PERMEABILITY AND SPECIFIC SURFACE OF PAPER

Throughflow parameters for various grades of paper of basis weights 25 -250 g/m2 were determined by application of the momentum transport equ ation. The use previously of the Darcy's law approximation leads to er rors in permeability of up to 50% for the combination of minimum basis weight and maximum throughflow rate tested. Specific surface was dete rmined by application of the Kozeny-Carman relation. The effect of wet ting-drying on permeability, specific surface and porosity was determi ned. Such a cycle produces a large increase in permeability, porosity is increased, specific surface is decreased, all from collapse of fibr illation on wetting.