Novel Nanofiber-based Coalescing Filter Media for Separation of Water Droplets from Ultra-low Sulphur Diesel Fuel

Professor Sadhan Jana and his students Dr. Stuti Rajgarhia and Dr. Rafael Benavides recently reported in Polymer, 93, 142-151 (2016) a facile means of fabrication of nanofibers from solutions of two immiscible polymers in two mutually miscible solvents using gas jet fiber method. The two polymers organize in interpenetrating network (IPN), side-by-side, or core-shell morphologies as function of the relative rates of evaporation of the two solvents. Specifically in IPN nanofibers, the two polymers are organized at scales smaller than 10 nm and accordingly, do not show preference for wetting either by water or by hydrocarbon liquids. This aspect is exploited in developing a composite filter media of IPN nanofibers coated onto glass fibers for separation of water droplets of average size 20 µm from the suspensions in ultra-low sulphur diesel (ULSD). The nanofibers are produced from hydrophobic polyvinyl acetate (PVAc) and hydrophilic polyvinyl pyrrolidone (PVP) by spinning the polymer solutions using gas jet fiber method. The nanofibers coat the individual glass fibers due to polar-polar interactions during the spinning process and render the filter media highly hydrophobic with water contact angle approaching 150° due to formation of thin sheets of polymer nanofibers around the glass fibers although no such coating is observed for only the hydrophobic polymer nanofibers. The increase in hydrophobicity leads to higher separation efficiencies and higher filter index values for separation of water droplets from ULSD.  The filter index of the composite filter media reach values as high as 3.05 (1/kPa) compared to 0.74(1/kPa) for filter media comprising of only the glass fibers. More detailed information about the work can be found in the article published in ACS Appl. Mater. Interf. 8, 21683-21690 (2016).