Applications of Silicone Oil

Silicone oils are constituted of a linear chain of siloxane repeating units (–Si–O) and a variety of side chains (radical side groups). Silicone fluids are used as hydraulic or damping fluids, dielectric fluids, electronic grade fluids, heating or cooling fluids, diffusion pump fluids, thermostatic fluids, paint additives and additives for home care products, lubricants and mould release agents. Consumer products that control flatulence often contain silicone oils. Silicone oil has been used as a vitreous fluid substitute in the treatment of refractory cases of retinal detachment. Silicone oils are also used in general medicine and surgery. Due to their hydrophobic and lubricating properties, silicone oils are considered suitable for maintaining surgical instruments. They are also used for DRE (Direct Rectal Examination). Silicone fluids are commonly used as a fluid in automotive cooling fan clutch assemblies and are still being used in new electronic fan clutches.

Imaging flow cytometry was used to distinguish protein aggregates from silicone oil droplets and to quantify protein-silicone oil interactions. Imaging flow cytometry can be used to distinguish between fluorescently labelled protein aggregates and silicone oil droplets with an accuracy of more than 95 per cent, irrespective of size; protein-silicone oil interactions can be assessed qualitatively by examining the image data or quantitatively by features extracted from the image data.

Properties of Silicone Oil

Heat Resistance

Silicone oils are extremely stable against thermal oxidation. For example, dimethicone DM-FLUID remains virtually unchanged when exposed to air temperatures of up to 150°C. Methylphenyl silicone oils have better heat resistance than dimethicones and can be used for long periods of time in environments up to 250 °C.

Low-Temperature Resistance

Silicone oils has excellent low-temperature resistance. DM-FLUID remains fluid even at -50°C. Methylphenyl silicone fluid was specially developed for low-temperature applications, so it remains fluid even in environments of -65°C. Since temperature has little effect on viscosity, these products are ideal for applications in cold regions.

Viscosity Stability

Silicone oils shows little change in viscosity due to changes in temperature. It is thus ideal for use as instrument oil in instruments used in airplanes, automobiles, and trains, and for other applications that make use of Silicone oil's viscous properties. Low-viscosity (10 mm2/s and below) products aside, DM-FLUID offers the advantage of less temperature-dependent viscosity change than common mineral and synthetic oils or other Silicone oils.

Thermal Conductivity

The thermal conductivity of dimethyl Silicone oil is lower than that of common organic compounds (nearly the same as that of benzene and toluene) and is roughly 25% that of water. Although thermal conductivity increases with higher viscosities, it becomes nearly constant at viscosities above 100 mm2/s. The thermal conductivity of DM-FLUID is 2.4-3.5x10-4 cal/cm·sec·°C at viscosities below 20 mm2/s, and roughly 3.7-3.8x10-4 cal/cm·sec·°C at viscosities over 50 mm2/s.

References:

[1] PROBST C. Characterization of Protein Aggregates, Silicone Oil Droplets, and Protein-Silicone Interactions Using Imaging Flow Cytometry[J]. Journal of pharmaceutical sciences, 2020, 109 1: Pages 364-374. DOI:10.1016/j.xphs.2019.05.018.