A percolation theory analysis of surface potential decay related to corona charged polypropylene (PP) electrets

摘要

We have studied the behaviour of 20 mum thick PP corona charging electrets, stored before and after they were charged, at various conditions of controlled relative humidity. The electret surface potential was measured for 250 days using a vibrating electrode with compensation. The time dependence of the surface potential was analysed by the percolation model for the 2D case. We have developed computer software for nonlinear programming. We have compared the experimental curves to the theoretical ones. We calculated the basic parameters that determine cluster formation and growth to an unbounded cluster, leading to a fast neutralization of electret charges. The percolation model allowed us to analyse electret surface discharge and to reveal the significant influence of the humidity level at which they have been stored. This is extremely important and should be taken into account in the study of the stability of electret sensors and devices that are used at room temperature and function under real conditions at various humidity levels. [References: 22]