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Keeping up with EV thermal management system components needs

3 March 2020
  • Meisen Li Advanced Engineering Manager, Thermal Management Systems

As the automotive industry continues its advancement of electric vehicles, there is an increased need for innovative materials solutions for thermal management systems (TMS). An effective TMS keeps the component operating temperature within a specific range, which ensures both optimal energy efficiency and an extended service life.   

Engineers often face challenges when choosing what plastics material solution to use for TMS component applications. They need to consider the heat exposure time and temperature of the material, plus, hydrolysis resistance with coolant (water-glycol solution). The material solutions used in electric vehicle (EV) TMS applications need to withstand moderate coolant temperatures, but with longer exposure times.

Compared to an internal combustion engine (ICE) vehicle, the operating time of the TMS in an EV is much longer—battery pack temperature needs to be managed within a narrow temperature range at all times, even when the vehicle is not being driven, such as when it is charging or parked in extreme cold temperatures.


Cold climates increase exposure time

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.


Taking PPS to the next level

For filled PPS grades, when exposed to coolant, the bonding interface between the glass fiber and resin is the key for hydrolysis resistance performance. To further improve the hydrolysis resistance, DSM’s Xytron G4080HR uses unique technology to create a strong bond between the glass fibers and PPS resin.

When comparing the bonding interface of Xytron G4080HR to a competitive PPS grade under an atomic force microscope, after 3,000 hours of aging with water-glycol coolant at 135°C, the interface of Xytron G4080HR showed that the bonding remains much stronger than the competition’s PPS grade. It is almost intact verses delaminated.

Also, Xytron’s innovative technology improves key material properties retention, such as tensile strength and elongation at break (EAB) after aging. This is especially apparent at the weldline’s strength, which is known to be the weakest portion of a component.

 With its superior long-term hydrolysis resistance, along with weldline strength retention, DSM’s Xytron G4080HR enables engineers to improve TMS components with more design flexibility and higher confidence in quality.

To learn more about Xytron G4080HR, or to request test samples, contact us or visit plasticsfinder.com for additional information, including technical data sheets. 

Choosing the right material solution for EV thermal management

   

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