Freudenberg Sealing Technologies has developed a new sealing system for busbar sealing in vehicle air-conditioning compressors. This elastomer-based solution withstands test pressures of over 100 bar in leak tests and offers a cost-efficient alternative to conventional glass seals. Designed for CO₂ compressors (R744), it also works well with other refrigerants.
Credit: Freudenberg Sealing Technologies 2026
Compressor with busbars
European regulations on fluorinated greenhouse gases are accelerating a transformation in the automotive industry: The fluorinated refrigerants R134a and R1234yf are gradually being replaced by alternatives. The natural refrigerants R744 (CO₂) and R290 (propane) are considered particularly viable for the future. However, using CO₂ in refrigerant compressors involves considerable technical challenges: The operating pressures in CO₂ air-conditioning compressors are many times higher than those required by conventional refrigerants in the compressor.
Tiny molecules, enormous pressure
One of the key tasks in this environment is to reliably seal electrical feedthroughs – busbars or pins – in the compressor housing. The tiny CO₂ molecules can enter the elastomer material through permeation. In the event of a rapid pressure, the trapped gas molecules can then expand suddenly and destroy the seal from the inside out – a phenomenon known as explosive decompression. Furthermore, the seals must meet the strictest mechanical requirements.
Material and design from a single source
Freudenberg Sealing Technologies has the answer to these challenges: a new sealing system that uses a wide range of materials. With this solution, the company draws on its deep materials expertise: It specifically developed materials for use in CO₂ compressors that resist explosive decompression and offer high media resistance to conventional refrigerants. This also involves using elastomer variants that offer a high comparative tracking index (CTI), thus reliably preventing creep currents from arcing at the busbar feedthrough.
The sealing contour was created with an integrated development approach that precisely coordinates manufacturability, component design and functional safety. Freudenberg Sealing Technologies masters this balancing act across the entire value chain: from the development and processing of challenging materials to the design of the suitable seal construction. In leak tests, the sealing system reliably withstood test pressures of more than 100 bar.
“With this change in refrigerants, manufacturers of air-conditioning compressors are facing entirely new sealing requirements. We offer them not just a technical solution to this challenge, but a true development partnership – from the material selection to a sealing contour that is ready for series production,” says Christian Jaschke, Product Manager at Freudenberg Sealing Technologies.
Less expensive and more flexible than glass
Compared with the glass seals that have frequently been used for this purpose, the new solution offers several advantages: The cost per sealed busbar/pin can be reduced by up to 30 percent, depending on the specific application. As there are typically three busbars per compressor, this creates significant potential savings. The compact design also helps optimize the installation space. This is a decisive factor in the densely packed compressor environment.
As a development partner, Freudenberg Sealing Technologies customizes the material, sealing contour and geometry to meet the requirements of the compressor manufacturer – offering high availability and short development cycles. The basis for this is a broad materials portfolio that covers a temperature range from –40 °C to more than 200 °C and offers high media resistance to a variety of refrigerants.
From development to application
There is strong interest in the industry: Freudenberg Sealing Technologies is currently working on concrete development projects with several vehicle compressor manufacturers. The first prototypes have already been validated. The technology is not limited to CO₂ refrigerant compressors. It can also be transferred to other high-pressure applications with different media – an advantage acquired during the intensive seal development for the particularly demanding refrigerant R744.