Surface potential and crystal structure of injection isotactic polypropylene electret at different charging voltages

Abstract

A kind of specialized mold for making injection electret was developed and a series of charged isotactic polypropylene (iPP) samples were fabricated by injection molding in a high voltage electric field. The injection electrets were studied via the surface potential decay measurement. Meanwhile, the oriented morphologies and crystal structure of samples were investigated by means of polarized light microscopy (PLM), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and fourier transform infrared spectroscopy (FTIR). The results showed that the injection electret provided excellent charge storage stability. The molecular chain was oriented in the direction of external field force and more fiber crystals were formed during the cooling process, which would result in the melting temperatures of electret samples increasing. Additionally, there was a trend of decrease in value of conformation regularity and degree of crystallinity under the electric field conditions. This work has certain significance as a reference for the design and development of new electret product by the traditional way of injection molding.