COMPOUNDS | THERMALLY CONDUCTIVE
Right: This EV charger plug cooling
element was developed by Envalior for Leopold Kostal using a thermally conductive Durethan PA6 grade
provide a thermal conductivity of 2.5 W/m·K in the direction of melt flow (in-plane) and 1.3 W/m·K perpendicular to it (through-plane), says Cichy. The company says thermal conductivity values of 1-2 W/m·K are usually sufficient at the typical wall thickness of most electronic parts to dissipate sufficient heat to protect the electronic parts. Despite the high content of thermally conductive filler (68 wt%) in the compound, Cichy says the Durethan PA6 compound exhibits good flow, with processing characteristics similar to a PA6 with up to 60% glass fibre content. The halogen-free flame- retardant grade also offers as UL 94 flammability rating of V-0 at 0.75 mm and provides a Compara- tive Tracking Index A value of 600 V (CTI, IEC 60112). “The tracking resistance gives designers greater
freedom in engineering the component, as they can arrange electrical assemblies even more compactly without having to worry about short circuits and device defects caused by creepage currents,” according to Cichy. Envalior says the thermally-conductive grade has potential for use in a range of electric vehicle components, including plugs, heat sinks, heat exchangers and mounting plates for power electronics.
Below: AluCoat aluminium- coated basalt fibres from FiberCoat provide
electrical and thermal
conductivity in a range of polymers
Functional fibres Specially formulated ceramics, metal particles and graphite are the primary materials chosen to provide heat dissipating properties in plastics. One of the latest additions to the compounders’ option list has been developed by FiberCoat, a 2019 start- up based at Aachen in Germany. It presented its thermally and electrically conductive AluCoat mate- rial additive at the JEC World 2023 exhibition in Paris, France, earlier this year.
Designed as a functional filler for use in techni- cal polymers, AluCoat materials are comprised of short, basalt fibres that are coated in a sheath of aluminum to provide a fibre with both thermal and electrically conductive properties (the electrical conductivity also providing a shielding function against electromagnetic radiation). The basalt
filaments, which are suitable for use in PE, PP or PA, also enhance mechanical properties. Material properties can be adjusted precisely by varying parameters such as the fibre shape, the sizing, or the density of the additive in the matrix. AluCoat loaded components do not require coating, painting or other additional processing and finishing steps, which can result in a reduction in components costs by up to 50%, according to FibreCoat CEO Robert Brüll.” The company says that its melting, coating, sizing and winding process is carried out on standard glass and basalt spinning lines with only the addition of a special coating module below the fibre formation area. This is said to help reduce the price of conduc- tive fibre solutions by up to a factor of ten. The trend in electronics to miniaturisation of components and assemblies means power density continues to increase. This means heat generation in the components can become a limiting factor for service life and makes thermal management an increasingly important issue for designers of assemblies. Current state-of-the-art heat sinks are still largely made of metals, such as aluminum, and rely on costly interface materials for electrical insulation.
Novel formulations Thermally conductive plastic alternatives could significantly reduce system complexity, according to 2018 German-start-up PlastFormance. It develops, produces and sells unique polymer compounds developed using a patented technol- ogy that can incorporate ceramic, metallic or graphite fillers into a wide variety of polymers at what Chief Operating Officer Maximillian Funck, describes as “unprecedented” levels. The company offers its Thermally Conductive
IMAGE: FIBERCOAT 16 COMPOUNDING WORLD | September 2023
(TC) series of compounds, which are said to provide thermal conductivity up to 15 W/m·K and are electrically insulating, for thermal management
www.compoundingworld.com
IMAGE: ENVALIOR
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