Elastomer compound for sealing solutions for thermal management of hybrid or electric vehicles

Close collaboration with Volkswagen Group

A new EPDM elastomer compound dedicated to refrigerant

To support the transition to electric vehicles, Hutchinson Precision Sealing Systems has developed a new elastomer blend for Volkswagen that is adapted to the operating constraints of the “R744 refrigerant”, which is highly promising for the thermal management of electric and hybrid vehicles, but requires all the circuit components, particularly the sealing parts, to be adapted. The development of this new elastomer material was made possible according to the expertise of the Hutchinson teams in the formulation of elastomer materials and close collaboration with the Volkswagen Group and a major thermal management equipment manufacturer.

In addition to laboratory tests, functional validations of the elastomer compound were carried out with expert appraisal of the parts, confirming the technical solution in the “EPDM 8EP3411” blend. Hutchinson sealing solutions made from “EPDM 8EP3411” are used in series production on vehicles equipped with the MEB platform, such as “ID.3”.

Elastomer compound with enhanced thermal performance

Compared with traditional EPDM materials, this elastomer blend offers enhanced thermal performance with a temperature range from minus 40 to plus 165 degree Celsius, corresponding to the optimum operating temperatures for heat pumps running on “R744”. A complete re-engineering of existing solutions enabled us to meet the new specifications. The “80 Shore A” hardness makes it suitable for high-pressure applications of up to 130 bar. The seal environment still needs to be designed to limit extrusion play. The development teams are currently working on an elastomer with a hardness of “90 Shore A” for the most extreme pressure conditions. Resistance to explosive decompression is a critical characteristic for elastomers in order to avoid physical degradation of seals (cracking, crazing, bubbles, etc.). Specific tests were carried out to arrive at the final formulation. “8EP3411” complies with the Norsok M710 standard: Rating 0, confirming the absence of defects after exposure.

Use of refrigerant in electric vehicles

The range of electric vehicles is a major issue for the development of electric vehicles. The range is further reduced by low outside temperatures. Unlike combustion-powered vehicles, there is no source of heat available to keep the battery at an ideal temperature and warm the cabin for passenger comfort. Thermal management therefore plays an essential role in optimizing the use of the energy available in the battery.

Energy-intensive electrical resistors

The industry currently uses electric resistors, which consume a lot of energy, or less energy-intensive automotive heat pump systems using fluorinated refrigerants. However, the thermodynamic properties of these refrigerants prevent them from operating at temperatures below minus ten degree Celsius. Fluorinated refrigerant gases also have a high environmental impact. “R134a”, for example, has a Global Warming Potential (GWP) of 1,430 compared with CO2, which has a GWP of 1. These gases, which include HFCs and HFOs, also generate PFASs and are already subject to regulation for industrial applications such as air conditioners or heat pumps, with the aim of banning them in the coming years.

Automotive manufacturers and equipment suppliers are increasingly interested in a refrigerant that will help them address the issues of vehicle autonomy, the environment and human health. The refrigerant “R744” (CO2) is a natural, non-flammable fluid, by definition PFAS-free, with a GWP of 1. Its thermodynamic properties mean that heat pump systems can operate at temperatures below minus ten degree Celsius and improve their coefficient of performance over a certain temperature range. Less energy is needed to heat the battery and the passenger compartment, which increases the range of electric vehicles.

Refrigerants in industrial systems and heat pumps

Already used in heat pump systems on buses and trains, and in industrial air conditioning systems such as supermarket refrigeration systems, environmental and now legislative constraints are likely to increase the use of “R744” more widely in industrial applications such as residential heat pumps. The planned end to the marketing of internal combustion engine vehicles in Europe in 2035, combined with environmental issues such as PFAS or GWP also make “R744” a serious option for becoming the standard refrigerant for automotive applications in Europe.