Silicone grease

Silicone grease is a waterproof grease made by combining a silicone oil with a thickener. Most commonly, the silicone oil is polydimethylsiloxane and the thickener is amorphous fumed silica. Using this formulation, silicone grease is a translucent white viscous paste, with exact properties dependent on the type and proportion of the components.

Use in industry

Silicone grease is commonly used for lubricating and preserving rubber parts, such as O-rings. Additionally, silicone grease does not swell or soften the rubber, which can be a problem with hydrocarbon based greases. It functions well as a corrosion-inhibitor and lubricant for purposes that require a thicker lubricant, such as the operating mechanism of the M1 Garand rifle.

Thermal grease often consists of a silicone grease base, along with added thermally conductive fillers. It is used for heat transfer abilities, rather than friction reduction.

Special versions of silicone grease are also used widely by the plumbing industry in faucets and seals, as well as dental equipment. These special versions are formulated using components not known to be an ingestion hazard. Electrical utilities use silicone grease to lubricate separable elbows on lines which must endure high temperatures. Silicone greases generally have a temperature range of -40 to 400 °C.

Use in the chemical laboratory

Silicone grease is widely used as a temporary sealant and a lubricant for interconnecting ground glass joints, as is typically used in laboratory glassware. Although silicones are normally assumed to be chemically inert, several historically significant compounds have resulted from unintended reactions with silicones: for example, the first salts of crown ethers (OSi(CH₃)₂)_n (n = 6, 7) were produced by reactions resulting from contacting organolithium and organopotassium compounds with silicone greases.^[1]

Consumer uses

Silicone-based lubricants are often used by consumers in applications where other common consumer lubricants, such as petroleum jelly, would damage certain products, such as latex rubber condoms and gaskets on drysuits. It can be used to lubricate fountain pen mechanisms, preserve O-rings in flashlights, to seal waterproof watches and for O-rings on air rifles. Silicone-based lubricants are also commonly used for remote control hobbies. Various household uses include lubricating light bulb threads to facilitate removal and discourage stuck bulbs (especially in outdoor lighting), door hinges, shower heads, threads on bolts, garden hose threads or any thread or mechanism that can be lubricated.

As an electrical insulator

Dielectric grease

Dielectric grease is a nonconductive grease. As such, it does not enhance the flow of electrical current. Thus electrical conductors should not be coated with dielectric grease prior to being mated. Dielectric grease is, however, often applied to electrical connectors, particularly those containing rubber gaskets, as a means of lubricating and sealing rubber portions of the connector.

The widest use of dielectric grease is in high-voltage connections associated with spark plugs. The grease is applied to the rubber boot of the plug wire. This helps the rubber boot slide onto the ceramic insulator of the plug. The grease also acts to seal the rubber boot, while at the same time preventing the rubber from becoming stuck to the ceramic. Generally spark plugs are located in areas of high temperature, and the grease is formulated to withstand the temperature range expected.

Another common use of dielectric grease is on the rubber mating surfaces or gaskets of multi-pin electrical connectors used in automotive and marine engines. The grease again acts as a lubricant and a sealant on the nonconductive mating surfaces of the connector. It is not recommended to be applied to the actual electrical conductive contacts of the connector because it could interfere with the electrical signals passing through the connector.

References

1. ^ Jamie S. Ritch and Tristram Chivers (2007). "Silicon Analogues of Crown Ethers and Cryptands: A New Chapter in Host–Guest Chemistry?". Angewandte Chemie International Edition 46 (25): 4610–4613. doi:10.1002/anie.200701822. ISSN 1433-7851. PMID 17546579.