Impedance spectroscopy of composites based on waste polymeric materials for electrical engineering purposes

Abstract

We have developed a high-sensitivity capacitance transducer and a method for measuring the complex of elec- trical indices of composites based on waste polymeric materials in the frequency range from 100 Hz to 1 MHz. The electrical properties of composites depending on the electric field frequency and the content and type of the filler have been investigated. Introduction. The development of effective methods for controlling and diagnosing the electrical properties of electrical-engineering composites based on waste polymeric materials is dictated by the necessity of their testing for the compliance of the complex of their electrical indices (relative permittivity, bulk electrical resistivity, dielectric loss tangent) with the norms regulated by the corresponding standards (1-3). The urgency of the problem is due to the fact that composites based on waste polymeric materials can find various applications in electrical engineering. For exam- ple, composites containing finely dispersed quartz sand or lignin as fillers can be used as electrical insulating materials, and composites based on powdery carbon fibers, powdery electrolytic copper, or rubber crumbs obtained from used tires can be used as current-conducting materials for a wide range of technical and household objects. In this connection, the purpose of the present work is to develop effective methods for controlling and diag- nosing composites based on waste polymeric materials with the aim of investigating their electrical properties depend- ing on the content and type of the filler in the electric field frequency range from 100 Hz to 1 MHz. Materials and Methods of Investigation. The technology of obtaining composites based on waste polymeric materials containing powdery carbon fiber (PCF), sand (S), PGRS powder, or powdery electrolytic copper (PEC) is as follows. Waste polyethylene film was ground with the help of a knife grinder. A certain quantity of fractured particles was placed on microrollers heated to a temperature of 115-120 o C, and the necessary quantity of powdery carbon fiber predried at a temperature of 150-200 o C was added to it portionwise; then the mixture was stirred for 5-7 min until a homogeneous mass was obtained. From the rolled sheet, composite plates with given sizes were formed by the method of hot pressing for 15-20 min at a temperature of 160-170 o C. To investigate the electrical properties of composites based on waste polymeric materials, we created a meas- uring facility incorporating a high-sensitivity capacitive transducer (sensor) and a small-sized digital immitance meter in which there is an interface for current control data output to the monitor of the personal computer screen. The de- sign of the high-sensitivity capacitive transducer is shown in Fig. 1. The capacitive transducer designed by us has the following advantages over the existing analogs: a) it permits obtaining information on the complex of electrical indices of composites based on waste poly- meric materials in the electric field frequency range between 100 Hz and 1 MHz; b) it permits determining the thickness of the composite plate by means of a micrometric device in the 0.1-6 mm range with an accuracy of 0.005 mm;