Charging characteristics of a nonwoven sheet air filter

Corona-charging characteristics of a nonwoven polypropylene sheet of 140-μm thickness are studied with respect to the charging conditions. When the grid voltage, V_g, which controls the surface potential of the film, is -3 kV, the surface potential profile of the charged sheet is nonuniform. The profile is very uniform when V_g is only 1 -kV. The average surface potential of the charge sheet is roughly -500 V in both cases if charging time is long enough (e.g. more than 30 min). The experimental results for charge decay with time, resistivity in normal or ion-rich conditions, and TSDC curves are also reported