The aim of this work is to understand mechanisms responsible for particles localisation in immiscible polymer blends. This study shows that carbon-black fillers localisation in polypropylene (PP)/ poly-ε-caprolactone (PCL) blends is strongly influenced by the viscosity ratio (rather than thermodynamic parameters through the wetting coefficient). The localisation of the fillers is explained by a competition of hydrodynamic forces applied on particles localised at the interface. The transfer of fillers is investigated at the droplet scale by observation of the relaxation of CB-filled PCL droplets suspended in PP matrix. CB particles are transferred from the PCL droplet to the PP matrix by a new mechanism, called “zip flow”, which involves the erosion of the droplet edges, leading to the extraction of particles localised there. The control of these parameters allows to localize fillers selectively at the interface and to reduce significantly the electrical percolation threshold.
