Silicone Oil

Synonym: Silicone Fluid

Silicone fluids is also called silicone oil, the typically clear, transparent liquids. The viscosity of silicone oils can vary greatly 0.65 to 2,500,000 cSt and the also little viscosity change in silicone fluids over a wide temperature range. Strong dielectric properties over a wide temperature range, low surface tension, odorless, low toxicity, and soluble in many solvents. The most common silicone oils are linear polysiloxane compounds, that orient in spiral chains, which easily glide and slip over one another.

Chemical Properties

Silicone oils are constituted of a linear chain of siloxane repeating units (–Si–O) and a variety of side chains (radical side groups). Because of their viscosity and their ability to repel water, they are referred to as oils. Silicone fluids are a series of silicone fluids with various viscosities and of excellent purity. To obtain low viscosity silicone oil, used the acid clay as catalyst, if want to produce high viscosity silicone oil or a viscous material can use alkaline catalyst. Their viscosities lie between 0.65 and 2,500,000 cSt, depending on the type. Within the silicone oils, the polymeric chains, which have a very high methyl density and thus low intermolecular association, glide and slip over one another: the oils are fluids. The silicone oils can be used as is, in dispersion or in emulsions.

The major differences among silicone oils depend on the molecular weight (MW), on the length of the linear chain, and on the chemical structure of radical side groups, radical end termination of the polymer chains, and the size distribution of the chain. Thus, each type of silicone oil has specific chemical and physical characteristics. Since there are only very weak intermolecular forces between the individual methylsilicone chains, they are liquid over wide ranges of their molecular weight.

Silicone oil insoluble in water, methanol, glycol and -ethoxyethanol, mutually dissolved with benzene, dimethyl ether, methyl ethyl ketone, carbon tetrachloride or kerosene, slightly soluble in acetone, dioxane, ethanol and butanol. It has a small vapor pressure, high flash point and ignition point, low freezing point.


Thermal stability: Silicone fluids have outstanding stability against thermal oxidation.

Cold resistance: Silicone fluids withstand low temperatures well. Methylphenyl silicone fluid, formulated for low temperature applications, maintains flowability even at -65°C.

Viscosity stability: There is little viscosity change in silicone fluids over a wide temperature range(from -60°C to 300°C)

Chemical stability: Silicone fluids are almost totally chemically inactive. Minimal change in physical properties over a broad temperature range.

Inert, non-corrosive, nontoxic: Silicone fluids have almost no adverse effects on metals and many other materials.

Low surface tension: Low surface tension and thus high surface activity.Silicone fluids have much lower surface tension than water and other common synthetic oils.

Good solubility: Good solubility in a wide range of solvents.

According to the type of organic groups, the corresponding application characteristics are as follows:

# Types Feature
1 Methyl Electrical insulation, heat resistance, other characteristics
2 Phenyl Heat resistance, cold resistance, compatibility
3 Hydrogen Reactivity
4 Ethyl Age resistance, surface properties, lubricity
5 Vinyl Weather resistance, age resistance, UV resistance, and toughness
6 Chlorophenyl Lubricity
7 Long chain alkane Lubricity, paintable release
8 Ammonia Reactivity, softness
9 Epoxy hydrocarbon Reactivity, smoothness, softness
10 Hydroxyl Reactivity
11 Carboxyalkyl Compatibility
12 Hydroxyalkyl Compatibility
13 Allyloxycarbonyl Lubricity, mold release
14 Polyether Water solubility, water dispersibility, surface activity
15 Perfluoroalkyl Lubricity, oleophobicity


According to the broad classification, silicone fluids can be divided into two categories: straight silicone fluids and modificd silicone fluids, In the most commonly used silicone oil, all the organic groups are methyl, called methylsilicone oil.

According to chemical structure 

According to the different classification of the substituent groups on the polysiloxane chain, silicone oil can be divided into: methyl silicone oil, phenyl silicone oil, ethyl silicone oil, hydroxy silicone oil, amino silicone oil, hydrogen silicone oil, vinyl silicone oil and polyether modified silicone oil. fluorosilicone oil and many other types.

By application

From the applications of view, it has damped silicone oil, diffusion pump silicone oil, hydraulic oil, insulating oil, heat transfer oil, brake oil, etc.

According to processing status

Primary products refer to silicone fluid products before being processed, including four categories of hydroxy silicone fluid, silicone functional silicone fluid, carbon functional silicone fluid and non-reactive modified silicone fluid. Traditionally, the first two types are called linear silicone fluids, and the latter two are called modified silicone fluids.

Secondary products are made of silicone fluid as raw materials, thickeners, surfactants, solvents and additives, etc., and processed into greases, emulsions and solutions by specific processes, such as silicone grease, silicone paste, defoaming agent, release agent, etc.

By form

Silicone fluid is often not used alone, but is made into an effective application method through a special formula; it is not used as a raw material, but as an auxiliary material to produce a certain effect. Generally speaking, there are three basic forms of silicone fluid on the market: pure silicone fluid, solution, and emulsion.

Pure silicone fluid

Pure silicone fluid is very stable, heat-resistant, frost-resistant, good in storage, has a high flash point and high ignition point, and has few storage and transportation problems.

Silicone fluid in solution state

In actual use, it is often necessary to dilute the silicone fluid solution, and it is not convenient for users to configure the solution by themselves. When using it, add active auxiliary agents (catalyst, cross-linking agent, etc.) to the solution to facilitate storage and use.

Silicone fluid in emulsion state

A large part of silicone fluid or products containing silicone fluid on the market are in the form of emulsion. Compared with solvent silicone fluid, it has the advantages of low price, being non-flammable and harmless to health.


Silicone oils have many uses due to their lubrication, dielectric and water repellent properties. The most common oils used in many applications are PDMS (polydimethylsiloxane). These inert oils are used as hydraulic fluids or damping fluids, dielectric coolants, power transmission fluids, electronics-grade fluids, heating or cooling fluids, diffusion pump fluids, antifoams, thermostatic fluids, paint additives and homecare product additives, lubricants (poor frictional lubrication)  , release agents, and many others.


# Name CAS
1 Methyl Silicone Oil 9006-65-9
2 Phenyl Silicone Oil 63148-58-3
3 Vinyl Silicone Oil 68083-19-2
4 Hydroxyl Silicone Oil 70131-67-8
5 Hydrogen Silicone Oil 63148-57-2
6 Epoxy Silicone Oil 9006-65-9
7 Polyester Silicone Oil 67674-67-3
8 OH Polymer 70131-67-8
9 Silicone Emulsion 9006-65-9
10 Phenyl Modified Silicone Oil 225927-21-9/17875-55-7/17962-34-4/18027-45-7/68957-07-3/865811-59-2
11 Silicone Diffusion Pump Oil 3390-61-2
12 Alcohol Hydroxyl Silicone Oil 68937-54-2
13 Alcohol Hydroxyl Long-Chain Alkyl Silicone Oil 68937-54-2
14 Hydroxyl terminated methyl vinyl silicone oil CAS: 67923-19-7