PM-125 Phenylmethyl Silicone Fluid

Product Description: 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.

Chemical Name: Dimethyl, Phenylmethylsiloxane

CAS No: 63148-52-7

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Availability: 1‐gallon (4kg net wt.), 5‐gallon pail (20kg net wt.), 55‐gallon drum (220kg net wt.)

Product Equivalent: Dow Corning® 550 Fluid

Service Temperature Range: 25°C to 230°C open to air/ 25° to 300°C closed to air


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.

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 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.

Typical Product Data:

Viscosity @ 25°C Specific Gravity Viscosity Temp Coefficient Pour Point °C Flashpoint °C Ignition Temp °C Refractive Index Surface Tension
125cSt 1.07 0.76 -51°C 315°C 482°C 1.500 24.5

Dielectric Properties:

Electrical Strength Permittivity @ 100Hz Permittivity @ 1MHz Dissipation factor @ 100Hz Dissipation factor @ 1MHz Volume resistivity Dielectric Constant
13.8kV/mm 2.77 2.77 0.0003 0.00005 1x10hz 2.77

Thermal Properties: Specific Heat

Temperature Specific Heat
0°C 1.418 kJ/kg. K
40°C 1.498 kJ/kg. K
100°C 1.615 kJ/kg. K
200°C 1.812 kJ/kg. K

Thermal Properties: Thermal Conductivity

Temperature Thermal Conductivity
25°C 0.00035 g cal/cm sec °C
50°C 0.00036 g cal/cm sec °C

Thermal Properties: Thermal Gel Time (open system)

Duration @ Temperature Thermal Gel Time
months @ 200°C 14 months
hours @ 250°C 1,200 hours
hours @ 260°C 200 hours

Viscosity to Temperature:

Temperature Viscosity (mm2/sec)
@ 99°C 20cSt(mm2/sec)
@ 38°C 84cSt(mm2/sec)
@ 25°C 125cSt(mm2/sec)
@ -29°C 22,000cSt(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

Applications Include:

  • 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

Industries & Fields of Research include:R&D, Education, Defense, Oil & Gas Exploration, Energy, Aviation, Aerospace, Life Sciences, Renewable Energies, Turbine Technology, Wind Power Technology, Temperature Control Technologies, Geothermal, Solar Industry, Sensor Technology, Geosciences, Electronics, Environmental, Electrical Testing, Optics, LED, Photonics, MEMS Technology, Refractive Index Matching Digital Display Technology, Flow Control, Flow Meters, Deep Sea / Subsea Technologies, Dielectric Fluids for Wire & Cable, Deepwater, ROV Technologies, Laser Technology Research, Earth & Atmospheric Sciences, Seismic Research, Oceanography Research, Physical Sciences, Chemical Engineering, Mechanical Engineering, 3D Printing Technology, Plasma Research, LCD Technologies, Polymer Research, Computer Engineering Research, Robotics Research, Plastic Manufacturing, Rubber Manufacturing, Hydraulics, Nanotechnology Research, Geothermal, Fuel Cell Technology, Hydrophobic Coatings, Lighting Systems, Seismology, Aeronautics, Pipe & Tubing Systems, Printing Industry, Industrial Cleaning, Touch Screen Technology, Fiber Optics, Touch Monitor Technology, Touch Screen Technology, Temperature and Process Controllers

Environmental: Silicone Fluids are exempt from Federal VOC regulations, including California (CARB) and OTC regulations. They are HAP‐free and do not contribute to ozone‐depletion and global warming. In addition, they meet RoHS Compliancy.