Effect of Temperature on Resilience of Natural and Synthetic Rubber

1943 ◽  
Vol 16 (4) ◽  
pp. 881-887
Author(s):  
H. C. Jones ◽  
E. G. Snyder
Keyword(s):  
Natural Rubber ◽  
Effect Of Temperature ◽  
Synthetic Rubber ◽  
Natural And Synthetic

Abstract The necessity of the substitution of synthetic elastomers for natural rubber has been forced on the rubber compounder by the exigencies of war. His background of a hundred years of research and compounding is his principal weapon for making this conversion in the shortest possible time. Too often he finds that this background fails and that practices invaluable in the development of natural rubber stocks are worthless in the case of synthetic rubber, or at least are subject to a different interpretation.

Properties of Ebonite. XXXVII. Electrical Properties of Synthetic Rubber Ebonites

1949 ◽  
Vol 22 (4) ◽  
pp. 1084-1091
Author(s):  
D. G. Fisher ◽  
L. Mullins ◽  
J. R. Scott
Keyword(s):  
Natural Rubber ◽  
Power Factor ◽  
Power Loss ◽  
Ionic Conduction ◽  
Effect Of Temperature ◽  
Plastic Yield ◽  
Styrene Copolymers ◽  
Synthetic Rubber ◽  
High Dielectric ◽  
Butadiene Styrene

Abstract Experiments were carried out to explore the possibility of making good electrical ebonites from various types of synthetic rubber. The ebonites produced were tested for permittivity and power factor over wide ranges of temperature and frequency. Thioplasts (Thiokols AZ and FA) apparently do not produce hard ebonitelike vulcanizates by the normal procedure. Neoprenes (GN and I) give ebonites, but with such high dielectric power loss as to be unsuitable for use as high-frequency dielectrics; moreover, if the mix contains zinc oxide, the ebonite has a very hygroscopic and therefore electrically unsatisfactory surface. Butadiene copolymers containing polar groups (butadiene-acrylonitrile types and Thiokol RD) give ebonites with high power loss, hence are not suitable for making high-grade electrical ebonites. Polybutadiene (Buna-85) and butadiene-styrene copolymers (GR-S, Hycar-EP, Buna-S) are much nearer to natural rubber as far as the radio-frequency (100 to 2,500 kc. per sec.) power loss of their ebonites is concerned. The GR-S ebonite examined was not so good as natural rubber at room temperature, but was superior above about 50° C. Buna-85 and Hycar-EP were superior to natural rubber over the whole temperature range; indeed, the high-styrene copolymers, as represented by Hycar-EP and Buna-SS, appear to be the best type of synthetic rubber for making ebonite with low power loss, especially at high frequencies and temperatures. The effects of changing temperature and frequency on permittivity and power factor are discussed. Attention is drawn to the big effect of temperature on power factor; this was less with polybutadiene and butadiene-styrene ebonites than with natural rubber ebonite, in keeping with the greater heat resistance of the former as judged by plastic yield tests. Comparison of the effects of rising temperature and decreasing frequency shows that these produce broadly similar effects on power factor, as would be expected on theoretical grounds, but that rising temperature superposes a second effect (an increase), presumably due to increased ionic conduction.

scholarly journals Historical and Recent Achievements in the Field of Microbial Degradation of Natural and Synthetic Rubber

2012 ◽  
Vol 78 (13) ◽  
pp. 4543-4551 ◽  
Author(s):  
Meral Yikmis ◽  
Alexander Steinbüchel
Keyword(s):  
Natural Rubber ◽  
Microbial Degradation ◽  
Environmental Biotechnology ◽  
Gram Positive ◽  
Gram Negative ◽  
Content Type ◽  
Key Enzymes ◽  
Degrading Bacterium ◽  
Synthetic Rubber ◽  
Natural And Synthetic

ABSTRACTThis review intends to provide an overview of historical and recent achievements in studies of microbial degradation of natural and synthetic rubber. The main scientific focus is on the key enzymes latex-clearing protein (Lcp) from the Gram-positiveStreptomycessp. strain K30 and rubber oxygenase A (RoxA) from the Gram-negativeXanthomonassp. strain 35Y, which has been hitherto the only known rubber-degrading bacterium that does not belong to the actinomycetes. We also emphasize the importance of knowledge of biodegradation in industrial and environmental biotechnology for waste natural rubber disposal.

Natural and Synthetic Rubber. I. Products of the Destructive Distillation of Natural Rubber

1929 ◽  
Vol 2 (3) ◽  
pp. 441-451 ◽  
Author(s):  
Thomas Midgley ◽  
Albert L. Henne
Keyword(s):  
Experimental Data ◽  
Natural Rubber ◽  
Atmospheric Pressure ◽  
Experimental Results ◽  
Double Bonds ◽  
Synthetic Rubber ◽  
Single Bonds ◽  
Natural And Synthetic

Abstract Two hundred pounds of pale crepe rubber have been destructively-distilled at atmospheric pressure. The distillate was fractionated and its components identified from C5 to C10, as shown in the table. Assuming that the Staudinger formula is correct, that the single bonds furthest from the double bonds are the weaker spots and that the formation of six-carbon rings is favored, it has been shown that nearly all of the compounds actually isolated could be predicted. The experimental results, together with forthcoming experimental data, are expected to be used to throw light upon the formula of the rubber molecule.

Kinetic Analysis of Organic Halides. II. Analysis of Macromolecules Built up of Monohalide Units

1951 ◽  
Vol 24 (2) ◽  
pp. 436-446 ◽  
Author(s):  
G. Salomon ◽  
C. Koningsberger
Keyword(s):  
Natural Rubber ◽  
Kinetic Analysis ◽  
Vinyl Chloride ◽  
Physical Factors ◽  
Organic Bases ◽  
Synthetic Rubber ◽  
Organic Halides ◽  
First Time ◽  
Natural And Synthetic

Abstract A number of hydrochlorides of natural and synthetic rubbers and allied polymers have been prepared and subjected to kinetic analysis with organic bases. The hydrochlorides of natural rubber react at 100° C at a rate identical to that of low-molecular tertiary chlorides. At 50° C the reactivity of the polymer is, however, reduced by physical factors. The hydrochloride of GR-S (a synthetic rubber made from butadiene and styrene) has been prepared for the first time by heating the swollen polymer with HC1 under pressure. Kinetic analysis of this product revealed two fractions: the expected secondary chloride, and a small fraction of a very reactive (tertiary?) chloride. After elimination of experimental difficulties, we succeeded in the preparation and kinetic identification of the pure tertiary hydrobromide of natural rubber. Attempts to prepare the secondary bromide under peroxide conditions failed. Kinetic analysis of two types of Neoprene revealed the presence of a small quantity of allylic groups in the polymer, while 95 per cent of the chlorine in Neoprene has the expected stability of a vinyl chloride. This stability can be used for the identification of Neoprene.

Liquid guayule natural rubber, a renewable and crosslinkable processing aid in natural and synthetic rubber compounds

2020 ◽  
Vol 276 ◽  
pp. 122933
Author(s):  
Xianjie Ren ◽  
Cindy S. Barrera ◽  
Janice L. Tardiff ◽  
Andres Gil ◽  
Katrina Cornish
Keyword(s):  
Natural Rubber ◽  
Synthetic Rubber ◽  
Rubber Compounds ◽  
Natural And Synthetic

Natural and Synthetic Rubber. XV. Oxygen in Rubber

1936 ◽  
Vol 9 (1) ◽  
pp. 74-82
Author(s):  
Thomas Midgley ◽  
A. L. Henne ◽  
A. F. Shepard ◽  
Mary W. Renoll
Keyword(s):  
Natural Rubber ◽  
Quantitative Data ◽  
Hydroxyl Group ◽  
Synthetic Rubber ◽  
Natural And Synthetic

Abstract It has been shown that natural rubber conthins oxygen, while synthetic rubber is oxygen free. This oxygen appears to be of an hydroxylic type, and its quantity corresponds to about one hydroxyl group for each one thousand isoprene units of the rubber molecule. Rubber has been allowed to oxidize and a mechanism is proposed to interpret the quantitative data recorded.

The Thermal Vulcanization of Synthetic Rubber

1958 ◽  
Vol 31 (1) ◽  
pp. 132-146 ◽  
Author(s):  
H. Luttropp
Keyword(s):  
Thermal Treatment ◽  
Natural Rubber ◽  
Dynamic Stress ◽  
Effect Of Temperature ◽  
Synthetic Rubber ◽  
Aging Phenomena ◽  
Lower Tensile Strength ◽  
Soft Rubber ◽  
Acrylonitrile Copolymers ◽  
Butadiene Styrene

Abstract It is shown that synthetic rubbers, in contrast to natural rubber, can be vulcanized to soft rubber by a simple thermal treatment without any previous admixture of sulfur or accelerators. This process has been designated as “Thermovulcanization” to distinguish it from the regular vulcanization procedure under heat with the addition of sulfur and accelerators. Various synthetic rubbers of Schkopau production have been investigated for their behavior in the process of thermovulcanization. Both butadiene-styrene and butadiene-acrylonitrile copolymers as well as the butadiene block polymerizate lend themselves to vulcanization by this thermal treatment. For the butadiene-styrene copolymer with higher styrene content, thermovulcanization leads to products which are not equivalent to the regular sulfur-accelerator vulcanizates. Natural rubber cannot be vulcanized to soft rubber by thermovulcanization. The investigation of the effect of temperature revealed that a temperature of 195° C, for example, was applicable for all the synthetic rubbers studied. The addition of active carbon was found to accelerate the thermovulcanization process and certain properties of the vulcanizates are improved. The results of some comparative studies are presented, and it is pointed out that thermovulcanizates and normal vulcanizates show agreement in some of their properties and vary in others. The thermovulcanizates, as compared with normal vulcanizates, show somewhat lower tensile strength and somewhat lower fatigue resistance. Also their resistance to swelling is lower. On the other hand they are better in abrasion, have somewhat improved elastic properties, and show improved resistance to aging including surface aging phenomena under static and dynamic stress.

Lignin as a Compounding Ingredient for Natural Rubber

1957 ◽  
Vol 30 (2) ◽  
pp. 639-651 ◽  
Author(s):  
I. Sagajllo
Keyword(s):  
Natural Rubber ◽  
High Resistance ◽  
Pilot Plant ◽  
Test Results ◽  
Dry Powder ◽  
Synthetic Rubber ◽  
Rubber Compounds ◽  
Pilot Plant Scale ◽  
Made In ◽  
Natural And Synthetic

Abstract Important claims have been made in recent years regarding the capacity of lignin to reinforce natural and synthetic rubber. In 1949 Dawson reviewed the literature on the use of lignin in rubber and drew particular attention to the work of Keilen and Pollak who had shown that in certain circumstances lignin could be considered to rival EPC black in its ability to yield strong GR-S vulcanizates with high resistance to tear. Raff and his coworkers subsequently showed that the reinforcement of GR-S by lignin is enhanced if the lignin, before coprecipitation with the latex, is subjected to oxidation; other workers studied the application of lignin to the reinforcement of different elastomers, the influence of coprecipitation conditions on the properties of the product, and the problem of overcoming the delaying effect of lignin on vulcanization of lignin-natural rubber coprecipitates. Keilen and Pollak in their experiments incorporated lignin into rubber by coprecipitation at the latex stage, but they indicated that similar results could be obtained if lignin “in the gelled state” was added to rubber by milling. No reinforcement was observed however when lignin was added to rubber as a dry powder. Lignin is potentially an abundant and cheap material which according to the above claims should extend the range of useful compounds available to rubber manufacturers. The present paper describes work undertaken to gain firsthand knowledge of the technique of coprecipitating lignin with natural rubber from preserved latex, to learn something about the properties of natural rubber compounds prepared from lignin coprecipitates, and to study possible ways of incorporating lignin into rubber by means other than coprecipitation. It also records test results for masterbatches prepared by the Rubber Research Institute of Malaya from fresh latex on a pilot plant scale.

Stress Relaxation of Natural and Synthetic Rubber Stocks

1944 ◽  
Vol 17 (3) ◽  
pp. 551-575 ◽  
Author(s):  
A. V. Tobolsky ◽  
I. B. Prettyman ◽  
J. H. Dillon
Keyword(s):  
Tensile Strength ◽  
Free Energy ◽  
Reaction Rate ◽  
Energy Of Activation ◽  
Effect Of Temperature ◽  
Rate Theory ◽  
Air Atmosphere ◽  
Synthetic Rubber ◽  
Commercial Nitrogen ◽  
Natural And Synthetic

Abstract 1. The complete decay of stress in the rubbers studied, held at constant elongation, appeared to involve the rupturing of a definite bond, either at some point along the molecular chain or at the cross-linking bond put in by vulcanization. In the case of a Hevea rubber gum stock the data could be fitted very well by ordinary reaction-rate theory, leading to the conclusion that the free energy of activation required for breaking the bond is 30.4 kcal. per mole of bonds. This result was found to be practically independent of the elongation, and of the presence of carbon black in a Hevea rubber tread stock. This is to be compared to a strength of about 90 kcal. per mole for the C—C bond. 2. In the case of other rubbers (Buna-S, Butaprene-N, Neoprene-GN, and Butyl) the activation free energy for breaking the bond did not vary by more than ±2.0 kcal. per mole from that of Hevea rubber. However, these differences were quite definite. For example, the relaxation of stress in GR-S was slower than in Hevea; a small difference in energy corresponding to a 2:1 ratio in the respective times of decay. 3. The effect of temperature on the relaxation of stress appeared to be of the general type characteristic of chemical reactions. By use of the ordinary formula for expressing rate of reaction in terms of energy of activation, one could predict very closely the behavior of the stress-log time curves at different temperatures. 4. Natural rubber and GR-S vulcanized with paraquinone dioxime and lead dioxide showed relaxation curves very similar to those of the sulfur vulcanized stocks. 5. Relaxation experiments in an ordinary air atmosphere and in an atmosphere of commercial nitrogen showed no appreciable differences. 6. Examination of stretched rubber bands in which the stress had decayed nearly completely (at 100° C) gave no evidences of gross oxidation, such as would make the rubber bands sticky or hard, or of surface deterioration. At higher temperatures, however, the rubber could be observed getting sticky, and then brittle. Specimens in which the stress had completely decayed showed very low tensile strength (by hand test). 7. Antioxidant added to a sulfur-stabilized Buna-S stock caused a definite retardation of the rate of relaxation. 8. Comparison of the results of these experiments with previously recorded observations in the literature indicated that the chemical reaction which ruptured the rubber structure and caused the decay of stress in these experiments (and concomitantly a lowering of tensile strength) was an oxidation of the rubber by small amounts of oxygen, the reaction rate being independent of the oxygen pressure in the range between that present in an ordinary air atmosphere and in a commercial nitrogen atmosphere. 9. The tests suggested a convenient and accurate laboratory method of determining the oxidizability of natural and synthetic rubber stock designed for service.

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