Structure and Properties of Loaded Rubber Mditures. XII. Dielectric Properties of Natural Rubber-Carbon Black Mditures

1955 ◽  
Vol 28 (1) ◽  
pp. 84-91
Author(s):  
A. I. Lukomskaya ◽  
B. A. Dogadkin
Keyword(s):  
Dielectric Properties ◽  
Carbon Black ◽  
Natural Rubber ◽  
Dielectric Losses ◽  
Structure And Properties ◽  
Frequency Range ◽  
Carbon Black Content ◽  
Vulcanized Rubber ◽  
Direct Current Conductivity ◽  
Frequency Curves

Abstract 1. The temperature and frequency curves of dielectric constant ε′ and coefficient of dielectric loss ε″ of unvulcanized natural rubber and simple rubber-carbon black mixtures, and also vulcanizates of natural rubber containing various proportions of thermal black or channel black, were studied in the frequency range from 50 to 2.5×107 cycles per second at 20° C, and in the temperature range from −75° to 152° C at frequencies of 103 to 4×104 cycles per second. 2. As in the case of sodium-butadiene mixtures, the addition of carbon black to the rubber leads to three kinds of dielectric losses, viz., a loss due to the nonuniformity of the dielectric, a loss due to the passage of a direct current (conductivity), and a loss due to structure formation. Vulcanization of rubber leads to the appearance of dipolar dielectric losses, which can be explained by the orientation of the sulfur dipoles in the electric field. Loading of vulcanizates causes a change of the dipolar dielectric properties, which depend both on the content and type of filler and on the type of vulcanized rubber. 3. For all the types of vulcanizates, the dependence of the dielectric properties (a measure of the orientation processes in the rubber phase) on the form factor ( a measure of the structure-forming capacity of the carbon black) corresponds to the dependence of the physical-mechanical properties on the carbon black content.

Poisson's Ratio for Stretched Vulcanized Natural Rubber

1969 ◽  
Vol 42 (2) ◽  
pp. 547-556 ◽  
Author(s):  
H. Sekiguchi ◽  
M. Kakiuchi ◽  
T. Morimoto ◽  
K. Fujimoto ◽  
N. Yoshimura
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Large Deformation ◽  
Poisson’S Ratio ◽  
Poisson Ratio ◽  
Poisson's Ratio ◽  
Elongation Ratio ◽  
Infinitesimal Deformation ◽  
Carbon Black Content ◽  
Vulcanized Rubber

Abstract Changes in the Poisson's ratio of natural vulcanized rubber due to elongation were investigated experimentally. The following results were obtained: If infinitesimal deformation at any instant during elongation is considered, it appears to be correct to take the Poisson's ratio at such instants as 0.5. If the apparent Poisson ratio when a certain standard mark is taken and a large deformation imparted is considered, and the elongation ratio is made α, the Poisson's ratio decreases from 0.5 in accordance with the equation log10 (1/m)=0.0204α2−0.261α−0.0628. This equation is valid for subsequent elongations, no matter what elongation situation is taken for the standard marks. These two results do not vary with the carbon black content or on repeated stretching.

The Dependence of Dielectric Properties on Crosslink Density of Rubbers

1978 ◽  
Vol 51 (1) ◽  
pp. 72-80 ◽  
Author(s):  
R. Bakule ◽  
A. Havránek
Keyword(s):  
Dielectric Properties ◽  
Natural Rubber ◽  
Crosslink Density ◽  
Unit Volume ◽  
Volume Distribution ◽  
Dicumyl Peroxide ◽  
Frequency Range ◽  
Polar Groups ◽  
Main Transition ◽  
Macroscopic Parameters

Abstract The dielectric properties of natural rubber, synthetic polyisoprene, andpolybutadiene samples crosslinked with sulfur and of natural rubber samplescrosslinked simultaneously with sulfur and dicumyl peroxide were studied. Inthe investigated systems, the number of polar groups in unit volume and thecrosslink density may be changed independently over relatively wide ranges.The measurements were performed in the frequency range from 101 to 105 Hzat various temperatures, and macroscopic parameters describing the dielectricproperties of the samples were evaluated. The position and intensity of thedielectric dispersion peak in the main transition zone is only slightly dependenton the crosslink density of the samples. These two values are mainly influencedby the amount of combined sulfur, or more generally, by the number and thedipole moments of polar groups in the sample. The influence of crosslink densityon the width of the absorption curve is very strong; the width increases withincreasing crosslink density. The possibility of explaining this effect in termsof the dependence of the free volume distribution function on crosslink densityis discussed.

Heats of Vulcanization of Synthetic Rubbers

1944 ◽  
Vol 17 (2) ◽  
pp. 404-411 ◽  
Author(s):  
P. L. Bruce ◽  
R. Lyle ◽  
J. T. Blake
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Chemical Reactions ◽  
Side Reaction ◽  
Heat Evolution ◽  
Butyl Rubber ◽  
Vulcanized Rubber ◽  
Principal Reaction ◽  
Low Sulfur ◽  
Quantity Of Heat

Abstract 1. The heats of vulcanization for natural rubber and Buna-S are nearly equal. The data for both materials indicate two different chemical reactions during vulcanization. At low sulfur percentages, the principal reaction forms soft vulcanized rubber and is accompanied by little or no heat evolution. Above the 2 per cent sulfur region, a second reaction predominates, forming hard rubber and producing a relatively large quantity of heat. 2. The presence of an accelerator (Santocure) in Buna-S has little, if any, effect on heat of vulcanization. 3. The addition of carbon black to Buna-S lowers the heat of vulcanization in the region above 4 per cent sulfur. The calories evolved in a 10 per cent sulfur compound decrease linearly with percentage of carbon black. 4. The heats of vulcanization of Buna-N (Hycar OR-15) indicate the presence of two chemical reactions. Unlike natural rubber and Buna-S, the ebonite reaction does not predominate until the sulfur concentration is raised above 10 per cent. 5. The heat of vulcanization of Butyl rubber with sulfur is equal to the heat evolved with natural rubber containing 0.6 per cent sulfur. If one sulfur atom reacts per double bond, the maximum amount combining would be 0.72 per cent sulfur. During the vulcanization of Butyl rubber with p-quinone dioxime and lead peroxide, a large amount of heat is evolved by a side reaction between the vulcanizing agents. The reaction involving the Butyl rubber produces about 6 calories per gram, a considerably higher value than the 1 calorie produced by sulfur vulcanization. 6. The heat of vulcanization of Neoprene-GN without added agents corresponds to a value for smoked sheet rubber containing 4.5 per cent sulfur. The addition of zinc oxide and magnesia decreases the heat of vulcanization.

Influence of Phase Composition on Dielectric Properties of Bismuth-Based Ceramics with Scheelite-Type Structure

2014 ◽  
Vol 602-603 ◽  
pp. 683-688
Author(s):  
Dionizy Czekaj ◽  
Agata Lisińska-Czekaj
Keyword(s):  
Phase Composition ◽  
Dielectric Properties ◽  
Solid State ◽  
Pressureless Sintering ◽  
Dielectric Losses ◽  
Frequency Range ◽  
Minor Phase ◽  
Reaction Route ◽  
Excess Amount ◽  
Solid State Reaction Route

Goal of the present research was to study dielectric properties of BiNbO4 ceramics fabricated by solid state reaction route followed with pressureless sintering. The samples were fabricated from the mixture of oxides, viz. Nb2O5 and Bi2O3. Apart from stoichiometric amount an excess of 3%, 5% and 10% by mole of Bi2O3 was used. It was found that an excess amount of Bi2O3 oxide caused formation of Bi5Nb3O15 minor phase in amount of 9wt%, 18wt% and 25wt%, respectively. The dielectric properties were studied by impedance spectroscopy within the frequency range ν=20Hz1MHz and temperature range T=RT550°C. It was found that the presence of the minor phase in amount of 18wt% caused a decrease in dielectric losses of the material under studies.

Dielectric Properties of PMN/CB/CIIR Composites

2009 ◽  
Vol 66 ◽  
pp. 234-237 ◽  
Author(s):  
Hao Yan ◽  
Zhi Xiong Huang ◽  
Yan Bing Wang
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Carbon Black ◽  
Lead Titanate ◽  
High Frequency ◽  
Dielectric Constants ◽  
Frequency Range ◽  
Magnesium Niobate ◽  
Chlorobutyl Rubber

The Magnesium Niobate-Lead Titanate (PMN) / conductive carbon black (CB)/ chlorobutyl rubber(CIIR) composites were prepared by blending-vulcanization method, and the dielectric properties were studied. The results showed that the dielectric constant and dielectric loss of composites increased nonlinearly when increasing the content of PMN or CB. From the curve of dielectric constant vs frequency, it is obtained that in the frequency range from 103 to 106 Hz, the dielectric constant of PMN/CB/CIIR composites decreased with the frequency increasing and the dielectric constants are more stable under high frequency.

Dielectric Studies of Admicelled Natural Rubber with Poly(3-Trimethoxysilylpropyl Methacrylate)

2013 ◽  
Vol 844 ◽  
pp. 373-376
Author(s):  
Suparat Nooma ◽  
Rathanawan Magaraphan
Keyword(s):  
Dielectric Constant ◽  
Composite Materials ◽  
Dielectric Properties ◽  
Chemical Modification ◽  
Natural Rubber ◽  
Microwave Frequency ◽  
Dielectric Studies ◽  
Frequency Range ◽  
Admicellar Polymerization ◽  
Methoxy Groups

In this work, 3-trimethoxysilylpropyl methacrylate (MPS) was used as a substrate for coating on natural rubber (NR) particles by admicellar polymerization. The incorporation of MPS monomer, consisting of silicon element and 3 reactive methoxy groups (R-Si(OCH3)), is expected to increase dielectric properties of NR. Under the admicellar polymerization, the R-Si(OCH3) groups can be hydrolyzed and condensed into polysiloxane existed on NR particles. This method aims to prepare composite materials from NR and MPS with various amounts of MPS. The effects of microwave frequency and chemical modification by admicellar polymerization were studied. The dielectric properties of admicelled natural rubber (adNR) with PMPS were investigated at 20 °C in a frequency range extended from MHz to GHz. The results showed that the dielectric constant of adNR increased with PMPS contents. To study the effect of crosslinking on the dielectric properties of adNR, the dielectric spectroscopy measurements were performed on prevulcanized and non-prevulcanized adNR. The investigation showed that the dielectric constant of non-prevulcanized adNR was less than prevulcanized adNR.

Determination of Free Carbon in Cured Rubber Stocks

1951 ◽  
Vol 24 (1) ◽  
pp. 224-227
Author(s):  
I. M. Kolthoff ◽  
R. G. Gutmacher
Keyword(s):  
Nitric Acid ◽  
Carbon Black ◽  
Natural Rubber ◽  
Osmium Tetroxide ◽  
Free Carbon ◽  
Vulcanized Rubber ◽  
Tert Butyl Hydroperoxide ◽  
Inorganic Fillers ◽  
Dilute Nitric Acid

Abstract A method for the determination of free carbon in vulcanized rubber stocks is described. The sample is softened in boiling p-dichlorobenzene before treatment with tert-butyl hydroperoxide in the presence of osmium tetroxide. No difficulties are encountered in the filtration of the carbon black. The carbon black is washed on the filter with dilute nitric acid to remove acid-soluble inorganic fillers. The method has been successfully applied to natural rubber, GR-S, Butyl rubber, and Neoprene. No correction is necessary.

Relaxation Processes in Vulcanized Rubber. III. Relaxation at Large Strains and the Effect of Fillers

1963 ◽  
Vol 36 (3) ◽  
pp. 697-708 ◽  
Author(s):  
A. N. Gent
Keyword(s):  
Stress Relaxation ◽  
Carbon Black ◽  
Natural Rubber ◽  
Progressive Failure ◽  
Large Strains ◽  
Relaxation Processes ◽  
Vulcanized Rubber ◽  
Rubber Vulcanizate ◽  
Finite Extensibility ◽  
Creep And Stress Relaxation

Abstract Some experimental measurements are described of stress relaxation and creep at room temperatures in vulcanizates of natural rubber, butyl, and SBR. In an unfilled natural rubber vulcanizate the rate of stress relaxation is found to rise sharply for extensions of more than about 200%. Reasons are given for attributing this to the growth of a crystalline phase. Similar rates are observed at all extensions for a carbon black filled natural rubber vulcanizate. This is shown to be in satisfactory accord with the Mullins-Tobin model structure for filled vulcanizates, when the whole of the observed relaxation occurs in “softened” regions at rates appropriate to the high local deformations. The failure of rubber-carbon black associations with time does not appear to constitute a major relaxation process. In noncrystallizing unfilled vulcanizates the rate of relaxation is found to decrease somewhat with extension, possibly due to finite-extensibility effects. Preliminary measurements on a filled SBR vulcanizate suggest that a significant contribution to the observed relaxation arises from progressive failure of rubber-filler associations in this case. The relation derived previously between the rates of creep and stress relaxation at equivalent deformations is confirmed in all cases, within experimental error. Its validity in highly-irreversible systems is thus established experimentally.

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