Significance and Use

1 This test method is used to measure the total and external surface area of carbon blacks based on multipoint nitrogen adsorption. The NSA measurement is based on the B.E.T. theory and it includes the total surface area, inclusive of micropores, pore diameters less than 2 nm (20 Å). The external surface area, based on the statistical thickness method (STSA), is defined as the specific surface area that is accessible to rubber.

2 CTAB Surface Area (formerly Test Method D3765) has been withdrawn. The CTAB value may be estimated from the STSA value using Eq 1. The equation is based on a linear regression of the STSA and CTAB measured values of the SRB 5 standards.

Scope

This test method covers the determination of the total surface area by the Brunauer, Emmett, and Teller (B.E.T. NSA) theory of multilayer gas adsorption behavior using multipoint determinations and the external surface area based on the statistical thickness surface area method.

Summary of Test Method

The total and external surface areas are measured by evaluating the amount of nitrogen adsorbed, at liquid nitrogen temperature, by a carbon black at several partial pressures of nitrogen. The adsorption data is used to calculate the NSA and STSA values.

Apparatus

1 Multipoint Static-Volumetric Gas Adsorption Apparatus, with Dewar flasks and all other accessories required for operation.

2 Sample Cells, that when attached to the adsorption apparatus, will maintain isolation of the sample from the atmosphere equivalent to a helium leak rate of <10–5 cm3/min, per atmosphere of pressure difference.

3 Balance, Analytical, with 0.1 mg sensitivity.

4 Heating Mantle or Equivalent, capable of maintaining a temperature of 300 6 10°C.

5 Oven, Gravity Convection, capable of maintaining a temperature of 125 6 10°C.

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