BS 7591-4:1993

This standard BS 7591-4:1993 Porosity and pore size distribution of materials is classified in these ICS categories:

• 17.040.20 Properties of surfaces

This Part of BS 7591 describes the evaluation of pore size characteristics (such as mean, maximum and the distribution of pore sizes) that allow the flow of liquid from one side of the wetted structure to the other. It is a comparative and usually non-destructive test. Pore size is commonly expressed as `pore diameter'. The pore diameter is calculated from the applied gas pressure, which causes the liquid filled pores to be emptied, resulting in a flow of gas through the sample.

The method is suitable for the study of through-pore materials, such as filter paper, paper, polymer membrane filters and cloth. It enables pore sizes to be estimated within the general size range of about 50 mm down to about 0.05 µm.

The test involves the application of pressures up to 1 MPa²⁾ (150 psi). For most materials this pressure does not cause compaction or deformation of the material which would result in a change in the pore structure.

The technique should be considered to be comparative, as for most porous media a theory is not available to allow an absolute calculation of pore size.

It is the recommended method for the evaluation of filter papers (see BS 6410).

²⁾ 1 Pa = 1 N/m².

Describes evaluation of pore size characteristics by application of gas pressure causing expulsion of liquid filled pores.