bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Quantitative Test for Ozone Resistance of Rubber Vulcanizates
Authors: Wilchinsky Z. W. , Kresge E. N. 
Published: February 2011

Abstract
A simplified procedure was developed for evaluating ozone resistance of rubber vulcanizates in terms of critical stress—strain and stored energy density parameters. A selected tensile force of appropriate magnitude is applied to a tapered specimen to produce a continuous range of stress. While thus stretched, the specimen is conditioned for 16 h, then exposed to ozone for 24 h. In the portion of the specimen where the stress is greater than a critical value σc, ozone cracking occurs, whereas in the portion of the specimen where the stress is less than σc there are no cracks. Values of σc the critical strain εc, the critical elastic stored energy Wc, and the elastic modulus E are determined from the position of the boundary between the cracked and uncracked zones, the average elongation of the stressed specimen, and the specimen geometry. The quantity Wc was found suitable for quantitatively characterizing ozone resistance by a single parameter.
Effect of Alkyl Group Structure on Cure Characteristics of N,N-Dialkylthio-Carbamyl-N′,N′-Dialkylsulfenamide Vulcanization Accelerators
Authors: Taylor R. D. 
Published: February 2011

Abstract
Wide variations in scorch times and cure rates can be attained with tetraalkylthiocabamylsulfenamides through variation in alkyl groups. Substituent effects are substantial on either the carbamate nitrogen or on the sulfenamide nitrogen. Both inductive effects and steric effects influence the scorch times and cure rates. Positive inductive effects shorten scorch times and increase cure rates. Steric hindrance at the sulfenamide nitrogen increases the scorch time. Branching at the carbon atom beta to the nitrogen has a larger effect on scorch time than branching at the alpha carbon. Thiocarbamylsulfenamides can give appreciably higher cure rates and cure efficiencies than their benzothiazole sulfenamide analogs.
Review of Unsolved Problems in the Protection of Rubber against Oxidative Degradation
Authors: Dunn J. R. 
Published: February 2011

Abstract
This review has outlined some of the problems involved in the protection of rubber against oxidative degradation. There are others which are related to health, such as the choice of additives which are safe in contact with foodstuffs and approved by FDA or equivalent bodies in other countries. The matter of toxicity of antioxidants has been reviewed by McCormick and by Leyland. With so many problems it is easy to understand why the literature and patent files on antioxidants continue to grow and why it is unlikely that a single ideal material will ever be developed to protect rubber against oxidative degradation.
Autoxidation and Antioxidants. Basic Principles and New Developments
Authors: Howard J. A. 
Published: February 2011

Abstract
There is no doubt that liquid-phase hydrocarbon autoxidation is one of the most thoroughly understood reactions in organic chemistry. Our knowledge of the elementary reactions involved in this process is so complete that it should be possible to calculate, with a reasonable degree of precision, the overall rate of autoxidation of a hydrocarbon or mixture of hydrocarbons, provided, of course, that the rate of chain initiation can be estimated. It should also be possible to make a reasonable intelligent guess at the stability of a solid system, with the reservations appropriate to the change of phase. With regard to inhibition, there is probably not a great deal of room for further improvement in the inherent efficiency of H-atom donating antioxidants. This is because a decrease in the strength of the X—H bond makes the hydrogen more susceptible to abstraction by molecular oxygen. Radical scavenging transition metal complexes also suffer from the limitation that the more reactive the complex is to ROO the more reactive it will be to O2. There may, of course, be further improvements in the efficiency of preventative antioxidants, particularly multi-functional antioxidants with the ability to decompose hydroperoxides and peroxides by several non-radical mechanisms and also scavenge free-radicals.
Elastomeric Springs for Seismic Shock Isolation
Authors: Vickers R. A. 
Published: February 2011

Abstract
We have described the development of seismic isolators to meet a specific requirement. The use of ventilated blocks serves to aid in obtaining a thorough cure, and the configuration and direction of the holes control the shape of the force—deflection curves. Figure 21 shows a completed spring installed on a Minuteman support structure.
A Technique for Evaluating the Hysteresis Properties of Tire Cords
Authors: Powers E. J. 
Published: February 2011

Abstract
A slow speed cyclic test has been developed to evaluate tire cord hysteresis properties. Programmed stress variations on an Instron were used to simulate the magnitude and sequence of cord stresses in a running step-loaded tire and relationships were formulated to approximate the dependence of cord heat generation on tire loads, air pressures, and temperatures. The test assumes that tire air pressure imposes a peak stress on cords and that increasing loads on a running tire cause increasing intermittent cord stress relief. Nearly linear relationships result between the log of work loss and the extent of stress relief, which affords a means of comparing cord hysteresis properties over a range of simulated tire loads. The validity of the slow speed results was verified at laboratory test speeds comparable to those encountered in normal tire use. Results generally agreed with long standing qualitative observations of tire cord performance. Commercial PET and nylon greige cords were used for test development and other cord materials, both greige and dipped, have been evaluated. A range of hysteresis properties was obtained on variations in polyester cords.
Environmental Effects on RFL Adhesion
Authors: Wenghoefer H. M. 
Published: February 2011

Abstract
Adhesion deterioration of RFL-dipped tire cord resulting from environmental factors such as ozone, nitrogen dioxide, humidity, ultraviolet light, and heat was investigated to quantify the amount of adhesion loss and to establish the mode of adhesion failure. It was found that ozone, humidity, and ultraviolet light cause substantial adhesion deterioration, especially during the initial hours of exposure. Synergistic effects of ozone/humidity were noted. Less pronounced was the detrimental effect of heat. Adhesion loss because of nitrogen dioxide or synergistic effects of nitrogen dioxide/humidity was not seen. Adhesion loss occurred most rapidly during the first six hours of ozone/humidity exposure, regardless of fiber or adhesive system used. Adhesive treated cords of nylon, polyester, and “Kevlar” aramid showed loss in adhesion; however, no correlation between type of fiber and extent of adhesion deterioration was found. The extent of adhesion deterioration was primarily dependent upon the specific adhesive dip used. Sensitivity of the RFL adhesives to ozone/humidity varied with one- and two-step adhesive systems; with polyester, one-step adhesive systems tested were generally less sensitive to environmental conditions than two-step adhesive systems. The latter, however, had better initial adhesion. Adhesion loss because of ultraviolet light exposure was severe for all RFL adhesives, regardless of fiber. Emission of ultraviolet light from fluorescent lighting was shown to be sufficiently intense to affect adhesion. The physical properties of RFL-dip films were unaffected by ozone or ultraviolet exposure, ruling out cohesive failure of the RFL adhesive as a cause of adhesion breakdown. Adhesion failure for samples tested after environmental exposure occurred at the RFL adhesive-rubber stock interface, indicating the adhesion deterioration to be a RFL surface phenomenon.
Short Fiber Reinforcement of Elastomers
Authors: Moghe S. R. 
Published: February 2011

Abstract
Based upon a simple mathematical model, the directional properties of elastomers mixed with uniaxially oriented short fibers are predicted. The model takes into account a probability distribution function for a number of fibers in any direction during fiber orientation. Theory is compared with experimental data on tensile modulus for a number of rubber compounds and fibers with good success. A possibility of characterizing calendering and extrusion processes in view of orientation and mechanical properties is discussed.
Elastically Ineffective Crosslinks in Rubbers
Authors: Tonelli A. E. , Helfand E. 
Published: February 2011

Abstract
A significant fraction of the crosslinks formed in the process of producing a rubbery network are elastically ineffective. The reason is that they close intramolecular loops which are not otherwise attached to the rest of the network. Calculations of this fraction are performed for cis-1,4-poly(isoprene) (natural rubber) as a function of the degree of crosslinking, the length of the chemical bridge which forms the crosslink, the initial molecular weight, and the degree of dilution when crosslinking in solution. For typical rubber networks, crosslinked in the dry state with from 0 to 2 per cent of the monomer units involved in crosslinks, the fraction of crosslinks wasted in the formation of elastically ineffective intramolecular loops is ca. 0.1–0.2. This fraction is approximately doubled and quadrupled for networks formed in solution with volume fractions of rubber equal to 0.5 and 0.1, respectively. Since a sizeable percentage of the intramolecular loops formed consist of a small number of polymer units, it is believed that entanglement between the loops and other chains of the active network does not serve to reduce greatly the fraction of elastically ineffective crosslinks.
Specific Solvent Effects in Swollen Polymer Networks
Authors: Yu C. U. , Mark J. E. 
Published: February 2011

Abstract
Stress—strain isotherms at 25° have been determined for uniaxially elongated poly(dimethylsiloxane) networks in the unswollen state and swollen consecutively with each of the following very dissimilar diluents : low molecular weight dimethylsiloxane fluid, n-hexadecane, 2,4-dichlorotoluene, and n-octyl acetate Five constant composition experiments were carried out, at values of the volume fraction ν2 of polymer of 1.00, 0.80, 0.60, 0.50, and 0.35. At ν2=0.80, the stress—strain isotherms were found to be independent of the nature of the diluent; at lower values of ν2, however, these isotherms were significantly different, thus demonstrating the existence of a “specific solvent effect” in swollen polymer networks. Interpretation of these data in terms of the statistical theory of rubberlike elasticity gave results in good agreement with previously reported specific solvent effects on the unperturbed dimensions of uncrosslinked poly (dimethylsiloxane) chains in solution. In neither case, however, do these effects correlate well with the cohesive energy density or dielectric of the diluent or solvent medium.
Applications of Integral and Derivative Thermogravimetry to the Analysis of Rubber Formulations
Authors: Swarin S. J. , Wims A. M. 
Published: February 2011

Abstract
Thermogravimetry, in the integral and derivative modes, can be used to determine the percentage composition of oil-extended EPDM and plasticized NBR formulations, even when the weight loss steps due to the various components overlap slightly. The percentages of extender oil or plasticizer, rubber, carbon black, graphite, and mineral filler can be determined in 2 hours or less from a single experiment. Derivative thermogravimetry also provides information on the volatility and identity of the extender oil in EPDM formulations, as well as the volatility and identity of the monomeric plasticizers in NBR formulations. Information about the type of carbon black in a formulation can also be obtained. Thermogravimetry appears to be an excellent method for the quality control and receiving inspection of EPDM and NBR formulations.
The Analysis of Rubber Vulcanizates—Identification of Amine Residues from Sulfenamide Accelerators by Thin Layer Chromatography
Authors: Higgins G. M. C. , McSweeney G. P. 
Published: February 2011

Abstract
The amine residues from sulfenamide accelerators can be identified in rubber vulcanizates by treatment of the latter with 4-chloro-7-nitrobenzo-2,1,3-oxadiazole (NBD-Cl) and examination of the products by thin-layer chromatography.
Chemical Stress-Relaxation and Other Studies on Styrene-Butadiene Rubber
Authors: Kalfayan S. H. , Rakutis R. , Silver R. H. 
Published: February 2011

Abstract
The aging of styrene—butadiene rubber (SBR) was studied by three methods: stress relaxation, infrared spectroscopy, and swelling measurements, with the purpose of supplying information pertinent to understanding the basic mechanism of its aging. Stress-relaxation measurements in air and nitrogen at elevated temperatures indicated that atmospheric oxygen is the principal cause of chemical stress relaxation of SBR, rather than heat. Intermittent stress-relaxation measurements showed scission and crosslinking occurring simultaneously during network breakdown, and it was concluded that random scission in the backbone is indicated to take place in preference to scission in the crosslinks. Activation energies obtained from relaxation rates at several temperatures was 28 ± 0.5 kcal, comparable to literature values of 30 ± 2 kcals. The rates of carbonyl and hydroxyl group formation in SBR in air at various temperatures were determined by ir spectroscopy, both induction and maximum rates, νm, being measured. Activation energies calculated from these rates showed lower values compared to those obtained from stress-relaxation measurements. This may be due to the possibility that the processes being measured are not the same in each case. The three peaks appearing in the carbonyl region were ascribed to carboxyl, ketone, or aldehyde, and perester. The presence of these groups was confirmed by microanalytical methods. The absorption centered at 3450 cm−1 was attributed to hydrogen-bonded OH groups, i.e., alcohols and hydroperoxides. Positive chemical tests were obtained for hydroperoxide. The number of new network chains formed, νe, obtained from swelling measurements agreed well with those obtained from stress-relaxation measurements. It was found that the rate of the number of new network chains formed increased rapidly during the latter states of oxidation.
The Chemistry of Vulcanization. VI. Action of the Zinc Salt of 2-Mercaptobenzothiazole on the Reaction of Diphenylmethane with Sulfur
Authors: Tsurugi Jitsuo , Fukuda Haruko 
Published: February 2011

Abstract
Literature on rubber vulcanization with thiazole type accelerators in the presence of zinc oxide indicates that the zinc salt of 2-mercaptobenzothiazole (ZMBT) is a transformation product of the benzothiazole accelerators. Therefore, it is important to investigate the behavior of this salt in the reacting mixture of sulfur and diphenylmethane (DPM), the latter having been utilized as a molecular model of rubber hydrocarbon in previous parts of this series. The reaction of DPM, sulfur and ZMBT in the absence of zinc oxide or zinc soap will now be reported. This is preliminary to the study of the mechanism of thiazole type accelerator action in the presence of zinc soap.
Electrical and Diffusion Processes in the Adhesion of Two Polymers
Authors: Morozova L. P. , Krotova B. A. 
Published: February 2011

Abstract
In previous publications one of us developed the concept of the electrical theory of adhesion. On the other hand, many authors have repeatedly expressed opinions concerning the role of diffusion processes during the formation of adhesive and auto-adhesive bonds. Owing to the discussion of this problem an experimental investigation of the formation of adhesive bonds acquired special significance, in particular during the addition of two high molecular materials for the purpose of clarifying the correlation of electrical and diffusion processes in the phenomena of adhesion. The shape of the adhesiogram is very significant in solving the question of the type of adhesive bond. The effect of the velocity of rupture is comparatively small if the adhesive bond depended on the phenomenon of diffusion. If the adhesive bond is of electrical nature the adhesiogram has generally three clearly expressed sections. With the aid of a roller adhesiometer we have taken the adhesiograms of a series of polymers (gum type BF, polyurethans, polyamides, a series of vinyl polymers, rubbers, guttapercha, cellulose esters, and on.). The adhesiograms of different combinations of these polymers with glass, metal and with rubbers of a Na butadiene and acrylo nitrile rubber base usually gave three clearly expressed regions. However, in some cases there were only two sections and the third was absent. Three probably exist in all but some may be located in an area of significant velocity and experimental determination becomes difficult. Under our experimental conditions of a time interval &lt;0.01 sec some could not be measured.
Dynamic Methods for Determination of Bond Strength between Rubbers and between Rubber and Cord
Authors: Tsydzik M. A. , Lukomskaya A. I. , Slonimskiĭ G. L. 
Published: February 2011

Abstract
The standard methods of determination of bond strength between layers of rubber and rubberized fabric and between rubber and other materials (GOST 6768-53, GOST 264-53 and others) are of the static type and do not give a clear assessment of the bond strength of multiply rubber structures which are subject during use to temperature influences and to complex deformations which are repeated many times. This drawback is partially compensated for by carrying out the tests at elevated temperatures. Nevertheless static tests, from their very nature, cannot reproduce the particular character of dynamic conditions. In recent years there have been developed in different countries a large number of dynamic methods of determination of bond strength, which often differ little from each other in principle. In connection with the establishment of production of tires of 100% synthetic rubber, and also the introduction of viscose cord, dynamic methods were established in the Nauchno-Issled. Inst. Shin. Prom. (Tire Research Institute) and at the Moscow and Yaroslavl Tire Works. These methods differ from each other in the nature of the action (repeated compression, repeated shear and the like) and in the shape, structure and dimensions of the specimens being tested, but were fairly similar in the testing routine. If the settling of the specimens in the testing period is negligible, then the testing routine may be regarded as one of constant dynamic deformation, or, more accurately, of constant ampliture of movement of the platens deforming the specimens. In 1954 we established in the mechanical testing laboratory of the Nauchno-Issled. Inst. Shin. Prom. a new method of determination of the bond strength of the rubber with rubber and of the rubber with the cord. The method allows tests to be carried out in repeated compression and in repeated shear in three principal sinusoidal cycles: 1) with constant dynamic loading, 2) with constant dynamic deformation and 3) with constant product of amplitudes of force and movement.
Degradation of Polyisoprene Networks by Oxygen
Authors: Bevilacqua E. M. 
Published: February 2011

Abstract
The insolubility of vulcanized rubber and the relatively low concentration at which oxidation reactions completely degrade the vulcanizate have made it necessary that indirect methods be used to study the reaction of molecular oxygen with rubber. The literature contains many reports of measurements of the absorption of oxygen by vulcanized rubber, which is easy and convenient experimentally. In some of these the rate of oxygen absorption has been the only property measured. This alone gives little information about the mechanism of oxidation, although the fact that the general form of curves of oxygen absorption as a function of time can be predicted by equations based on the known mechanism of oxidation of low molecular weight olefins is indirect support for similar mechanisms of oxidation of polymers. The technologically important reaction accompanying oxidation of natural rubber is scission, not detected by gas absorption measurements. It has been studied principally by determining the decay in stress of a sample at constant strain. The results suggest that scission occurs by a first order process at selected sites in the network. This has been interpreted to mean that crosslinks are the primary locus of oxidation in vulcanized rubber. Estimates of the amount of oxygen required for breaking a bond are available only for samples vulcanized with sulfur. From these it may be calculated that initially 4– 5 moles of oxygen is required per scission, when allowance is made for the effect of entanglements on stress. A marked difference between the relaxation of peroxide-cured and sulfur-cured samples has been reported. Horikx has made an extensive investigation of the solubility and swelling of oxidized vulcanized rubber. His results show that the hydrocarbon chain must be broken during oxidation. The mechanism of scission of unvulcanized rubber has been determined; in this work it was found that low molecular weight products are an important index of scission reactions. The present report describes preliminary work on the scission mechanism in vulcanized natural rubber which has two objectives; to repeat Horikx's experiments with vulcanizates incapable of further cure, and to determine whether low molecular weight products accompany the scission reaction.
Chemical Reactions Induced by Polymer Deformation
Authors: Watson W. F. 
Published: February 2011

Abstract
A review is given of the work establishing the mechanico-chemical mechanism for degradation by the cold mastication of rubber. The relevance of this mechanism to industrial practice, in particular the addition of fillers and vulcanizing agents during mastication, is considered. The degradation by mechanical treatment is shown to apply to a wide range of polymers which are not rubbery at normal temperatures. The mechanism has also predicted the formation of block polymers by the milling together of polymers or a polymer containing a monomer. These predictions have been fulfilled.
The Rotomill—A Continuous Mixing Device
Authors: Juve A. E. , Beatty J. R. , Kline R. H. 
Published: February 2011

Abstract
The Rotomill is a simple device capable of mixing a wide variety of rubber compositions on a continuous basis. We believe that it is the first practical device for achieving this objective. The virtues of continuous operation are better control, greater uniformity, susceptibility to automation and greater economy. While large production units have not yet been built, there appears to be no insuperable obstacles to doing so.