On the in-plane permeability of water-saturated fibre webs

An apparatus for the measurement of the in-plane permeability of water-satu rated fibre webs was built. A circular fibre web was compressed between mio plain surfaces and water flowed radially through the compressed zone. The in-plane permeability was measured as a function of total web porosity at t wo different grammages (30 g/m(2) and 60 g/m(2)), with two different pulp t ypes (softwood bleached kraft and thermo-mechanical pulp, TMP) and over two different now lengths (0.5 and 2 mm). Permeability was found to decrease exponentially with decreasing total poro sity. The slope of this curve was found to be greater for softwood bleached pulp than for the TMP. Grammage had a considerable influence on the permea bility with lower grammage webs having higher permeabilities. Flow distance had a small but significant influence on the measured permeability.