Oct 26 2009
In 25 years, more than 1 billion DuPont™ Hytrel® thermoplastic elastomer constant-velocity joint (CVJ) boots have kept vehicles moving without material failure. Hytrel® boots can survive 150,000 miles of continuous flexing, pelting and thermal cycling while rubber boots last for about 50,000 miles.
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CVJs allow a rotating shaft to transmit power from the transmission to the wheels in automobiles. CVJ boots protect critical joints from contaminants outside and keep lubricants inside. Boot cracks or tears can lead to CVJ failure.
“In the late ‘70s, when automakers turned to front-wheel drive vehicles to meet fuel economy standards, boots were typically rubber without the flex fatigue and contaminant resistance of Hytrel®,” said Eric Randa, automotive chassis segment manager – DuPont Engineering Polymers. “Thermoplastic elastomers made a huge step change – more than doubling durability and allowing engineers to design smaller, more compact, less costly boots.”
Today, vehicles sport four or more inboard and outboard CVJ boots, prop-shaft boots and rear-wheel-drive boots, most of them made with thermoplastic elastomers, such as Hytrel®.
The original CVJ boot for General Motors-Saginaw Steering Division, molded by ABC Group Inc. of Canada, has been nominated for a Society of Plastics Engineers Hall of Fame award. Granted annually to applications in continuous use for 10 years or more, the award recognizes significant and lasting contribution to the application of plastics in automobiles.
“Today Hytrel® serves as the benchmark for excellent balance of grease resistance, high temperature durability, low temperature flexibility and historically proven performance,” Randa said.
Hytrel® invites thinner design for better packaging in tight spaces, vastly improves performance and durability for greater service life. Compared with co-polyesters, Hytrel® delivers the optimal combination of flexibility and stiffness, protecting against expensive repairs.
DuPont offers a portfolio of products to balance performance and cost and plans to launch several new lower-cost grades with improved processing in the next year.