Thermoplastic Elastomers

A new ASTM International standard will provide a fast and effective way to test production lots of thermoplastic elastomers in order to quantify and predict how well they process and what ultimate physical properties will be imparted to final molded or extruded products.

D7605, Test Method for Thermoplastic Elastomers - Measurement of Polymer Melt Rheological Properties and Congealed Dynamic Properties Using Rotorless Shear Rheometers, was developed by Subcommittee D11.12 on Processability Tests, part of ASTM International Committee D11 on Rubber.

According to John Dick, senior engineer, applications, Alpha Technologies and a D11 member, the new standard will quantify lot- to-lot variations in the plant receiving area that relate to quality variations.

"This standard can be used in plant quality problem-solving situations," says Dick. "It has the practical advantage of relating to subtle variation in molecular changes that traditional methods cannot detect, let alone determine why this performance variation is occurring." These variations include rubber-to-plastic resin ratios, curative concentration for dynamic vulcanization, DV temperature, quality of the rubber itself, concentration or type of oil and filler and resin effects.

Subcommittee D11.12 is currently looking for interested parties from both D11 and D20 on Plastics to participate in interlaboratory testing in order to develop a precision statement for D7605. Dick says that D11.12 is particularly seeking laboratories that have rotorless shear rheometers such as the RPA, APA, VTM and/or ATD.

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ONTACT Technical Information: John S. Dick, Alpha Technologies • Akron, Ohio • Phone: 330-848-7207 • E-mail: O ASTM Staff: Joe Koury • Phone: 610-832-9804 • E-mail: O Upcoming Meeting: Dec. 6-9 • December Committee Week • New Orleans, La.

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