Effect of latex volumetric concentration on void structure, particle packing and effective particle size distribution in a pigmented coating layer

A series of coating formulations was prepared by mixing calcium carbonate, ground to two particle size ranges, gcc60 and gcc901, having 60 w/w% < 2 μm and 90 w/w% < 2 μm, respectively, with latex binders of low and high Tg each having different equivalent spherical particle diameters. These coating formulations were prepared by keeping the carbonate volume concentration constant while the solids content in the mix was raised by the addition of the latex volume fraction. The viscosity of the coating formulations was measured by Brookfield viscometry. Representative coating layers were prepared from the same mixes by applying them onto aluminium foil. Two different coating weights were applied and the coating layers were dried at room temperature. The final dry coatings have been subsequently analysed with mercury porosimetry in order to characterise their porous structure. The void structures were modelled using network simulation software that, with mercury porosimetry intrusion curves as input, generates a simplified three-dimensional void network structure representative of the sample. In the present study, the software model was used to calculate the sizes of the representative particles, or 'skeletal elements', which fit between the simulated voids, providing information not only of the pore space but of the effective particle and/or agglomerate packing that generates that void space.