Search

Polypropylene electrets 20 μm thick charged in a negative corona were studied. The samples were charged to different initial surface potentials and were stored under various pressures for 30 minutes. Then, the surface potential was again measured. The dependence of the electret surface potential on the pressure, under which the electrets were kept after charging, was investigated. As the pressure was lowered from 1000 mbar to 0.1 mbar a sharp decay of the surface potential occurred. It was established that a main parameter determining the surface potential decay is the ratio of the pressure to initial surface potential, and only one generalized curve describes all results obtained. Analyses of the equation described the results obtained was done. [ABSTRACT FROM AUTHOR]

The aim of the present work is the development of technology for formation of corona charged electret films from polylactic acid and investigation of their structural, optical and electret properties. Polylactide films with different degree of crystalinity were prepared by casting of poly-L-lactide and poly-DL lactide blended solutions. Then glass transition, crystallization and melting temperatures, as well as the crystalinity degree were determined by a differential scanning calorimetry. The charging of the samples in a corona discharge was carried out by means of a conventional corona triode system. Sample surface potential was measured by the method of the vibrating electrode with compensation. The time dependences of the sample surface potential under room conditions were studied for 50 days. The effect of lower pressure on the surface potential of charged samples was investigated. It was established that the reduced pressure leaded to the surface potential decay of the PLA electrets. The same effect was earlier observed for other polymer films. The optical characteristics—surface refractive index and optical dispersion, were determined by the method of the disappearing diffraction pattern using a laser refractometer. [ABSTRACT FROM AUTHOR]