Methyl phenyl silicone oil is a clear, colourless silicone fluid in which some methyl groups are replaced by phenyl groups (CAS 68083-14-7). This gives it much higher thermal stability, lubricity and refractive index than standard dimethyl silicone oil. The 500 cSt grade is used as a heat transfer, bath, dielectric and optical matching fluid.
- Formulation
- Phenyl methyl polysiloxane fluid, CAS 68083-14-7.
- Transparent, colourless liquid, free from impurities and lumps.
- Viscosity of 450 – 550 mPa·s (Brookfield, 25°C).
- Technical Features
- Refractive index: 1.4980 – 1.5050 at 25°C.
- Specific gravity: 1.00 – 1.02.
- Flash point: 375°C – 450°C.
- Water solubility: Insoluble; strongly hydrophobic.
- Thermal stability: Several times higher than dimethyl silicone fluids.
- Compressibility: Much lower than dimethyl silicone fluids; stable under high pressure and high shear.
- Dielectric strength: High.
- Uses
- High-temperature laboratory bath fluid.
- Heat transfer fluid.
- Dielectric fluid.
- High-temperature, high-pressure hydraulic and flow control fluid.
- Calibration fluid.
- Refractive index matching fluid, including high-RI fluids for LEDs and optics.
- Base fluid for high-temperature silicone lubricants for plastic and rubber parts.
Advantages: high flash point, much better lubricity than dimethyl silicone oil, viscosity that drops quickly on heating for easy pumping and circulation, and solubility in a wide range of organic solvents.
FAQs on Silicone Oil
What is the difference between methyl phenyl silicone oil and dimethyl silicone oil?
Methyl phenyl silicone oil has phenyl groups on its silicone backbone. This gives it several times higher thermal stability, greater lubricity, lower compressibility and a higher refractive index than dimethyl silicone oil.
Why is it used as a heat transfer and bath fluid?
Its high flash point and thermal stability let it run at high temperatures for long periods. Its viscosity also drops quickly when heated, so it pumps and circulates easily in baths and heat transfer systems.
What is its refractive index used for?
Its refractive index of 1.4980 – 1.5050 is close to that of glass and many optical materials. This makes it suitable as an index matching fluid in LEDs, optics and calibration work.
Which solvents does methyl phenyl silicone oil dissolve in?
It dissolves in aliphatic and aromatic hydrocarbons, alcohols, ethers, ketones and esters, such as acetone, toluene and xylene. Unlike dimethyl silicone oil, it is also soluble in aqueous alcohols.
Can it be used in lubricants and greases?
Yes. It offers much better lubricity than dimethyl silicone oil and blends well with metallic soaps and organic additives. It is used as a base fluid for high- and low-temperature lubricants and greases, including those for plastic and rubber parts.