A comparison of the various liquid interaction radii derived from experiment and network modelling of porous pigmented structures

Pigment particles, such as calcium carbonate, can be compacted to form tablets without any addition of a binder by the application of high pressure in a die. Using different pressures an array of porosities can be obtained maintaining the pore surface chemical and overall geometric uniformity of the samples [Tappi J. 83 (2000) 77]. These structures can be used to test for a range of liquid interactions. The experimental data measured in this work allow for a unique assessment of the various equivalent hydraulic radii obtained from (i) surface area/porosity correlations, (ii) imbibition, (iii) liquid permeation and (iv) mercury intrusion. It is found that the radii derived from the different liquid interaction methods are dissimilar. The distinct differences are discussed in terms of the specificity of the approaches used in probing the pore structure, highlighting the mechanistic distinction between the intrinsic properties of a porous structure and its interaction with liquid saturation flow, intrusion and imbibition, respectively. The values are also compared with simulations of the structures and their interaction with liquids, using the pore network simulator Pore-Cor. [Pore-Cor is a software package of the Environmental and Fluid Modelling Group, University of Plymouth, PL4 8AA, UK.]. It is shown that the modelling is most representative at low porosity but the restricted pore and throat size range limits the representative modelling of absorption phenomena in structures of higher porosity. The combined data indicate the existence of different pore segregation mechanisms which are proposed to, at least partly, underlie the observed phenomenological dissimilarities seen for these complex porous network structures.