What are Silicone Oils?

The most common silicone oils are linear polysiloxane compounds, that orient in spiral chains, which easily glide and slip over one another. Silicone oils offer great thermal stability and fexible and flowable forms at extreme temperatures. Polydimethylsiloxane is the predominant silicone polymer made, but other organic groups (phenyl, vinyl, epoxide or amino) can be added to the siloxane polymer that can in some cases offer special characteristics or reactivity.

Chemical structure

The repeating backbone of silicone oils and other siloxane polymers consists of alternating silicon and oxygen atoms.  Silicone oils are comprised of linear repeating chains of silicon and oxygen, with each silicon atom also having two carbon-based substituents, which are most often methyl groups.  The silicone oils can possess a degree of polymerization, in other words the average number of repeating siloxane groups in a polymer chain, ranging from several units to several thousand units.  Replacing a small portion of the methyl groups with phenyl groups or amino functional groups can change how the siloxane polymers interact with other materials.  Adding reactive organic groups to siloxane polymers can also allow for siloxane polymers to be integrated into various type of organic polymers, which can result in some unique properties when compared to standard organic polymers.

Silicone oil properties

The viscosity of silicone oils can vary greatly 0.65cs to 2,000,000cs and the viscosity remains constant across a wide range of temperatures.  Silicone polymers also exhibit remarkable thermal stability (up to 250°C) when compared to some organic polymers, due to special characteristics of the chemical bonds between silicon and oxygen in the polymer chain.  Silicones spread on surfaces very easily, due to their very low surface tension, and have high compressibility when compared to different hydrocarbon and mineral oils.  Siloxane polymers have good dielectric properties and remarkable resistance to shear stress, natural ageing, oxidation and hydrolysis.

Revision sheet

Technology Oils
Definition ​Oil: any liquid polymerized siloxane with organic side chains.
General information ​Siloxane, the polymer backbone consists of alternating silicon and oxygen atoms (...Si−O−Si−O−Si…)
Oil: low Mw, range from around several hundred to several hundred  thousands g/mol.
Typical properties Oil: liquid or half solid.
Both Oil and gum obtain resistance of high/low temperature, weatherability, waterproof, environment friendly, none toxicity and so on . Many of them are used as the raw materials of silicone rubber or other products.
Processability Chlorosilanes to distillation and hydrolysis to prepolymer to chain extender to different oil types
Application/final products ​As raw materials for silicone rubber or other materials. Silicone oils are primarily used as lubricants, heat transfer oil or hydraulic fluids.


Why use silicone oils?

Silicone oils are used in products you may use in everyday life. Let’s take a closer look at your facial tissues. Thanks to the excellent soft hand feeling and good hydrophilicity of some types of siloxane polymers, top grade facial tissues have been using silicone type softeners to improve the “soft feel” of tissues. Silicone oil improves the softness and silk-like smooth feeling of the tissues, with minimum impact on tissue strength.

Silicone type softener benefits:

  • Emulsions with excellent shear stability are suitable for various additive processes
  • Treated tissues with good water absorption and permeability
  • Treated tissues maintain the whiteness
  • Improvement of antistatic and antibacterial properties of tissues


Related applications

The most common oils used in many applications are PDMS (polydimethylsiloxane). These inert oils are used as hydraulic or damping fluids, dielectric fluids, electronics-grade fluids, heating or cooling fluids, diffusion pump fluids, thermostatic fluids, paint additives and homecare product additives, lubricants and release agents. A certain number of these applications require the use of modified oils (e.g* phenylated oils in order to increase heat stability), as well as solubility in organic systems and compatibility with organic compounds. Silicone oils are also widely used in cosmetics, pharmaceutical and medical applications.

Useful links