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New PBT grade from LANXESS for automotive electronics
Hydrolysis-resistant and flame-retardant
The engineering plastic polybutylene terephthalate (PBT) is increasingly in demand as a material for sensors, plug connectors and housings of actuators and control units. This is thanks to its electrical properties, dimensional stability, chemical resistance and excellent ability to withstand continuous temperatures. The growing demand is due to the growing use of electronics in the automotive sector. The LANXESS High Performance Materials business unit has thus developed a wide range of hydrolysis-stabilized PBT grades for safety-related components in particular that need to remain functional in a hot and moist environment, such as under the hood. One example of a new product is Pocan BF 4232 HR, which offers excellent hydrolysis stability and outstanding flame retardance. “This combination of properties makes the material particularly suitable for applications in electric vehicles where flame retardance requirements are stricter due to the higher currents,” explains Jochen Endtner, an expert in PBT product development at LANXESS.
UL 94 V-0 passed for test pieces from 0.4 millimeters
The new PBT, which is reinforced with 30 percent glass fibers, passes the UL 94 flame test of U.S. testing organization Underwriter Laboratories (UL), achieving the best classification of V-0 at a test specimen thickness of just 0.4 millimeters. “It achieves this excellent classification in all colors required for the test, which is the exception rather than the rule for materials of this type,” says Endtner. These results are registered on the UL Yellow Card for this grade. The new PBT’s hydrolysis resistance can be seen in the climatic aging test at 85 °C and 85 percent relative humidity, which is prescribed in numerous technical specifications. Even after 100 days’ storage, the tensile stress at break and elongation at break are still over 80 percent of the already high baseline values.
Low-distortion, flame-retardant and low-migration
LANXESS is one of the few suppliers to also offer low-distortion and flame-retardant PBT grades with hydrolysis stabilization. These are the material of choice for geometrically complex and large housing parts. One example is the new Pocan AF 4130 grade, a blend of PBT and ASA (acrylate styrene-acrylonitrile) reinforced with 30 percent glass fibers. “Its very low tendency to warp is complemented by high flame retardance. Components made of this material exhibit a very good surface quality. In addition, they have very low emissions according to a thermal desorption analysis in line with VDA 278 and can thus be used in a variety of ways in the automotive sector,” says Endtner. As well as plug connectors, the blend material is also particularly suitable for producing flame-retardant housing parts, as it is listed on the UL Yellow Card with a good classification of 5VA for a test specimen 1.5 millimeters thick. Despite the proportion of ASA in the blend, the hydrolysis resistance has been improved significantly over a flame-retardant PBT standard material with 30 percent glass fibers.
Good flow characteristics, wide processing window
Another special feature is the LANXESS hydrolysis-stabilized PBT grades that have been optimized in their processing behavior and chemical resistance. They exhibit a wide processing window and good flow characteristics. “For instance,” says Endtner, “Pocan B 3233 HR, which has 30 percent glass fiber reinforcement, enables longer flow paths than comparable standard PBTs – especially in case of low wall thicknesses. This simplifies injection molding of intricate thin-walled component geometries.” This PBT, too, is highly stable in a hot and moist environment, with the result that the mechanical properties degrade very slowly under the above-mentioned hydrolysis conditions. Hydrolysis-stabilized material grades with a glass fiber content of 15 percent are also part of the range. One example is Pocan B 3216 HR, which stands for very high stability in warm, moist conditions, combined with outstanding processing properties.
LANXESS is a leading specialty chemicals company with sales of EUR 8.0 billion in 2014 and about 16,300 employees in 29 countries. The company is currently represented at 52 production sites worldwide. The core business of LANXESS is the development, manufacturing and marketing of plastics, rubber, intermediates and specialty chemicals. LANXESS is a member of the leading sustainability indices Dow Jones Sustainability Index (DJSI World) and FTSE4Good.