Study on charge storage characteristics of PP film electret charged by interface polarization method

Electret attracts increasing attention nowadays because of its lasting and stable electrostatic field. To achieve the widespread use of electret material, higher density and better stability of the electret charge storage as well as well-distributed electrostatic field must be ensured at the same time. Based on the mechanism of interface polarization on double-layer media, a novel charging technology for electret is reported in this paper; and PP film is successfully charged through an auxiliary layer to form electret by this proposed method. Effect of charging temperature and charging voltage on the charge storage performance of the as-prepared PP film electret is investigated by means of surface potential measurement. Also its charge storage performance at high temperatures is explored by thermally stimulated discharge technique. Furthermore, its electrostatic field distribution in the directions of X and Y is measured. Results show that the interface polarization charging is more excellent than the corona charging. At a certain temperature, the surface potential of PP film electret increases with increasing charging voltage and both are in a good linear relationship. This is in good agreement with the theoretical analysis in terms of the equation of electret charge accumulation during the charging process. It is shown that in the case of constant charging voltage within the range of 0.53.0 kV, the effect of charging temperature is not obvious when the temperature is below 75 ℃; however, when the temperature is higher than 75 ℃, the surface potential of PP film electret increases with increasing temperature. In addition, its surface potential may change a little with time so it has an excellent charge storage stability. The distribution of its surface potential shows that it exhibits an homogeneous electrostatic field due to interface polarization charging.