THE DARK-FIELD CUT SURFACE (DFCS) TEST FOR ESTIMATING THE DISPERSION OF CARBON-BLACK IN RUBBER COMPOUNDS

A test for estimating the dispersion of carbon black in rubber compoun ds is described. It works by examining the freshly cut surface of a sp ecimen at low magnification in dark field illumination. Roughness of t ile surface related to the presence of carbon black causes increased r efection under dark field illumination, The illumination of each field of view is examined as 100 subdivisions and the relative values of th ese readings give a numerical estimate of the dispersion. Details of h ow this is done and the corrections applied to the results are describ ed. A second paper(1) reports some initial results obtained with the t est.The test works well for certain elastomers, notably NR and SBR. Th e biggest advantage of the test is its ability to work rapidly and che aply on small zones at relatively high magnification. This opens up th e possibility of detailed studies of macroscopic variations in dispers ion, done in reasonable times and at reasonable casts.