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, ?ac, 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.
Highlights
DIELEKTRIČNE OSOBINE KOMPOZITA OD POLIETILENA NISKE GUSTINE I ČAĐI*U ovom radu su ispitivane dielektrične osobine kompozita od polietilena niske gustine (PENG) i čađi u zavisnosti od temperature i frekvencije
Električna AC provodnost se mjerila pomoću uređaja Agilent 4285 A u frekventnom opsegu od 80 kHz do 13 MHz
The dissipation factor as a function of temperature of the pure LDPE and LDPE/carbon black (CB) composites at frequency 142 kHz
Summary
U ovom radu su ispitivane dielektrične osobine kompozita od polietilena niske gustine (PENG) i čađi u zavisnosti od temperature i frekvencije. U skladu sa tim analizirani su dielektrični gubici u funkciji temperature (od 120 do 355 K) i frekvencije (od 80 kHz do 13 MHz). Temperaturna zavisnost jednosmjerne električne provodljivosti i dielektričnih osobina polimernih kompozita može biti složena. Pojava naglog povećanja provodnosti u uskom opsegu koncentracija čađi oko perkolacionog praga, predstavlja jedan od fenomena zbog koga ovi materijali imaju veliku primjenu [3,4,7]. Prisustvo punioca značajno utiče na dielektrične relaksacione prelaze polimerne matrice. U ovom radu, ispitivali smo dielektrične osobine kompozita od polietilena niske gustine i čađi. Mjereni su električna provodljivost i dielektrični gubici u funkciji temperature, frekvencije i koncentracije čađi. Posebna pažnje je posvećena uticaju koncentracije čađi na dielektrične relaksacione prelaze
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