TPV Replaces EPDM in Automotive Window Sealing

Celanese Corporation (Celanese, a specialty materials producer) and Cooper Standard (Cooper Standard, an automotive sealing-system supplier) converted an automotive side-window glass run channel from EPDM thermoset rubber to Santoprene TPV. The program has now received the 2026 SPE Automotive Hall of Fame award, but the useful evidence is older and more specific: the material change survived the move from development into series production and was later reported to represent approximately 55% of the global glass run channel market.

That is the part of the story worth keeping. This was not a TPV sample replacing rubber on a display stand. Cooper Standard, using design and manufacturing capability from Jyco, worked with the Santoprene team to adapt the material and profile for the channel in which a vehicle side window travels. The requirement was not simply lower weight. The channel had to maintain the weather, dust and noise sealing that had made EPDM the incumbent.

The reported program delivered a second requirement as well: a manufacturing route that made the change commercially workable during a mid-cycle vehicle program. TPV extrusion required less capital investment and less production space than rubber processing. That constraint decided the choice because the OEM could convert an existing program without treating the material change as a new vehicle architecture.

The reported comparison is specific to the glass run channel application and the part design used in the program:

The two figures describe different things. The first is a part-level result against the EPDM baseline. The second is a later market-position claim, not a test result from the original vehicle program. It should not be used to imply that every automotive seal has moved from EPDM to TPV.

The glass run channel

The glass run channel is a demanding place to replace a thermoset elastomer. It guides the moving window while maintaining contact around the glass and resisting exposure to weather. The cited program therefore had to prove sealing performance in an extruded profile, not merely show that TPV could be compounded, moulded or recycled.

The public account says Santoprene TPV matched the rubber-like sealing required against weather, dust and noise. It also identifies the material and component as a joint development rather than a resin substitution made after the profile had already been fixed. That distinction matters to processors. A TPV grade cannot be judged separately from the die design, profile geometry, friction interface, flocking or assembly method used in the channel.

The production decision also rested on scrap handling. Unlike thermoset EPDM, TPV can be reprocessed, allowing production scrap and offcuts to return to the material stream. That is a process advantage for a converter managing start-up waste and profile-trim losses. It is not the same as proof that an installed glass run channel has entered a closed-loop recycling system. The available program description establishes reprocessability, not a measured end-of-life recovery rate.

The incumbent that lost the part

EPDM held the channel because it supplied familiar elastic sealing and established rubber-processing practice. TPV won this application by combining comparable sealing function with a different production equation. Lower density and profile optimisation reduced the reported part weight by approximately 30% to 50% compared with EPDM, while extrusion reduced the capital and floor-space burden described for rubber processing.

That combination gave the OEM a reason to accept a material change during a vehicle program already in motion. A weight claim alone would not have been enough. Nor would recyclability alone. The deciding constraint was whether the sealing profile could meet the vehicle requirement while fitting a manufacturable conversion path.

The later market-share statement should still be handled carefully. Approximately 55% of the global glass run channel market is a company-announcement figure, and the cited material does not provide the denominator, geographic breakdown, vehicle-program list or independent methodology behind it. It supports the conclusion that TPV adoption in this component is substantial. It does not establish a universal replacement of EPDM across automotive window seals.

What the specification still leaves open

The award confirms recognition of the application and the commercial significance claimed for it. It does not disclose the exact window-channel geometry, vehicle platform, production volume, qualification duration, weathering protocol, friction target, compression set, noise measurement or failure limit. Those are the checks a converter or OEM quality group would still demand before transferring the result to another profile.

The same caution applies to recycled-content TPV. Celanese has extended the Santoprene portfolio with ECO-R grades containing post-consumer recycled content, while HEXPOL has described automotive TPE grades with recycled content ranging from 10% to more than 80% in its broader portfolio. Those figures belong to material offerings and other applications; they are not evidence that recycled-content TPV has replaced virgin Santoprene in this glass run channel.

HEXPOL has separately reported circular TPV grades with recycled content of up to 28% and described closed-loop reprocessing as a property of TPV. Again, that supports the processing case, not a qualification result for the Celanese-Cooper Standard profile. A buyer changing the resin in a window seal would still need the grade, source of recyclate, lot control, odour and emissions data where applicable, and a complete durability file for the actual part.

The defensible conclusion is narrower than the headline. TPV replaced EPDM in a named automotive glass run channel because the part retained the required sealing function while reducing weight and simplifying the production economics. The award shows that the conversion became a durable program solution. It does not turn every automotive window seal into a TPV opportunity without profile-specific validation.