Elastomer seals need no post-cure
27 June 2011
Materials scientists at Federal-Mogul Corporation have developed a novel seal material for its Unipiston bonded hydraulic clutch pistons that eliminates a costly and energy-intensive curing process, reducing the environmental footprint of the company’s manufacturing operations
Federal-Mogul’s Unipiston bonded hydraulic clutch pistons convert hydraulic pressure into the mechanical force needed to engage clutch packs in automatic and dual-clutch transmissions. Making use of a novel new moulding technique, the company has eliminated the oven post-cure process from the production of the elastomeric seals used in its market-leading Unipiston products.
The production of bonded piston seals has historically required that the parts are baked or cured in an oven for up to 12 hours at approximately 175°C. By eliminating the oven post-cure process, Federal-Mogul calculates that the annual natural gas consumption at its Frankfort, Indiana plant alone will decrease by 40 billion BTUs, reducing its annual CO2 emissions by nearly 2000 tonnes.
An indication that the manufacturing process is becoming just as important as the point-of-use emissions, this is also a good example of how technology developments can offer both environmental and commercial benefits. Federal-Mogul president and CEO Jose Maria Alapont says the new K16 elastomeric material (developed at its Ann Arbor, Michigan technical centre) is an example of his company’s commitment to creating a greener future through technology and innovation. “As the process is integrated into our sealing manufacturing facilities, the environmental benefit is immediate,” he says. “Our expertise in polymer chemistry and process control has produced a practical, cost-effective and environmentally friendly answer to a highly complex technical challenge.”
The finished K16 seal meets or exceeds the performance of previous seals both in terms of wear resistance and life expectancy and is based on proven long-chain elastomers. According to Federal-Mogul’s global director Sealing Technology and Innovation, Larry Brouwer, the company intends to expand K16 technology for other product applications, such as gaskets for oil pans or valve and engine covers or virtually any other sealing application.
Elastomers are normally formed by cross-linking millions of polymer molecules through vulcanisation, which is traditionally carried out in two steps. In the first step, known as press cure, the elastomeric compound is forced into a mould that defines the desired shape. In this step, vulcanisation is initiated by subjecting the compound to heat and pressure. Until now, the second step of vulcanisation occurred during oven post-cure, during which the compound is kept at a constant, elevated temperature for an extended period of time.
“Federal-Mogul’s search for more environmentally friendly processes led us to a combination of polymer chemistries and press cure conditions that produced the right elastic properties without energy-intensive curing or the use of expensive rubbers,” explains Mr Brouwer. “We developed a process monitoring and control system that adjusts the press cure time to compensate for any variation in temperature or material characteristics. This is the key to stabilising the cross-links between the polymers without a post-cure stage.”
The successful introduction of K16 on the company’s Unipiston product range is in production for several major OEMs, and plans are to integrate this innovation at Federal-Mogul facilities around the world.
In the first application of K16 technology at Frankfort, parts are now transferred directly from moulding to shipping, bypassing the old oven post-cure process and reducing part processing time. Implementation of the company’s K16 technology has generated additional benefits at the Frankfort plant, including reductions in part travel distance and work-in-process inventory.
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