New elastomer goes for a drive

Akron, OH—It takes a hardy plastic to hold up to the grease, grime, rocks, salt, and extreme temperatures found beneath a moving car. Advanced Elastomer Systems has now developed a thermoplastic vulcanisate (TPV) that appears to be up for this rough ride.

Called Santoprene 7028, the new material targets the "boot" that protects the transmission's constant-velocity joint and contains its grease. According to Sajid Shah, an automotive program manager for Advanced Elastomers, a European OEM has picked 7028 for the CVJ boots on its latest 4WD transmission.

Traditionally made from thermoset rubbers or copolyesters, CVJ boots require a material with an elusive balance of properties that includes resistance to abrasion, low temperatures, fatigue, and grease. Shah reports that Santoprene 7028 fits the bill on all these points. "It's a very special Santoprene," he says. At 40 Shore D, 7028 occupies the hard side of the company's 7000 Series, a family of olefinic thermoplastic elastomers that withstand temperatures as low as -80C, with dynamic compression recovery down to -40C. The grade also exhibits fatigue-fighting compression-set values.

Thanks to an edge in the specific-gravity department, 7028 may also help reduce part weights. Shah estimates that 7028 produces CVJ boots that weigh at least 20% less than those made from previous elastomers.

While intended for blow-molded CVJ boots, 7028 can also be injection-molded or extruded for other applications that call for abrasion resistance at low temperatures. Mid-Atlantic Regional Editor

For more information about elastomers from Advanced Elastomer Systems: Enter 536