Sealing the Deal Recyclability helps plastic win new application

Eating, breathing and sleeping automotive weather seals isn't glamorous work, but at Advanced Elastomer Systems (AES) - and at automakers - it's worth the trouble. Weather seals are those flexible rubber strips that ring the perimeter of doors, hoods and decklids, locking out the elements and making interiors cozy and quiet.

If they do their job, nobody notices. In fact, some luxury automakers go to considerable trouble - and expense - to hide them, covering the black synthetic rubber with fabric so it matches the vehicle interior and allows them to totally blend into the background.

But if weather seals fail, just a little bit, they are a major annoyance to consumers and destroy a vehicle's quality reputation: Wind whistles and water leaks are deadly to customer satisfaction.

Ford Motor Co. reportedly spent $35 million extra during the development of the current generation Taurus to triple-seal the doors because the previous generation - which had only two door seals - was plagued by complaints about wind noise.

Akron, OH-based AES, a limited partnership between Exxon Corp. and Solutia Inc. (formerly Monsanto), has a more pragmatic interest in rubber weather seals. It wants to replace them with Santoprene, a rubber-like plastic generically called a thermoplastic elastomer (TPE). Weather seals have been the Holy Grail in this segment of the plastics business for years. TPEs already are used on most vehicles now as fuel line covers, steering bellows, interior trim and console mats. But they are relatively small parts amounting to only a few pounds per car.

Weather seals present a huge new opportunity for TPEs, amounting to about 200 million lbs. (91 million kg) per year, says Robert Eller, an Akron, OH-based consultant who has done several studies on the automotive weather stripping market. Mr. Eller says vehicles use an average of 15 lbs. (7 kg) of weather strip material per car.

Bob Liskiewicz, vice president-automotive at AES, is more optimistic: he estimates cars and trucks use 17 lbs. (8 kg) to 22 lbs. (10 kg) of weather seals. Whatever the case, if AES can convince automakers to convert only a fraction of those seals to TPE, the Santoprene business will shoot through the proverbial roof.

After years of trying, AES finally is on its way. It has won what it says is the auto industry's first major TPE weather seal application - for tailgates on Mitsubishi MotorsCorp. mini commercial vehicles that go on sale this month in Japan. The new seal is the first use of a new technology that co-processes a solid section and a foamed section with a metal carrier.

Why switch to a new material when conventional synthetic rubber has been doing a good job for decades? Mr. Eller says recyclability is the main driver. Thermoset rubber is difficult to recycle. TPE can be melted down and reused easily. TPE also is lighter than rubber, and can be designed to incorporate thermoplastic retaining clips and inserts rather than metal.

AES's Mr. Liskiewicz says if TPEs were used for all weather seals, it eventually could result in a savings of 8 lbs. (4 kg) to 10 lbs. (4.5 kg) per car. AES also claims the new application represents a 5% to 10% cost savings versus thermoset rubber because of "system cost" savings in processing and manufacturing. On a weight basis, Santoprene is more expensive.

Recyclability, therefore, will be the primary driver for switching from conventional weather seals to TPEs, at least short term. That helps explain why a Japanese automaker is the first to use the technology and why a European carmaker will likely be next. Skyrocketing landfill costs, taxes, legislation and other factors palce a higher demand for recyclability in those markets.

MMC estimates that if it switches all rubber used in weather seals to TPE, it can increase its recycling rate by 0.5%; one small step in making its vehicles 90% recyclable by 2000.