High Temperature Silicone Heat Transfer Fluids

Chemical Name: Diphenyl‐Dimethylsiloxane (DPDM‐400), Phenylmethylsiloxane (PM‐125)

PDMS Silicone Heat-stabilized (HT-110)

CAS No: 68083‐14‐7 (DPDM‐400), 63148‐52‐7 (PM‐125)

Description: DPDM‐400 & PM‐125 High Temperature Silicone Heat Transfer Fluids are clear, colorless, and odorless linear Phenyl‐based Silicone Oils. They are formulated for high temperature applications and have a service temperature range of 25C to 300C (closed system).

DPDM‐400 and PM‐125 are characterized by their high flash points, long‐term stability at high temps, hydrophobic nature, high dielectric strength, low vapor pressure, low thermal expansion, high heat capacity, stability under high pressure, and high RI values.

DPDM‐400 & PM‐125 possess high VTC values (viscosity‐to‐temperature coefficients). When heated, their viscosity will lower very quickly making them easy to pump and circulate in high temperature baths / high temperature systems. However, they are not recommended for cold temperature as their viscosity will conversely thicken very quickly.

Unlike conventional PDMS Silicone fluids, DPDM‐400 and PM‐125 have Specific gravity of 1.07...heavier than water. For certain applications such as Down‐hole / Oil & Gas Exploration, a high temperature, and hydrophobic fluid that is heavier than water is needed. If so, both of these fluids are good candidates.

If a wider service temp range and lower viscosity at ambient are needed, the HT‐110 High Temperature Silicone Heat Transfer Fluid should be considered. To confirm, the HT‐110 is a PDMS Silicone Oil with a viscosity of 100cSt @ 25C. It is heat‐stabilized with an iron‐siloxane additive and will remain stable at elevated temperatures. HT‐110 has a lower VTC value and does not thicken as acutely as the PM‐125 & DPDM‐400 when chilled. It can be used for wider temperature ranges from ‐40°C to 250°C (open) and ‐40°C to 300°C (closed).

However, due to the heat‐stabilizer additive, the HT‐110 has a brownish color and odor when heated. If you need to see instrumentation within the fluid or foresee odor being a concern, it is not be a good choice.

See also Silicone Bath Fluids & Dielectric Silicone Fluids

Silicone Heat Transfer Fluids are widely used in Flow Control, Temperature Control, Electronic Control and Pressure Control Technologies & Instruments. They are particularly effective for use in instruments and gauges that will operate at extreme temperatures and high pressure.

Silicone fluids are hydrophobic and prevent humidity from entering the gauge/instrument housing. This is very important. The presence of water can cause damage to the sensitive parts within the gauge/instrument housing. Ultimately, Silicone Heat Transfer Fluids will extend the service life of the equipment that it fills and provide accurate readings even in the harshest of conditions.

Product Data:

Product Viscosity Specific Gravity Refractive Index Pour Point Flash Point (open cup) V.T.C Thermal Expansion cc/cc °C Thermal Conductivity g/cal/cm/sec °C
DPDM-400 400cSt 1.07 1.505 -30°C 315°C 0.82 0.00073 0.00032
PM-125 125cSt 1.07 1.500 -51°C 315°C 0.76 0.00075 0.00035
HT-110 100cSt 0.960 1.4030 -65°C 315°C 0.60 0.00095 0.00037


  • Stable at Extremely High Temperatures
  • High Resistance to Oxidation
  • High Flash Points
  • High Dielectric Strength
  • High Heat Capacity
  • Stable at High Pressures
  • High VTC (PM‐125 & DPDM‐400): viscosity lowers very quickly when heated…easy to pump & circulate fluid
  • Hydrophobic Nature
  • High Refractive Index Values for PM‐125 & DPDM‐400
  • Inert to virtually all components
  • Low vapor pressure at elevated temperatures
  • Low volume expansion at elevated temperatures

Applications Include:

  • Heat Transfer Medium for High Temperature
  • High Temperature Heat Transfer Fluid for Flow Control
  • High Temperature Heat Transfer Fluid for Temperature Control
  • High Temperature Heat Transfer Fluid for Electronic Controls
  • High Temperature Heat Transfer Fluid for Pressure Control
  • Protect internal components of gauges and instruments against vibration, freezing & corrosion
  • Dielectric Coolants for electronic sensors
  • High Temperature Hydraulic Fluid
  • High Temperature & High Pressure fluid for Subsea
  • High Temperature & High Pressure fluid for Oil & Gas Exploration
  • High Temperature Dielectric Fluids for Lighting Systems
  • High Refractive Index Matching Fluids
  • High RI Matching Fluids for LED and Optics
  • VOC Exempt Fluids for Renewable Energies
  • High Temperature Silicone Oil for Seismic Research
  • High Temperature Silicone Damping Fluid: Dampen vibration in gauges, instruments, meters and control equipment
  • High Temperature Silicone Lubricants for Rubber Parts
  • High Temperature Laboratory Bath Fluid
  • High temperature circulating bath fluid
  • High Temperature Calibration Fluid

Industries & Fields of Research include: R&D, Education, Defense, Oil & Gas Exploration, Energy, Aviation, Aerospace, Telecommunications, Rotorcraft, Renewable Energies, Couplings Manufacturers, Automotive, Valve & Gasket Manufacturers, Turbine Technology, Pressure Control Technology, Temperature Control Technologies, Process Measure & Control Technologies, Flow Management Products, Electro‐Hydraulic, Temperature Measurement Technologies, Geothermal, Electronics, Sensor Technology, Geosciences, Environmental, Electrical Testing, Optics, LED, Architectural Testing, Photonics, MEMS Micro‐Electro‐Mechanical Systems, Refractive Index Matching Digital Display Technology, Flow Control Technology, Deep Sea / Subsea Technologies, Wire & Cable Industry, Fluid Power, Cable Manufacturers, Telecommunications Cables, Deepwater, ROV Technologies Earth & Atmospheric Sciences, Seismic Research, Oceanography Research, Geothermal, Physical Sciences, Chemical Engineering, Mechanical Engineering, Polymer Research, Computer Engineering Research, Robotics Research, Wind Technology, Plastic Manufacturing, Thin Film Coating Technology, Hydraulics, Lighting Systems, Seismology, Aeronautics, Pipe & Tubing Systems, Fiber Optics Technology, Touch Monitor Technology.

Silicone Heat Transfer Fluids are widely used in the following: pressure gauges, pressure control instruments, pressure testing equipment, temperature testing equipment, temperature control equipment, pumps, pipeline equipment, flow testing equipment, flow level sensors, electronic sensors, level controllers, rotary dampers, geothermal monitoring equipment, seismology instruments, temperature recorders, temperature measurement equipment, process instruments, process recorders, level sensors, control valves, calibration equipment, flow control instruments, laboratory research instruments, digital display meters, gravity meters, testing equipment, testing instruments, monitoring equipment, pulsation dampeners, level instruments, electro hydraulic actuators, flow meters, thermostats, industrial thermometers, dashpots, aviation instruments, aviation gauges, electronic timer systems, control cables, optical instruments, aviation gyroscopes, process control equipment, test equipment, shock testing equipment, high pressure gauges, subsea gauges, process, gauges, subsea instruments, subsea cables, shock dampeners for R/C vehicles, underwater vehicles, deep sea instruments, deep sea lighting equipment, deep sea cameras, deep sea sensors, deep sea robotics, liquid filled gauges, level controllers, rotary dampers, temperature and process recorders, control valves, calibration equipment, flow meters, thermostats, industrial thermometers, monitoring systems, avionic gauges and aviation instruments.

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 and are REACH Compliant.