Submicron polypropylene (PP) fibers of three different sizes (300 nm, 600 nm, and 900 nm) were prepared via electrospinning. The fibers were blended with microglass (MG) fibers to form composite media in varying fiber concentrations to obtain PP to MG fiber surface area ratios (AR) of 0.5, 1 and 2. The effects of fiber size and amount of electrospun PP fibers on wettability and filtration performance of the blended PP + MG media were measured. The wettability of the filter media were characterized by a modified Washburn test and expressed as the lipophilic to hydrophilic (L/H) ratio. The wettability characterization shows that hydrophobicity of filter media increases with the amount and size of electrospun PP fibers. In liquid-liquid coalescence experiments the amount and fiber diameter of the electrospun PP fibers significantly affected the separation efficiency and the pressure drop as compare to MG fiber only media. The separation efficiency was greatest for the smallest fibers (300 nm) and the intermediate AR of 1.0. The pressure drop tended to increase with the amount of PP fiber and with fiber diameter. (C) 2013 Elsevier B.V. All rights reserved.