Effect of Temperature and Frequency on the Dielectric Constant, Power Factor, and Conductivity of Compounds of Purified Rubber and Sulfur

1934 ◽  
Vol 7 (2) ◽  
pp. 342-370 ◽  
Author(s):  
A. H. Scott ◽  
A. T. McPherson ◽  
Harvey L. Curtis
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Power Factor ◽  
Water Soluble ◽  
Effect Of Temperature ◽  
General Character ◽  
Soluble Salts ◽  
Electrical Measurements ◽  
Separate Paper ◽  
Rubber Compounds

Abstract The electrical measurements given in this paper differ from those previously reported by the authors and by other investigators in that they were made on specimens prepared from purified rubber. The purification, which involved the removal of proteins, resins, and water-soluble salts, affected all the electrical properties to some extent, but did not alter the general character of the variation in electrical properties with composition, temperature, or frequency. The results of the present investigation afford comprehensive data on the electrical properties of rubber-sulfur compounds, and may form a basis for designing rubber compounds for specific electrical uses. They also demonstrate the inadequacy of the simple numerical coefficients that are sometimes employed to evaluate the changes in the electrical properties with temperature and frequency. A discussion of the results from the standpoint of modern dielectric theory is not included in the present paper, but is contemplated for a separate paper.

Properties of Ebonite. XXX. Influence on Properties of Ebonite of the Type of Raw Rubber Used, with Special Reference to Purified Rubbers

1949 ◽  
Vol 22 (1) ◽  
pp. 232-244
Author(s):  
D. G. Fisher ◽  
J. R. Scott ◽  
W. H. Willott
Keyword(s):  
Dielectric Properties ◽  
Electrical Properties ◽  
Dielectric Loss ◽  
Natural Rubber ◽  
Power Factor ◽  
Breakdown Strength ◽  
Practical Importance ◽  
Water Soluble ◽  
Plastic Yield ◽  
Latex Rubber

Abstract Tests have been made on unloaded ebonites prepared from ordinary commercial types of natural rubber, special (deproteinized) rubbers having reduced contents of protein and(or) other water-absorbent substances, and a whole-latex rubber containing relatively large percentages of these substances, to determine to what extent these substances influence the electrical properties of the ebonite and, hence, whether any technically useful improvement can be effected by using specially prepared rubbers. Permittivity and power factor at 106 cycles per second, but particularly power factor, are somewhat improved by using the special rubbers, so that the dielectric loss can be reduced by about 30 per cent. In addition, the increase in dielectric loss caused by exposure to high humidity or by a rise of temperature is in general lessened by the use of these rubbers. Similar, though smaller, improvements in the properties of the ebonite are obtained by washing ordinary commercial rubber (smoked sheet). Although a definite improvement in dielectric loss is obtained, it does not seem probable that purification of natural rubber would lead to ebonites with dielectric properties approaching those of polystyrene, for instance. It seems unlikely that even complete elimination of the water-absorbent impurities would reduce the dielectric loss by more than 50 per cent; the rubber-sulfur compound itself thus appears to be responsible for a fair proportion of the loss normally observed. The large percentages of water-soluble substances present in whole-latex rubber increase the permittivity and especially the power factor of the ebonite made from it. The dielectric properties of ebonite are related, though not closely, to its water-absorbing capacity and that of the raw rubber used, low absorption being in general accompanied by low dielectric loss and reduced sensitiveness to humidity variations. There is only a rough parallelism between the water absorptions of raw rubbers and the corresponding ebonites. Probable reasons for this are indicated. It is concluded that water absorption tests on raw rubber form a useful, though only approximate, guide to its value for making electrical ebonite; electrical tests on the ebonite must be the final criterion. Apart from very impure whole-latex rubber, no correlation can be traced between the inorganic content (ash) of ebonite and its electrical properties. The probable reason for this is indicated. There is evidence that the dielectric loss of ebonite may increase with the passage of time. In view of its obvious theoretical and practical importance, this phenomenon requires further study. No technically useful advantage as regards breakdown strength, volume resistivity, surface resistivity, or stability to light, by the use of the special rubbers, is evident in the present work. The plastic yield characteristics of ebonite are not appreciably altered by using special rubbers. Estimations of uncombined sulfur and also plastic yield tests show that one of the deproteinized rubbers vulcanizes more rapidly than the rest, which differ little among themselves.

scholarly journals Electrical Properties of Sunflower Achenes

2014 ◽  
Vol 17 (4) ◽  
pp. 109-113 ◽  
Author(s):  
Ján Novák ◽  
Ivan Vitázek
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Moisture Content ◽  
Electric Field ◽  
Loss Tangent ◽  
Dielectric Heating ◽  
Electrical Measurements ◽  
Engineering Research ◽  
Dielectric Constant And Loss ◽  
Properties Of Materials

Abstract This work contains the results of measuring the electrical properties of sunflower achenes. The interest in electrical properties of biological materials resulted in engineering research in this field. The results of measurements are used for determining the moisture content, the surface level of liquid and grainy materials, for controlling the presence of pests in grain storage, for the quantitative determination of mechanical damage, in the application of dielectric heating, and in many other areas. Electrical measurements of these materials are of fundamental importance in relation to the analysis of quantity of absorbed water and dielectric heating characteristics. It is a well-known fact that electrical properties of materials, namely dielectric constant and conductivity, are affected by the moisture content of material. This fact is important for the design of many commercial moisturetesting instruments for agricultural products. The knowledge of dielectric properties of materials is necessary for the application of dielectric heating. The aim of this work was to measure conductivity, dielectric constant and loss tangent on samples of sunflower achenes, the electrical properties of which had not been sufficiently measured. Measurements were performed under variable moisture content and the frequency of electric field ranging from 1 MHz to 16 MHz, using a Q meter with coaxial probe. It was concluded that conductivity, dielectric constant and loss tangent increased with increasing moisture content, and dielectric constant and loss tangent decreased as the frequency of electric field increased.

Electrical Properties of Elastomers and Related Polymers

1963 ◽  
Vol 36 (5) ◽  
pp. 1230-1302 ◽  
Author(s):  
Archibald T. McPherson
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Price Competition ◽  
Modern Technology ◽  
Point Of View ◽  
Electrical Behavior ◽  
Electrical Measurements ◽  
Wide Range ◽  
The Individual ◽  
High Dielectric

Abstract Interest in the electrical behavior of elastomers stems from several widely different sources. From the theoretical standpoint electrical measurements provide a valuable tool for the study of the molecular structure of elastomers and other polymers and the relation of structure to properties. From a practical point of view an understanding of the electrical behavior enables the manufacturer of wire and cable to produce insulation that will better withstand the severe conditions of space flight, or that will meet price competition and show a profit. The present day applications of elastomers are so many and varied that nearly any type of compound is likely to be employed for some practical purpose. A cable for x-ray equipment, for example, may be made wholly from elastomers with conductor, insulation, and jacket each from a different compound. At one time when almost the only electrical use of rubber was to provide the highest practical degree of electrical insulation it was correct to speak of “good” and “poor” electrical properties. Now, however, an elastomer that is a poor insulator may be excellent in an antistatic application. Communication cables require an insulation of the lowest practical dielectric constant, but for power cables a layer of insulation of high dielectric constant next to the conductor may be essential to prevent excessive electrical stresses. Modern technology not only calls for a wide diversity of electrical properties but it often requires further that elastomers having these properties be available in a wide range of mechanical properties. For example, the insulation on a cable for use in an airplane must be as thin and light as possible to save weight while an unarmored cable for laying in shallow water must have insulation that is thick and tough for mechanical protection and of high specific gravity to prevent the cable's being moved by waves or tide. Thus, the diversity of present and possible future applications is such that no one in the industry is likely to escape for long some contact with an application involving an electrical property. Accordingly, this review has been prepared to acquaint the rubber chemist and technologist with current information in the field. In the 25 years that have elapsed since an earlier review was prepared by the same author a great deal of work has been done on the relation between the properties of polymers and their molecular composition and structure. It is now possible to predict the properties of some polymers from their structural formulas, and a beginning has been made in relating the properties of simple elastomeric compounds to the properties of the different ingredients. However, knowledge in the field is still far from the state at which it would be possible to compile a table of functions such that the electrical properties of a multi-ingredient insulating compound could be computed from the properties of the individual ingredients.

A Method for the Purification of Rubber and Properties of the Purified Rubber

1932 ◽  
Vol 5 (4) ◽  
pp. 523-529 ◽  
Author(s):  
A. T. McPherson
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Electrical Properties ◽  
Power Factor ◽  
Inert Gas ◽  
Hydrolysis Products

Abstract Purified rubber was prepared by the digestion of crude rubber or latex with water at about 190° C., followed by extraction with water and with alcohol, and drying in an atmosphere of inert gas. The digestion hydrolyzed the proteins, and the extraction removed the hydrolysis products, resins, and other impurities. The purified rubber contained about 99.5 per cent of rubber hydrocarbon. Properties of the rubber hydrocarbon at 25° C. were: density, 0.9060; refractive index, 1.5184; dielectric constant at 1000 cycles per second, 2.37; power factor at 1000 cycles per second, 0.0015; conductivity at the end of 1 minute, 2.2×10−7 mho. The electrical properties measured on 14 samples were apparently independent of the botanical source or the kind of crude rubber.

Dielectric Measurements in the Study of Carbon Black and Zinc Oxide Dispersion in Rubber

1939 ◽  
Vol 12 (2) ◽  
pp. 317-331
Author(s):  
A. R. Kemp ◽  
D. B. Herrmann
Keyword(s):  
Particle Size ◽  
Dielectric Constant ◽  
Zinc Oxide ◽  
Dielectric Properties ◽  
Carbon Black ◽  
Water Soluble ◽  
Oxide Dispersion ◽  
Dielectric Measurements ◽  
Thermal Decomposition Process ◽  
Rubber Compounds

Abstract The dielectric constant, power factor, conductivity and d.c. resistivity of rubber compounds containing various types and quantities of zinc oxide and carbon pigments have been measured. It has been shown that the dielectric properties of rubber compounds having high loadings of zinc oxide depend on the particle size and purity of the zinc oxide used. The French process oxides with the smallest particle size were found superior to other grades. Water-soluble impurities in zinc oxide are shown to have a deleterious effect on dielectric properties, especially in the presence of moisture. The effect on dielectric properties of adding carbon black to a rubber compound has been shown to be dependent on the type and amount of black added, and on the nature of its dispersion in the rubber. The dielectric properties of rubber compounds containing “soft” black made by the thermal decomposition process are shown to be distinctly superior to, and widely different from, those of the same compounds containing equal amounts of channel process black. The general conclusion has been reached that the smaller the particle size and the better the dispersion of carbon pigments in the rubber, the greater will be the increase in the dielectric constant and conductivity, and the greater will be the decrease in resistivity.

Effect of Pressure on the Dielectric Constant, Power Factor, and Conductivity of Rubber-Sulfur Compounds

1936 ◽  
Vol 9 (3) ◽  
pp. 449-467
Author(s):  
Arnold H. Scott
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Sulfur Content ◽  
Power Factor ◽  
Sulfur Compounds ◽  
Constant Power ◽  
Current Frequency ◽  
Effect Of Pressure ◽  
The Third

Abstract This paper reports the results of a study on the effect of pressure on the dielectric constant, power factor, and conductivity of rubber-sulfur compounds, and is the third paper of a series dealing with the electrical properties of rubber-sulfur compounds. The previous papers dealt with the effect of sulfur content, temperature, and current frequency on these electrical properties. The results reported in the present paper have been corrected for changes in the dimensions of specimens caused by changes in pressure. The required data for making these corrections were obtained from a detailed study of the compressibility of rubber-sulfur compounds which has recently been completed.

scholarly journals Electrical Prope Rties of Popcorn Grains

2013 ◽  
Vol 16 (2) ◽  
pp. 43-46
Author(s):  
Ján Novák
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Moisture Content ◽  
Electric Field ◽  
Loss Tangent ◽  
Dielectric Heating ◽  
Electrical Measurements ◽  
Engineering Research ◽  
Dielectric Constant And Loss ◽  
Properties Of Materials

Abstract This work contains the results of measuring the electrical properties of popcorn grains. Interest in electrical properties of biological materials resulted in engineering research in this field. The results of measurements are used for determining the moisture content, the surface level of liquid and grainy materials, for controlling the presence of pests in grain storage, for a quantitative determination of mechanical damage, in applications of dielectric heating, and in many other cases. Electrical measurements on these materials are of fundamental importance in relation to the analysis of quantity of absorbed water and dielectric heating characteristics. It is a well-known fact that electrical properties of materials, namely dielectric constant and conductivity, are affected by the moisture content of material. This fact is important for the design of many commercial moisture-testing instruments for agricultural products. The knowledge of dielectric properties of materials is necessary for the application of dielectric heating. The aim of this work was to perform the measurements of conductivity, dielectric constant and loss tangent on samples of popcorn grains, the electrical properties of which had not been sufficiently measured. Measurements were performed under variable moisture content and the frequency of electric field in the range from 1 MHz to 16 MHz, using a Q meter with a coaxial probe. It was concluded that conductivity, dielectric constant and loss tangent increased with increase of moisture content, and dielectric constant and loss factor decreased as the frequency of electric field increased.

Permafrost: electrical properties of the active layer measured in situ

1977 ◽  
Vol 14 (4) ◽  
pp. 582-586 ◽  
Author(s):  
J. Wong ◽  
J. R. Rossiter ◽  
G. R. Olhoeft ◽  
D. W. Strangway
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Active Layer ◽  
Electrical Measurements ◽  
Apparent Conductivity

The dielectric constant and apparent conductivity of the active layer on Involuted Hill near Tuktoyaktuk, N.W.T., were measured in situ for both summer and winter. Measurements were made using resonating antennas near 100 MHz. The apparent values for the dielectric constant were 26 to 64 in the summer, and about 7 in the winter; for the conductivity, values of 0.012 to 0.12 mhos m−1 (0.012–0.12 S m−1 in summer, and about 10−4 mhos m−1 (10−4 S m−1) in winter, were obtained. The low losses observed in winter indicate that EM sounding should be possible in the area when the active layer is frozen. It is concluded that the antenna method is a quick and inexpensive means of making in situ electrical measurements near 100 MHz.

Change of Electrical Properties of Rubber and Gutta-Percha during Storage under Water

1931 ◽  
Vol 4 (1) ◽  
pp. 39-53
Author(s):  
Harvey L. Curtis ◽  
Arnold H. Scott
Keyword(s):  
Dielectric Constant ◽  
Direct Current ◽  
Power Factor ◽  
Marked Change ◽  
Dielectric Constants ◽  
The Other ◽  
Time Interval ◽  
Electrical Measurements ◽  
Copper Salts ◽  
Gutta Percha

Abstract A number of samples of rubber and gutta-percha were stored under water for about seven years and electrical measurements made on them periodically to determine the effect of aging on the resistivity, dielectric constant, and power factor. The dielectric constant was measured under three different conditions, namely, 60 cycles alternating current, pulsating direct currentusing 0.6 second charge with 0.1 second discharge, and pulsating direct current using the same time of charge with 1 second discharge. In all cases the dielectric constants increased with time unless failure was approached. A sample was considered to have failed when measurement of its capacitance became impracticable. The changes of the resistivity and power factor varied from sample to sample. The approach of failure was first indicated by the resistivity. When a curve was plotted with time the sample had been under observation as abscissa and resistance of the samples as ordinates, the curves of the sample which failed showed a break or marked change in direction several months before actual failure occurred. With similar curves for power factor and direct-current dielectric constant, breaks occurred at a later time. The time interval between the break in the resistivity curve and the breaks in the other curves was a function of the rate of decrease of the resistivity. These facts indicate that the failure of a sample is the result of its decrease in resistivity. This decrease in resistivity has been ascribed to the formation of fine holes through the material. This explanation was confirmed by the microscopic examination of microtome sections of the samples which failed. These sections showed fern-like figures projecting into the rubber. All of the samples that failed were in the form of tubes, with water electrodes both inside and outside the tubes. Some copper salts were inadvertently allowed to form inside the tubes. The catalytic action of these copper salts accelerated the aging, and probably changed its character.

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