ADDITIVES | THERMALLY CONDUCTIVE
Controlling the charge
This cooling element is part of the charge controller used in a Germany-manufactured electric sports car and is produced in Durethan BTC965FM30 from Lanxess. This thermally conductive but electrically insulating PA6 prevents overheating during the charging process and meets the strict requirements for flame- retardant properties, tracking resistance and design. According to Bernhard Helbich, Technical Key Account Manager
at Lanxess, the special mineral heat-conducting particles, which the company declines to identify, give the compound an in-plane thermal conductivity of 2.5 W/m.∙K and 1.3 W/m.K through plane. �
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partnerships are required to allow successful implementation and grow confidence. “Radical Materials is able to offer standard as well as custom designed compounds and can support with material selection, measurement of thermal and mechanical performance and small-scale development trials to full production,” he says. For non -electrically insulating applications, compounds are typically carbon-based and commonly a form or blend of graphite. “If electrical insulation is an issue in the final compound then specific grades of boron nitride are common but, from a commercial standpoint, these would typically be blended with selected minerals of lower cost,” says Vince. One project the company is currently working on is for an injection moulded electronics housing where the additive is graphite-based and the component performs with an achieved through-
Right: Thermal image showing surface temperature and heat spread across a standard polymer (top sample) and thermally conductive polymer (lower sample) after one minute contact with a heat source
plane thermal conductivity of around 1.5W/m.K and in-plane around 8-9W/m.K.
Interface options Thermal interface materials (TIMs) — also known as gap fillers – are used to improve battery cooling in EVs. These crosslinking or non-crosslinking materials can have a thermal conductivity of up to 3 W/m.K or even higher. Depending on the base polymer, filling levels of 90 wt% or more are required to achieve such levels of thermal conduc- tivity. With standard filler particles, such levels cannot be achieved at all or only with significant losses in processing and flow properties, says HPF The Mineral Engineers (a division of Quarzwerke), which supplies various high-performance fillers. In a recently published technical information
paper, the company says that by using fillers from its Silatherm Plus and Extra range of modified aluminosilicates, these filling levels can be achieved in combination with good flow proper- ties. “If the filler is provided with an individually matched coating, the already achieved filler levels of 90 wt% can be raised even up to 93 wt%,” the study says. “By filling the voids between individual battery cells in a battery pack with soft-curing or paste-like TIM, the battery can be cooled efficiently even under heavy electrical loads and connected to the active cooling system.” HPF has developed various fillers that allow high filling levels at low viscosities. “This is possible by utilizing packing density optimised products and the selection of a suitable surface coating,” the company says. Products in the Silatherm Plus 1432 and 1443 series are based on specially shaped mineral particles that differ slightly in packing structure and achievable thermal conductivities. Products from the Silatherm Extra series, which HPF says are cost-optimised, have different flow
50 COMPOUNDING WORLD | August 2022
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IMAGE: RADICAL MATERIALS
IMAGE: LANXESS
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