bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Degradation of Elastomers. 2. Oxidative Degradation of Natural Rubber Vulcanizates at Different Elongations and Temperatures. II
Authors: Hillmer Karl-Heinz , Scheele Walter 
Published: February 2011

Abstract
The results of measurements of stress relaxation in natural rubber vulcanizates are reported. In the earlier work, the conditions were denned under which the drop in tension of a vulcanizate—after a pre-relaxation in pure nitrogen—follows a zero order law when tested in oxygen. The temperature dependence of the rate of relative tension relaxation was determined for 8 different vulcanizates. With a constant activation energy of about 29 kcal/mole, the vulcanizates differed in their relative relaxation rates at most by two powers of ten. Several general observations on the course of tension relaxation under different conditions were made on the grounds of experimental evidence. Good qualitative agreement was found with relations reported by Berry and Watson.
Diffusion Processes in the Vulcanization of Tire Stocks
Authors: Blokh G. A. , Kormilzeva Z. P. , Boguslavskiĭ D. B. , Bakharev B. I. , Tikhomirov B. P. 
Published: February 2011

Abstract
1. The diffusion of radioactive S35 during vulcanization of rubber compounds used for tire building was investigated. 2. It was shown that during the vulcanization process an intense diffusion of the radiosulfur between plies can take place. 3. It was established that in the boundary layers “cushion-breaker” and “breaker-carcass” the concentration of the vulcanizing groups is increased; this may be the cause for different kinetics of the vulcanization reaction within any ply and at the boundary between plies. The increased concentration of vulcanizing groups should influence the spatial configuration of the boundary regions and the working qualities of polylayer articles.
The Influence of Activators on the Vulcanization Process. I. The Influence of Zinc Oxide on the Rate of Combination of Sulfur with Rubber
Authors: Beniska J. , Dogadkin B. 
Published: February 2011

Abstract
In this work the effect of zinc oxide and stearic acid on the kinetics of sulfur combination with rubber was traced, in stocks containing accelerators as well as in stocks without the latter. It was proved that ZnO does not increase the rate of sulfur combination in sodium catalyzed polybutadiene rubbers (SKB-25). On the contrary, in stocks with mercaptobenzothiazole, zinc oxide decreases the rate of sulfur combination. In vulcanizates ZnS is formed in the presence of ZnO. The largest amount of zinc sulfide is formed in stocks with phenyl-2-naphthylamine and with stearic acid.
The Influence of Activators on the Vulcanization Process. II. The Influence of Zinc Oxide on the Structure of Vulcanizates
Authors: Beniska J. , Dogadkin B. 
Published: February 2011

Abstract
The influence of zinc oxide and stearic acid on the structures of vulcanizates was traced in stocks with mercaptobenzothiazole by means of the kinetics of swelling. It was found that zinc oxide in the presence of stearic acid has a marked influence on the rate and degree of crosslinked network formation in vulcanizates. In the formation of crosslinks (sulfur bridges) a number of reactions participate: the direct combination of rubber molecules with biradicals of sulfur, during which polysulfide bonds are mainly formed; the oxidation of rubber mercaptans (-SH groups), which is followed by the formation of mono-sulfide, disulfide and polysulfide links; and the decomposition of polysulfide links, which is followed by the formation of new crosslinks with a smaller number of sulfur atoms per crosslink. Zinc oxide has a varying influence on the individual reactions : the first two are activated by it, and the last one is retarded by it, because it does not react with the polysulfide sulfur to form zinc sulfide.
Bulk Polymerization in Natural Rubber Swollen by Methyl Methacrylate
Authors: Swift P. Mc L. 
Published: February 2011

Abstract
Methyl methacrylate absorbed into dry natural rubber has been polymerized under conditions of low heat loss, using as initiator AZBN, alone or in combination with an activated peroxide. With AZBN as sole initiator, some deductions are made from the change of temperature with time, as to the change in molecular weight of the polymer formed as the. reaction proceeds. No graft polymer is formed. With the mixed catalyst system polymerization starts at room temperature. The process has been carried to a semitechnical scale, and some of the properties of the products are given. In general the materials resemble the corresponding materials prepared in natural rubber latex, but have markedly better hot-tear resistance. About 25% of the polymethyl methacrylate is present as a graft polymer.
Swelling of Latex Particles
Authors: Morton Maurice , Kaizerman Samuel , Altier Mary W. 
Published: February 2011

Abstract
A theoretical relation has been derived for the equilibrium swelling of latex particles. The equilibrium solubility and rate of solution of solvents were measured on a series of polystyrene latex fractions of varying particle size. The solvents used were styrene, toluene, and chlorocyclohexane. It was found, as predicted by theory, that the equilibrium amount of solvent imbibed by latex particles is a direct function of the particle diameter and an inverse function of the interfacial energy at the surface of the particles. The molecular weight of the polymer has no effect on the equilibrium swelling, within the range from 100,000 to several million molecular weight units. The rate of imbibition of these solvents appears to be extremely rapid, indicating that equilibrium solubility would appear to be maintained in most polymerization reactions. The fact that a particular solvent is a “good” solvent for the polymer does not necessarily result in a greater swelling of the particles, since the solvent may show a higher interfacial energy against the aqueous phase. The soap titration method is best for determining the average particle size of a latex for purposes of predicting equilibrium swelling.
The Infrared Spectroscopic Identification of Rubber before and after Cure to the Soft and Hard Rubber States
Authors: Hummel Dieter 
Published: February 2011

Abstract
The IR-spectroscopic identification of soft rubbers may be made by : 1. Breaking down the vulcanizate on a mill followed by boiling with o-dichlorobenzene and then the spectroscopic examination of the polymer recovered from the solution. 2. Thermal degradation of the vulcanizates followed by spectroscopic examination of the liquid and gaseous products of pyrolysis. The rubber base of hard rubbers is determined by spectroscopic examination of the materials obtained by thermal degradation of mixtures of the hard rubbers with zinc dust or powdered calcium.
Bond Strength at the Cord-Impregnant (Adhesive)-Rubber Boundary Layer
Authors: Uzina R. V. , Dostyan M. S. 
Published: February 2011

Abstract
The casing construction studied here comprises cord layers-adhesive layerrubber (Figure 1). Owing to the action of external forces and internal tensions, while the cover is in service, separation may occur. Separation takes three forms: (1) the adhesion type, i.e., when the adhesion becomes less than the cohesion of the bonded materials ; (2) the cohesion type, when the adhesion is greater than the cohesion of the bonded materials ; and (3) the combined type when the adhesion approaches the cohesion. In order to eliminate adhesion type separation, it is necessary to increase the bond strength of the system. This can be done by three methods: (1) changing the type of cord; (2) using impregnating compositions; and (3) changing the rubber compound. The type of cord has a marked effect on the bond strength. For example cotton cord results in considerably greater bond strength value than artificial or synthetic fibers. The composition of the rubber compound also shows a marked effect on the strength of bonding with cord. The introduction of a series of plasticizers into the mix results in a fall in the strength of the rubber/cord bonds, and the use of active fillers causes the strength to increase. The effect of cord type and the composition of the casing rubber on the bond strength in the construction studied will be the subject of a separate investigation. The present report deals with the effect of the composition of the impregnating layer on the strength of the bond between the impregnated cord and the rubber.
Application of Strain Gages to the Study of (Tire) Cord at High Elongation Rates
Authors: Pavlov N. N. , Yaminskaya E. Ya , Krymov B. M. 
Published: February 2011

Abstract
1. A new simplified method of recording the stress-strain curve of elastic materials using strain gages was developed and tested. 2. It was found that there is a substantial influence of rate of deformation on the character of the stress-strain curves of the samples tested. 3. It was established that the work of breaking the tested samples decreases with increasing speed of stretching.
Rotary Power Loss Machine
Authors: Bulgin D. , Hubbard G. D. 
Published: February 2011

Abstract
Rubberlike polymeric materials, particularly in the technical form when compounded with carbon black, are imperfectly elastic and the associated energy loss is of considerable practical significance. In some applications a high energy loss is of value to provide high damping, but in many cases and particularly in tires, the temperature rise due to the losses may be a limiting operational factor. The losses cause the tire to exhibit rolling resistance which, in the case of solid tires, can be related accurately to the modulus and resilience of the rubber. An analysis of this system has been carried out by Evans, while Tabor has considered the case of rigid cylinders and spheres rolling on flexible rubber surfaces. In the case of pneumatic tires the composite nature of the construction of fabric and rubber and the complex system of strain distribution make the calculation of rolling resistance from polymer properties extremely complicated. In order to approach this problem it is necessary to know the modulus and resilience of the materials used over a very wide range of temperature and a range of amplitude of deformation and of frequency. The required temperature range may be from −60° C to above 200° C, but the frequency range over which appreciable amplitudes are involved does not extend beyond approximately a thousand cycles per second while the amplitude of deformation does not exceed 50 per cent. In order to investigate adequately the many possible combinations of polymers and compounding systems, the values of resilience and modulus are required over the above range of conditions, and various instruments have been described which measure some or all of these properties. The rebound pendulum was one of the earliest instruments and is widely used for the measurement of resilience because of its inherent simplicity of operation and high accuracy, but as normally operated at a fixed temperature does not provide sufficient information for evaluation of materials for use in tires. This type of instrument also is not well suited for determination of modulus owing to its single cycle method of operation. The vibrator type instruments give more complete information but normally demand a high degree of skill in their operation and in the interpretation of results and are more suited to research than routine work.
Dependence of Dielectric Relaxation Spectrum of Rubber on Stretching
Authors: Müller F. H. , Huff K. 
Published: February 2011

Abstract
The loss angle of a weakly vulcanized rubber sample, as a function of temperature and frequency, changes as the sample is extended. Even at slight extension the loss angle maximum is depressed and shifts by several degrees to lower temperatures. The results are discussed in relation to earlier investigations of changes in the dielectric spectrum when various other rigid high polymers are stretched. Such experiments are interesting, since the close connection between dielectric and mechanical spectra permits conclusions to be drawn about modifications in mechanical behavior caused by stretching. A new method is presented for obtaining additional quantitative data regarding mechanical behavior in the nonlinear region.
The Significance of Rheology in Rubber Processing. 2. Studies of Latex
Authors: Edelmann Kurt , Horn Edith 
Published: February 2011

Abstract
After referring to the importance of rheological studies for the ever growing applications of latex in industry, results are reported for the study of the rheological behavior of several Buna latexes, using a Höppler Rheo-viscometer. The flow curves obtained in this way show a different type of non-Newtonian flow from solutions of rubber. The region of η0, viscosity at rest, is absent. With increasing velocity gratient, the viscosity becomes smaller and smaller and finally reaches a constant value at a relatively high velocity gradient. That is, non-Newtonian flow passes gradually over into Newtonian flow. For those latexes whose Newtonian flow lies within the measurable range, a general flow equation is given which includes the Newtonian portion of the shear stress together with a stress correction. This equation of flow can be used to define the rheological behavior of the latexes. The cause of this type of rheological behavior is found in the thixotropic properties of the latex system. If a Höppler Rheo-viscometer is used and measurements are made first at increasing and then at decreasing shear stresses, the plotted data show a hysteresis loop which is evidence of thixotropy. With those latex systems for which the Newtonian flow behavior falls within the limits of the measurements, and whicn can be called fluids, the viscosities measured with decreasing shear stresses lie below those which are measured with increasing shear stresses. On the other hand, highly concentrated latexes which can be considered as having a gel structure throughout, such as the 70% Buna-Latex S3 used in this work, display a different kind of thixotropic behavior. In such cases, the viscosities measured with decreasing stresses are higher than those measured with increasing shear stresses. A different flow equation is needed to define this different type of thixotropy.
Comparison of Accelerated and Natural Tests for Ozone Resistance of Elastomers
Authors: Vacca G. N. 
Published: February 2011

Abstract
While other data are available, it is believed that the data summarized herein are sufficient to give a good average picture of results obtained in static accelerated ozone versus outdoor exposure tests. At The Bell Telephone Laboratories where most of the work has been with black stocks, results indicate that correlation is dependent on the base polymer in the stocks under test. Thus, in polymers which are inherently resistant to ozone, protective systems are very effective and correlation is very good. This has been true of black neoprene stocks and evidence indicates that it may also be true for butyl stocks. With natural, SBR and NBR rubbers, protection is more difficult and results vary more widely. With the introduction of the newer and more effective antiozonants such as the dioctyl-p-phenylene diamines, correlation is much better. It has been argued that absolute correlation should not be expected since in outside tests there are influences affecting cracking behavior which are absent in the indoor tests. These include sunlight, rainfall, arid temperature as well as ozone concentration fluctuations. It has been observed that specimens from some stocks exposed in the late fall of the year will go through the following summer without cracking, while specimens from the same stock exposed in late spring will crack in a few days. This probably results from a combination of factors. Low ozone concentration coupled with low temperature greatly reduces susceptibility to crack formation and may provide time for stress relaxation or, perhaps, for the formation of a protective coating through the effects of sunlight activated changes in the surface. In the accelerated ozone test, temperature and ozone concentration are carefully controlled and other variables are absent. The test will at least isolate the effect of ozone which alone is responsible for cracking. Aside from the effect of location and season of the year, there is also the question of the duration of the outdoor exposure to be used as a criterion. This may vary widely as between tires where a 4 or 5 yr period will suffice and utility or communication wires where periods in the order of 20 yr are involved.
Ozone Resistance of Rubber Insulations
Authors: Couch W. H. , Hunt G. H. , Pratt O. S. 
Published: February 2011

Abstract
The results of experiments on the ozone and corona cutting of rubber high voltage insulation show that the relaxation of mechanical stress in the insulation plays an important role. Studies were made to establish the stress decay characteristics of various formulations based on natural rubber, SBR and butly rubber. A method was developed for correlating the stress decay and ozone resistance characteristics which permits the performance of bent samples of any formulation to be predicted at ozone concentrations up to 0.2%. Comparisons were made between the cutting in an intense corona discharge and that in high concentrations of ozone outside of the discharge. These comparisons show that the results of ozone tests at constant load together with stress relaxation tests may be used to predict the performance of rubber insulation in corona discharge. Tests were carried out in the products of corona discharge at pressures less than atomospheric. These tests lead to the conclusion that at very low pressures (ca. 1 mm Hg) cutting is caused not by ozone but by atomic oxygen. Compounds based on a variety of polymers were exposed to atomic oxygen and it was found that butyl rubber cuts rapidly in atomic oxygen while natural rubber, SBR, neoprene, and Hypalon do not. Antioxidants do not protect butyl rubber against cutting in atomic oxygen, but surface coatings were found to offer protection.
Factors Influencing the Ozone Resistance of Neoprene Vulcanizates under Flexure
Authors: Murray R. M. 
Published: February 2011

Abstract
The need for dynamic testing conditions, such as mild flexing, to study the attack of ozone on elastomeric vulcanizates, has become increasingly apparent. Many rubber goods, such as belts, tire sidewalls, and hose, are subjected to intermittent or continuously fluctuating strains in service and to evaluate their ozone resistance under constant stress or strain conditions is unrealistic and often leads to entirely erroneous conclusions. For example, it is well known that under static strain a vulcanizate's ozone resistance is enhanced by compounding with a wax which migrates to its surface and forms a protective film. However, numerous investigators have reported that when a wax film is continuously ruptured by dynamic testing, the vulcanizate is even more vulnerable to ozone attack than if no wax were present. Other surface films also may act detrimentally under dynamic conditions. One such film may form under static exposure by the migration of antiozonants to the surface of a sample where they or their ozone reaction products provide a shield against ozone. Also, diene elastomers, even when not under stress, react with ozone without cracking and it has been postulated that the thin films formed as a result of this reaction are less extensible and consequently more subject to rupture on flexing than the unreacted rubber beneath them. It may well be found that the resistance of any surface barrier to dynamic stresses is the limiting factor for many products in service. Consequently, techniques for testing under dynamic conditions are needed at least to supplement testing under constant stress or strain in ozone. Ozone exposure under dynamic conditions may prove to have analytical advantages over the static method. First, because dynamic tests accelerate ozone attack over that obtained statically even though no increased strain is impressed. This permits the more ozone resistant elastomers to be tested at lower concentrations of ozone than would be possible statically. By testing in more dilute ozone, the correlation between results obtained under atmospheric exposure and the ozone cabinet should be better. Also, it seems likely that compounding ingredients which improve ozone resistance under dynamic conditions should provide improvement under static conditions as well, even though the converse is not necessarily true.
The Effect of Carbon Black on Thermal Antioxidants for Polyethylene
Authors: Hawkins W. L. , Hansen R. H. , Matreyek W. , Winslow F. H. 
Published: February 2011

Abstract
Carbon black has been shown to function as a mild thermal antioxidant for polyethylene at 140° C. The amount of protection increases with concentration and is dependent on the chemical nature of the carbon surface. This antioxidant effect is shown by a variety of carbon blacks with a considerable range of particle size, but very coarse carbons in comparable weight concentration exhibit no antioxidant effect. Recent studies concerned with the chemical nature of the carbon black surface indicate the presence of various oxygenated groupings which may account for the weak antioxidant activity of some carbon blacks. In all cases examined, conventional amine and phenol antioxidants in polyethylene are adversely affected by carbon black. This effect can be attributed to adsorption followed by chemical decomposition of the antioxidant on the carbon black. The chemical nature of the carbon black apparently influences the adsorption since the loss in activity of amine antioxidants is much more pronounced with acidic than basic carbon blacks. Whereas the effect of carbon black on antioxidant behavior is observed over a wide pH range, the effect decreases and finally disappears as the particle size of the carbon black is increased.
New Thermal Antioxidants for Polyethylene Containing Carbon Black
Authors: Hawkins W. L. , Lanza V. L. , Loeffler B. B. , Matreyek W. , Winslow F. H. 
Published: February 2011

Abstract
Antioxidants which contain a thioether bond are usually more effective than the simple compounds from which they are derived. More significant is the effect of carbon black on these improved antioxidants, generally resulting in even greater protection than in the clear polymer. This is in contrast to the behavior of conventional antioxidants which do not contain a thio-bond. In all cases examined, these conventional antioxidants lose a large proportion of their effectiveness in the presence of carbon black. Recent studies concerned with the chemical nature of the carbon black surface strongly suggest the presence of reactive chemical groupings which may account for the weak antioxidant activity of some carbon blacks. Apparently the carbon black surface interacts with organo-sulfur antioxidants since this unique behavior has not been observed in other materials of comparable particle size, such as alumina, titania, or silica, nor do these materials themselves inhibit polyethylene oxidation. Thioethers and disulfides which contain no amine or phenol groups and hence no active hydrogen constitute another class of antioxidants which are unusual in that they attain a significant degree of activity only in the presence of carbon black. Although the mechanism through which these simple compounds function as antioxidants has not been established, there is considerable evidence that a relationship exists between antioxidant activity and bond dissociation energy. Some thiols may act to a slight extent as conventional antioxidants in clear polyethylene, but when carbon black is present, they appear to function through the same mechanism as do the simple organo-sulfur compounds which contain no active hydrogen. It is significant that within the general class of organo-sulfur antioxidants, alkyl compounds exhibit strong antioxidant activity in the presence of carbon black, and are often comparable with their aromatic counterparts.