Silicones comprise a set of synthetic polymers made up of an inorganic frame consisting of a series of bonds between Silicon and Oxygen atoms (-Si-0- Si) and variously branched side functional groups of an organic nature, typical of carbon-carbon (C-C) bonds.
The remarkable versatility of this polymer in industrial contexts has stimulated the developer to compose numerous variants which, for simplicity's sake, are grouped into three main categories:
The best-known silicone oils can be divided into six main categories:
Silicone fluids are classified not only by their chemical composition but also on the basis of their average molecular weight or the dynamic viscosity value measured at a reference temperature of 25° C.
Silicone oils are available on the market with standard viscosity values and tolerances usually between +/-10%.
The silicone oils most commonly used in industrial lubrication belong to the dimethyl silicone family and are the best value for money, being available in a very broad variety of viscosities with remarkable properties that make them the preferred choice where harsh operating conditions are foreseen.
The main characteristics of silicone oils can be summarised as follows:
The dynamic viscosity value of a silicone oil is not always constant but can vary in relation to temperature as well as the dynamic stress to which it is subjected. This design parameter should be taken into account if the oil is responsible for the proper functioning of shock absorbers, soft-closing kinematics, dampers or viscous coupling units.
Silicone oils are either used directly for lubrication or as the formulation basis for silicone greases, which differ in their adhesive and cohesive capacity at friction points.
Silicone greases are preferred to silicone oils due to their superior ability to withstand centrifugation and mechanical loading.