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...). 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.
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. 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. 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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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.
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.
The viscosity of silicone oils can vary greatly 0.65 cs to 2,000,000 cs 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.
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.
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:
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.