Glass-fiber reinforced polyamide 6 for automotive battery housings, lightweight without sacrificing performance

Latest: As electric vehicle (EV) production increases and charging infrastructure develops, longer journeys become more feasible, and automakers have a responsibility to further reduce vehicle weight. One of the remaining relatively untapped applications is battery housing. Several consortia and individual companies are scrambling to develop commercial solutions.

For example, Lanxess and Kautex Textron are conducting feasibility studies on direct long-fiber thermoplastic (D-LFT) and polyamide 6 (PA6) resins. Meanwhile, Aimplas is developing sustainable structural battery enclosures for lightweight vehicles based on reusable, recyclable long-fiber thermoplastic composites. A discharged battery pack will be hot-swappable. Among other developments, the Vestaro consortium is taking a new approach based on lightweight sheet molding compounds for high-voltage battery module housings.

Switch from PA6,6 toPA6

LANXESS has also made progress in peripheral components for electric vehicle batteries and is again at the forefront. According to the polyamide supplier, PA6 and PA66 are materials with very similar properties, but they often compete with each other. Recently, the tight price situation of PA66 and its temporarily limited supply has led it to even be replaced by PA6 in traditional applications. However, new developments in parts that are usually made of PA66 are now increasingly being implemented directly with PA6.

A current example is the housing of an on-board battery charger used in an EV compact car made by a German automaker. It consists of Durethan BKV50H3.0 from LANXESS using 50%
Heavyweight short glass fibers are highly reinforced. The manufacturer of the material combination consisting of the housing and the charger is Leopold Kostal GmbH & Co.
KG (Luedenscheid, Germany), a global system supplier of automotive, industrial and solar electrical and electrical connector systems.

This large-scale application highlights the fact that PA6 compounds do not necessarily It is hydrolytically stabilized for use in glycol-water coolant cooling applications in electric vehicles. Bernhard, Technical Key Account Manager, Lanxess Performance Materials business unit
Dr. Helbich explained: “We believe that in the future this type of polyamide 6 product will become very common in the mass production of housings and other thermal management components for electric vehicles. For fluid connectors in cooling systems or This is especially the case for applications such as control units.”

Electric powertrains have different thermal management requirements

Plastic components in the cooling circuit of internal combustion engines have long been dominated by PA66. This is because this thermoplastic is very resistant to hot coolants such as water-glycol mixtures. However, the thermal management requirements of pure electric powertrains are shifting towards lower temperatures. For all-electric vehicles, the long-term heat resistance of polyamide 6 compounds to water-glycol mixtures is sufficient for most components, even significantly extending the stress time in some cases. As a result, during vehicle operation, the housing can permanently withstand temperatures up to 85°C without any problems and can achieve burst loads of up to 10 bar. Long-term testing of the samples also showed little reduction in the mechanical properties of the compounds in the water-ethylene glycol mixture. Even after 1500 hours of storage at 110°C and 1.5 bar. Therefore, the material meets the technical requirements of a major German car manufacturer for water-cooled components for electric vehicles.

The casing is about 29 cm long and 12 cm wide, with a considerable flange length. The housing is screwed to the aluminum housing of the charger along with a sealing ring. The high strength and stiffness exhibited by the PA6 compound ensures that the housing meets stringent sealing requirements. Bernhard Helbich commented: “For this purpose, we have worked closely with Kostal to optimize the performance of the mechanical parts, and by simulating the filling, we have determined how to achieve the lowest possible shrinkage and warpage values ​​in the injection molding process. .”

In addition, Durethan
BKV50H3.0 adopts copper-free H3.0 thermal stabilization, which will not cause electrical corrosion of metal parts in the cooling circuit. It is resistant to media commonly found in electric vehicle operation, such as oil, grease, battery electrolyte and road salt.