ASTM D8644-25

1.1 This practice describes the procedure for the blending of recovered carbon black, the procedure for the reduction of gross samples of recovered carbon black to the appropriate size for testing and the preparation of the sample for testing. These techniques are intended to minimize variations in measured characteristics between test samples. Standard terminology relating to recovered carbon black samples is found in Terminology D8178.

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

1.3 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.

1.4 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.

4.1 Several test methods for recovered carbon black require the reduction in sample size or the blending of the test sample to reduce the variation of the measured characteristic. Other factors being equal, larger samples will tend to be more representative of the total supply. This practice provides procedures for reducing the large sample obtained from the bag and bulk sampling practices to a convenient size for conducting a number of tests to describe the material and measure its quality in such a manner that the smaller portion is most likely to be a representation of the bulk sample. Failure to follow the procedures in this practice could result in providing a nonrepresentative sample to be used in subsequent testing. Individual test methods provide for minimum amounts of material to be tested.

4.2 Practice A, Reduction of Sample Size, is typically used to obtain an aliquot from a large sample, splitting a recovered carbon black sample into two or more equal portions, or reducing a blended recovered carbon black sample from Practice B to a specified sample size. The final sample is always smaller than the original sample and would not be considered to be a “well blended” sample.

4.3 Practice B, Blending of Recovered Carbon Black using a Riffle Splitter, or Practice C, Blending of Recovered Carbon Black by Manual Homogenization is typically used to prepare a homogeneous sample. The final blended sample size is the same as the original unblended sample size. The homogeneous sample may be used for several tests (see Note 2) or may be reduced in size by Practice A.

4.4 When a sample is to be blended and reduced, the sample should be blended (Practices B or C) before reduction (Practice A). The blending and reduction must be done before the sample is dried (Practice D).