Different electrostatic methods for making electret filters

Three charging techniques (viz., corona charging, tribocharging, and electrostatic fiber spinning) were used to charge fibers or fabrics of different polymer types. Corona charging is suitable for charging monopolymer fiber or fiber blend, or fabrics. Tribocharging is only appropriate for charging fibers with dissimilar electronegativity. Electrostatic fiber spinning combines the charging of polymer and the spinning of the fibers as a one-step process. It was observed that two dissimilar fibers following tribocharging had higher filtration efficiency than the corona-charged polypropylene fibers. An electrostatic spinning process produced nanofibers exhibiting extremely high efficiency by mechanical filtration mechanisms. Little charge was retained in electrospun polyethylene oxide fibers; however, polycarbonate and polyurethane retained a great amount of charge. (C) 2002 Elsevier Science B.V. All rights reserved.