// Blog November 18, 2020

Testing the Thermal Conductivity of Filled Polymer: CoolMag 28

Today's need for conductive potting compounds is building the future of electric vehicle and battery performance.

Filled polymers are attractive because their properties are highly customizable, allowing engineers to design a material with the right combination of thermal and mechanical properties for the target applications. Additionally, they are lightweight in comparison to other composite materials. A filled polymer aircraft part may have a fraction of the mass a steel part would have, while retaining similar strength.

[Spanish] Vea acá el seminario web grabado con CoolMag28 y C-Therm

In thermal management, filled polymers are often used as potting compounds in electronics, to reduce thermal contact resistance and secure electrical components. Potting compounds are designed to be solid or gelatinous materials which provide structural support and physical protection of electronic components while also displacing heat and gas to prevent gas phenomena such as corona discharge. Increasingly, there is demand for potting compounds with improved thermal conductivity for better heat dissipation in high performance electronic devices. Accurate and repeatable measurement of thermal conductivity at a wide range of temperatures is a critical performance check – easily completed in the lab with
C-Therm’s Trident Thermal Conductivity Instrument.

Testing Thermal Conductivity

A great example of a filled polymer potting material is CoolMag™, designed to offer improved thermal performance relative to neat silicone potting materials. 

It is known that Conducted Heat Transfer happen as the transmission of phonons, the metal conductivity is very high thanks to its high amount of free electrons, using the right material structures with enough capacity for vibration and right lattice allow phonon transmission without electrons movements.

This is the foundation of CoolMag™28, a package of micro and nano particles with size ratios R, R/2, R/4, … R/2n increase diffusivity by using high density, high specific heat and high thermal conductivity crystals bonded by a minimum layer of a high inorganic content polymer based in SiO2 like PDMS, resulting in a solid isotropic structure.

The advantage? an isotropic structure makes the 1D problem of heat transfer from a hot point to a colder one a new 3D challenge as the hot point is now surrounded by a 3Dimensinal matrix of micro and nanoparticles transferring heat through closed surfaces (Isotherm surfaces):

Electric Vehicle Correction Choke with Potting Compound

Above: 3 Phase 7 KW, Power Factor Correction Choke set for an Electric Vehicle. The open-air part reaches 180ºC at full power with a liquid cooled plate, the part injected at low pressure with Coolmag™28 nano composite reaches 105ºC at the same conditions. 

CoolMag™ is a thermally conductive composite PDMS based elastomeric compound of encapsulant two component system, designed for Power Electronics in Automotive, especially in Electrified Vehicles with multiple functionalities:

  • Heat Transfer, reduction of hot spots and minimizing average temperature of systems.
  • Electric Isolation
  • Mechanical protection.

Flame and fire protection (Retardant and Extinction). CoolMag™ is designed to provide thermal conductivity, electrical safety, hazard protection, mechanical and fire protection for electronic encapsulating applications.

The following graph below shows how high current Chokes with Coolmag™28 is stable at 65ºC at full load and how without CoolMag™28 reach Curie Temperature in just 300 seconds.

Inductance with and without CoolMag28 Resin

Heat transfer data was collected for thermal conductivity analysis using a C-Therm Trident Instrument with the Flex TPS (double-sided) test method, to better understand thermal performance of a sample of CoolMag™ 28. The sample specimen offers nearly tenfold improvement over the expected thermal conductivity of a neat silicone resin.

Premo Thermal Potting Compound Samples for Thermal Conductivity Testing

Properties of Thermally Conductive Potting Compound CoolMag 28


To learn more about C-Therm and the Trident Thermal Conductivity Instrument, visit www.ctherm.com or contact sales@ctherm.com

To learn more about CoolMag™ visit www.coolmag.net or contact x.mirabet@kadion.com

Press Contact

This information was written and curated in collaboration with Kadion by Ana Paula de Castilho, Regional Manager for Europe and South America.

Ana Paula de Castilho, C-Therm Regional Manager


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