Introduction to Silicone Rubber Adhesives

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It is due to the unique properties owned by organic silicon materials, even though it cannot be compared to epoxy type, phenolic type and polyimide when being used as structural adhesive. However, it is widely applied as being used as non-structural rubbers, and in some case, it cannot be altered by other materials such as the adhesion between solar battery boards of airships. It could stick to metal, plastic, rubber, glass and other materials. It could be used in many industries like universe space, manufacturing of aircrafts and automotive, electronics, constructions and medical cares.

If we categorize the organic silicon adhesive according to the sources of raw materials, the general categorization could be the adhesive made from silicone resin and the ones made of silicone rubbers. The former one is mainly applied in adhesion between metal and heat-resisting non-metallic materials. The bonded part could be used between -60℃ ~ 200℃; The latter one is used to bond heat-resisting rubbers, rubbers and metals and some other non-metallic materials. In heat-resisting adhesives, organic silicon adhesive is one of the excellent types. It could be divided to high-temperature-resisting adhesive, heat-resisting sealants, high-temperature-resisting strain adhesive and heat-resisting pressure sensitive adhesive.

It is since the development of space navigation, manufacturing of aircrafts, electronics and many other advanced industries or fields. The demand of new high-temperature-resisting rubber and high-temperature-resisting adhesive is rapidly increasing in recent years. Silicone rubber is widely applied due to its excellent thermal stability, cold resistance, electrical property and weather resistance; as for silicone rubber adhesive, its weaknesses are low inner strength and low adhesion, but these could be improved by adding fillers. Now it is widely used as the non-structural adhesive.

If we categorize silicone rubber by the solidification method, they could be divided into HTV and RTV. It is due to the adhesion is low for HTV silicone rubber adhesive, and the manufacturing devices are complex thus the application is vert restricted. HTV silicone rubber is mainly used to produce vulcanized products. Single-component RTV silicone rubber has better adhesions to most base materials; when adding tackifiers, double-component RTV silicone rubber and LTV silicone rubber could also be granted excellent adhesions. Liquid silicone rubber adhesive not only has the adhesion between metal and non-metallic materials, but also has good adhesion to material that has low surface energy like silicone rubber. It is since 60s of 20^th century when RTV silicone rubber came out, the development of it is getting faster and faster. RTV silicone rubber not only contains excellent properties like oxidation resistance, cold resistance, odor resistance, electrical isolation and humid resistance, its biggest feature is the convenience use. However, it has bad adhesion and solvent resistance thus it cannot be used as structural adhesive. Silicone rubber adhesive is now the important product in organic silicon industry and it is widely used in electronics, universe navigation, medical use, constructions and automotive.

Silicone rubber sealants and adhesives have the following properties:

1.      It has excellent cold and heat resistance. It could be used between -65 ~ 232℃ for a long time. As for a short usage, the highest working temperature could be maximum 260℃. In extreme temperatures, it will not be hardened, breached or aged.

2.      It has excellent dielectric capacity. When it is applied in electrical devices, silicone rubber sealant or adhesive will perform excellent dielectric property when the temperature switch is wide. It also contains excellent waterproof, humid resistance, isolation and non-corrosive properties. Therefore, it could protect, seal and isolate parts or devices which are easy to be corrosive.

3.      Excellent weather resistance and radiation resistance. It will not be affected by rain, snow, hail, UV radiation or odor.

4.      Excellent breathability, low surface tensile strength and chemical stability. In some extreme environments, it has good chemical corrosion resistance and it could endure corrosions from most organic and inorganic chemicals, lubricants and some other solvents.

5.      Excellent adhesion strength. Silicone rubber adhesive or sealant has excellent adhesion strength to surfaces of glass, lumbers, silicone resin, vulcanized rubber, natural and composited fiber, many plastics and metals.

Categorization and Components of Silicone Rubber Sealant and Adhesive

Silicone rubber is the main component of silicone rubber sealant or adhesive, it is macromolecular linear polysiloxane in the form of oily elastomer. Actually, the solidification temperature reflects different solidification mechanisms.

High-temperature solidification silicone rubber sealant or adhesive could be used to bond silicone rubber and silicone rubber or silicone rubber with metals. It is due to the low adhesion of it and the complex devices, its application is restricted.

Room temperature solidification silicone rubber sealant or adhesive usually takes hydroxyl-end linear polysiloxane as the main material, by the effects from crosslinking agent and hydroxyl to make the adhesive to have solidification. This kind of adhesive is easy to use and simple to operate,and its adhesion temperature is proper. Therefore, it is more and more popular within industrial departments and becomes one important part of elastomer adhesives.

It is due to these excellent properties of these silicone rubber sealants or adhesives. Therefore, it is one liquid sealing material which is present widely-used, it is called liquid pad. It could solve many problems which many other common rubber adhesives are hard to deal with. For instance, it could solve the adhesion problem between many non-polar materials that have low surface energies like polyethylene, polypropylene, teflon and silicone rubber.

Summary

Organic silicone rubber adhesive or sealant is one of the main products in today’s daily life- especially in construction material areas like sealing of windows. Also, it could be applied in many other uncommon industries since it did has many excellent physical or chemical properties. Thus these products are having a high commercial and industrial values in the foreseeable future.

In today’s article, we have introduced some basic information of silicone rubber adhesive or sealant’s components, mechanisms and some excellent properties. In the future articles, we will also try to introduce some other aspects of these excellent and widely-used products.