Envalior has developed Xytron M5080ET, a new PPS compound, polyphenylene sulfide, intended for overmolding and functionalization of busbars used in electric vehicles. The impact-modified material was designed primarily for applications in which components must operate at temperatures exceeding 150°C while maintaining high resistance to stress cracking during thermal shock. According to the company, the solution addresses rising temperatures in EV powertrains resulting from higher operating voltages, higher current levels, and more compact assembly designs. These factors increase the requirements placed on the thermal resistance of overmolded busbars, including those used in power control units and electric drive axles.
Arthur Rieb, business development manager at Envalior, emphasizes: "Our compound was developed to ensure that, throughout the entire service life of the vehicle, the function of the busbars is not impaired by stress cracks and that no short circuits occur that would lead to failure of the entire assembly."
The new PPS compound is reinforced with a 50% by weight mixture of glass fiber and mineral components, and its formulation has been optimized for an economical material price. The company reports that the material has already been positively approved by several customers, and various development projects related to its use in series production have been successfully completed.
Thermal expansion closer to copper
In electric vehicles, busbars are responsible for safely conducting electrical energy between the high-voltage battery, control unit, drive, and charging system. They are made of copper and overmolded with plastic to provide electrical insulation from the surrounding environment. In such components, the problem is usually the significant difference between the thermal expansion of copper and plastic, which promotes the formation of stress cracks in the polymer layer during abrupt and frequent temperature changes. According to Envalior, the advantage of the new compound is that, unlike comparable materials, its thermal expansion is closer to that of copper, also perpendicular to the melt flow direction and glass fiber orientation in the part. This stability is said to be maintained even at high temperatures, which significantly reduces the risk of stress cracks.
As Arthur Rieb states: "Tests conducted at Envalior have shown that our new compound exhibits more than 70% higher stress crack resistance in thermal shock tests conducted in the temperature range from -50°C to 180°C, compared with similar PPS compounds. This is also supported by the fact that the weld lines in the component, created by converging melt fronts, are around 17% stronger than in comparable materials. As a result, this translates into a long service life and a high level of safety for the busbars."
The company notes that the material's high stability during thermal shock is also important because PPS itself had already shown the best stress crack resistance among plastics used for busbar overmolding.
Flammability performance and dimensional stability
Xytron M5080ET is intended to offer high flame resistance, required in plastic applications in batteries and electric drive systems, where occupant protection in the event of fire is important. The material achieves a V-0 classification in the UL 94 test conducted by Underwriters Laboratories Inc. with a specimen thickness of 2 mm. The compound also features high volume resistivity and high dielectric strength before and after aging, including at elevated temperatures. In addition, high creep resistance and low water absorption are intended to result in dimensional stability of the components.
Arthur Rieb says: "All this ensures the electrical safety and mechanical functionality of the busbar throughout its entire service life. In addition, the high dimensional stability of the compound enables the design of very compact assemblies."
Detailed information on the new PPS material for busbars is provided by the company in its Material Advisor tool.
Xytron M5080ET is intended primarily for busbars that must withstand temperatures above 150°C. The material shows more than 70% higher stress crack resistance in thermal shock tests at temperatures from -50°C to 180°C compared with similar PPS compounds
