New TPE Chemistry Yields Rubberlike Compounds that Provide Excellent Oil Resistance

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A new class of thermoplastic elastomers (TPEs) provides exceptional oil resistance and highly rubberlike properties--a com bination previously available only in TPEs costing 25 to 50% more per pound, it was announced today by Teknor Apex. In addition, the materials exhibit valuable engineering properties like flexibility at subzero temperatures.

Called Flexalloy (registered trademark) OR (Oil Resistant) TPEs, the products are PVC/elastomer blends that exhibit softness, elasticity, and tactile properties comparable to other TPEs in the same price range, according to Phil Morin, Industry Manager. "But formulating and compounding advances have enabled us to eliminate the greatest deficiency of competing materials: swelling, shrinkage, or disintegration after prolonged exposure to oils."

Applications for Flexalloy OR products are expected to include appliance, automotive, footwear, wire and cable, and other products exposed to hydrocarbon-based oils, animal fat, automotive fluids, and other aggressive substances. Some examples are grips, bellows, shrouds, seals, gaskets, boots, and insulation.

Teknor Apex is introducing ten grades of the TPEs: five injection molding grades with Shore A hardnesses from 40 to 60, and five grades for extrusion, calendering, and extrusion blow molding, with hardnesses from 40 to 60. Flexalloy OR TPEs are processa ble on conventional equipment.

"These blends are based on new resin and stabilization technology as well as advanced polymeric modifiers," said Dexi Weng, Polymer Development Chemist for Teknor Apex. Weng was a co-presenter of the paper "New PVC Elastomers" introducing the materials at the Society of Plastics Engineers' Regional Technical Conference (RETEC) "Thermoplastic Elastomers: The Flexible Alternative," which took place on Sept. 30-Oct. 1 in Akron, OH.

The oil resistance of the new materials matches that of more costly oil-resistant TPEs such as polypropylene/nitrile rubber blends and chlorinated polyolefin blends, Weng said.

The 41% average compression set of Flexalloy OR TPEs is also nearly equivalent to that of a more costly thermoplastic vulcanizate (TPV) after 22 hrs. at 70°C, according to Weng. (Compression set is a measure of an elastomer's resistance to deformation, with lower values indicating better recovery.) "Thermoplastic urethanes (TPUs) and other block copolymers, on the other hand, generally exhibit compression set values in the 60 to 80% range under the same test conditions," said Weng.

Another important benefit of Flexalloy OR TPEs relates to the extremely low temperatures at which they become brittle: ranging from -41 °C to -54 °C. "This unique performance is critical for transportation, building and construction, and other applicati ons exposed to subzero temperatures," Morin said.

Contact: plastics@teknorapex.com