Diphenyl Oxide(101-84-8), Diphenyl(92-52-4). Equivalent to Therminol VP- 1 & DOW Therm A

Diphyl Heat Transfer Fluid

Product Overview

Diphyl® is a clear, pale yellow liquid with a low viscosity with high temperature Heat Transfer Fluids for the application in liquid and vapour phase. It consists of a Eutectic mixture of diphenyl oxide and biphenyl. The fluid solidifies at approx. 12.3°C Diphyl® Heat Transfer Fluids has a high boiling point of 257°C and with the help of Nitrogen Blanketing System it can be operated at a maximum application temperature of 400°C. Diphyl® will not ignite spontaneously before reaching an auto ignition temperature above 615°C.

Characteristic Data

Parameter Unit Diphyl
Diphenyl oxide content (GC) % 72-75
Biphenyl content (GC) % 25-28
Chlorine content mg/kg max. 10
Range of application °C 400°C
Density (20° C) kg/m² approx. 1062
Kinematic viscosity (20° C) mm³/s approx. 4.12
Boiling temperature (1.013 bar) °C approx. 257
Flash point °C approx. 115
Max. film temperature °C approx. 410


Why Choose Prisco Chem


To be a reliable supplier by providing innovative products in service solutions.


To be a Leader in Heat Transfer Fluids (HTF) Business and grow our portfolio of speciality chemicals.


To provide customers with top quality products and services in a most responsible manner.

Work Ethics

Ethics is not definable, it is not implementable when it is not a part of individual consciousness. It involves not only our thinking but also our feelings.


Diphyl Heat Transfer Fluid is a specialized fluid, also known as Hot Oil, designed for efficient heat transfer in various systems. What sets it apart is its high boiling point of 257 °C at atmospheric pressure, allowing for pressure-free operation at temperatures up to 250 °C. This distinguishes Diphyl® as an ideal choice for diverse applications, especially in high-temperature environments.

Diphyl excels within a broad temperature range, with a maximum application temperature of 400 °C. Pressure requirements are minimal, reaching only 10.7 bar at this upper limit. The fluid’s versatility makes it suitable for low, medium, and high operating temperatures, catering to a wide array of heat transfer needs.

Yes, Diphyl is designed for operation in both liquid and vapor phases. Its high boiling point, coupled with low to medium viscosity, ensures optimal performance in heating and cooling processes within a liquid or vapor phase. This adaptability is particularly advantageous in inert gas atmospheres.

To ensure safe operation, it is essential to design facilities with a surface temperature limit of 410 °C. Additionally, operators should adhere to recommended pressure and temperature guidelines provided by the manufacturer. Proper handling, storage, and regular system maintenance are crucial for the long-term performance and safety of Diphyl.

Diphyl high boiling point and minimal pressure requirements contribute to simplified plant designs, even in high-temperature regions. The fluid’s thermal stability and performance characteristics make it an efficient choice for straightforward and cost-effective heat transfer system configurations, ensuring ease of operation in challenging environments.


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