ASTM D412

Proper tensile testing of vulcanized (durable) rubber and thermoplastic elastomers per ASTM D412 is quite useful since these compounds are one of the most complex and universally used materials where both elasticity during stretching and recoil upon release are needed. Rubber compounds used in footwear, tires, sports equipment, gaskets and many other applications are formulas that have been optimized with precise amounts of several materials. One simple and common elastomer example, used in many toys, is plasticized PVC. And on the other end of the spectrum in terms of complexity, there are specialty elastomers used in aerospace applications which maintain high performance specifications even in extreme temperature environments.

 

Tensile testing of vulcanized rubber and thermoplastic elastomers in a universal testing machine evaluates the residual elongation of a test sample after first being stretched and then allowed to relax in a specified procedure. Elongation of these materials consists of both permanent (plastic) and recoverable (elastic) components, so accuracy in the time specified for stretching and recovery is critical. ASTM D412 references two test methods:

 

Method A is for dumbbell (dogbone)-shaped specimens, while Method B is for flat cut ring specimens. The standard calls for samples which have not been pre-stressed to be measured for tensile stress, tensile stress at a given elongation, tensile strength, yield point, and ultimate elongation.

 

Solutions for ASTM D412 typically include these types of components:

 

Both the premium MTS Criterion® and the economical MTS Exceed® universal testing machines are ideal for tensile testing of vulcanized rubber and thermoplastic elastomers per ASTM D412. They both come in a variety of force capacities and frame styles, ranging from 1-column tabletops to larger 2-column floor-standing models. For these high elongation materials, taller frame options are available. The 30kN and 100kN models also have dualzone test spaces to reduce set-up times if you frequently change test requirements. And as an alternative to a new load frame, you can modernize the software and controls of your old test system with an MTS ReNew™ Upgrade.