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March 16, 2016

4 Min Read
Polyamide 6 in fan module thermally conducts, electrically insulates

The new thermally conductive polyamides from Lanxess (Cologne, Germany) are reportedly making a big impression in their first applications. For example, the modular flange for a drive used in car interior ventilation systems is made from the recently launched polyamide 6 Durethan BTC 75 H3.0 EF. The thermoplastic, which is reinforced with a 75 percent mineral content, is replacing a polyamide with a glass fiber/mineral mix for thermal conductivity.

Thermally-conductive fan module flange boasts tight dimensional tolerances.

“Compared to conceivable alternative materials, our compound conducts heat better and is the most cost-effective solution. It performs best in terms of mechanical properties, resistance to thermal aging and flowability and, thanks to its electrically neutral stabilization, helps prevent contact corrosion,” explains Stefan Theiler, an expert in highly filled polyamides at Lanxess.

Robert Bosch GmbH is using the flange made with this material in a fan module that is being incorporated into the cooling system fitted inside the passenger compartments of several international automakers. SFS intec GmbH, which is based in Korneuburg, Lower Austria, is manufacturing the flange.

Among other things, the modular flange is designed to conduct the operating heat generated in the motor winding and the electronics of the fan module to the outside. This helps to protect the fan module from thermal overload. “Due to its excellent thermal conductivity and outstanding electrical insulation properties, our material plays its part in making sure the fans operate reliably throughout the car’s service life,” says Theiler. At 1.4 W/mK, thermal conductivity is around five times higher than that of standard polyamide 6 with 30 percent glass fiber reinforcement. It is at a similarly high level to that of polyamides that use aluminum oxide as a thermally conductive mineral and, in terms of through plane, is comparable to that of boron nitride-filled polyamides. “Compared to boron nitride systems, our compound has better mechanical properties, is more cost-effective and conducts heat on a largely isotropic basis, i.e. almost identically in all directions,” adds Theiler.

The modular flange is a complex precision component with tight dimensional tolerances that can be met thanks to the polyamide’s isotropic shrinkage. Another advantage of the material is its high long-term thermal resistance up to 120 °C. Its halide-free electric stabilization prevents corrosion of the copper contacts, which are integrated into the modular flange. Excellent flowability also ensures that the melt pressure does not cause deformation in the contacts as the material is injection molded around them. Theiler continues: “The high degree of functional integration also helps deliver a cost-effective component solution. For example, injection molding is used to integrate the copper contacts, fastening elements and fixings for the electronics and fan motor.”

Theiler believes that the new polyamide is particularly well suited for use in the housing parts of electronic systems, which tend to be prone to failure due to the heat generated during operation. “For instance, we are thinking of lids for control housings, covers for small motors and LED components such as cooling elements.” When used in applications such as these, the material can also replace die-cast metals. Indeed, it is electrically insulating and offers greater design freedom, which makes it easier to produce geometrically complex and more compact, space-saving components. Furthermore, when used in injection molding, it produces parts that do not need reworking and offers a cost-effective way of integrating functions.

Lanxess is continuing to expand its range of thermally conductive materials. The latest example alongside Durethan BTC 65 H3.0 EF – a 65 percent mineral-filled polyamide 6 – is Durethan TP 723-620, which is reinforced with a 70 percent mineral content. This halogen-free flame-retardant polyamide 6 exhibits outstanding thermal conductivity in the direction of flow of approx. 2.5 W/mK and offers extremely good light reflection and flame retardance. It passes the flame retardance test prescribed by the US UL 94 V (Underwriter Laboratories) standard, achieving the best classification of V-0 (1.5 millimeters).


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