When an EV operates in cold climates, the TMS needs to keep the batteries warm while the vehicle is at a stop. This significantly increases the exposure time to water-glycol coolant when compared to ICE vehicles. The TMS needs to withstand 1,000 to 3,000 hours of coolant exposure for an ICE vehicle; for fully electric vehicles, the TMS needs to withstand 6,000 to 10,000 hours of coolant exposure.
This extensive chemical aging causes the properties of many material solutions to drop dramatically. For EVs, with the increased coolant exposure time, many engineering plastics materials are facing challenges maintaining the material properties after long aging, as they did with shorter exposure times—such as Polyamide 66 (PA66), long chain Polyamides (LCPA), and Polyphthalamide (PPA).
However, Polyphenylene sulphide (PPS) resin is a better material for EV TMS applications because it has much better material properties retention after long coolant aging. PPS has an intrinsically different configuration from polyamides—its stable molecular structure is based on thioether bonds and benzene rings that enable PPS to withstand even with concentrated sulfuric acid. This makes PPS highly chemical resistant, and the stronger material with long-term hydrolysis resistance. All PPS grades in the Xytron family are optimized for hydrolysis resistance, chemical resistance, and peak temperature performance.
The graph below shows performance of materials at various temperatures and exposure times. The white line demonstrates that, as exposure temperature increases, some materials are no longer suitable for the application. The yellow line shows that as the exposure time increases, materials that may be able to take the heat during low exposure times are unable to withstand longer exposure times.