bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rubber, Polyisoprenes and Allied Compounds. V. The Chemical Linking of Rubber and of Other Olefins with Phenol-Formaldehyde Resins
Authors: Cunneen J. I. , Farmer E. Harold , Koch H. P. 
Published: February 2011

Abstract
Rubber combines readily with maleic anhydride up to a limit of one molecule of the latter per isoprene unit of the former. The comparative ease of occurrence of this reaction made it seem feasible to use maleic and similar unsaturated anhydrides (or acids) as a means of linking rubber chemically with various types of hydroxylic compound, the ethylenic carbon pairs of the maleic molecules serving to form C—C links with the rubber, and the anhydro groupings to form ester links with hydroxy compounds. Although it was possible to carry out this linking process successfully in a number of examples, the combination of rubber with phenol-formaldehyde resins could be much more satisfactorily effected if the rubber-maleic anhydride compound was not preformed, but, instead, a somewhat oxidized rubber together with maleic anhydride, phenol, and formaldehyde were simply heated together until resin formation occurred. Subsequently, it was found that considerably oxidized rubber (oxygen, approximately 10–13%; M, 3000–4000) reacted more readily than slightly oxidized rubber, the product being a thermosetting resin of Bakelite type, remarkable in possessing valuable residual thermoplastic properties. Investigation of the chemical reaction by which this resin is produced has given rather unexpected results in the field of additive reactions, and has thrown new light on the process of resinification.
The Course of Autoöxidation Reactions in Polyisoprenes and Allied Compounds. VII. Rearrangement of Double Bonds during Autoöxidation
Authors: Farmer E. Harold , Koch H. P. , Sutton Donald A. 
Published: February 2011

Abstract
In Part V of this series, it was reported that a typical drying-oil ester, methyl docosahexaenoate, showed a marked increase in its capacity to absorb ultraviolet light as the result of exposure to atmospheric oxygen in the illumination of the laboratory. The rapid peroxidation of the polyene system which set in during this exposure promoted a structural change apparently of a conjugative nature. The nature of this change is now examined. Two types of unconjugated unsaturation are, however, taken into consideration: (1) the methylene-interrupted unsaturation, ⋅C:C⋅C⋅C:C⋅C⋅C:C⋅, characteristic of numerous unconjugated drying-oil acids such as linoleic, linolenic, and various polyene fish-oil acids, and (2) the more widely spaced unsaturation found in rubber and in other unconjugated polyisoprene hydrocarbons. The structural changes that ensue on oxidation are of particular interest in relation to the free-radical mechanism of olefinic peroxidation already formulated by Farmer, Bloomfield, Sundralingam, and Sutton, in which the olefin is regarded as passing through the stages:
Flex Life and Crystallization of Synthetic Rubber
Authors: Fielding J. H. 
Published: February 2011

Abstract
The crystalline structure of stretched natural rubber has been the subject of much experimental work in the past. A great deal of this has been devoted to the more theoretical aspects, such as x-ray patterns, thermal effects, and volume change. It is now known that neither Buna-N nor GR-S has a fiber diagram when stretched and that Butyl-B and Neoprene do have such patterns. Since the industry is now in the process of changing from natural rubber to GR-S, it is of interest to see just what this lack of crystallinity means from a compounding and performance standpoint. It is possible that many of our ideas based on rubber must change, that GR-S must be considered to be a new material, and that radical changes in formulation and construction must be made.
Temperature Coefficient of Vulcanization of Buna-S
Authors: Cheyney La Verne E. , Duncan Robert W. 
Published: February 2011

Abstract
Temperature coefficient of vulcanization may be defined as the increase in time of vulcanization necessary to produce a given property in the vulcanizate per unit range of temperature decrease, the latter being taken usually as either 10° F or 10° C. Coefficients of vulcanization for natural rubber stocks have been determined by several investigators. Although the data vary somewhat with the worker and with the stock investigated, the general range of temperature coefficients is close to 2.0 per 10° C. This is regarded as evidence of the chemical nature of the vulcanization reaction. The values obtained from physical test data do not always agree with those from combined sulfur analyses. This has been interpreted as an indication that the chemical reaction between the rubber and sulfur is not a simple bimolecular one, and that the rate of change of physical properties is not directly related to the rate of chemical combination of rubber and sulfur. A number of studies were published recently on the effect of variables on the vulcanization of Buna-S (now called GR-S in the United States) and on the properties of the resulting vulcanizates. In addition, compounding reports have been issued by manufacturers of rubber chemicals, as well as confidential reports submitted to the Rubber Director's office by rubber manufacturers. None of the published investigations, however, have been concerned with the determination of numerical relations among the properties of vulcanizates obtained at various temperatures. The properties of Buna-S vulcanizates differ markedly from those of rubber in certain characteristics, while possessing certain similarities in others. The only published mention of the effect of temperature on Buna-S stocks was in a release from the office of the Rubber Director, giving tables for conversion of cure to a standard temperature. These tables are based on a temperature coefficient of 1.43 per 10° F. The source of this information is not available, however.
Funtumia and Ceara Vs. Hevea
Authors: Martin G. 
Published: February 2011

Abstract
It has to be admitted that both Ceara and Funtumia have some advantages over Hevea. Neither is so exacting regarding climate, and Ceara will thrive on soil unsuitable for Hevea. Ceara has the advantage of quick growth, and Funtumia yields an appreciable amount of rubber per tapping per tree. On the other hand, both of them are difficult to tap, and the trees are easily damaged. The yield per acre is much less than that given by Hevea and the quality of the rubber produced under the best conditions is from 5 to 8 per cent inferior. The crux of the problem is to increase the yield per acre, with a corresponding reduction in tapping costs. Until this has been achieved it is difficult to believe that either tree will receive the serious attention of planters after the present emergency has disappeared.
Processes of Reclaiming Rubber and Their Relative Merits
Authors: Owen E. W. B. 
Published: February 2011

Abstract
1. A more complete reclamation is possible by the thermal and pan process than with the alkali process, and both the former effect a saving in time. 2. The thermal process calls for a higher temperature, but the after-treatment consumes less power for grinding. The pan process makes use of a lower temperature; but the expenditure of more power for grinding before and after treatment, as well as a drying period, are entailed. 3. The new products are neutral, and softer than alkali reclaim. 4. Accelerated with BA, stocks with these new types of reclaim give poor results. On the other hand, MBT offers good prospects, both for aging and acceleration. 5. Whether refined or not, the pan reclaim produced a tensile strength 95 per cent of alkali reclaim, and the thermal reclaim 80 per cent, in MBT stocks. 6. With modified acceleration, thermal reclaim stock can be made to give improved tensile properties. 7. Laboratory abrasion resistance of both new types was superior to the standard, the losses being 92 per cent and 74 per cent for thermal and pan reclaims, respectively. 8. The permanent set was lower despite the softener in the pan reclaim. 9. Despite the lack of refining, articles formed by extrusion from stocks containing thermal and pan reclaims compared favorably with those from alkali reclaim with regard to surface finish. 10. Thermal reclaim ages extremely well. Independent workers in the field of thermal reclaim have been able to exercise a finer control of the process, and a large scale plant is in course of erection as a result of the improvements effected. Further work is proceeding, and it is hoped that a product superior in all respects to alkali reclaim will be obtained.
The Retraction of Stretched Rubber
Authors: Stambaugh R. B. 
Published: February 2011

Abstract
For some time we have been making measurements of the velocities acquired by rubber strips when retracting after being stretched. The rubber band is stretched in front of two photocells, cutting off two sharply focussed light beams. When the strip is released, the beams impinge successively on the photocells, the first of which starts the charging of a condenser, and the second of which stops the charging current. The resulting voltage on the condenser is thus a measure of the time required for the free end of the rubber strip to traverse the distance between the two light beams. Retraction velocities of the order of several hundred miles per hour have been observed. To explain some of our results and to secure a more detailed picture of the mechanism of retraction, we have also taken pictures of retracting rubber strips, with a high-speed stroboscopic lamp. These seemed to be of sufficient general interest to present here.
Rheological Properties of Natural and Synthetic Rubbers
Authors: Kelsey R. H. , Dillon J. H. 
Published: February 2011

Abstract
One of the important factors determining the processing characteristics of a rubber or unvulcanized rubber stock is the “plasticity”. This term has been used by rubber technologists to define the rate at which a material can be made to flow under a set of conditions of stress, geometry, and temperature. Strictly speaking, plasticity is not a quantitative term but, because of past usage, it seems justifiable to continue to employ it as an inverse index of resistance to flow. Three principal types of instruments have been employed for measuring plasticity of rubberlike materials: parallel plate, rotating disk or cylinder, and extrusion plastometers. The parallel-plate type, like the rotary type plastometer, is designed to operate with no slippage between rubber and confining surfaces, and both operate at rather low rates of shear. The rotating disk plastometer, however, permits attainment of thixotropic equilibrium and simple calculation of the mean shearing stress at a given average rate of shear. All extrusion plastometers described in the literature have employed rather short, large bore extrusion tubes, which permit appreciable slippage between rubber and tube walls, and have operated at a constant driving pressure and temperature, the rate of efflux serving as the plasticity index. The existence of slippage, of course, eliminates the possibility of calculating absolute consistency (inverse of plasticity), but is an advantage in that factory processing conditions, where slippage is a factor, are simulated. High rates of shear of the order of magnitude of those existing in factory extruders may be readily attained with extrusion plastometers. It has been argued that high rates of shear in a plastometer are desirable from the standpoint of predicting processability, since the shear stress vs. rate of shear relationship for rubberlike materials departs radically from linearity.
GR-S, an Elastically Inverted Polymer
Authors: Braendle H. A. , Wiegand W. B. 
Published: February 2011

Abstract
To the compounder faced with the necessity of making tires of GR-S, three main problems need to be faced; (1) processing and handling, including building tack; (2) hot running of the tires on test wheel or road, and (3) heat embrittlement and flex-crack growth. Ways and means have been devised to make processing of GR-S possible, even though not so easy as with natural rubber. Laboratory investigation of the hysteresis and heat build-up characteristics of GR-S has so far followed closely the lines developed for natural rubber. These fall into distinct types. Probably the oldest are rebound tests. Rubber balls are dropped onto solid steel plates or, conversely, steel balls are dropped onto firmly supported rubber test slabs. The Lüpke pendulum employs a horizontal ram with a double V filar suspension. The pendulum with a rigid arm by which the degree of penetration of the hammer may also be determined has found wide acceptance as a means of measuring impact resilience. The damping effect on free vibration of rubber members is measured on an oscillograph or a torsion pendulum as a means of evaluating hysteresis. Much ingenuity has been shown in the various forms of flexometers which have been developed to duplicate to a greater or lesser degree the amplitude and frequency of vibration and load carrying conditions of service to predict heat build-up. These tests have two things in common. They subject the specimen to relatively low deformations, and they show GR-S to have greater hysteresis than natural rubber. Useful as flexometer tests are in predicting heat build-up of rubber when used as a shock absorber, they throw no light on the mechanism of failure of GR-S due to rapid flex cut growth. This is particularly true when these tests are carried out in the laboratory under substantially isothermal conditions and at ordinary room temperatures. The obvious reason is that the deformations induced fall far short of the strains just antecedent to rupture. The problem, therefore, demanded the study of rubber stretched nearly to rupture.
Observations on the X-Ray Structure of Rubber and the Size and Shape of Rubber Crystallites
Authors: Gehman S. D. , Field J. E. 
Published: February 2011

Abstract
In former times, we used to be painfully aware of the shortcomings and elastic imperfections of Hevea rubber. With its disappearance, we have come to think of it as having an ideal balance in physical properties for a rubberlike material which it has been difficult to approach with synthetic polymers. for this reason, it is still important to investigate the molecular structure of Hevea rubber and to try to understand the characteristics of this structure which are responsible for its physical properties. X-Ray diffraction methods can be applied to the problem of the molecular structure of Hevea rubber and a few synthetic rubbers, such as Butyl rubber and Neoprene, because crystallization occurs upon stretching. A detailed description of the x-ray diffraction results with rubber is available in a review article and need not be repeated here. It should be pointed out that the story obtained from the x-ray structure is not complete because there are important aspects of the structure which are not revealed by this means. It is not possible to measure directly the length of the chain molecules. The nature of the amorphous phase, such as the system of cross-linking of the long chain molecules on vulcanization, does not become evident in x-ray patterns. The physical properties of Hevea rubber must depend on a delicate balance of primary and secondary valence forces. The x-ray method does not permit any direct measurement of these forces but merely shows the geometrical arrangement which results from the molecular forces. Even with these limitations, much valuable information can be secured on the nature of the molecular rearrangements which occur upon stretching. Deductions can be drawn from the x-ray diffraction results regarding the form and spatial relationships of the long chain polymeric molecules and the manner in which they interact under stress. Correlations can then be looked for between the crystallization and the physical properties.
The Physical Chemistry of Rubber Solutions
Authors: Gee G. 
Published: February 2011

Abstract
The physicochemical behavior of rubber may conveniently be described in terms of two main factors, (1) its long-chain character, and (2) its chemical nature. It is frequently possible to neglect one of these; e.g., Farmer and his coworkers have shown that much light can be thrown on the organic chemistry of rubber from a study of structurally related, low-molecular hydrocarbons. In the following we shall, in the main, consider rubber as a typical member of the class of long-chain compounds, and much of this section is therefore of general application to linear high polymers.
Determination of Total and Combined Sulfur in Butyl Rubber
Authors: Rehner John , Holowchak Joseph 
Published: February 2011

Abstract
Methylethyl ketone has been shown to be a much more effective solvent than acetone for the removal of extractable sulfur and certain accelerators from Butyl rubber vulcanizates in a standard Soxhlet extraction. The use of this extraction agent, together with combustion of the original and extracted samples in the Braun-Shell sulfur apparatus, provides a satisfactory procedure for determining the amounts of total and combined sulfur in Butyl compositions.
The Testing of Rubber in Compression
Authors: Blow C. M. , Fletcher W. P. 
Published: February 2011

Abstract
With the increased use of rubber as an engineering material, considerable attention has to be paid to the characteristics of natural and synthetic rubbers in compression. For oil seals, in particular, what is loosely termed permanent set of the rubber must not be so great as to lead to breakdown of efficiency. Up to the present the need for laboratory evaluation of different rubbers for this property has been met by tests which involve measuring the dimensional changes in a test-piece subjected to a constant strain or stress for a certain time and then allowed to recover for a certain time. Although it gives some indication of behavior, this method of test suffers from the great disadvantages that the time factor is arbitrary and the change of dimension is measured, whereas in service the dimension of the rubber is maintained virtually constant by the rigid members of the system. In other words, in the case of a sealing ring on a piston working in a cylinder, the effectiveness of the seal depends, in large measure, on the pressure exerted by the rubber on the cylinder wall. As this pressure decays, so, it is believed, the sealing efficiency decreases.
Rubber, Polyisoprenes, and Allied Compounds. VII. Action of Nitric Oxide
Authors: Bloomfield George F. , Jeffrey G. A. 
Published: February 2011

Abstract
The reaction of nitric oxide with the olefins cyclohexene, 1-methylcyclohexene, dihydromyrcene, and rubber presents characteristics of a free-radical, chain reaction. In the products, the molecular ratio of combined oxygen to nitrogen is considerably in excess of 1:1, the nitrogen atom being generally directly linked to carbon. In many instances definite nitro compounds have been isolated, and a considerable part of the attack appears to proceed at the ethylenic carbon atoms, either by substitution or addition of NO2 and N2O3 groups. The precise reaction mechanism is obscure.
Properties of Hard Rubber. XIII. Experiments on Thermal Effects during Vulcanization
Authors: Church H. F. , Daynes H. A. 
Published: February 2011

Abstract
The characteristics and technical importance of the internal heating effect during the vulcanization of hard rubber, due to the exothermic reaction between rubber and sulfur, are recalled, and the conditions under which thermal instability may occur are outlined. The necessity of avoiding even slight increases in internal temperature when vulcanizing material for research purposes is emphasized. Experiments are described in which sheets of rubber-sulfur mixings of various thicknesses were vulcanized in a platen press at various temperatures, and the internal and surface temperatures were measured throughout the vulcanization period by means of thermocouples. The time-temperature curves are reproduced. The relations between internal temperature rise, platen temperature, and thickness of sheet are indicated. The choice of maximum safe thickness for a given platen temperature or of maximum safe platen temperature for a given thickness is shown to be very critical. The rise of temperature is greater in open steam vulcanization than in press-vulcanization, for a reason which is pointed out. It is important that these limiting factors in the use of high-grade rubber-sulfur materials should be taken into account in designing hard rubber articles.
Applications of Ultraviolet Spectrography a Study of the Transformations of Tetramethylthiuram Disulfide When It Functions as a Direct Vulcanizing Agent
Authors: Dufraisse Charles , Jarrijon André 
Published: February 2011

Abstract
In addition to sulfur, which is the most common vulcanizing agent, rubber mixtures usually contain various kinds of accessory ingredients, both inorganic and organic. Among the organic ingredients, some, notably accelerators and antioxidants, are present in relatively small proportions, and these are susceptible to transformation during vulcanization. However, only in rare cases has it been possible to isolate in definite form the products of these transformations, and consequently it is difficult to interpret the part played by these substances during vulcanization. Since, with few exceptions, each accelerator and each antioxidant has its own characteristic absorption spectrum in the ultraviolet region, spectrography constitutes in general an important method for following the behavior of accelerators and antioxidants. This method has been demonstrated by Dufraisse and Houpillart, who have developed a special technique for obtaining ultraviolet absorption spectra and examining them, frequently with interesting conclusions to be drawn from such analyses.
A Solution Method for the Compounding of Goldenrod Rubber
Authors: McKennon Forrest L. , Lindquist J. Raymond 
Published: February 2011

Abstract
A solution method of compounding rubber has been devised. It is particularly suitable for compounding a soft natural rubber such as that recovered from goldenrod, but it does not appear to be restricted to goldenrod rubber. No particular inherent disadvantage of solution compounding is indicated with hevea rubber. By proper choice of solvent and compounding chemicals, the interesting possibility is presented of improving the quality of those rubbers in which proper dispersion of chemicals is difficult. This method also shows possibilities of being a valuable research tool in the pretreatment of soft synthetic elastomers as a preliminary step to evaluation of their rubber-like qualities.
Comparison of the Structures of Stretched Linear Polymers
Authors: Huggins Maurice L. 
Published: February 2011

Abstract
Published x-ray data from crystalline selenium and tellurium and from stretched sulfur (amorphous), polyethylene, polyisobutylene, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, polyoxymethylene, polyoxyethylene, polyethylene disulfide, polyethylene tetrasulfide, and polyphosphonitrile chloride are compared. In most cases the experimental identity-distance in the direction of the chain axes and the expected interatomic distances and interbond angles are found to be in agreement with the assumption that the chain atoms form a regular spiral, unidirectional in each chain and of uniform pitch. Apparent exceptions are briefly discussed.