In a collaboration with HELLA, LANXESS has developed a thermoplastic compound for the manufacture of flame-retardant housing components for electric vehicle battery systems.
The product, Pocan AF4130, is a blend of polybutylene terephthalate (PBT) and acrylic ester-styrene-acrylonitrile (ASA) and contains 30% by weight glass fibres and a halogen-based flame retardance package. The material is said to deliver extremely low warpage and shrinkage, combined with high flame retardance.
HELLA is using the compound to fabricate housings for a battery management unit (BMU) and two cell monitoring units (CMUs) for a German manufacturer of battery systems. The parts are currently in use in the lithium-ion battery system of a German compact car.
The housings of the BMU and CMUs have large, flat surfaces as well as complex geometries along the edges and on the inside. Thanks to an innovative design, they can be injection moulded cost-effectively as single components. The contact pins for the connectors must not bend when the housings are mounted on the printed circuit boards. The tolerances for the spacing between the connector mounts and the cut-outs for the pins are therefore extremely close.
“This is precisely where the outstanding dimensional stability of our blend Pocan AF4130 pays off,” explains Marc Marbach, Head of Sales Segments E&E in the LANXESS High Performance Materials (HPM) business unit.
As required for this application, the material achieves the best classification of V-0 (0.75 mm) in UL 94 fire testing by Underwriters Laboratories and it is listed on the UL Yellow Card with a good classification of UL 94 5VA (1.5 mm). It has also been given a UL f1 listing for use in outdoor applications involving exposure to UV light and water.
“Our compound thus has a good chance of also being used for electrical components such as photovoltaic plugs and sockets,” says Marbach.
According to LANXESS, surfaces made of the thermoplastic are very low-emission, as demonstrated by thermal desorption analyses conducted in accordance with VDA 278 (German Association of the Automotive Industry). This makes it suitable for many vehicle applications requiring very low volatile and condensable emissions, such as components for the automotive interior. The blend is also highly resistant to typical media used in motor vehicles, such as fuels, oils, cleansers and car care products, as proven in extensive media storage tests conducted by LANXESS for HELLA in accordance with the supply specification LV 124, used by many automotive manufacturers. It also displays good resistance to an electrolyte widely used in lithium-ion batteries. The corresponding test was additionally conducted under load in compliance with DIN EN 22088-3. Marbach reports that no cracks were evident in the samples even after 1,000 hours of exposure.
LANXESS provided HELLA with support in developing the housing components as part of its HiAnt customer service package. HPM delivered suggestions for optimal component design, provided the material data required for the computer-aided design of the parts to meet expected loads and for the mould flow analyses, and supported the initial injection moulding trials. LANXESS further determined the blend’s halogenide content for HELLA by means of ion chromatography and conducted odour testing to VDA 270.
Image provided by LANXESS
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