What is silicone oil?

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.

Molecular structure of silicone oil  
The repeating skeleton of silicone oil and other siloxane polymers consists of alternating silicon and oxygen atoms.  Silicone oil consists of linear repeating chains of silicon and oxygen, and each silicon atom also has two carbon-based substituents, which are usually methyl groups.  Silicone oils can have a certain degree of polymerization, in other words, the average number of repeated siloxane groups in the polymerization chain, ranging from a few units to several thousand units.  Replacing a small fraction of methyl groups with phenyl or amino functional groups can alter the way siloxane polymers interact with other materials.  Adding active organic groups to siloxane polymers also allows siloxane polymers to be integrated into various types of organic polymers, which can yield some unique properties compared to standard organic polymers.  

Silicone oil properties  
The viscosity of silicone oils can vary widely from 0.65Cs to 2,000,000cs, and the viscosity remains constant over a wide temperature range.  Silicon polymers also exhibit significant thermal stability (up to 250°C) compared to some organic polymers, due to the special properties of the chemical bond between silicon and oxygen in the polymer chain.  Because of their low surface tension, silicones spread easily on the surface and have higher compressibility compared to different hydrocarbons and mineral oils.  Siloxane polymers have good dielectric properties and remarkable resistance to shear stress, natural aging, oxidation and hydrolysis.