Polyphenyl ether
Ultra-high-vacuum fluids
Table:
Table 3: Diffusion Fluid Property Comparison

Fluid Property

Polyphenyl Ether

SANTOVAC 5

Silicone

Dow Corning

Hydrocarbon Oil

Apiezon

Vapor Pressure, Torr at 25 °C

4x10−10

2x10−8

5x10−6

Molecular Weight

446

484

420

Density at 25 °C

1.20

1.07

0.87

Flash Point, °C

288

221

243

Boiling Point at 1.3 mbar, °C

295

223

220

Viscosity (cSt) at 25 °C

1000

40

135

Viscosity (cSt) at 100 °C

12.0

4.3

7.0

Surface Tension, Dynes/cm

49.9

30.5

30.5

Refractive Index at 25 °C, 589 nm

1.67

1.56

1.48

Thermal Stability

Excellent

Good

Poor

Oxidation Resistance

Excellent

Excellent

Poor-Fair

Chemical Resistance

Excellent

Good

Poor

Radiation Resistance

Excellent

Good

Fair

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