Material properties are very important to model correctly when calculating solutions for multiphase flows with non-Newtonian fluids. The models can make the solution converge or diverge depending on how it is chosen. This paper mainly focuses of the applicability of solid pressure and viscosity models in Ansys CFX. The main goal is to create a list of criterions that material properties must fullfill to ensure that the solution converges. Furthermore a test environment in MATLAB was made that verifies if the models satisfies the list of criterions. It was found that as long as the material properties has continous derivatives without removable singularities and are non imaginary on their domain they are applicable in Ansys CFX. It was also found that if there was a discontinuity in their domain the discontinuity could be moved outside of the domain using an assymetric model for the volume fraction.