ASTM D4620-02(2007)

The surface area of zinc-oxide in rubber can significantly affect cure activation and vulcanizate properties.

The specific surface area of zinc-oxide is usually measured by nitrogen absorption which requires the use of equipment not normally found in rubber laboratories. This test method allows a ranking of zinc-oxide samples according to their surface areas with respect to a known standard using a simplified procedure involving mixing of rubber compounds and measuring cure times with oscillating disk or rotorless cure meters.

This test method may be used for quality control, research and development work, and comparison of different zinc-oxide samples.

1.1 This test method specifies the standard materials, mixing procedure, and test method for ranking zinc-oxide samples according to their specific surface area in a standard test formula based on chloroprene rubber (CR).

1.2 The ranking is based on the cure time of the standard CR formulation.

1.3 The accurate surface area cannot be determined by this test method, since factors other than surface area may influence the cure times to some extent (for example acidity, heavy metal traces, etc.).

1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.