Effect of microstructure and pure component properties on the dissolution rate of a binary composite material

A computational method for predicting the effective dissolution rate of a multi-component solid material, such as a tablet compressed of a powder blend, has been developed. The material microstructure is represented as a three-dimensional array of discretisation points (voxels) that carry information about the component present at each location. The dissolution of the composite material is then simulated by eroding the structure according to given intrinsic dissolution rates specific for each component. Computer simulations of the effect of composition and pure component properties on the overall dissolution rate of a random binary composite have shown several interesting phenomena: (i) a strongly non-linear, percolation-type behaviour for the dependence of effective dissolution rate on composition in the presence of a both fast- and slow-dissolving components; (ii) significant increase of the exposed surface area during dissolution due to interfacial roughening, again in the presence of both fast- and slow-dissolving components. Engineering correlations allowing the estimation of the overall dissolution rate from composition and pure component intrinsic dissolution rates have been proposed.