Effect of Air Humidity on Charge Decay and Lifetime of PP Electret Nonwovens

The effects of air humidity on the charge decay and lifetime of polypropylene (PP) electret nonwovens manufactured by the pneumothermic method are presented. The PP fabric samples were corona-charged from a needle electrode under high voltage. The thermally-stimulated equivalent surface voltages were measured at a linear heating rate in a temperature range from 293 K to 395 K. The results of the measurements showed that the equivalent voltage depends on the structural properties of the PP nonwovens as well as the conditions of formation. The selected electret nonwovens were next placed in a chamber whose humidity was controlled within a range of 39% to 94%, and the decay of the electret charge was measured and analysed. The results show that conditioning the samples at a higher humidity influences the changes of the equivalent voltage and the lifetime of the electret fibre