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The currents measured in oxidized low-density polyethylene after a dc step voltage excitation show maxima in the range of minutes to hours for temperatures between 20 °C and 80 °C and for field strengths between 20 and 200 kV/cm. The current maxima are shifted to shorter times by increasing the field strength or the temperature. The transient currents, which are explained by the build-up of an electronic...
Current transients observed when PE slabs with various electrode arrangements are illuminated are shown to be thermal in origin. In an externally applied field the current is mainly due to capacitive changes, while in zero external field the current from a previously polarized sample is due to nonlinear expansion of the dielectric and the resulting change in the profile of the immobile charge, i.e...
Static or volume expansion systems are used to generate accurately known pressures in the high and medium vacuum range for vacuum gauge calibrations. To determine the volume ratios in such systems, different methods can be used. We have tested the method of using a spinning rotor gauge for measuring pressures before and after an expansion for several gases and compared it with two other independent...
Ionization gauges are commonly considered to have identical sensitivity to hydrogen and deuterium due to the identical atomic configuration of the two gas molecules. We compared, experimentally, the sensitivity of twelve hot ionization gauges to hydrogen and deuterium and found significant differences between gauges. These differences depended on the specific gauge and systematically changed with...
The problem of the oxidation of polyethylene has been investigated and discussed in various papers from the aspect of the chemical reactions involved in this process. The main steps are known and measurements of, say, oxygen uptake in thin samples of an oxidation inhibited polymer yield information on the thermo-oxidative stability of the material. The results obtained are valid subject to the experimental...
Experiments of dc-conduction and dielectric breakdown in polyethylenes with different amounts of carbonyl groups incorporated in the polymer chain have been performed to elucidate the nature of conduction in the polymer. The experiments show that the dipolar C=O-groups are the localized states acting as hopping sites in an electronic transport process. According to the random distribution of hopping...
It is generally accepted that the conduction mechanism in low density polyethylenes without additives is due to a hopping transport of injected electrons. Earlier publications showed that carbonyl groups in the bulk may act as hopping sites. The aim of this paper is to present a transport model*) which describes the observed currents and explains the conduction mechanism in polyethylene. The model...
The successful use of polymeric insulating materials in electrotechnical applications requires a long-term stabilization of their initially excellent mechanical and electrical properties against degradation. One of the usual means of stabilization is to add special additives at low concentration levels. Apart from the necessary chemical effectiveness, the additives have to comply with certain physical...
The range of conduction phenomena observed in polyethylene (PE) is quite variable. In ultraclean materials, in which ionic impurities and Poole-Frenkel enhanced ionization are less likely, the currently accepted view is that carriers are injected from the electrodes. Strong experimental evidence that the injected carriers are electrons when contacting polyethylene with a metal comes from the work...
In recent investigations of the electrical conductivity of organic high polymers, evidence has accumulated, indicating that in many polymers the charging and discharging currents, or at least parts thereof, may be attributed to the movement of electronic rather than ionic charge. The measurement of non-isothermal discharge or thermally stimulated currents (TSC) can thus yield information on the trapping...
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