TPE boots that booted rubber still on the road 25 years later

Although there have been many subsequent victories by thermoplastic elastomers (TPE) over rubber in automotive applications, one replacement that just turned 25 years old and still does not have a material failure helped pave much of the way. Canada’s ABC Group Inc. first used DuPont Hytrel TPE in a constant-velocity joint (CVJ) boot application in 1984, and in the years since more than 1 billion boots have been placed in service without material failure, with each surviving 150,000 miles of continuous flexing, pelting, and thermal cycling. How far can the Hytrel CVJ boots go? According to DuPont, a vehicle equipped with Hytrel CVJ boots could travel around the Earth’s equator six times, while rubber boots could only make the 25,000-mile trek twice.
 

In the late 70s, automakers adopted front-wheel drive vehicles to help meet fuel economy standards. At the time, boots were typically made of rubber and lacked the flex fatigue and contaminant resistance of an elastomer. Constant-velocity joints allow a rotating shaft to transmit power from the transmission to the wheels, and the boots protect that critical component from contaminants outside, while keeping lubricants inside. Any cracks or tears in the boot can lead to CV joint failure.

According to Eric Randa, DuPont Automotive chassis segment manager, “Thermoplastic elastomers were a huge step change—all of the sudden the durability was more than doubled so consumers no longer had to deal with boot failure, engineers could now design smaller, more compact, less costly boots, and automakers could worry less about service-life limitations.”

The initial application reduced part weight by 40%, cut piece price and tooling costs, and established a “service for life” benchmark that eliminates the need for replacement under normal driving conditions. Today, vehicles utilize four or more inboard and outboard CVJ boots, prop shaft boots, and rear-wheel-drive boots, with the vast majority composed of TPEs.

The original CVJ boot for General Motors-Saginaw Steering Division that was molded by ABC Group has been nominated for a Society of Plastics Engineers Hall of Fame award. That honor is granted annually to applications that have been in continuous use for 10 years or more and have made a significant and lasting contribution to the application of plastics in automobiles. —[email protected]