LANXESS has developed a compound Pocan AF4130 in collaboration with Germany-based HELLA KGaA Hueck. It serves as a housing material for a battery management unit (BMU) and two cell monitoring units (CMU). The combination of polybutylene terephthalate (PBT) and acrylic ester-styrene-acrylonitrile (ASA) contains 30 % glass fibres by weight and a halogen-based flame retardance package.
HELLA fabricates the BMU and CMUs for a German manufacturer of battery systems for motor vehicles. The highly flat devices currently are used in the lithium-ion battery system of a German compact car. “The particular advantages of the material are its extremely low warpage and shrinkage, combined with its high flame retardance. We see great potential for application in precision components for vehicle battery systems,” said Marc Marbach, head of Sales Segments E&E in the LANXESS High Performance Materials (HPM) business unit.
The housings of the BMU and CMUs have large, flat surfaces with complex geometries along the edges and on the inside. Due to an innovative design concept, they can be cost-effectively injection moulded 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 Marbach.
As required for this application, the material achieves the best classification of V-0 (0.75 millimetres) in UL 94 fire testing by the US testing organisation Underwriters Laboratories Inc. It further is listed on the UL Yellow Card with a good classification of UL 94 5VA (1.5 millimetres). The material is destined for the injection moulding of flame-retardant housing components. It additionally has 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,” said Marbach.
Surfaces made of this thermoplastic are very low-emission, as demonstrated by thermal desorption analyses conducted by LANXESS in accordance with VDA 278 (German Association of the Automotive Industry). “It is therefore also suitable for many motor vehicle applications requiring very low volatile and condensable emissions, such as components for the automotive interior,” added Marbach.
The blend is 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. “No cracks were evident in the samples even after 1,000 hours of exposure,” explained Marbach.
LANXESS provided HELLA with extensive support in developing the housing components. These services are part of its HiAnt customer service package. For example, HPM delivered suggestions for optimal component design, provided all the characteristic material data required for the computer-aided design of the housing parts to meet expected loads and for the mould flow analyses, and supported the initial injection moulding trials. The specialty chemicals company further determined the blend’s halogenide content for HELLA by means of ion chromatography and conducted odour testing to VDA 270.