite Insulator

1.Features of silicone rubber

Heat and cold resistance

Since silicone rubber has high bond energy and good chemical stability, its heat resistance is better than that of organic polymers. Furthermore, since the intermolecular interaction force is weak, the glass transition temperature is low and the cold resistance is good. Therefore, its characteristics will not change when used in any area on the earth.


Since the surface of polysiloxane is a methyl group, it is hydrophobic and can be used for waterproofing.

Electrical performance

The number of carbon atoms in the silicone rubber molecule is less than that of organic polymers, so its arc resistance and leakage resistance are very good. In addition, even if burned, insulating silicon is formed, so it has excellent electrical insulation. 

Permanent deformation

The permanent set characteristics (permanent elongation and compression set) of silicone rubber at room temperature/high temperature are better than those of organic polymers.

2.Classification of silicone rubber

According to the characteristics before vulcanization, silicone rubber can be divided into two types: solid and liquid. According to the vulcanization mechanism, it can also be divided into three types: peroxide vulcanization, addition reaction vulcanization, and condensation reaction vulcanization. The difference between solid and liquid silicone rubber is the molecular weight of polysiloxane. Solid silicone rubber can be vulcanized by anyone of peroxide vulcanization and addition reaction, usually called high temperature vulcanized rubber (HTV) and heat vulcanized rubber (HCR). Although the liquid silicone rubber material vulcanized by addition reaction can be vulcanized at room temperature, it is called liquid silicone rubber (LSR), low temperature vulcanized rubber (LTV) and two-component room temperature vulcanized rubber (RTV) due to the different molding methods and vulcanization temperatures. ).

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