Partial wetting in a ternary polymer blend is the thermodynamic state where all three phases meet at a three-phase line of contact. Pickering emulsions, where solid particles situate at the interface of two other phases is a classic example of this state. This paper studies the presence of partial wetting in PE/PP/PS and in PE/PP/PC ternary polymer blends and examines, in particular, the influence of polyethylene viscosity on PS droplet formation at the PE/PP interface. Quantitative analysis of PS droplet growth and coverage at the PE/PP interface during static annealing were obtained by image analysis. A new approach was established to estimate the co-continuous PE/PP coarsening rate and was found to be in agreement with previous studies. In this work it is shown that the polyethylene viscosity can be of significant importance in ternary partial wetting when the interfacial driving force for partial wetting is weak and viscosity directly affects the quantity and size of PS droplets at the interface during annealing. The equilibrium between droplet stability at the interface, as predicted by spreading theory, and the interfacial mobility generated by coarsening determines the PS droplet size and surface coverage at the PE/PP interface. A ternary PE/PP/PC system, which displays a strong partial wetting driving force, was also investigated. The morphology of the blend system studied demonstrated a clear dominance of partial wetting over complete wetting. (C) 2011 Elsevier Ltd. All rights reserved.