ASTM D7723-18

5.1 The incorporation of fillers into the rubber matrix is characterized by their macrodispersion as an indicator of the quality of mixing. This test method provides a measure of the macro-dispersion of reinforcing fillers, like silica and carbon black, as well as of inert fillers. Based on their polymer nature, different types of rubbers can show a different degree of acceptance for the incorporation of fillers, as indicated by their macro-dispersion.

5.2 Macro-dispersion of carbon black and silica in rubber compounds may be measured by different methods. Carbon black provides a direct physical reinforcement; silica requires a silane coupling agent in order to initiate reinforcement, and therefore, a different technology of mixing. Silica is also a non-conductor, making electrical methods of dispersion measurement impracticable. This test method is specifically appropriate for the characterization of the microdispersion in silica technology.

5.3 This test method also can measure the mixing quality of colored rubbers. It uses variable exposure in order to be able to image a wide range of colors.

5.4 This test method is intended for use in research and development as well as in quality control of filler processability in rubber and may be used for both the evaluation of production processes or referee purposes.

1.1 This test method covers a procedure to measure the macro-dispersion of fillers in a rubber matrix by quantifying the surface roughness of a freshly cut specimen using an optical microscope in reflection mode.

1.2 The method provides a procedure to measure the quality of mixing of reinforcing fillers such as silica and carbon black, as well as inert fillers such as chalk, clay and other solids.

1.3 The method includes a sample preparation procedure for filled uncured rubber compounds as well as filled cured rubber compounds.

1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.