MT-705 diffusion pump fluid is a colorless to light straw, single component for ultrahigh vacua in the range of 10E-9 to 10E-10 torr untrapped and 10E-11 torr trapped. The vapor pressure and backstreaming rate of MT-705 Diffusion Pump Fluid are low enough that use of traps or refrigeration may not be necessary for all ultrahigh and ultraclean vacuum applications. It has the highest phenyl content of all silicone diffusion pump fluids, and hence, the best resistance to radiation. Additionally, MT-705 has a high spontaneous ignition temperature. Replacement for and equivalent to Dow Corning DC-705. Sold as DS-705 and Invoil 705 elsewhere.
MT-702 and MT-704 are available in separate listings.
| SPECIFICATION | MT-702 | MT-704 | MT-705 |
| Molecular Description | Mixed phenylmethyl dimethyl cyclosiloxane | Tetramethyl tetraphenyl trisiloxane | Pentaphenyl trimethyl trisiloxane |
| Color | Clear | Light Straw | Clear/Light Straw |
| Ultimate Untrapped Vacuum (torr) | 10E-5 | 10E-7 to 10E-8 | 5 E-9 |
| Ultimate Trapped Vacuum | – | to 10E-11 | to 10E-11 |
| Extrapolated Vapor Pressure at 25 ºC | 1 x 10E-6 | 2.1 x 10E-8 | 5 x 10E-10 |
| Specific Gravity at 25 ºC | 1.07 | 1.07 | 1.09 |
| Viscocity at 25 ºC | 45 | 39 | 175 |
| Flash Point, open cup (ºC) | 193 | 221 | 243 |
| Boiling point, 0.5 torr (ºC) | 180 | 215 | 245 |
| Typical Boiler Temperature (ºC) | 190 | 220 | 260 |
| Heat of Vaporization (kcal/gm mole) | 21.7/190 ºC | 25.5/200 ºC | 28.2/250 ºC |
| Surface Tension (dynes) | 30 | 37.3 | 36.5 |
| Molecular Weight | – | 484 | 546 |
| Price per gallon | $375.00 | $475.00 | $595.00 |