ASTM D6556 Total and External Surface Area by Nitrogen Adsorption

Scope:

Based on multipoint nitrogen adsorption, this ASTM D6556 test method determines the total and exterior surface area of carbon blacks. The N.S.A. measurement is based on the B.E.T. theory and covers the total surface area, microspores, and pore sizes less than 2 nm. Based on the statistical thickness approach (STSA), the exterior surface area is defined as the specific surface area accessible to rubber.

Procedure:

In ASTM D6556, the total and external surface areas are calculated by calculating the amount of nitrogen absorbed by a carbon black at various partial nitrogen pressures at liquid nitrogen temperature. The N.S.A. and STSA values are calculated using the adsorption data.

Specimen size

Multipoint Static-Volumetric Gas Adsorption Apparatus, complete with Dewar flasks and other attachments. The specimen is taken as per the requirements of the method.

Data

P/Va (Po – P) = 1/VmC + C – 1/VmC × P/Po

Where

P is the manometer pressure in kPa, 

Po is the saturation vapor pressure of nitrogen in kPa, 

Vm is the volume of nitrogen per gram that covers one monomolecular layer in standard cm³/g, 

C is the B.E.T. constant whose numerical value depends on the heat of adsorption of the monomolecular layer.

Conclusion:

Based on multipoint nitrogen adsorption, this ASTM D6556 test method determines the total and exterior surface area of carbon blacks. The N.S.A. measurement is based on the B.E.T. theory and covers the total surface area, microspores, and pore sizes less than 2 nm.