Standard Test Method for Carbon Black—Void Volume (VV)

The void volume of a carbon black expressed as a function of applied pressure, VV, is a carbon black structure property. Structure is a generic term that is a function of the shape irregularity and deviation from sphericity of carbon black aggregates. The greater a carbon black resists compression by having substantial aggregate irregularity and non-sphericity, the greater the compressed volume and void volume. Also, the more that a carbon black resists compression, the greater the energy required to compress the sample per unit void volume.

Structure, traditionally measured by OAN (Test Method D 2414) and COAN (Test Method D 3493), is a property that strongly influences the physical properties developed in carbon black-elastomer compounds for use in tires, mechanical rubber goods, and other manufactured rubber products. Several studies within D24 have demonstrated that void volume data can be used to estimate OAN and COAN numbers of carbon blacks using mathematical models derived from void volume-pressure data and oil absorption data. The models may vary depending on whether dynamic or static void volume measurements are used and the number and types of carbon blacks included within a modeling data set. If necessary, OAN and COAN estimates from void volume models can also be normalized using current SRBs (as practiced in Guide D 4821). Any estimates of OAN or COAN derived from prediction models using void volume-pressure data should be labeled appropriately (that is, Test Method D 6086) to avoid confusion with OAN or COAN data obtained directly from oil absorption methods.