Full Throttle with Flame-Retardant Polycarbonates
Electric vehicles not only prevent local emissions, they can also be fun. The design of a racing car's traction battery is one of the most important components for the course of the race. The construction of the battery uses flame-retardant materials.
Founded in 2012, E.Stall Esslingen is participating in various international Formula Student events with an electrically powered racing car. One of the biggest events is the Formula Student Germany competition, which takes place every year at the Hockenheimring. Since the 2018 racing season, Covestro has supported the E.Stall Esslingen team with flame-retardant materials. In its Leverkusen pilot plant, the plastics manufacturer extrudes sheets of the PC+ABS blend Bayblend®, which the student teams uses to produce frames and brackets for its battery modules. These modules are based on lithium-ion battery cells in the so-called pouch format.
Flame-retardant materials for safe batteries
In the design department for the battery, the various disciplines of the students at Esslingen University of Applied Sciences complement each other – from electrical engineering to electronics and mechanical engineering. In addition, the Formula Student specifies certain design requirements in its rules and regulations, among others with regard to safety in handling lithium-ion cells. Apart from active monitoring and control of the battery, the regulations explicitly require the use of flame-retardant materials in accordance with the Underwriters Laboratories' flame-retardant standards according to category UL 94 V-0.
"We are delighted that Covestro is supporting us again in the 2019 season with polycarbonate blend sheets, which we can process easily," explains Raphael Raff, who is currently in charge of the high-voltage sub-project at E.Stall Esslingen. Compared with the previous year, a PC+ABS blend with around 10 percent lower density and high mechanical, electrical and thermal properties was selected for the racing team together with the product experts from Covestro in order to remove even more weight from the racing car's battery.
Products for large automotive series
For mass production, designers are looking for materials that meet the strict requirements of car manufacturers in vehicle operation but which are also easy to process. Compared to semi-crystalline materials, amorphous plastics such as polycarbonates have the advantage that they are virtually shrinkage-free in the injection moulding process and have very low water absorption. This facilitates being able to design thin-walled, distortion-free components. Polycarbonates can also be provided very well with flame protection.
Covestro continues to develop its portfolio for battery applications. For cell holders to hold cylindrical battery cells, pouch cell frames, battery housings and similar applications, the focus is on both unfilled and mineral-filled, along with glass-fibre-reinforced flame-retardant Bayblend products. Covestro also offers thermally conductive polycarbonate grades of the Makrolon TC product family that can contribute to battery thermal management.