Charging characteristics for electret filter materials

In order to save energy at the time of dust collection, the authors have tried to provide as much charge as possible to electret filter. Polypropylene (PP) (nonwoven, by melt-blowing) and polytetrafluoroethylene (PTFE) (layering of PTFE fibers in wet system and heat dried) were used as a sample. High voltage DC corona, pulse corona and pulse with DC corona were applied to the sample materials. The discharge characteristics were investigated in order to provide larger charge for the materials. The results indicate that the pulse with somewhat slower rise time with DC superimposition provides a large charge. The maximum charge obtained was approx. 45 μC/m2 in the case of PP and approx. 10 μC/m2 in the case of PTFE.