Silicone Fluids

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These synthetic fluids are organo-silicon oxide polymers and have exceptional chemical stability both at high temperature and when in contact with most gases and vapours. They provide a range of general purpose fluids for ultimate vacuum from about 10⁻⁵ to 10⁻⁹ mbar, and are particularly useful in industrial processing applications due to their exceptional ruggedness. High throughputs of air, water vapour and corrosive gases can be pumped without fluid degradation. The fluids can withstand repeated admission of atmospheric air while at operating temperature and are widely used in valveless quick-cycle pumping processes. They have low toxicity and good resistance to gamma radiation.

Fluid breakdown products (due to bombardment and so on) tend to be electrically insulating and so we do not recommend these fluids for physical electronic applications such as mass spectrometers and surface analysis systems. The fluids are indifferent lubricants. Their decomposition is catalysed by traces of alkali metals (for example, caesium) and their use should be avoided where possible.

Silicone 704

Silicone 704 is a Tetramethyltetraphenyltrisiloxane based fluid for producing high vacuums in the range 10⁻⁷ to 10⁻⁸ mbar. This fluids exhibits extreme chemical, thermal, oxidation, hydrolysis and radiation resistance. It also has extremely low back-streaming properties.

Silicone 704 is intended for use in particularly tough, rugged applications including vapour deposition of thin films by sputtering or evaporation, electron beam operations and high vacuum furnaces, melting, degassing and sintering, refractory metals and thick film deposition. It is also suitable for all aspects of vacuum coating such as optics and automotive components and the UHV characteristics are particularly useful for thin film, surface technology, thermonuclear and plasma physics applications.

Typical ultimate vacuum achievable at 20°C

Vapour pressure @ 25°C

Boiling temperature at 1.3 mbar (approx)

Viscosity cSt @ 25°C

Pour point °C

TFlash point °C

Specific gravity at 25°C

8.0x10-9mbar

1x10-9mbar

215 °C

37-42

-34

>210

1.06-1.07

Documentation

Spectroscopy magazine

Silicone 705

Silicone 705 is a Pentaphenyltrimethyltrisiloxane based fluid for producing ultra high vacuums in the range 10⁻⁹ to 10⁻¹¹ mbar due to extremely low vapour pressure and back-streaming rates It exhibits extreme chemical, thermal, oxidation, hydrolysis and radiation resistance.

Silicone 705 is intended for use where ultrahigh and ultraclean vacuum conditions are required. The UHV characteristics particularly useful for thin film, surface technology, thermonuclear and plasma physics applications as well as electron microscopes. Extreme stability and high spontaneous ignition temperature make it ideal for use in space-simulation chambers. Low vapour pressure and low backstreaming rate make cold and refrigeration traps unnecessary for pressures in the 10⁻⁸ mbar range. However with a liquid nitrogen trap ultimate pressures of 10⁻¹¹ mbar can be achieved.

Typical ultimate vacuum achievable at 20°C

Vapour pressure @ 25°C

Boiling temperature at 1.3 mbar (approx)

Viscosity cSt @ 25°C

Pour point °C

TFlash point °C

Specific gravity at 25°C

8.0x10-11mbar

2x10-11mbar

245 °C

165-185

-14

>243

1.09-1.10

Santovac® 5 diffusion pump fluid

This synthetic fluid is a polyphenyl ether developed from fluids originally produced as lubricants for space vehicles. It has exceptionally low vapour pressure, exceptional thermal stability and a tendency to wet surfaces less readily and ‘creep’ to a lesser extent than is common with most fluids. The fluid is employed for the cleanest high vacuum and ultra high vacuum applications down to less than 10⁻⁹ mbar (for example, electron microscopes, mass spectrometers and surface physics studies) where its excellent high vacuum performance and low tendency to migrate into the pump system particularly recommend it. The fluid is chemically stable, non-corrosive, safe and non-toxic at normal operating temperatures. Fluid breakdown products (due to bombardment and so forth) tend to be electrically conducting. Lubricating qualities are good and the fluid finds application to lubricate mechanisms in vacuum systems.

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