Diffusion Pump Fluid
Tetramethyltetraphenyltrisiloxane & Pentaphenyltrimethyltrisiloxane as diffusion pump oil
Tetramethyltetraphenyltrisiloxane (CAS No. 3982-82-9, know as 704 fluid) and Pentaphenyltrimethyltrisiloxane (CAS No. 3390-61-2, known as 705 fluid), both methyl phenyl silicone fluids are commonly used as diffusion pump oil. Their low vapor pressure minimizes backstreaming of oil vapor into the vacuum chamber, ensuring a high vacuum level is maintained. The excellent thermal stability and oxidation resistance allow them to withstand the high temperatures generated during diffusion pump operation. Their chemical inertness prevents contamination of the vacuum environment and ensures compatibility with sensitive equipment.
704 is suitable for high vacuum level at 10^-7 Torr to 10^-8 Torr in untrapped systems. 705 is preferred for ultra-high vacuum (10^-9 Torr to 10^-10 Torr, untrapped system). Due to its extremely low vapor pressure, the traps or refrigeration are not needed for 705.
GW-MP704 & GW-MP705 technical index
We provide Dow Corning 704, Shin-Etsu HIVAC F-4; Dow Corning 705, Shin-Etsu HIVAC F-5 equivalent diffusion pump oil. The following table summarize their technical characters.
| Product Name | Chemical Name | Ultimate Vacuum (untrapped)/torr | Saturated Vapor Pressure (SVP)/torr | Refractive Index | Specific Gravity at 25°C | Viscosity at 25°C | Flash Point | Boiling Point | Congealing Point |
|---|---|---|---|---|---|---|---|---|---|
| GW-MP704 | Tetramethyltetraphenyltrisiloxane | 10E-7 to 10E-8 | 2 x 10E-8 | 1.557 | 1.065 | 40 | 210°C | 215°C | -35°C |
| GW-MP705 | Pentaphenyltrimethyltrisiloxane | 10E-9 to 10E-10 | 5 x 10E-10 | 1.582 | 1.097 | 175 | 243°C | 245°C | -14°C to -18°C |
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