Fibrous materials are widely used as air filter media because of their high filtration efficiency (FE) and low-pressure drop contributed by their large fiber surface area and high fabric porosity, respectively. In addition to the FE by the mechanical mechanisms such as direct interception, inertial impaction and Brownian diffusion of the particles on the fiber surface, electrostatic charging of the materials greatly improve the FE by the electrostatic attraction of the particles from the charges in the fibers. Electrospinning is a process that can produce nano to micro fibers with the fiber diameter from 10 nanometers to around 1 micron, a range that is much smaller than that of the conventional nonwoven fabrics. It has been reported that the electrospun fabrics provide a much higher FE than the conventional nonwoven fabrics such as spunbond, needle-punched and meltblown fabrics. The corona charging of the electrospun fabrics has not been reported. This paper will present the effect of corona charging of the electrospun fabrics on their charge properties and their corresponding filtration efficiencies. Polar materials such as polyethylene oxide and polyurethane as well as nonpolar materials such as polystyrene and polycarbonate have been produced by electrospinning for this study. The charges and the FE have been measured by the surface charge potential measuring system and by an automated aerosol tester, for both the virgin and the corona-charged electrospun fabrics. This study also includes the effects of storage, heat treatment and substrate differences on the surface charge decay of electrospun filtration media.
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