Factors That Influence the Negative Corona Charging of Nonwoven Filter Media

摘要

The aim of this paper is to analyze the corona charging and charge decay of nonwoven fabrics, by using the surface potential decay (SPD) measurement techniques and its (tdV_s/dt) versus (log t) representation. Samples of nonwoven polypropylene (PP) fibrous media were exposed to negative corona discharges, using a triode-type electrode arrangement, energized from a DC high-voltage supply operating as a constant current generator. Using the above-mentioned mathematical transformation and varying some experimental conditions, it has been possible to identify the contribution of different physical mechanisms to the SPD. The effect of charge injection assisted by the negative corona as well as that of neutral excited species present in the discharge were clearly pointed out. The experiments demonstrated that the initial potential and the dynamic of the potential decay are substantially affected by the air humidity. Thermal conditioning improves the charging state of nonwoven fabrics.