Silicone Rubbers for Special Purposes

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Besides the different types of modified silicone rubbers, there are also many silicone rubbers which are designed for the special usages of applications. Today’s blog will introduce some of these types of silicone rubbers.

Conductive Silicone Rubber

Filling type of conductive silicone rubbers is to use silicone rubber as the foundation, and to fill conductive fillers and crosslinking agents to vulcanize them together to be manufactured. To compare with general conductive rubbers, the advantages of conductive silicone rubbers are small volume resistivity, low hardness, cold and heat resistance, aging resistance and good formation and manufacturing processes. It is now the conductive silicone rubber which has the largest consumption quantity. It is very good at being used to manufacture conductive, complex shaped and slim structural conductive rubber products. It is widely used in aerospace, electrics, computers, constructions, medicine and food. It could also be used as anti-static materials and electromagnetic shielding materials.

It is according to the difference in foundation rubbers and processing methods, we could produce RTV conductive silicone rubbers, HTV conductive silicone rubbers, PSA conductive silicone rubbers and low-temperature conductive silicone rubbers.

Also, it is according to the categories of conductive filler systems, they could be divided into carbonate conductive filler, metallic conductive filler, nano-conductive filler and some others.

Metallic powders have excellent conductivity. To add metallic powders into silicone rubbers could significantly increase its conductivity. It is important filler in making conductive silicone rubbers. To compare with carbonate fillers, the economy and craftiness are worse and metallic fillers have limited improvement on silicone rubber foundation’s physical mechanical properties. The common metallic powders are gold, silver, bronze, nickel, iron and aluminum slim powders. Among them, the gold powder has the best performance but expensive. It cannot be the main conductive filler and mostly used in advanced field; Silver powders have excellent weather resistance and conductivity, and the conductivity is at the same level as the gold powder and higher than bronze, aluminum and nickel. Therefore, even though silver is expensive, silver powder is still widely used in recent electronics industries.

As for carbonate fillers, some non-metallic filler also have very high conductivity. When we add it to silicone rubber, we not only could get conductive silicone rubber but also could maintain the original properties of silicone rubbers. To compare carbonate filler with metallic filler, even though the former one has a worse conductivity, but it is more stable than the latter one and it is hard to be oxidized which has a strengthening ability to silicone rubber. Thus carbonate filler could guarantee the physical properties of silicone rubbers and to increase its weather resistance and abrasion resistance. It also has the advantages like it has a rich resource and low cost. However, it is also hard to be dispersed and the conductive silicone rubber made from it has a bigger resistivity which is usually not lower than 0.5Ω·cm.

Carbon blacks are cheap and easy to be processed. They are also chemically stable, good to be dispersed and hard to be oxidized when being used and could strengthen the filled rubbers.

As for the nano conductive fillers, they are one of the main paths to increase the conductivity of silicone rubbers. The nano particles have the features of small particle size and large specific surface square which lead to the manifestation of small-size effect, surface effect and some other effects. In other words, when the particle radius of powder reaches nano-level, the conductive filler will perform many excellent properties like light mass, good mechanical proeprties, good conductivity and easy to be processed which show broad application fields.

Foam Silicone Rubber

Foam silicone rubber is a new, soft, porous and multifunctional macromolecular elastomer. It is made from the silicone rubber which has been foaming. Foam silicone rubber material refers to the composited material which is to use silicone rubber materials as the foundation with inner porous materials which have many air foams. It is also called sponge silicone rubber or microporous silicone rubber. It not only keeps the excellent properties of silicone rubber, but also has the properties like light weight, sound isolation, heating resistance, electrical isolation, sealing ability and some other excellent ones. It is used as high-effectively material in national defense, aerospace, traffics, electronics, industry and agriculture. Some functional and high-efficiency foaming materials are also playing utmost important roles in militia and aerospace and many other advanced areas.

If to divide foam silicone rubber by vulcanization conditions, there are RTV foam silicone rubber and HTV foam silicone rubber. If by porous structure, generally there could be closed-porous, open-porous and mixed-porous structures. If by density, there are three levels which are low-foaming, medium-foaming and high-foaming.

Heat-Shrinkable Silicone Rubber

Heat-shrinkable silicone rubber is one new type which is developed in 60s of 20^th century. It has the unique properties of general silicone rubber like cold and heat resistance, humidity resistance and excellent electrical properties. It also has the feature that to cover the whole item tightly and shrink to 50% when being heated under 150℃ in simple ways. The operation is simple which is very convenient for do it at once. It is widely used in different kinds of electronical parts, the isolations, protections and connections of instrumentations.

Moulding Silicone Rubber

RTV silicone rubber has excellent simulation, demoulding and very low shrinking rate. It also has properties like easy to be shaped and resistance on aging and heating. Therefore, it is a very excellent moulding material. Many formation craftiness all use RTV silicone rubber to make moulds to replace metallic moulds or moulds made of other materials. At present, silicone rubber soft moulds are widely used in high-frequency leather and shoes manufacturing, copies of relics, plastic formation and the formations of waxes and some alloys. The corresponding performances are also excellent.

Summary

As we can see, different silicone rubbers could be applied in absolutely different industries by containing different excellent physical or chemical properties. This is also why silicone rubber is now so popular in today’s organic silicone market.