Silicone oil: uses; compressibility and viscosity

Uses of Silicone oil

Silicone oil has smoothness, softness, hydrophobicity, good chemical stability, excellent electrical insulation and high and low temperature resistance and many other excellent characteristics. Therefore, it has been extremely widely used in the fields of medicine, daily chemical products, food, construction and so on. At present, silicone oil has rapidly become an indispensable auxiliary oil in vitreoretinal surgery.

Compressibility of Silicone oil

Unlike mineral oils, silicone oils are extremely compressible and do not condense when pressurised. Silicone oils are much more compressible than petroleum insulating oils or synthetic lubricants, making them ideal for use as shock absorber oils. Silicone oils with a viscosity of 10 centistokes or higher have a compressibility of 1.34% at 2,000 psi at room temperature. Lower viscosity fluids are more compressible than higher viscosity fluids.

Viscosity of Silicone oil

Silicone oils have a high viscosity (1.000–5.000 cs) and, once dispersed, the small droplets will tend to recoalesce back as a large bubble. The viscosity of different types of silicone oil, which is expressed in centistokes (1 cs = 10⁻⁶ m²/s), arises from the molecular weight and from the length of the polymers: increasing a silicone oil's molecular weight results in an increased polymer chain length and consequently an increase in its viscosity. Silicone oils currently used have a viscosity ranging from 1.000 (MW 37 kDa) to 5.000 cs (MW 65 kDa).

References:

[1] DANIEL CONSTANTIN BRANISTEANU. Intraocular pressure changes during and after silicone oil endotamponade (Review).[J]. Experimental and therapeutic medicine, 2020, 20 6: 204. DOI:10.3892/etm.2020.9334.