bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nondestructive Aging Tests for Rubber
Authors: Shaw R. F. , Adams S. R. 
Published: February 2011

Abstract
An improved laboratory method has been developed for evaluating the effects of aging. The test-specimens are subjected to definite loads or extensions at repeated intervals during exposure to the deteriorating influence of heat, light, air, and ozone. The degree of deterioration is evidenced by an elongation increase for specimens that become cracked and for a decrease in elongation for those that become heat-hardened. The test data are obtained on the same specimen at varying time intervals, are reproducible, and are measured in the low elongation range in which most rubber is used in service.
Improvements in Accuracy of Hardness Testing
Authors: Scott J. R. 
Published: February 2011

Abstract
Most hardness tests depend on penetration by an indentor under load, the penetration being measured by the movement of the plunger carrying the indentor. This movement must be measured from a zero position, and the fixing of this position has been the cause of most of the difficulties in obtaining accurate hardness measurements. In most instruments one of the following devices has been adopted : (1) Zero Load—a known small load is applied to the indentor, and its position under this load is taken as the zero; or (2) presser foot—an annular foot, surrounding the indentor, rests on the rubber test-piece, and the depth of indentation is measured relative to the plane of this foot. Rubber test-pieces generally are not perfectly flat and parallel-sided, even though nominally so. This fact leads to errors in hardness measurements by instruments using either of the devices (1) or (2) mentioned above. Moreover, if plied-up test-pieces are used to obtain the required thickness, or in testing articles that are very thick compared with their lateral dimensions, large errors can arise if no foot is used. The best general procedure is, therefore, to use both a zero load and a presser foot. Experimental data support this conclusion, which has been embodied in the revised British Standard Method (B.S. 903-1950) and in the recommendations of Committee ISO/TC/45—Rubber. Most published standard hardness tests make no provision for avoiding errors due to friction in the measuring device (usually a dial micrometer gauge). Results of tests show that by applying gentle vibration during the test, much more consistent readings are obtained, and it is possible to get better agreement between different laboratories and instruments. Lubrication of the surface of the test-piece with talc produces a definite though small further improvement in uniformity of results. It is, therefore, a useful additional precaution.
The Crystallization of Vulcanized Natural Rubber at Low Temperatures
Authors: Russell E. W. 
Published: February 2011

Abstract
A series of natural rubber vulcanizates have been crystallized at −36° − 26° −17.5° and −2° C and the changes followed dilatometrically. As for raw rubber there is a maximum rate of crystallization at about −26° C; vulcanization decreases the rate and alters the shape of the temperature-rate curve. The amount of combined sulfur is the chief factor in determining the rate and extent of crystallization of pure-gum vulcanizates. Cross-linking, where it is efficient so that the chains between the cross-links are chemically unaffected, also depresses the rate and extent of crystallization. The use of vulcanizates which crystallize slowly permits melting to be accomplished at much lower rates of heating than was previously possible with raw rubber. Two stages of melting are distinguished the first occurring under the influence of forces between the crystalline and amorphous regions and the second analogous to the melting of low molecular weight crystalline substances.
Stress—Temperature Studies of Transitions in Rubbers
Authors: Witte Robert S. , Anthony Robert L. 
Published: February 2011

Abstract
The stress-temperature method was employed as a means of studying the apparent second-order transition occurring in rubbers. The rubbers studied were a natural rubber gum, a Butyl gum, a loaded GR-S, and a loaded Hycar OS-10. Pronounced stress relaxation was observed for all rubbers at temperatures not too far below the transition region, but not at temperatures a few degrees above the transition. For both the Butyl and the Hycar OS-10 rubbers, the transition temperature was observed to depend strongly on extension, the transition temperature decreasing with increasing sample extension. No such dependence on extension was observed for the natural rubber stock. Comparison data were also obtained from volume dilatometric studies. With the exception of the data for natural rubber, the transition temperatures determined by the volume dilatometric method were somewhat lower than the lowest values obtained in the stress-temperature studies.
The Application of Polarized Infrared Radiation to Problems in Molecular Structure
Authors: Sutherland G. B. B. M. , Jones A. Vallance 
Published: February 2011

Abstract
The infrared spectra of rubber and of both forms of gutta-percha have been investigated between 5 and 15 µ under various conditions. When rubber and gutta-percha are each in the amorphous state, their infrared spectra are closely similar, although not identical; in the crystalline state, marked differences occur between the spectra of these three forms of polyisoprene. Using polarized radiation, the dichroic ratios of bands which can be assigned with certainty are in general qualitative agreement with the crystalline structures proposed by Bunn. The spectrum of rubber crystallized by freezing has been examined at low temperatures, and it is shown that apparent intensity changes occur in certain absorption bands on crystallization. The importance of this effect in using infrared methods to estimate the degree of crystallinity produced in rubber by stretching is emphasized. Assignments of a few of the main bands are discussed, but no attempt is made to give a complete interpretation of the spectra.
Oxidation of Unvulcanized Cold Rubber Influence of Adsorption by Carbon Black
Authors: Sweitzer C. W. , Lyon Francis 
Published: February 2011

Abstract
Previous investigations have shown a large difference between the amount of rubber insolubilized by carbon black in dilute solvent systems and in standard mill mixes. The purpose of this study, after reconciling these extremes, was to evaluate the role of adsorption in the insolubilization of rubber in mill-mixed compounds. An adsorption test was employed which eliminated the solvent effect of the dilute system and the mastication effect in mill mixing. Results showed that carbon black, depending on the temperature and atmosphere conditions imposed on the rubber carbon films, represses the scission, cross-linking, and gelation reactions of GR-S X-478. This repressive effect is ascribed to the adsorption and inactivation by the carbon black of the oxidized intermediates through which these various reactions proceed. The magnitude of this effect was found to vary with the type, loading, and surface chemistry of the carbon. This approach not only offers promise as a means for predicting the behavior of carbon black in rubber compounds, but also, because of its applicability to the study of all rubber-carbon systems, offers possibilities of providing additional information on the mechanism of the carbon-rubber bond.
Kinetic Analysis of Organic Halides. IV. Analysis of Macromolecular Polyhalides
Authors: Salomon G. , Koningsberger C. 
Published: February 2011

Abstract
Chlorination products derived from natural rubber and some synthetic polymers have been subjected to kinetic analysis with aniline at 100° C and piperidine at 20° C. The influence of the chlorinating agent on the structure of the reaction products has been elucidated. It is shown that allylic chloride groups, the rubber dichloride, (see PDF for diagram) and rubber polychlorides can be identified and separated kinetically. By a combination of kinetic and infrared analysis the structure (see PDF for diagram) can be proved as the primary reaction product of direct chlorination.
Studies of the Vulcanization and Structure of Polyacrylic Rubber
Authors: Semegen S. T. , Wakelin J. H. 
Published: February 2011

Abstract
Several characteristic features of the vulcanization of polyacrylates have been demonstrated. The fact that alcohol is formed and liberated during cure has been demonstrated; this finding might favor a Claisen type condensation. On the other hand, the fact that a copolymer of methyl acrylate and acrylic acid can be plasticized with alcohol and assumes a chain spacing comparable with that of cured polymethyl acrylate, whereas the uncured PMA and unplasticized copolymer are appreciably different in chain spacing, might favor a controlled hydrolysis and hydrogen association as the mechanism. The latter mechanism would be more compelling if the methyl acrylate/acrylic acid copolymer when alcohol plasticized showed other evidences of vulcanization, in situ, such as increased resistance to methylethyl ketone or reduced thermoplasticity in addition to increased rubberiness. Several different x-ray diffraction patterns are shown in Figures 6 to 15. Note the progression in spacing for the inner halo as the number of terminal carbons in the side chain increases. In comparing the pattern of α-carboxypimelic acid, a highly crystalline compound, with the patterns of the esters of the acid, we note the influence of hydrogen binding on the side chain association to produce a regular 3 dimensional structure, while esterification with relatively unreacting alkyl groups decreases cross-bonding between chains so much that the structure assumes a liquid configuration similar to that of the various polyacrylates.
Chlorinated Rubber from Latex
Authors: van Amerongen G. J. 
Published: February 2011

Abstract
This work was undertaken to find new ways for producing chlorinated rubber from rubber latex. Methods have been applied during which coagulation of the latex and hyprochlorination of the rubber are avoided. Passing gaseous chlorine through stabilized and strongly acidified Hevea latex proves to be a satisfactory method for the chlorination of rubber. To avoid coagulation of the latex, certain nonionogenic or cationogenic emulsifiers have to be added. A high acidity of latex prevents the formation of hypochlorous acid and improves the mechanical stability of the latex. A chlorinated rubber latex is produced, the chlorinated rubber of which contains virtually no oxygen and up to 61 per cent of chlorine. By subjecting this chlorinated rubber latex or the dry isolated chlorinated rubber to an aftertreatment, products of a satisfactory solubility and with a chlorine content up to 72 per cent have been obtained. Judging from the reactivity with aniline, maximum chemical stability is at 65 per cent chlorine content. As a similar chlorination technique is applicable to rubber hydrochloride and synthetic rubber latexes, it is seen that latexes in general are good starting materials for the production of chlorinated derivatives. Moreover, stable chlorinated rubber latexes are obtained which can be used as such, making new applications possible. Technical advantages of chlorinating rubber in latex above rubber in solution are the much higher rubber concentration which can be used, and the ease of cooling the less viscous latex during the reaction. For some applications it is advantageous that the original high molecular weight of the polymer can be conserved.
Heat Sensitization of Latex by the Zinc Salt of Mercaptobenzimidazole
Authors: Delattre Robert 
Published: February 2011

Abstract
The process of heat sensitization of latex by means of the zinc salt of mercaptobenzimidazole offers the following advantages. (1) Satisfactory heat sensitivity, even when the stability of the latex to cold has been increased by the addition of ammonia, soap, or other suitable protective agent. (2) Satisfactory heat sensitivity when the ammonia in the latex has been converted to the combined state by the addition of formaldehyde. (3) Permanence of heat sensitivity. (4) Remarkable stability to cold when the latex has been heat-sensitized. (5) Negligible dilution of latex when the heat-sensitizing agent is added. (6) Regularity of the conditions of gelation. (7) Elimination of the washing operation after gelation. (8) Effective heat sensitization, even in the absence of zinc oxide. (9) Compatibility of the zinc salt of mercaptobenzimidazole with all compounding ingredients ordinarily employed in latex processes and in the rubber industry in general. (10) Compatibility of the heat-sensitization process with the reinforcement of latex by means of precondensed resins. (11) Absence of any influence on vulcanizing conditions. (12) Improvement of the aging of rubber products, because the zinc salt of mercaptobenzimidazole is an antioxygenic agent of the deactivating type and an inhibitor of the degradation of rubber by copper and other harmful metals. (13) No influence on the color of rubber products, since the zinc salt of mercaptobenzimidazole has no discoloring effect, even after a product containing it has been exposed for a long time to light. (14) No influence on water absorption, since the zinc salt of mercaptobenzimidazole is not hygroscopic. (15) Invariable properties and good stability of the heat-sensitizing agent during storage. (16) Possible use of the zinc salt of mercaptobenzimidazole in latex which has been degraded biochemically. (17) Extensive applications which are possible. This list of advantages may or may not be complete, and only the future will tell, but it may even now be regarded as certain that the new process will find a notable place among the various techniques for processing latex.
Mechanical Stability Testing of Hevea Latex
Authors: Madge E. W. , Collier H. M. , Duckworth I. H. 
Published: February 2011

Abstract
In recent years the mechanical stability testing of latex has received increased attention, and an apparatus has been developed in the United Kingdom which has certain advantages over those previously described in the literature. Various factors relating both to the instrument and to the method of testing are discussed and the influence of these factors on the accuracy of the results is considered. Some indication is given of the way in which the mechanical stability test can be used to evaluate changes brought about by various additions and treatments of the latex.
The Zinc Oxide Stability of Latex
Authors: van Gils G. E. 
Published: February 2011

Abstract
A review of the factors which determine the zinc oxide stability of latex has been given. The work of Lepetit and our own experiments lead to the conclusion that the zinc oxide stability of latex is determined in the first place by substances which promote the solubilization of zinc oxide (minus factors); in the second place by substances which stabilize the colloid against the activity of the complex zinc cations or reduce the activity of these ions (plus factors). It has been generally accepted that the higher the KOH number of a latex, the lower is the zinc oxide stability. Since the KOH number is based primarily on neutralization of the acidic components of the serum only, a general correlation with zinc oxide stability could not be found when latexes of different origin were examined. Intrinsic factors or factors depending on the properties of the latex itself that influence zinc oxide stability are: (1) the dry rubber content of the latex, where high values are accompanied by low zinc oxide stability values and vice versa; (2) the yellow content fraction of latex, which in increasing amounts adds to the stability of the latex; (3) the protein content of the latex which, when degraded either artificially or naturally, reduces the zinc oxide stability. The effect of materials added to latex on zinc oxide stability includes: (1) fatty acid and sulfonic acid soaps, which have only slight influence; (2) Emulphor-O, sequestering agents, and sodium phosphates and silicates, which have a stabilizing effect; (3) ammonium salts and amines, which have a marked destabilizing effect, although triethanolamine hydrochloride is not active. Quebrachitol has a slight destabilizing effect.
Evaluating Dynamic Fatigue of Adhesion of Tire Cords to Rubber Stocks
Authors: Lyons W. James 
Published: February 2011

Abstract
A practical reasonably quick method for evaluating the resistance of the adhesive bond between tire cord and rubber stock to flexural (dynamic) fatigue has been developed. The method employs the Roller-Flex machine, on which the test cords, cured in rubber and under tension, are subjected to rapid cyclic flexure by being passed back and forth around small steel rollers. The resistance of the adhesive bond to dynamic fatigue is evaluated by a measurement of the cord adhesion by the familiar H pull-out test, after the sample has been flexed on the machine for a 10-hour period. There is a continual decline in cord adhesion as the flexing period is prolonged. Ten hours were selected as the flexing period in the standard test. A difference of 6 pounds per inch between samples was found necessary for significance at the 5 per cent level. Dynamic adhesion measurements by this method have been found to correlate reasonably well with adhesion performance in road tire tests.
Ozone Deterioration of Elastomeric Materials. Preliminary Results of a Study by Infrared Spectroscopy
Authors: Allison A. R. , Stanley I. J. 
Published: February 2011

Abstract
The work described consists of explorative studies with the ultimate objective of developing an accelerated ozone aging test for elastomers based primarily on compositional changes rather than on the conventional variation in physical characteristics. Infrared spectrographic techniques were found to be admirably suited for the reflection of accumulation or depletion of specific structural linkages in polymer molecules undergoing ozonization. Purified gum specimens of Hevea, GR-S, nitrile rubber, Neoprene, and GR-I were dissolved in chlorinated hydrocarbon solvents such as ethylene dichloride or o-dichlorobenzene, and subjected to a stream of ozonized oxygen containing approximately 50 p.p.m. of ozone. Infrared spectrograms of films cast from the treated solutions show progressive intensification of clearly defined absorption bands at 2.9 and 5.8 mµ, reflecting the functional groups hydroxyl and carbonyl, respectively. Methods for quantitating these changes by calibration against reference compounds are described. A means is available for following ozone degradation of polymers in terms of specific variations in molecular structure. Basic information of this nature is potentially useful in the development of an accelerated ozone aging test correctable with aging under conditions of actual service.
Ozone Crack Depth Analysis for Rubber
Authors: Rugg John S. 
Published: February 2011

Abstract
The factors that control weathering and ozone resistance are not fully understood. A major deterrent to a better understanding of these factors is the lack of a satisfactory quantitative method of analyzing the results of ozone and weathering tests. A method has been developed which follows the change in crack depth as the criterion of the extent of damage that has taken place. It has been shown that, when crack growth takes place, the depth increases proportionally. The depth of the crack is measured with the 20 × microscope in a cross-section made normal to the length of the cracks. The major cracks, which have the directing influence on the extent of cracking, are the deepest ones, and are all nearly the same length. This method has been used to analyze results of ozone cracking in which commonly recognized variables were employed. The results confirm some previously reported trends with quantitative data. This method can be used in measuring the effect of compounding variables, where results are desired in terms of a dimension of actual ozone cracking. This method is performed with moderate ease, does not require specialized equipment, is independent of human judgment, and is directly related to the growth of ozone cracks. It should contribute to a better understanding of the factors that control weathering and ozone resistance of natural rubber and other elastomers.
Yield Stress in Frozen Rubbers
Authors: Buist J. M. , Stafford R. L. 
Published: February 2011

Abstract
The work reported on the low temperature shear deformation properties of natural rubber and Neoprene-GN gum compounds shows that, under the conditions of storage and applied stress investigated, there is little evidence of a yield effect with Neoprene-GN. It is suggested that the very large temperature-stiffening of this polymer is too great to give the yield effect under the low shear stresses studied. In tension, however, the yield effect is very marked with Neoprene-GN. On the other hand, a definite yield effect is shown as a result of shear deformation measurements on natural rubber stored at −40° C, whereas previous tension tests failed to detect this. It is shown that, under suitable conditions of storage time and at high shearing stresses, a natural rubber unit might fail in service by yielding and giving too much deflection. The more usual type of failure of a shear unit in service arises from loss of flexibility and hence deflection properties; the oil-resisting rubbers are particularly likely to suffer from this defect. The x-ray data on natural rubber and Neoprene-GN gum compounds failed to reveal any evidence of random crystallite formation in the unstretched frozen rubbers. If the yield effect is due to crystallite formation in the unstretched state at low temperatures, then the crystallites are too small to be detected under the conditions of this investigation. In this connection, it is emphasized that a temperature of −40° C is below the temperature for maximum rate of development of crystallization for both rubbers. With both natural rubber and Neoprene-GN, crystallization resulting from stretching occurs more readily and at lower elongations at −40° C than at room temperature. In the case of Neoprene-GN stored at −40° C and then stretched, crystallization does not increase with elongation as it does at room temperature. It is suggested that this is due to the cold-drawn state of Neoprene-GN on stretching after storage at −40° C. These investigations have important practical and theoretical implications. Suggestions have often been made to include a test for crystallization in any characterization of compounds for low-temperature resistance. The results of the present work emphasize that the important factor is the time of storage at low temperature and the effects that this produces on crystallization and yield stress. The presence of crystallization is not so important as its continued development under long period exposure or its reorientation under applied stress.
Vitrification of High Polymers in Periodic Deformation
Authors: Bartenev G. M. 
Published: February 2011

Abstract
As is known, high polymers are readily supercooled and retain their amorphous structure below their crystallization points. Changes of the physical properties in the temperature range of crystallization are a linear function of temperature. When the temperature is lowered further, high polymers remain in their amorphous liquid state; this is indicated in particular by their retaining their high elastic properties below the crystallization temperature. However, with further decrease of temperature, the linear character of the changes of physical properties is no longer evident, and the latter undergo more or less abrupt anomalous changes. In particular, there is a change of the polymer from the amorphous-liquid state with high elasticity into a hard vitreous form, which, as is known, is not related to changes of the structure of high polymeric substances. Vitrified polymers, like amorphous liquids, possess amorphous structures. A number of investigators have found similar anomalies in the heat capacity, heat expansion, dielectric properties, and high elastic properties of various polymers during transition to the vitreous state.