Thermally stimulated current spectroscopy of polymers

We show the usefulness of thermally stimulated current (TSC) spectroscopy by applying this technique to detect minute changes in the higher order structure of cc form polypropylene. Polypropylene films irradiated with CO2 pulse-laser light or ultrasound were examined by TSC, wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The TSC method has extreme sensitivity to detect very small changes in the higher order structure that can not be detected by the WAXD and DSC methods at all. It was confirmed by the TSC method that irradiation with the laser light or ultrasound introduced crystalline defects and that some of them acted as deep charge traps. Vacuum deposition of metal electrodes on polypropylene films also introduced crystalline defects depending on the kind of metals used. Numbers of the deep traps introduced by Al and Bi deposition were estimated as projected surface charge trap densities by the TSC method. Typical values of them were 2.4x10(9) cm(-2) and 1.0x10(9) cm(-2) for Al and Bi deposition, respectively. For electrets of crystalline polymers such as polypropylene and polyethylene, their charge stability was controlled by changing the higher order structure of these polymers.