Abstract
Temperature is one of the important factors in polymer molding processes. A non-intrusive technique which obtains temperature distribution in dies or nozzles is expected. Electrical Capacitance Tomography (ECT) is a suitable system for satisfying the requirement to acquire two-dimensional capacitance distribution. However, it also draws relative permittivity distribution because capacitance is a function of relative permittivity. The relative permittivity distribution probably indicates the temperature distribution, because relative permittivity has temperature dependence. There are number of previous reports about temperature dependence of polymeric relative permittivity. The temperature ranges are usually lower than the point where polymers are melted. We describe polymeric relative permittivity under such high temperature. Capacitance is determined with an impedance analyzer which has a two-electrode cell, and relative permittivity is calculated from the capacitance. Sample polymers are polypropylene (PP), polycarbonate (PC) and polymethyl methacrylate (PMMA). The temperature dependence is changed complicatedly. It depended on the polarity existence or the measuring frequency. Some points where showed same values of relative permittivity in spite of different temperature were found. Capacitance distribution does not mean temperature distribution directly. There is necessary of considering new measurement method with a combination of relative permittivity and other electrical properties, such as dielectric loss or dielectric loss tangent.
