BS ISO 7743:2011

Rubber, vulcanized or thermoplastic. Determination of compression stress-strain properties. | Status: Superseded, Withdrawn

1 Scope This International Standard specifies methods for the determination of the compression stress-strain properties of vulcanized or thermoplastic rubber using a standard test piece, a product or a part of a product. Four procedures are given:

• — using standard test piece A with the metal plates lubricated (method A);
• — using standard test piece A with the metal plates bonded to the test piece (method B);
• — using standard test piece B (method C);
• — using a product or a part of a product with the metal plates lubricated (method D).

The four procedures do not give the same results. Method A (test piece A, lubricated) gives results which are dependent only on the modulus of the rubber and are independent of the test piece shape, provided that complete slip conditions are achieved. Effective lubrication is sometimes difficult to achieve, however, and it is prudent to inspect the variance in the test results from replicate test pieces for indications of erratic slip conditions. Method B (test piece A, bonded) gives results which are dependent on both the modulus of the rubber and the test piece shape. The dependence on test piece shape is strong and, consequently, the results are markedly different from those obtained with lubricated test pieces. Method C (test piece B) gives results which are independent of both the test piece shape and the lubrication conditions. This test piece is more appropriate and more convenient when intrinsic material properties are to be determined (see Annex A for details). For products (method D), the result is dependent on the shape, but as tests on products are mainly comparative, this is acceptable.

NOTE For well-specified product shapes, such as O-rings, the result can be correlated to the hardness value.

Provision is made for the use of test pieces of different size and/or shape from the specified test pieces, but extrapolation of the results obtained to other sizes and shapes can prove impossible. Information on the effect of size and shape of test piece and of bonding or lubrication is given in Annex A. The method is not suitable for materials that exhibit high set.