Thermoplastic elastomers really do get better all the time. Bob Eller, whose consulting firm tracks TPE technology, notes that the suppliers of these materials have applied a couple of strategies to improving these materials. One important strategy comes down to altering the plastic and rubber building blocks of these materials. Read on to see two such examples, one that boosts heat resistance and another that improve chemical and abrasion resistance. Another route to improving these materials relates to the use of additives that change functional characteristics. “Look for new foaming technologies in particular,” Eller says. One example here involves the use of proprietary foaming technology for thermoplastic urethanes (TPU) Eller describes other important elastomer trends in a forthcoming multi-client study that looks at the full variety of specialty TPEs. Among the trends he’s noticed are greater TPU use in automotive sealing applications and a shift toward larger and larger overmolded parts. For more information on the study, visit Robert Eller Associates at www.robertellerassoc.com.
TPV Takes The Heat
Thermoplastic vulcanizates (TPVs) based on olefins and EPDM rubber have chalked up plenty of success as a material for blow-molded automotive duct and boot components. But the heat limitations of these TPVs have favored rubber components and metal heat shields for components nearest the engine. Zeon Corp. has now brought out a new-blow molding grade of its nylon-acrylate TPV for a variety of automotive boots, bellows and ducts located in high-heat quarters of the car. Called Zeotherm 120-90B, the new material enables blow molded parts to survive continuous use temperatures as high as 175 C and a maximum temperature of 190 C. “Olefinic TPVs are good to continuous use temperatures of about 140 C,” says Brian Cail, Zeon’s new business manager. He adds that Zeotherm 120-90B also retains its properties in the face of various automotive fluids and at temperatures as low as -40 C, making it a good fit for rack-and-pinion and CVJ boots as well.The new material is available in hardnesses ranging from 90 Shore A to 45 Shore D. For more information, go to www.zeotherm.com.
Chemists in search of the ideal balance ofproperties have cooked up TPEs based on different kinds of thermoplastics. One of the newest comes from A. Schulman Inc., which has come up with a new elastomer built around an ionomer. Currently in pilot production, this Invision FX material offers improvements in scratch, mar, abrasion and chemical resistance compared to SEBS-based and olefinic TPV elastomers, according to Jeff McCoy, product manager for the company's TPEs. In stringent scratch tests used by the automotive industry (FLTM BN 108-13), the material has achieved the top rating of one on a scale from one to five, versus three to four for the other two types of TPEs, McCoy reports. With its superior chemical resistance, the new ionomer-based TPE also fight stain, making it a good fit for various appliance and automotive interior applications, McCoy continues. Tensile strength for a 75 Shore A grade is 5.6 MPa and a tear strength of 49 kN/m. Harder grades have even better strength values. "Ionomer turns out to be a nice material to built a TPE around," McCoy says. Invision FX is not, however, intended for high heat applications. Its heat resistance tops out at about 90 C, not as high as TPVs based on olefins and EPDM but similar to what SEBS elastomer can handle. A. Schulman currently offers the new material in hardnesses ranging from 75 Shore A to 40 Shore D.For more information on A. Shulman's elastomers, go to www.aschulman.com.
Zeon’s new high-temperature TPV targets blow-molded automotive ducts and boots.
Foaming TPUs with gas to reduce their density has been possible for yeas, but this need to inject the gas added some unwelcome complexity to the manufacturing systems--in the form of extra hardware and process control needs. BASF has developed what promises to be a simpler way to foam these materials. The company’s proprietary method requires no injected gas. Instead Elastollan Light uses proprietary heat-activated foaming agent that consists of “micro-beads” that first expand and then collapse to create the material’s cell structure. According to Stephane Morin, a BASF business development manager, the resulting material offers a 50 percent reduction in density--from a specific gravity of 1.2 for the unfoamed material to 0.65, saving significant amount of material in applications that use urethane foams for tasks such as cushioning, sound absorption, and gasketing. For more information, visit www.plasticsportal.com