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Silicone fluids have unique properties because they are not products of petroleum or organic chemistry. They were the first, and are still the only, major class of polymers that are products of inorganic chemistry. Silicone fluids consist of a broad range of different materials with the following characteristics:

  • Wide service temperature range
  • Low viscosity changes vs. temperature
  • Thermal stability
  • Low flammability
  • Shear stability
  • Dielectric stability
  • High compressibility
  • Chemical inertness
  • Low surface tension
  • Low toxicity

These features have facilitated the adoption of silicones as dielectric, hydraulic, heat transfer, power transmission, and damping fluids. They have found applications when incorporated as additives into plastics and rubbers as process and release aids, into coatings for flow and level control, and into process streams as antifoams. Other unique properties have led to their introduction in acoustical applications such as ultrasonic sensors and sonar buoys. Light refractive and index matching properties have allowed the use of silicones in fiber optics and optoelectronics. This proliferation of applications has engendered many improvements and refinements of silicone fluids.

Silicone fluids can be divided into six general classes:

The conventional fluids, also referred to as polydimethylsiloxanes, exhibit all the properties of the silicone family. The other classes of fluids can be considered modifications of the conventional fluids in which one set of properties has been enhanced, but generally other properties are altered or sacrificed.

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Silicone Fluids Property Profile Guide

PropertiesCommentConventional Silicone FluidsThermal Silicone FluidsOrganic Compatible Silicone FluidsFluorosilicone FluidsHydrophilic and Polar Silicone FluidsLow Temperature Silicone FluidsTypical Hydrocarbon (Paraffin) Fluids
Thermal PropertiesHigh temp (°C)1,000 hr in air, max175°260°150°190°135°235°130°
High temp (°C)indefinite O2 free, max200°280°230°260°
Low temp (°C)pour point, low value-70°-73°-50°-47°-50°-100°-30°
Rheological PropertiesViscosity (cSt)range3-2 x 10750-3 x 105500-1 x 10480-1 x 10420-5,0004-400
Visc-temp coefficientlow value0.510.610.750.840.5
Electrical PropertiesDielectric strength (volts/mil)range360-400400-420175-200300-400
Deielectric constantrange, 100 Hz2.50-2.772.78-2.952.5-36.95-7.35
Mechanical PropertiesCompressibility (%)at 20,000 PSI9.15.5~5-87.5~711.94.4-4.9
Density (g/cc)0.90-0.980.98-1.150.88-1.041.25-1.301.00-1.070.76-1.090.8-0.9
Compatibility PropertiesWater solubilityinsolubleinsolubleinsoluble - partialinsolubleinsoluble - solubleinsolubleinsoluble
Hydrocarbon solubilityaromatic/aliphaticsoluble/partialsoluble/solublesoluble/solubleinsoluble/insolublepartial/insolublesoluble/solublesoluble/soluble
Optical PropertiesRefractive index nD25range1.393-1.4031.428-1.5821.443-1.4931.336-1.3871.441-1.4541.335-1.5881.410-1.430
Release and Wettability PropertiesSurface tension (dynes/cm)range19.2-21.620.5-28.522.0-39.525.7-28.723.6-27.015.9-26.721-28
Wear/Lubricity PropertiesFour ball wear (mm) at 75 °C, 40 kg load steel on steel, 1 hr2-31.8-
Notes: All data on this table are for comparative purposes. The classes of fluids have a range of properties that do not represent the performance of an actual fluid. Values reported for fluids including the paraffin hydrocarbon oil are without additives such as EP agents or stabilizers.