Due to the complex flow kinematics developed in processes involving mixing of, at least, two phase blends (e.g., the phase inversion phenomena that takes place in the production of Thermoplastic Vulcanizates), traditional modelling processes, that use meshes, are extremely difficult to employ, mainly due to the high mesh distortions promoted or the mesh operation manipulations that would be required. For these the use of smooth particle hydrodynamics (SPH) based methods, i.e., a mesh free method based on Lagragian particles, would be adequate. This work describes the development and assessment of an incompressible formulation for the SPH method, named ISPH (incompressible SPH), adequate to model mixing processes that involve more than one phase. The formulation developed required the implementation of innovative procedures to correct handle the interface between materials. The developed code is verified through traditional benchmark problems, namely: Taylor-Green vortices, Raleigh-Taylor instability and Lid-driven cavity. After verification the code used in a mixing process case study, showed that it is able to predict the viscous encapsulation of polymers, a well known phenomena in flows involving materials with high different viscosity levels.