From latex gloves to bowling balls, hardness is a critical indicator of product performance. ASTM D 2240, Standard Test Method for Rubber Property–Durometer Hardness, was revised this year to include tolerances and specifications for a new “Type-M” Durometer for micro-hardness testing, as well as improved procedures for Durometers A, B, C, D, DO, O, and OO contained in the previous edition. The method has been approved by the Department of Defense and adopted by the American National Standards Institute.

Created by a task force of ASTM Subcommittee D11.10 on Physical Tests within Committee D11 on Rubber, D 2240 determines the indentation hardness of thermoplastic elastomers, vulcanized (thermoset) rubber, elastomeric materials, cellular materials, and some plastics.

The Type-M durometer tests products not easily measured by existing instruments, such as “medical tubing, latex gloves, and condoms,” according to Michael Kent Warner, International Sales Development, CCSi, Inc., Poulsbo, Wash., who led the revision of D 2240. The Type-M:
• Is considerably less expensive than the micro-hardness durometer needed for the existing International Rubber Hardness Durometer Test;
• Measures small, thin, irregularly-shaped materials, such as O-rings, that cannot be easily measured with the IRHD; and
• Accommodates production-controlled environments with a faster test.
Type-M Durometers measure rubber or plastic specimens with a thickness or cross-sectional diameter of 1.25 mm (0.050 in.) or greater, although specimens of lesser dimensions may be successfully accommodated under conditions specified in D 2240 with a hardness range between 20 and 90.

For further technical information, contact Michael Kent Warner, CCSi, Inc., 2032 Hostmark St., N.E. #4-E, Poulsbo, WA 98370 (360/697-6993). Committee D11 meets June 25-28, Norfolk, Va. For meeting or membership details, contact Staff Manager Tim Brooke, ASTM (610/832-9729). //

Copyright 2000, ASTM