bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accelerated Ozone Weathering Test for Rubber
Authors: Crabtree James , Kemp A. R. 
Published: February 2011

Abstract
It has been previously shown by the authors that two separate and distinct factors are responsible for the changes which rubber compounds undergo when exposed outdoors : a light-energized oxidation and attack by ozone which is normally present in the atmosphere in minute concentration. The former acts independently of stress in the rubber, the latter only when the material is stretched. Since sunlight, ozone, and temperature vary hourly, daily, seasonally, and with locality, the overall result to the exposed material depends on the balance between the causative factors and is unique, since any given combination of such factors is not duplicated. It is, therefore, essential that the susceptibilities of a given compound to damage by these two factors be determined separately. The information thus furnished will then make it possible to estimate the durability of the compound under any given set of conditions. Damage by light-energized oxidation can be mitigated to any great extent only by physical protection from light, which can be partially achieved by incorporation of carbon black or ferric oxide. It is likely to be the major factor in the case of light-colored goods. Susceptibility can be readily gauged by measurement of the oxygen absorbed when the material is irradiated in air or oxygen under controlled conditions. The present obstacle to formulation of a standard test is the lack of a constant and reproducible light source which simulates sunlight. This article is principally concerned with the ozone factor. In the case of rubber goods containing appreciable loadings of carbon black, such as insulated cable jackets and hose, by far the most important cause of deterioration is the familiar cracking at stressed locations by the ozone of the atmosphere, popularly and erroneously referred to as “light cracking”.
Hysteresis and Methods for Its Measurement in Rubberlike Materials
Authors: Dillon J. H. , Gehman S. D. 
Published: February 2011

Abstract
After a piece of rubber undergoes a mechanical distortion, it is never the same again. The truth of this statement depends, of course, on the degree of precision and discrimination of the observations. Superficially, and for most most practical purposes, it may appear to be unaltered. The point is that in any deformation of rubber there are always some irreversible processes which lead to the conversion of mechanical energy into heat and to a departure from the behavior of an ideal elastic material. Tests which have been used to evaluate hysteresis loss in rubberlike materials may be classified as follows : 1. Low-speed stress-strain loop. 2. Impact resilience. 3. Free vibration. 4. Forced vibration at resonance. 5. Forced vibration ; nonresonance. We shall first discuss the general principles involved in these different methods of testing and then will describe the experimental procedures and results in more detail. For relatively large, slow deformations, depending on the experimental conditions, imperfections in elasticity become evident as hysteresis, permanent set, creep, time lag for recovery or stress relaxation.
A Simple Cold Test for Vulcanized Polymers
Authors: Leeper Harold M. 
Published: February 2011

Abstract
The freeze resistance of vulcanized polymers has been evaluated for the past two years at this laboratory by a method which involves measurements of primary creep at successively lower temperatures. This method has been found to be particularly useful when it is desired to know, within 5° or 10° F, the temperature at which the polymer ceases to function as a rubberlike material. In a laboratory of this kind, where considerable work is done in evaluating new polymer types and where the polymerization variables studied often are of such a nature as to produce relatively large changes in the freeze resistance of the vulcanized polymer, a tolerance of 5° to 10° F has been found to be a workable value. The test is simple and can be carried out with the Shore A durometer or the A.S.T.M. hardness tester, one or both of which are generally available in a rubber laboratory. Its simplicity notwithstanding, the test is reasonably objective. Both the durometer and the A.S.T.M. tester are handled in the conventional manner, and readings are taken five and 30 seconds, respectively, after the pressure plate or presser foot contacts the specimen. The degree of creep is recorded as the difference in hardness points between these two readings. It is a matter of experience that, for most polymers, the amount of creep or flow exhibited at successively lower temperatures increases gradually, reaches a maximum, and then begins to decrease at a relatively high rate. The temperature at which this rapid drop-off occurs is considered significant because at this point the polymer begins to lose, at an accelerated rate, the fluidity which it had at higher temperatures and is being transformed into a hard, nonrubberlike material.
Moulding Anisotropy
Authors: Gurney W. A. , Gough V. E. 
Published: February 2011

Abstract
It has long been an accepted fact that the properties of vulcanized rubber articles are not uniform in all directions. Vulcanized rubber is, in general, an anisotropic material, and the results obtained from tests vary, to a greater or less extent, with the direction in which the strain is applied or the measurements are made. In much experimental work elaborate precautions have been followed whereby replicate samples have been taken in the same directions from the rubber material. The cause of anisotropy has always, as far as the authors are aware, been attributed to the methods of processing or shaping the raw stock. This is the view taken by the authors of one of the most recent publications. As calendering is an operation that produces an extreme distortion of the raw stock, such processing effects are considerable, and the resulting anisotropy has been known for many years as calender grain, or in appropriate cases, as extruder grain. It has been evident, however, for some years that the theory that the method of preparation of the raw stock is the sole or even the major cause of anisotropy is not adequate to explain certain phenomena. Some products exhibit pronounced anisotropy, although their method of preparation does not involve much distortion of the raw stock, and in other cases, such variation in properties as does exist does not give any correlation with the direction of processing. Consideration of cases such as these have led to the conclusion that the movement of the stock during moulding is an important factor in the problem, and one that, as far as can be seen from the literature, has been hitherto neglected.
Proper Preservation and Storage of Latex
Authors: McGavack John 
Published: February 2011

Abstract
During the war years, when the maintenance of a stockpile of natural rubber latex was of critical importance, great opportunities were offered to establish new and improved techniques for its preservation and storage. Eight precautions are essential if latex is to be kept in good condition during long-term storage: (1) it should be kept free from bacteria; (2) it should have a sufficiently high pH level, which depends on the type of latex ; (3) it should be maintained at uniform total solids ; (4) its temperature should be uniform and properly regulated; (5) it should undergo minimum exposure to oxygen; (6) storage vessels should have smooth side walls and should be properly sterilized; (7) it should not be exposed to either indirect or direct light, and (8) it should have a low KOH number. Every one of these items must be considered carefully if the latex is to be maintained at highest quality. Each one will be discussed separately.
Control of pH of Neoprene Latex
Authors: Livingston H. K. , Walsh R. H. 
Published: February 2011

Abstract
One of the major contributions to the development of the use of rubber latex in manufacturing processes has been the introduction of methods for regulating the pH of the latex compounds. On the basis of this knowledge the coagulating dip process, the use of heat-sensitive latex mixes, and the use of gelling agents have become standardized and accepted methods of manufacturing rubber goods. Most of the techniques used in rubber latex manufacturing processes have been applied to the alkaline Neoprene latices, such as Types 571 and 60. However, in the case of the gelling agents the methods normally used to control coagulation of natural-rubber latex do not always apply to Neoprene latex. An investigation was made of the effect of pH reduction on the reaction between Neoprene latex and gelling agents, and also of methods for the control of this reaction. The effectiveness of the gelling agents as coagulants arises from the delayed formation of hydrogen ions or multivalent metallic ions in the latex which these agents produce under certain specified conditions. A good example of this phenomenon is the reaction that takes place when sodium fluosilicate is added to either natural rubber or Neoprene latex. The sodium fluosilicate hydrolyzes in the latex forming sodium fluoride, hydrofluoric acid, and silicic acid. Twiss and Amphlett state that the reaction probably proceeds according to the following equation:
Exposure Cracking of Rubber
Authors: Fielding J. H. 
Published: February 2011

Abstract
Exposure cracking, sometimes referred to as sun-checking or weather checking, is a term used to describe the behavior of stretched rubber when exposed to the atmosphere under conditions which cause cracking. Cracking can occur when a rubber product under slight tension is exposed to the atmosphere or to ozone. It can occur whether the product is at rest or in motion, in sunlight or in the shade ; or whether the exposure is in the daytime or at night. Susceptibility to cracking may be different under these different conditions. In a recent very excellent and comprehensive paper by Newton, many known facts about weathering and cracking were assembled, and the theory was proposed that all cracking of stretched rubber under exposure is due to ozone. A careful distinction was drawn between this and the crazing or weathering which occurs on unstretched rubber. If, as he contends, ozone is the active agent, the term “sun cracking” is obviously incorrect, and the term “exposure cracking” is to be preferred in describing the behavior of stretched rubber when exposed to atmospheric conditions or ozone. In spite of the fact that we now consider all cracking of this type to be due to ozone, the testing of compounds for resistance to cracking is not a simple matter. The more obvious laboratory test methods disagree frequently with each other and with service behavior. It is difficult offhand to explain why a stock containing wax, which is excellent under static exposure of test strips, may be very bad as a tire sidewall ; why an inflated tire stored in the shade may crack worse than a similar tire stored in the sun ; why a tire on a parked car may crack worse than a running tire ; or why a good compound in resisting sun exposure may appear to be inferior in resisting ozone. The present work adds further weight to the new well-established ozone theory. It demonstrates clearly, however, that neither outdoor nor indoor testing is a simple matter. This work also offers for consideration new testing methods and some explanation of their meaning.
The Rheology of Processing Quality of Raw Rubbers
Authors: Mooney M. 
Published: February 2011

Abstract
After a crude rubber, such as Hevea or GR-S, has been compounded with the ingredients necessary for vulcanizing, or curing, the raw mix must be formed in some way before it is cured. This forming operation is nearly always either calendering or extruding. Naturally, it is important that the stock should take the desired form as closely as possible; but in practice it is found that elastomers are in general difficult to form. It seems to be inevitable that those materials which exhibit long-range elasticity after curing also exhibit considerable elasticity before curing and refuse, therefore, to hold their shape after a forming operation. This and other processing troubles were handled in the early history of the rubber industry simply by trial-and-error methods in the factories. Later, particularly during the last ten years, further progress in processing problems was made by introducing various plastometers and other devices for testing specific properties of the raw stock. These test methods replaced simple tests by hand and by visual inspection, and made it possible to set up specifications for some of the stock properties empirically found necessary for acceptable processing. As a final step in processing control, there are now being developed, in the industry, methods for making quantitative measurements of particular processing defects. Such methods involve a small or full-scale processing operation under standardized conditions, and a standardized procedure for quantitative evaluation of the results in terms of departures from perfection. In the present discussion of processing quality of raw stocks in the rubber industry, various specific processing defects are described, various rheological methods used for testing raw stocks are mentioned, and finally, a few experimental results are reported which show correlations between some of the rheological tests and quantitative measurements of certain processing properties.
Properties of Hard Rubber. XXI. Influence of Vulcanization Temperature
Authors: Church H. F. , Daynes H. A. 
Published: February 2011

Abstract
In previous reports the properties of hard rubber made from rubber and sulfur were studied with particular reference to the effects of varying the rubber-sulfur ratio and vulcanization time. In the present report, a continuation of this investigation, the influence of temperature of vulcanization of similar materials is studied. Materials having rubber-sulfur ratios of 65/35 and 70/30 were vulcanized in a press at three different temperatures, namely, 165°, 155°, and 135° C, the times of vulcanization employed being estimated to be equivalent to 5 hours at 155° C. As a check on the estimate of the equivalent times, small samples of the same materials were vulcanized for various shorter and longer periods and were tested for plastic yield temperature and percentage of free sulfur. The main materials were tested for the following properties by the methods described in the previous report : Combination of sulfur, density, cross-breaking strength and elongation, impact strength, plastic-yield temperature, permittivity and power factor at audio and radio frequencies, and surface discoloration in sunlight. Certain anomalous figures were obtained in the impact test results which were thought to be due to the necessity of carrying out the longer vulcanization processes in stages. Arrangements were made accordingly to conduct the vulcanization continuously in such cases. This procedure brought about a considerable improvement in the results. These results confirmed the conclusion reached in the previous report that impact strength is very sensitive to untraced variables in manufacture. The results of the permittivity and power factor tests are discussed at some length, since they afford useful information on a number of other variables, principally rubber-sulfur ratio, frequency, and temperature of test. In a general discussion of the results, the choice of the best vulcanization temperature is examined. It is concluded that the selection of the best temperature involves compromise between opposing tendencies in the different properties.
Properties of Hard Rubber. XXII. Development of Proof Impact Test for Insulating Materials. Comparison of Pendulum and Falling-Weight Machines
Authors: Dock E. H. , Scott J. R. 
Published: February 2011

Abstract
A comparison has been made of impact tests by the pendulum machine (Izod) and by the falling-weight machine (Izod and Charpy), using fabric board, paper board, molded resin (Bakelite), and ebonite, each in four types of test-pieces; unnotched, saw-cut notch, V-notch with 1 mm. root radius, and V-notch with 0.5 mm. root radius. The effect of notching on impact strength varies from one material to another, and may alter their order of merit. Saw-cut and V-notches with the same root radius nearly always give about the same results, and reducing the root radius usually (but not always) reduces the impact strength. The pendulum machine always gives higher results than the falling weight-machine in Izod tests, and the ratio varies with the material, though not sufficiently to alter the order of merit. Under the conditions used in the present tests with the falling-weight machine, Charpy tests (70 mm. between supports) nearly always give higher values than Izod tests (22 mm. striking distance), but both arrange the materials in the same order of merit. Standard errors are worked out for the pendulum test results; V-notched specimens appear to give, if anything, the best accuracy. The sources of variability in test results, and hence of errors in the final value, are discussed in an attempt to compare the accuracies of the two machines. Although an exact comparison could not be made, there appears to be no great difference between the two machines as regards the accuracy of the result obtained with a given number of test-pieces. The four types of test-piece differ very little, on the whole, in this respect. With the falling-weight machine, the Charpy test appears to give rather better accuracy than the Izod test. There is no definite evidence that the amount of excess energy in the pendulum test influences the result, except perhaps with Bakelite. The variability of all four materials tested is such that a maximum excess energy limit of 25 per cent cannot be adhered to without excluding either the weakest or the strongest specimens and so obtaining a false mean. In Izod tests on the pendulum machine a 20 mm. striking distance gives higher values for fabric board than a 35 mm. striking distance; the former has the advantage that no incomplete breaks occur, as happens with the longer striking distance. Attention is drawn to certain advantages and disadvantages of the two types of machine, and to the necessity for defining a “break” in the case of laminated materials, where cracks or incomplete breaks are frequent.
Elasticity Measurements on Polychloroprenes
Authors: Kinell Per-Olof 
Published: February 2011

Abstract
A brief survey of modern opinion as to the nature of the rubberlike state in certain high polymers is given. The behavior of unvulcanized and vulcanized rubber samples has been investigated with a Polanyi dynamometer. By means of Wall's formula for entropy changes on stretching, certain constants characterizing the samples have been calculated. The use of these constants for comparison purposes has been discussed.
Performance of Butyl Inner Tubes. Influence on Tire Life
Authors: Lightbown I. E. , Verde L. S. , Brown J. R. 
Published: February 2011

Abstract
Since the first scientific paper on Butyl rubber was presented, numerous publications have described the properties and compounding technique of this polymer. Although Butyl has been referred to as a specialty rubber, it can also be used to replace natural rubber in many applications. Butyl was found to be a remarkable barrier to the passage of gases, including air. The polymer also deteriorated very little on aging and had excellent tear resistance. Because of these properties Butyl was first considered for inner tubes, and in this application Butyl has found its largest commercial acceptance. Automobile inner tubes were first made experimentally in September, 1940. With Butyl made in the Standard Oil pilot plant this experimental work continued until April, 1943, when the first government plant began producing Butyl commercially. From that time until the present Butyl has been used successfully to manufacture all types and sizes of inner tubes ranging from bicycle tubes of 1¼-inch cross-section to earth-mover tubes of 24-inch cross-section. Butyl tubes were first used by the United States Army for service in the European war theater in May, 1944. The following month Butyl was used in essential civilian trucks; but not until September, 1945, was sufficient Butyl available for civilian automobile tubes.
Lignin for Reinforcing Rubber
Authors: Keilen J. J. , Pollak Arthur 
Published: February 2011

Abstract
Lignin, as made from the waste black liquor of the sulfate wood pulp process, is an effective reinforcing agent for synthetic or natural rubbers when incorporated into latex by the coprecipitation or master-batching procedure. GR-S, reinforced in this manner with 38.5 volumes of lignin, yields vulcanizates having a tensile strength of 2900 pounds per square inch and a tear resistance of 380 pounds per inch, values exceeded only with channel black. With 77 volumes loading the tensile strength of 2800 pounds per square inch and tear resistance of 550 pounds per inch are higher than those for any other pigment tested. In abrasion resistance lignin vulcanizates are between carbon blacks and the common inorganic fillers. Shore hardness values are close to those for channel black. Lignin-reinforced rubbers weigh appreciably less per unit volume, owing to the low specific gravity, 1.3, of lignin. The brown color of lignin permits a wide color range, without sacrifice of mechanical properties, by blending with white pigments. Lignin coprecipitates require only a brief milling time for complete mastication. Details are given on the preferred procedure for preparing master batches of lignin and GR-S. Other suggested incorporation procedures made possible by the colloidal properties of lignin are reviewed.
Dispersoidal Analyses of Hevea Latex
Authors: Hessels J. H. E. 
Published: February 2011

Abstract
For the purpose of determining the weight-distribution curve of the rubber particles in Hevea latex according to their diameter, two methods were employed, namely, photomicrographic dispersoidal analysis and sedimentation analysis. In addition to the fact, that the first method is very laborious, its precision does not prove to be high, mainly because a significant percentage of the particles is too small to be determined microscopically in the visible spectrum. Sedimentation analysis with the help of a modified pipette method according to Andreasen was found, however, to be very suitable for the purpose. By an accurate regulation of the viscosity, specific gravity and temperature of the suspension it became possible to determine the weight-distribution curve of latex to a diameter of about 0.4µ within a creaming time of 10 to 14 days, while the total percentage of still smaller particles was also determined at the same time. This method is accurate, not too laborious, and lends itself very well to a series of investigations.