A theoretical approach to understanding microstructure-tensile modulus relations in paper coatings

A computational approach is described that aims to predict the tensile modulus of paper coatings comprising a geometrically complex microstructure. Variably shaped particles were packed within a voxel matrix and an algorithm employing both morphological dilation and erosion used to control the addition and spreading of binder. The completed packing, consisting of both particles and binder, was sliced to yield 2-dimensional planes. The tensile modulus of each plane was then predicted using an algorithm based on a modified matrix method. The algorithm mimicked precisely the voxel dimensions using rectilinear grid elements with a central node in each. The model results follow expected trends, but may be under predicting the tensile modulus. This is quite possibly due to the missing latex-particle connections ordinarily present in the 3^rd dimension. The magnitude of binder spread about the particle surfaces did not appear to affect the global tensile modulus in the low binder fraction packings. This could be down to either of two contradicting reasons. Either the effective regions of binder are 'fully saturated' in every packing, or, in the lower packings, there is not enough binder to make more/stronger particle-particle connections. It is believed that ground calcium carbonate (GCC) packings require more binder to reach optimal binder content as compared to kaolin. This is deemed to be a function of their packing geometry and the resulting microstructure.