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How silicone lubricants work
The purpose of lubrication is to:
1. Separate two moving surfaces with a softer and easier-to-shear liquid material or lubricant located between the surfaces.
2. Use pressure to increase the liquid’s viscosity, enabling it to separate the two moving surfaces and reduce the coefficient of friction or the force needed to move them against one another under an applied load.
Silicone oils, pastes, and greases contain long, linear polymers that slip easily over one another. This free movement gives them their lubricating properties.
Silicone pros and cons
Because of their low methyl-to-methyl intermolecular interactions and high backbone flexibility, silicone materials have:
* A low glass transition temperature and remain liquid at room temperature, even at high molecular weight
* High boiling points, and their viscosity is less affected by temperature changes than organics
However, the surface tension of silicone fluids is very low, and they tend to spread more than organics.
Their high spreading and high compressibility limit the internal pressures (viscosity increases) that can build within silicone materials when they are used as lubricants. This limits their load-carrying capacity compared to organic lubricants with the same initial viscosity. However, silicone lubricants do have sufficient load-carrying capacity for all metal-to-plastic and plastic-to-plastic lubrication applications.
Silicone benefits for lubrication
Silicone lubricants perform under extreme conditions of heat and cold.
* Aggressive environments have less effect on silicones compared to organic lubricants.
* The oxidation resistance of silicones makes them suitable for long-life applications.
* Because of their inertness to most chemicals, silicone lubricants are widely used in the chemical industry and in food and beverage processing.
* The wide temperature capability of silicone-based lubricants is unsurpassed.
Typical silicone lubricant applications
* Silicone compounds – grease-like materials composed of silicone fluids and silica fillers – are used for their sealing, dielectric, non-metal-to-metal lubricating and release properties.
* Silicone greases – solid to semisolid materials consisting of a lubricating fluid, a thickening agent, and additives – are used on rolling-element bearings and other moving parts.
* Silicone pastes – grease-like materials containing a very high percentage of solid lubricants – are used for assembly and lubrication of highly loaded, slow-moving parts.
* Silicone anti-friction coatings – lubricating “paints” – cure to form dry, solid lubricant coatings that are bonded to the surface.
* Silicone dispersions – finely divided solid lubricants suspended in lubricating fluids – are preferred when it is necessary to apply solid lubricants in liquid form.
Courtesy: Dowcorning.com
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