new line of PBT products from LANXESS with outstanding tracking resistance

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Specialty chemicals company LANXESS has developed new polybutylene terephthalate (PBT) compounds for use in electrical and electronic assemblies. Under the Pocan E name, the company now offers a range of products comprising short glass fiber reinforced grades particularly suitable for electromobility and electrical/electronics (E/E) industry applications thanks to their resistance to routing and insulating properties.

With their resistance to tracking, the new compounds obtain the best possible score of 600 in the CTI A test (Comparative Tracking Index – IEC 60112) and therefore meet the requirements of the highest insulation class according to IEC 60664-1. “Previously, glass fiber reinforced PBT compounds with such high tracking resistance were not readily available on the market. We have now closed this gap. We have also managed to endow the materials with other advantages such as optimized mechanical properties as well as excellent flowability, hydrolysis resistance and flame retardant properties, plus they are very suitable for coloring – orange, for example,” says Dr. Claudia Schmid-Daehling, who shares responsibility for the PBT product development at LANXESS High colorability is important for various safety-relevant components such as high-voltage connectors that must be clearly color-coded.

Tracking resistant even above 600 volts

Plastic parts of electrical and electronic components must be increasingly resistant to unwanted leakage currents. The reasons for this are the high currents and high voltages in electric vehicles, the trend towards miniaturization of device components and ever-shorter distances between metal contacts in connectors and terminals.

Leakage currents occur when electrically conductive paths – facilitated by impurities – form on the surface of insulating materials, such as thermoplastics. This leads to short circuits and, in the worst case, damage to the device. If the insulating materials have a high tracking resistance, this reduces the risk of such defects. The CTI A test according to IEC 60112 has become an established test method. Even though the maximum CTI A value is 600, a plastic can also be used when higher voltages of up to 1500 volts (direct current) are present. Using design guidelines according to IEC 60664 / VDE 0110-1, it is possible to “translate” the CTI test result accordingly and optimize component design for higher voltages. Schmid-Daehling explains: “This means that our new Pocan E product line can also be used with the significantly higher nominal voltages that are required for fast charging of electric vehicles, for example.

Insulation properties not very dependent on humidity and heat

The fundamental advantage of all new structural materials in the Pocan E range is that their outstanding electrical insulation properties are hardly dependent on temperature or humidity under typical operating conditions of high voltage connectors and terminals, e.g. . In addition, the components obtained show a particularly high dimensional stability, are almost completely resistant to stress cracks and are distinguished by their exceptional chemical resistance.

Better fluidity and impact resistance

New compounds with a CTI A test score of 600 include Pocan B3215E, Pocan B3217E and Pocan B3235E. They are reinforced with 10, 16 and 30% short glass fibers by weight, respectively, and offer a much higher fluidity than the corresponding standard materials. This facilitates the production of delicate and thin-walled component geometries in the injection molding process. “Also, in the case of the Pocan B3215E and B3217E, the Izod impact resistance scores are around 40 or 50 percent better,” says Schmid-Daehling.

Hydrolytically stable compounds

Pocan B3233HRE and Pocan B3216XHRE are two examples of PBT materials that are both hydrolytically stabilized and highly resistant to tracking. The latter is reinforced with 16% short glass fibers by weight. In sample tests based on the rigorous long-term hydrolysis tests of the American Society of Automotive Engineers (SAE/USCAR-2 Rev. 7), it achieves “Class 5” – the highest possible rating. “In addition, its impact strength and elongation at break are considerably higher than those of the corresponding standard compounds,” explains Schmid-Daehling. Pocan B3233HRE, which contains 30% short glass fibers by weight, achieves a “Class 4” rating in the USCAR hydrolysis test. Another of the strengths of the compound is its good flowability, which is maintained even at higher processing temperatures.

Halogen-free flame retardant properties can also be achieved

The new Pocan E line also includes Pocan BFN4231HRE, a PBT compound containing 25% short glass fibers by weight, which is both flame retardant and hydrolysis stabilized. The halogen-free and flame-retardant structural material meets the requirements of the UL 94 flammability test of the American test institute Underwriters Laboratories Inc., obtaining the V-0 classification with a specimen thickness of 0.75 millimeters. Its high resistance to hydrolysis is demonstrated by its “Class 3” rating in sample testing according to SAE/USCAR-2 Rev. 7.

More detailed information on the LANXESS e-Mobility product line and Pocan can be found at https://lanxess.com/en/Products-and-Solutions/Focus-Topics/LANXESS-e-Mobility and https: //lanxess .com/en/Products-and-Solutions/Brands/Pocan.

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