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Dimethyl Silicone Oil

PM-125 Phenylmethyl Silicone Fluid

Chemical Name:Dimethyl, Phenylmethylsiloxane
Product Category:Dielectric Silicone Fluids Silicone Fluids
Structural Formula:silicone-oil-63148-62-9-_11_65_b_116566
CAS No.:CAS No. 63148-62-9
Molecular Formula:C6H18OSi2
Molecular Weight:162.38 g/mol

PM-125 Phenylmethyl Silicone Fluid

PM‐125 Silicone Fluid is a clear, colorless and odorless Phenylmethyl Silicone Oil with a viscosity of 125cSt @ 25°C. It replaces methyl groups found in conventional PDMS Silicone oils with a high percentage of Phenyl groups. In doing so, thermal stability and resistance to oxidation are significantly increased. PM‐125 provides long term stability at 230°C (open to air) and 300°C (closed to air). The fluid is further characterized by its high flash point, high dielectric strength, stability at extreme pressures, good heat capacity values, excellent lubricity and inertness to virtually all substrates.

Typical Product Data:

Viscosity @ 25°C125cSt
Specific Gravity1.07
Viscosity Temp Coefficient0.76
Pour Point °C-51°C
Flashpoint °C315°C
Ignition Temp °C482°C
Refractive Index1.500
Surface Tension24.5
Dielectric Properties:

Electrical Strength13.8kV/mm
Permittivity @ 100Hz2.77
Permittivity @ 1MHz2.77
Dissipation factor @ 100Hz0.0003
Dissipation factor @ 1MHz0.00005
Volume resistivity ohm.cm1x10hz
Dielectric Constant2.77
Thermal Properties: Specific Heat

TemperatureSpecific Heat
0°C1.418 kJ/kg. K
40°C1.498 kJ/kg. K
100°C1.615 kJ/kg. K
200°C1.812 kJ/kg. K
Viscosity to Temperature:

TemperatureViscosity (mm2/sec)
@ 99°C20cSt(mm2/sec)
@ 38°C84cSt(mm2/sec)
@ 25°C125cSt(mm2/sec)
@ -29°C22,000cSt(mm2/sec)
Viscosity/Temp Coefficient: 0.76
Viscosity @ 25°C: 125cSt


  • High Flash Point
  • High thermal Stability
  • Viscosity lowers quickly when heated:
  • Easy to pump/circulate at elevated temps
  • High Refractive Index RI 1.425
  • High Dielectric Strength
  • Hydrophobic
  • Stable under high rates of pressure
  • Stable under high rates of shear
  • Excellent Lubricity
  • High Temperature Laboratory Bath Fluid
  • High Temperature Heat Transfer Fluid
  • High Temperature Dielectric Fluid
  • High Temp /High Pressure Fluid
  • High Temperature Fluids for Flow Control Fluid
  • High Temperature Calibration Fluid
  • Refractive Index Matching Fluid
  • High RI Matching Fluids for LED and Optics
  • High Temp Silicone Lubricants for Plastic Parts
  • Silicone Lubricants for Rubber Parts

Packaging Specifications

Packaging Specifications
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PM-125 Phenylmethyl Silicone Fluid: Guide

As a calibration fluid, PM‐125 Silicone Fluid is widely used in Flow Control, Temperature Control and Motion Control technologies. Again, its advantage over conventional oils is that it will not break down at high temperatures and it will not coagulate at high pressures. It is widely used for instruments, gauges, sensors, meters and devices that are subject to extreme temperatures and high pressures.

PM‐125 is a high phenyl content silicone fluid. In comparison to conventional PDMS silicone oils, PM‐125 has much higher thermal stability and remains stable at temperatures > 230°C (open system). When heated, its viscosity lowers very quickly which makes it an excellent choice for high temperature laboratory baths and heat transfer systems that have to circulate and pump the fluid. Conversely, it is not recommended for cold temperature systems due to its acute viscosity increase at lower temps.

PM‐125 Silicone Fluid has a higher RI value (1.500) than conventional PDMS silicone. It an excellent RI index matching fluid and optical fluid for use in sensor /imaging / LED and Photonics technologies that require a higher RI value than conventional fluids.

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