Fuel filtration properties and mechanism of a novel fibrous filter produced by a melt-process

A porous filter comprised of polypropylene (PP)/polyamide 6 (PA6) micro-/nano-fibers has been produced from a novel melt-based plastics co-extrusion and exfoliation process technology for the separation of microscale water droplets from diesel fuel. The filter media have a mean pore size of 11 µm, a porosity greater than 85%, a surface area of more than 12x the value for an electrospun medium, tough mechanical properties, and a contact angle of 124°, all of which make the co-extruded filter a superior fuel filter. An improvement in water-separation from diesel fuel feed stream from 62-85% water-removal was achieved by the co-extruded and exfoliated PP/PA6 fibrous media in comparison to a commercial fuel filter under identical test conditions and pressure drop. The fuel/water separation mechanism was identified as a capture-coalescence-release process. It has been found that the highest performance fuel filter required small pore sizes and large surface area for droplet capture, due to the hydrophobic nature of materials required for successful droplet release, and a high porosity for minimizing flow resistance. In addition to the proof of concept water separation demonstration, studies into (a) the effect of increasing the barrier substrates thickness and (b) surface corona treatment to alter the hydrophilicity of media surfaces on the filtration efficiency co-extruded, exfoliated filters are reported.