Standard Active Last Updated: Jul 13, 2022
ASTM D3849-22

Standard Test Method for Carbon Black—Morphological Characterization of Carbon Black Using Electron Microscopy

Significance and Use

4.1 Carbon black morphology significantly affects the transient and end-use properties of carbon black loaded polymer systems. A carbon black’s particle size distribution is its single most important property, and it relates to degree of blackness, rubber reinforcement, and ability to impart UV protection. For a given loading of carbon black, blackness, reinforcement, and UV protection increase with smaller particle size. Aggregate size and shape (structure) also affect a carbon black's end-use performance, as higher carbon black structure increases viscosity and improves dispersion. The stiffness (modulus) of elastomer systems becomes significantly higher with increasing structure. The preferred method for measuring carbon black morphology (for example, size and shape) is transmission electron microscopy (TEM), but due to the semi-quantitative nature of TEM, it is not suited for mean particle size (MPS) certification. While useful morphological information can be obtained from TEM measurements within a laboratory, due to their inherent between-laboratory variability, TEM generated values should not be used for specification purposes.

4.2 Certification of carbon blacks for UV protection (weatherability) in certain plastics applications has historically been performed using TEM generated mean particle size values. ASTM Committee D24 has demonstrated that due to challenges with obtaining quantitative primary particle size data, particularly between laboratories, a qualification test based on surface area has been implemented, as detailed in Test Method B.

4.3 Carbon black aggregate dimensional and shape properties are dependent upon the nature of the system in which the sample is dispersed, as well as the mixing procedure.

Scope

1.1 This test method covers (1) the morphological (for example, size and shape) characterization of carbon black from transmission electron microscope images which are used to derive the mean particle and aggregate size of carbon black in the dry (as manufactured) state, from CAB chip dispersion or removed from a rubber compound and (2) the certification of mean particle size using a correlation based on statistical thickness surface area measurements.

1.2 The values stated in SI units are to be regarded as the standard. The values 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.

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Details
Book of Standards Volume: 09.01
Developed by Subcommittee: D24.81
Pages: 9
DOI: 10.1520/D3849-22
ICS Code: 83.040.20