Hemijska Industrija (Jan 2010)
Dielectrical properties of composites LDPE+CB
Abstract
There is currently great interest in the technological properties of conductive polymer composites because their cost-performance balance. They have a wide range of industrial applications -in anti-static materials, self regulating heaters, current overload and overheating protection devices, and materials for electromagnetic radiation shielding. Measurements of the electrical properties of polymer composites are one of the most convenient and sensitive methods for studying polymer structure. A polymer composite differs substantially from a free polymer in a wide range of properties. The presence of filler affects both the electrical, as well as mechanical properties. One of the most important characteristics of conductive polymer composites is that their electrical conductivity increases nonlinearly with the increase of the concentration of filler particles. When the concentration of filler particles reaches a certain critical value, a drastic transition from an electrical insulator to a conductor is exhibited. This conductivity behavior resulting in a sudden insulator-conductor transition is ascribed to a percolation process, and the critical filler concentration at which the conductivity jump occurs is called ‘percolation threshold’. In the past few years, a lot of studies have been carried out to analyze the percolation phenomenon and mechanisms of the conductive behavior in conductive polymer composites. It has been established that the electrical conductivity of conductive polymer composites uncommonly depends on the temperature. Some of such composites show a sharp increase and/or decrease in electrical conductivity at specific temperatures. The conductive temperature coefficient (CTC) of conductive polymer composites has been widely investigated. In these work we investigated how concentration of the CB affects the dielectrical properties of the composite LDPE+CB. The ac electrical conductivity, σac, for such composites was measured. The temperature and frequency dependence of the dissipation factor were analyzed. It was found that the ac conductivity and dissipation factor were highly affected by the concentration of the filler.
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