What is the generic name for silicone oil?

J. Allcock & Sons we have been supplying silicone products (silicone oil, silicone emulsion, silicone grease, and more) to many industries since the 1970′s. Therefore we have decided to explain some of the chemistry behind the two most popular; silicone oil and silicone emulsion. We hope you find it useful.

Silicone Oil

First of all, silicone oil has many different names; silicone fluid, polydimethylsiloxane, dimethicone, dimethylpolysiloxane, dimethyl siloxane, PDMS. J. Allcock & Sons have branded our silicone oil Allcosil 200 (which only adds further to the confusion!)

Technically, we believe that polydimethylsiloxane best describes the oil. Poly (Latin for many), dimethyl (two methyl (CH3) group) siloxane (Silicone and Oxygen).

The chemical structure of polydimethylsiloxane is:

n= number dimethylsiloxane units.

Buyers of polydimethylsiloxane will be aware that it is available in a number of different viscosities. The most common being; 100cSt(centistoke), 350cSt and 1000cSt. The number of dimethylsiloxane units depicts the size of the polymer chain which determines the viscosity. The smaller the polymer chain the lower the viscosity (e.g. 100 cSt) , the bigger the polymer chain the higher the viscosity (e.g.1000cSt).

Our one product in the Allcosil 200 range that is slightly different is our lowest viscosity Allcosil 200; 0.65cSt. Allcosil 200/0.65 has only two units, this means that it is not a polymer, but a dimer. The dimer is hexamethyldisiloxane.

The chemical structure of hexamethyldisiloxane is:

It is clear that when you compare it to the polydimethylsiloxane structure that the dimer is very similar to polydimethysiloxane.

The polymer chain length also has an effect on other properties of the oil.

Viscosity, cSt Flashpoint, °C COC Freezing Point,°C Specific Gravity, @ 25°C Surface Tension, mN/m Refractive Index, @ 25°C 0.65 -4 -67 0.760 15.9 1,375 1 40 -85 0.816 17.4 1,382 2 48 -90 0.830 18.1 1,387 3 62 -100 0.900 18.9 1,392 5 136 -100 0.910 19.7 1,397 10 162 -65 0.930 20.1 1,399 20 230 -60 0.950 20.6 1,400 50 280 -55 0.959 20.7 1,402 100 >300 -55 0.965 20.9 1,403 200 >300 -50 0.970 21.0 1,403 300 >300 -50 0.970 21.1 1,403 350 >300 -50 0.970 21.1 1,403 500 >300 -50 0.970 21.1 1,403 1000 >300 -50 0.970 21.2 1,403 5000 >300 -50 0.975 21.4 1,403 10000 >300 -50 0.975 21.5 1,403 12500 >300 -50 0.975 21.5 1,403 30000 >300 -50 0.975 21.5 1,403 60000 >320 -50 0.975 21.5 1,403 100000 >300 -50 0.976 21.5 1,404 300000 >300 -45 0.976 21.5 1,404 1000000 >300 -40 0.976 21.5 1,404

(1000000 cSt, longest polymer chain.)

It is clear from the table showing properties, that after 50cSt, the polymer chain length becomes less important in effecting the properties.

According to the FDA Regulation 21 CFR, certain viscosities are food grade. For more information, please contact us.

Silicone Oils have many uses due to their lubrication, dielectric and water repellent properties.

Silicone Emulsion

Silicone Emulsion contains 3 ingredients; polydimethylsiloxane, emulsifier & water.

The key ingredient is the emulsifier which encapsulates the polydimethylsiloxane oil and holds it in suspension.

A typical emulsifier used in making silicone emulsions is ethoxylated glycol ethers. These emulsifiers have a hydrophobic (dislikes water) and hydrophilic (likes water) part to their structure. The hydrophobic faces the polydimethylsiloxane and the hydrophillic faces the water. This creates a barrier between the water and the polydimethylsiloxane.

Here is a really good picture i found on google. A surfactant (Surface active agent) is just a type of emulsifier.

Unfortunately emulsifiers, due to their chemical make-up, are vulnerable to bacteria. Bacteria can digest certain emulsifiers causing the polydimethylsiloxane to float to the top or disrupt the pH enough for non-digestible emulsifiers to split from the oil. This is called splitting. Splitting in an emulsion can be seen and smelt. The smell comes from the bacterial growth, it usually smells like sour milk.

Emulsions are a key mould realease/lubricant and antifoams for many industries.Our biggest selling emulsion is Allcosil 435 FG, this is sold to the food packaging industry. It is food grade and kosher certified.

 

If you have any questions, please feel free to leave a comment.

Any liquid polymerized siloxane with organic side chains

A silicone oil is any liquid polymerized siloxane with organic side chains. The most important member is polydimethylsiloxane. These polymers are of commercial interest because of their relatively high thermal stability and their lubricating properties.[1]

Structure

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Like all siloxanes (e.g., hexamethyldisiloxane), the polymer backbone consists of alternating silicon and oxygen atoms (...Si−O−Si−O−Si...).[citation needed] Many groups can be attached to the tetravalent silicon centres, but the dominant substituent is methyl or sometimes phenyl. Many silicone liquids are linear polymers end-capped with trimethylsilyl groups. Other silicone liquids are cyclosiloxanes.[citation needed]

Applications

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Silicone oils are primarily used as lubricants, thermic fluid oils or hydraulic fluids. They are excellent electrical insulators[2] and, unlike their carbon analogues, are non-flammable. Their temperature stability and good heat-transfer characteristics make them widely used in laboratories for heating baths ("oil baths") placed on top of hotplate stirrers, as well as in freeze-dryers as refrigerants.[citation needed] Silicone oil is also commonly used as the working fluid in dashpots, wet-type transformers, diffusion pumps and in oil-filled heaters. Aerospace use includes the external coolant loop and radiators of the International Space Station Zvezda module, which rejects heat in the vacuum of space.[3]

The class of silicone oils known as cyclosiloxanes has many of the same properties as other non-cyclic siloxane liquids but also has a relatively high volatility, making it useful in a number of cosmetic products such as antiperspirant.

Some silicone oils, such as simethicone, are potent anti-foaming agents due to their low surface tension. They are used in industrial applications such as distillation or fermentation, where excessive amounts of foam can be problematic. They are sometimes added to cooking oils to prevent excessive foaming during deep frying. Silicone oils used as lubricants can be inadvertent defoamers (contaminants) in processes where foam is desired, such as in the manufacture of polyurethane foam.

Silicone oil is also one of the two main ingredients in Silly Putty, along with boric acid.

Silicone oil may be used as a gun lubricant. It is compatible with the rubber, plastic and metal parts frequently found in firearms. Due to the high surface adhesion of silicone oil, it forms a persistent film which may be useful in protecting guns during extended storage.

Medical uses

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Consumer products to control flatulence often contain silicone oil.[citation needed] Silicone oils have been used as a vitreous fluid substitute to treat difficult cases of retinal detachment, such as those complicated with proliferative vitreoretinopathy, large retinal tears, and penetrating ocular trauma.[4] Additionally, silicone oil is used in general medicine and surgery. Because of silicone oil's water repellent and lubricating properties, it is considered an appropriate material to maintain surgical instruments. They are also used in digital rectal examinations (DRE).

Automotive use

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Silicone oil has been commonly used as the fluid in the automobile cooling fan clutch assemblies, and is still being used in the newer electronic fan clutches.[5]

References

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