bluuebunny/crossref_metadata_2025 huggingface dataset:
The model of self-generated seismo-electromagnetic oscillations of the LAI system
Authors: Kachakhidze M. K. , Kereselidze Z. A. , Kachakhidze N. K.
Published: February 2011

Abstract. Very low frequency (VLF) electromagnetic radiation (in diapason 1 kHz–1 MHz) in the atmosphere, generated during an earthquake preparation period, may be connected with the linear size characterising the expected earthquake focus. In order to argue this hypothesis, a very simple quasi-electrostatic model is used: the local VLF radiation may represent the self-generated (own) electromagnetic oscillations of interactive seismoactive segments of the lithosphere-atmosphere system. This model qualitatively explains the well-known precursor effects of earthquakes. In addition, using this model after diagnosing existing data makes it principally possible to forecast an expected earthquake with certain precision. As a physical basis of the working hypothesis is the atmospheric effect of polarization charges occurring in the surface layer of the Earth, it is possible to test the following constructed model in the Earth's crust, where the reason for polarization charge generation may be different from piezo-electric mechanism, e.g., some other mechanism.
Chemical Unsaturation of Rubbers Vulcanized with Polynitro Compounds and Benzoyl Peroxide, and Its Possible Bearing on Vulcanization
Authors: Fisher Harry L. , Gray A. E.
Published: February 2011

STUDIES on the chemical unsaturation of ordinary vulcanized rubber show that vulcanization has caused no change in the unsaturation of the rubber hydrocarbon beyond that which can satisfactorily be accounted for by the chemical combination of sulfur on the basis of one atomic equivalent of sulfur to a C5H8 group. If such is the case with sulfur vulcanization, it becomes very desirable to know whether there is any change in the unsaturation when rubber is vulcanized with substances other than sulfur, namely, polynitro compounds and benzoyl peroxide.
Effects of Ozone on Stretched Rubber
Authors: Haushalter F. H. , Jones Webster N. , Schade J. W.
Published: February 2011

The similarity of the results obtained under various tensions in sunlight and in an atmosphere containing ozone is striking and may be significant of some progressive change in the structure of the rubber which renders it at a certain point unusually susceptible. The study here outlined is incomplete, but is presented in the hope that it may give other investigators an added method of studying problems connected with the structure or with the oxidation of rubber.
Influence of the Sulfur-Rubber Ratio on the Physical Properties of Hard Rubber
Authors: Pearsall David E.
Published: February 2011

Investigation of the sulfur-rubber ratio indicates that values below 30 produce rubber whose physical strength is too low and whose flexibility and flow under heat arid load are too great for general use. At a sulfur-rubber ratio of 45, the rubber appears to have reached a point where the physical strength is near its maximum value and the deflection is at a minimum. Thus, the compounds having sulfur-rubber ratios between 30 and 45 appear to possess all the properties that are desirable in hard rubber. It is possible to form specifications for hard rubber in which physical tests are used as requirements. Such specifications should be of more value than those which depend upon chemical tests, as they determine the strength of the rubber and the conditions under which it can be best used. Comparable results are obtained in transverse and tensile tests using both the horizontal-pendulum and vertical-floating-beam types of machine; in both cases, however, a more accurate means of measuring the tensile elongation is desirable. In the horizontal machine both cross-heads move so that the speed stated is as somewhat inaccurate; however, the stress-strain diagrams plotted this by machine are advantageous. The tensile strength test appears to give values which can be held within reasonable limits and closely checked. It is believed that when a more accurate means of measuring the tensile elongation is available this result will be of greater value. The transverse deflection is considered more reliable than the transverse strength. In the impact test, better agreement in the results was obtained from the pendulum type machine than from the falling hammer machine. Both the Charpy and Izod methods appear to be suitable. Although there is no agreement between them as to actual values, the curves (Figure 6) show similar trends. The falling hammer test for impact strength is believed to be unsuitable, as is shown by the lack of uniformity in the results. A deformation under heat test, such as Test No. 1, enables one to differentiate between rubbers of varying sulfur-rubber ratios in a comparatively short time. This test appears to be useful as a requirement in specifications on hard rubber. The softening point tests are not considered as important as the heat-deformation tests, because the temperature to which the rubber will be subjected is usually known and it is desired to find the actual deformation that takes place.
Specifications for Rubber Goods and the Value of Performance Tests
Authors: Bierer J. M. , Davis C. C.
Published: February 2011

Present specifications, including those of the U. S. Government, the railroads and the cities, are fundamentally wrong, and in spite of elaborate physical and chemical requirements not only fail to assure the purchase of satisfactory goods but actually prevent the purchase of serviceable goods in the most economical manner. The paper is an indictment of specifications of this type, and is well justified because of the recent development of performance tests and of improved methods of compounding, which warrant sweeping changes in specifications. In support of the argument that those who purchase rubber goods by specification are neither aiding nor encouraging physical and chemical developments and are not even taking advantage of what is known, recently developed tests for imitating service conditions, such as abrasion tests, flexing machines and the oxygen-aging test and such adjuncts as reclaimed rubber and antioxidants are discussed, with the inclusion of new data. All of these developments are ignored by the writer of specifications, and at present there is general confusion and extravagance in the purchase of goods. In conclusion a plan is suggested for rectifying the extravagance and ignorance now prevailing.
The Preparation of Pure Rubber from Latex by Means of Alkali, and Its Separation into Sol-Rubber and Gel-Rubber
Authors: Pummerer Rudolf , Pahl Hans
Published: February 2011

The protein in an ammonia-preserved latex was hydrolyzed with alkali for two days at 50° C. Creaming took place, and the cream was separated, treated twice with alkali, finally washed, dialyzed to remove the remaining alkali, and coagulated with acetic acid. The coagulum was extracted with acetone. The remaining highly purified product, “total rubber,” contains an ether-soluble and an ether-insoluble (or difficultly soluble) portion. It is probably a combination of this sol- and gel-rubber that gives rubber its important physical characteristics. The gel-rubber can slowly be transformed into the sol-rubber by means of certain solvents. The hydrochlorides were prepared and the reactions of the pure rubber hydrocarbon with tetranitromethane were studied. The purified rubber can be vulcanized to a soft and a hard rubber, and the latter was found to have exceptionally good electric insulating power.
New Derivatives of Rubber
Authors: Bruni Giuseppe , Gieger E.
Published: February 2011

ALTHOUGH the numerous researches of Harries, Staudinger, Pummerer and their collaborators have in recent years enriched our knowledge of the chemistry of rubber, the number of derivatives of rubber prepared up to the present is very few, and the number of atomic groups or radicals which it has been possible to introduce in the polyisoprene chain is still smaller. The reason for this is that rubber itself and its halides and hydrohalides have only a limited reactivity because of their colloidal nature and their slight solubility. Among those already known, the most interesting derivative is that obtained many years ago by C. O. Weber by the action of phenol on rubber dibromide. This was considered by Weber to be a phenolic ether, whereas Fisher, Gray and McColm have recently shown that it is a condensation product of hydrorubber and has free phenol groups.
Importance of Temperature and Humidity Control in Rubber Testing. Progress Report of the Physical Testing Commitee, Rubber Division, A.C.S. (Dated Dec. 8, 1927)
Authors: Partenheimer J. E. , Bridgwater E. R. , Cranor D. F. , Curtis E. B. , Schade J. W. , Shepard N. A. , Somerville A. A. , Vogt W. W. , Wormeley P. L.
Published: February 2011

The purpose of the work which this committee has undertaken is to determine the effect of the variables which influence the results of physical tests on rubber. The investigation has proven that variations in temperature which may occur from day to day in an uncontrolled testing room may affect the physical tests to as great a degree as a 25 to 40 per cent change in the time of cure, while relative humidity affects the results to only a minor degree. Furthermore, variations in the absolute humidity of the room in which the unvulcanized rubber is stored between the time of mixing and the time of curing may affect the tensile strength and modulus of rubber compounds to as great a degree as does the temperature after curing. It is, therefore, apparent that laboratory tests which are conducted under uncontrolled conditions of temperature and humidity may give highly erroneous results and may even give misinformation which is worse than no information at all. The committee, therefore, recommends that mixed stock prior to curing and cured stock prior to testing be conditioned for not less than twenty-four nor more than twenty-eight hours at 82 deg. F. ± 2 deg. and 45 per cent relative humidity ± 3 per cent and that the testing room be maintained at 82 deg. F. ± 2 deg. If a temperature of 82 deg. F. cannot be maintained for conditioning the mixed stock prior to curing, the committee recommends a relative humidity corresponding to the temperature used which gives an absolute humidity equal to that obtained under the former conditions. The temperature of the testing room should be controlled within the above stated limits, but it is not necessary to control the humidity of the entire room. A small conditioning cabinet in which the standard humidity is maintained has been found to be sufficient.
Conversion of Rubber into Thermoplastic Products with Properties Similar to Gutta-Percha, Balata, and Shellac. I—Methods of Preparation and General Properties
Authors: Fisher Harry L.
Published: February 2011

By heating in sheet form a mixture of rubber with approximately 10 per cent of its weight of either an organic sulfonyl chloride or an organic sulfonic acid, for several hours at 125–35° C., the rubber is converted into tough, thermoplastic products resembling gutta-percha and hard balata. If heated similarly in bulk there is a pronounced exothermic reaction and the products formed are hard and thermoplastic like shellac. p-Toluenesulfonyl chloride and p-toluenesulfonic acid are suitable reagents. A mixture of 7.5 parts of p-phenolsulfonic acid and 100 parts of rubber, under similar conditions, gives a flexible product similar to gutta-percha, which is soluble in benzene, is a very good adhesive, and is the basis of the Vulcalock process.
Factors in Processing Reclaimed Rubber
Authors: Shoaff P. S.
Published: February 2011

Production of reclaimed rubber of uniformly good physical and chemical properties is dependent first upon judicious classification and blending of raw materials. Grinding to a state in which no large particles are present, but without an excess of fines, allows a minimum devulcanizing time at a given temperature, decreases the tendency to depolymerize to an objectionable extent, and reduces the requirement for softeners. These conditions facilitate further processing to a smooth product of good quality with the desired plasticity and with optimum compounding, milling, calendering, and tubing characteristics. Devulcanization at high temperatures tends to reduce the tensile slightly and to increase the elongation as compared with treatment at lower temperatures. Alkali reclaims require efficient washing to remove residual caustic and the recovery of fines from the wash liquors involves problems of settling and filtration or screening. Drying of wet-processed reclaims at high temperatures or for an excessively long time results in tacky products, just as does over-devulcanization. A minimum amount of milling and refining at normal temperatures is desirable to preserve the quality, therefore previous processing should be thorough and uniform. Some comparisons of types of equipment are made and some desirable future developments are discussed.
Protective Paint from Rubber
Authors: Gray Harold
Published: February 2011

A protective paint has been prepared from rubber which can be used commercially. The chief features of the new paint are: (1) good adhesion to metals; (2) resistance to acids, alkalies, corrosive gases, and corrosive chemicals in general; (3) low permeability to moisture, salt solutions, salt spray, etc.; (4) the film is tough and can be bent without injury at sub-zero temperatures; (5) the film does not flake when cut, and rust spreads very slowly from an exposed area. On account of its unusual set of properties, this paint should have a wide range of usefulness, particularly in chemical and other plants where metal parts are subjected to excessive corrosive conditions.
Effect of Heat on Raw Rubber
Authors: Park C. R. , Carson C. M. , Sebrell L. B.
Published: February 2011

A study has been made of the effect of heat upon crude rubber. Heating in steam for 24 hours at 158° C. plastifies the rubber to about the same extent as about five passes through a tight mill. The chemical characteristics are changed in such a way as to indicate that a portion of the protein materials and fatty acid esters has been hydrolyzed. The rate of cure is increased in the case of most crudes for mercaptobenzothiazole and pure-gum mixes, but is less affected in the case of hexamethylenetetramine, diphenylguanidine, and ethylidene aniline. The stress-strain curve is affected by the heating in such a way as to make it more convex toward the strain axis. A study has been made of the chemical constituents of the heated rubber which have been responsible for changes in curing characteristics. It is believed that the amines, nitrogen bases, and alkaloids are the principal active material responsible for the peculiarities of heated rubber.
Preparation of Butadiene
Authors: Birch Stanley Francis
Published: February 2011

OF THE numerous methods available for the preparation of butadiene in the laboratory, those described by Thiele and by Ostromuislenskii are probably the most convenient. Both, however, suffer from the disadvantages which usually characterize operations at comparatively high temperatures; the exact conditions are difficult to find, the process is long and tedious, and finally involves the separation of the required material from a complex mixture. It has long been known that butadiene occurs in the various products obtained when oils are heated to a high temperature. Caventou first isolated butadiene in the form of its tetrabromide from illuminating gas, and Armstrong and Miller definitely established the presence of butadiene in the liquid obtained by compressing oil gas. The work of numerous later investigators has confirmed their results and has shown that the more drastic the heat treatment to which the oil is submitted the greater is the tendency for butadiene to be formed. For this reason vapor-phase cracking of petroleum, which is carried out at a much higher temperature than liquid-phase cracking, yields products specially rich in butadiene.
“Normal Aging” of Compounded Rubber
Authors: McKee Ralph H. , Depew Harlan A.
Published: February 2011

Nine compounds were chosen for an investigation of “normal aging” under various conditions and after different times of storage. The report is divided into three parts: (I) aging of cured test slabs stored under different atmospheric conditions, including wet and dry; (II) aging of rubber under strain; (III) comparative aging of cured and uncured rubber. Tables and curve sheets selected from a large mass of data are given to illustrate how these nine rubber compounds age. THE aging of rubber products is the net resultant of chemical reactions and changes of a physico-chemical nature. It has long been recognized that conditions of storage have an important influence on the normal aging of rubber products. Rubber products stored in a warm place deteriorate more rapidly than when stored in a cold place, and it probably was recognition of this fact that led to the development of the Geer accelerated-aging test, which accelerates aging solely by increasing the temperature during storage. Oxygen is also an important factor in the aging of rubber products. In normal storage the oxygen concentration varies very little, and depends only on the barometric pressure.
Carbon Blacks and Their Use in Rubber. II—Experiments in Cured Rubber
Authors: Goodwin Norris , Park C. R.
Published: February 2011

This is the second part of a study of several carbon blacks to determine what characteristics of the black are most largely responsible for imparting to rubber those properties which will make for long life in a tire tread. In Part I the characteristics of the blacks themselves as well as their behavior in uncured rubber were compared. This article discusses their action when compounded in cured rubber stocks containing various accelerators—mercaptobenzothiazole, diphenylguanidine, hexamethylenetetramine, ethylidene-aniline, litharge—and a base mix of rubber and sulfur. IN ORDER to determine what factors in the physical make-up of a given carbon are most largely responsible for the behavior in rubber which determines its suitability in a tire tread, it is essential that we should know what particular property or properties of rubber are responsible for long life in a tire tread and what measurable characteristics of rubber may be used as an index of the life of the tire tread. It has been variously held that tensile, stiffness, resilient energy, etc., are measures of resistance to abrasion. With such a wide diversity of opinion it would be obviously unwise to lay too much weight on any one property.
Plasticity Determinations in Crude Rubber. Influence of Different Factors on the Changes in Plasticity When Keeping the Rubber
Authors: de Vries O.
Published: February 2011

Rubber that contains less than the normal proportion of serum substances shows a larger increase in plasticity on keeping than the ordinary plantation product. Coagulation from latex diluted 1: 1 has a distinct effect, coagulation from latex diluted 1: 9 has a marked effect in this direction; extraction by soaking in water, or washing during milling, may have an appreciable effect. As rubber that contains all the serum substances gets harder on keeping, there must be—presumably at a content of serum substances in the region of that of normal plantation rubber—a point where the plasticity remains about constant on keeping. This proportion of serum substances may be regarded as the most desirable from the standpoint of uniformity, especially constancy in plasticity on keeping. The changes in plasticity on keeping are little influenced by the age of the trees (soft rubber from young trees changes little on keeping), by the nature of the acid (acetic or formic) and the proportion of acid used for coagulation, by mechanical treatment (rolling to sheet or crepe, milling a smaller or larger number of times), by heating during drying and by smoking. The rubber gets very weak on keeping when a large dose of sodium acetate bad been added to the latex; finely cut (not washed) pieces from matured coagulum get very weak on keeping, in contrast to crepe from matured coagulum that gets somewhat harder on keeping, about as or somewhat more so than ordinary crepe. Coagulation by heating has little influence; coagulation by alcohol seems to cause the rubber to get somewhat softer on keeping. Crepe from ammoniated latex changes about in the same way as the control from fresh latex; films from ammoniated latex evaporated in the air got very hard on keeping, just as films from fresh evaporated latex.
The Reactions of Aniline and Its Homologs as Accelerators of Vulcanization
Authors: Kimishima Takeo
Published: February 2011

The accelerating action of aniline and its homologs can be considered from two points of view. The one is whether there are exothermic phenomena caused by the accelerators and the effect of those phenomena upon vulcanization. The other is the chemical effect upon vulcanization caused by reaction products derived as a result of chemical reaction of an accelerator and sulfur. In other words, the object of consideration in the former is the effect of thermal change, while that in the latter is the effect caused by chemical change. Leaving the former for later discussion, the writer will first describe the result of his experiments concerning the reaction products of accelerators and sulfur and the effect of these products upon vulcanization. In an investigation of this kind it is extremely difficult to extract and determine the effective elements from material derived from an accelerator in the process of vulcanizing reactions of rubber. No case has yet been known where a satisfactory result was realized by such a method. Therefore, the writer has first taken up the investigations of reactions of an accelerator with sulfur and by separating and refining each of the various reaction products approached the matter of vulcanization itself, and under various conditions caused these reaction products to act upon rubber. Thus the writer has followed the plan of establishing the reaction mechanism of accelerators by seeing the changes, both chemical and physical, together with their effect upon vulcanization.
A New Tetramethylbutadiene
Authors: Macallum A. D. , Whitby G. S.
Published: February 2011

The present investigation was undertaken largely as part of a study of the influence of methyl substitution on the polymerizability of butadiene. The data available on the way in which and the extent to which polymerization is affected by the position and the number of methyl groups which may be introduced as substituents into the molecule of butadiene are far from complete. Both the a- and the b-methylbutadienes are polymerizable to rubbers. Of the dimethylbutadienes, the bg- and ad- are polymerizable; the gem-dimethyl compound appears, according to observations of Kyriakides and others, to be polymerizable, but according to a statement of Harries only with difficulty. It would appear that methyl substitution in the terminal positions of butadiene has, compared with such substitution in the middle positions, an unfavorable effect on the ease of polymerization. It would appear, further, from the limited data available, that increase in the number of methyl substituents in butadiene diminishes the ease of polymerization, since bg-dimethylbutadiene polymerizes less easily than isoprene and ad-dimethylbutadiene less easily than piperylene. The available information regarding the polymerizability of tri- and tetramethylbutadienes is very meagre. The known trimethylbutadienes (aag- and aad-) have not been studied from the point of view of polymerization. From its behavior on distillation, Pribytek considered aadd-tetramethylbutadiene (diisocrotyl) to show an inclination to polymerize, and it has been mentioned in the patent literature as polymerizable. Lebedeff, however, found it to be practically lacking in ability to polymerize when heated at temperatures up to 250. Another tetramethylbutadiene which has been described, viz., the aagd-compound, has not been studied in regard to polymerization.
Recent Scientific Advances in Connection with Guayule
Authors: Spence David
Published: February 2011

RECENT scientific advances in connection with guayule have been made along botanical and biological as well as chemical lines. The work of Dr. W. B. McCallum in definitely identifying many different varieties of guayule and subsequently propagating in California a few selected strains that best respond to intensive cultivation marks a distinct advance in the scientific development of this subject, and his successful efforts in seed selection and propagation will always stand as a monument to his skill and perseverance in this connection. His work is not only of fundamental importance in any study of the effect of environment on natural growth, but also has clearly shown that the available rubber or yield of rubber from the shrub is determined to a large extent by the variety of shrub which is cultivated. The bridge between mariola, with its three per cent of available rubber, and the best varieties of guayule as now growing in California, is apparently spanned by an almost infinite number of varieties of guayule differing in form, size, color, rate of growth, etc., as well as in their hydrocarbon content.
Sources and Application of Cooling Water
Authors: Jennings H. K.
Published: February 2011

IN the Firestone plants, the application of water for cooling purpose has progressed from year to year along the following lines. The original installation of mill rolls included a stuffing box in one end of the roll, with two 1 1/2″ holes in the end of this stationary box, one being the water inlet with a 1″ perforated standard pipe extending across the entire length of the inside of the roll. The coding water filled the entire cavity of the roll, placing it under line pressure with a drain through a 1″ pipe to the other connection in the stationary stuffing. box. This water is returned to a common header system and finds its way into the storm sewer system. This method of mill roll cooling required approximately 40 gallons of water per mill per minute, the water entering the roll at a temperature of 56° and leaving at approximately 60°, or a temperature rise of only 4° F. With this method, the difference between the temperature of the outgoing water and the stock was 85°. This method was exceedingly inefficient and used a large quantity of this scarce well water. Several years later it became necessary that more efficient means be found for cooling mill rolls. At that time the engineers designed an aluminum fin vane that extended the entire length of the inside roll cavity with a tip that forced the water directly against the inside surface of the steel roll. This aluminum vane also acted as a paddle which kept the water agitated as the roll revolved, and coming more rapidly in contact with the roll surfaces.
Chilled Iron Rolls in the Rubber Industry
Authors: Pickering N. W.
Published: February 2011

PROBABLY no single part of a machine is more vital to the manufacture of rubber products than the chilled iron roll. It is used in most operations from the cracking and washing of the crude rubber to the final accurate calendering where the variation is limited to fractional thousandths. As you gentlemen are familiar with the history and development of the rubber industry, it is not necessary to go into any details connected therewith, but it might be well to recall to your mind the fact that the vulcanizing of rubber was developed in the year 1844 at Naugatuck, Connecticut, a town located about ten miles from Ansonia, where Farrel Foundry and Machine Company was started in 1848. The discovery of the vulcanizing process made possible the practical use of rubber, and manufacturing of the product on a small basis very soon started, developing into one of the largest industries of the United States. In Mr. Farrel's diary of 1854 there is an entry regarding his negotiations with a Mr. Goodyear of Naugatuck, and finally the memorandum of agreement of sale of a three-roll 20×48″ calender for $2,400 and a four-roll 20 × 48″ calender for $3,400. The calenders were designed and built but the chilled iron rolls had to be imported from England. There were already some mills in this country which had imported chilled iron rolls for rolling copper and brass products and for calendering paper.
Open Mill Mixing vs. Internal Mixers
Authors: Crisp P. P.
Published: February 2011

AT the present time about 80 per cent of all the mixing at the Miller Rubber Company is done in internal mixers. All tires, tubes, heels and in fact all stocks with the exception of highly colored bath caps, water bottles and the like are mixed on these machines. The transition from mill to internal mixer has been gradual as there were many difficulties to iron out, both in the original mixer itself as well as in the operation. Our first experience with the internal mixer dates back to 1916 when we installed a small machine. The troubles encountered with this machine were largely due to the inability of getting rid of the heat generated during the mixing operation. In 1919 we installed the first mixer with which we mixed tire tread socks with some degree of success. Our biggest difficulty at this time was not the dispersing of the powders or pigments in order to meet gravity and tensile specifications, but was rather due to the fact that the mixed stock refused to run through the calendars and tube machines on account of being too stiff.
Dispersion of Pigments in Rubber. I—Microscopical Studies of Agglomeration and Flocculation
Authors: Grenquist Ernst A.
Published: February 2011

A literature review has been given dealing chiefly with the different factors that influence and regulate the dispersion of pigments in rubber, especially agglomeration and flocculation. Suggestions have been offered in regard to the validity of different physicochemical dispersion laws for the system rubber—pigment. The nature of agglomeration and flocculation of carbon black and zinc oxide has been described. Experimental evidence has been presented showing changes taking place in the dispersion of pigments during vulcanization. The distribution of carbon-black pigments in highly compounded treads has been discussed. The particles appear to assume a loose network formation which perhaps is an indication of the reënforcement of the system.
Carbon Black. I—A Study of Its Volatile Constituents
Authors: Johnson C. R.
Published: February 2011

The rates of evolution of gas from carbon black with variation of time, temperature, and pressure have been determined. Complete analyses have been made of five types of carbon black, which involve an organic combustion of the original sample, an organic combustion of the sample after the gases have been removed, a determination of the loss in weight represented by the gases removed, analyses of the gases removed, and finally a complete accounting, or balance, of the carbon in the steps considered. In an attempt to supply some missing information not revealed by the foregoing, some special gas analyses under varying conditions were made. The relationship between the amount and composition of volatile matter evolved from carbon blacks and the properties imparted to vulcanized rubber when compounded with these blacks has been studied.
Machine for Testing Rubber Products Used to Absorb Vibration
Authors: Abbott Franz D.
Published: February 2011

Data have been presented to show that the commonly used physical tests such as stress at break, stress at 400 per cent elongation (modulus), ultimate elongation, set at break, set after repeated stretch, and static compression-set fail to evaluate properly the resistance of vulcanized rubber to dynamic fatigue of flexure under compression, whereas flexureset as determined in a new machine (the compression flexometer) herein described does evaluate stocks properly as determined by service and dynamometer tests. Accordingly, resistance to flexure under compression (dynamic fatigue) is suggested as a much more important property of rubber products used to absorb vibration under compression than any of the above-mentioned tests.
Dispersoidological Investigations. XXIII. Contributions to the Dispersoidology of Rubber. Part I—The Structure of Jellies and of Other Coagula of Ammonia-Preserved Hevea Latex and Hevea Vultex
Authors: von Weimarn Vultex P. P.
Published: February 2011

In the course of my dispersoidological investigations of natural silk, I succeeded in obtaining it in such a highly elastic state as may truly be called a rubber-like state. However, the highly elastic state of silk is not a lasting one; sometimes it persists only for several minutes, sometimes for several hours, seldom does it last for several days and rarely in the extreme for about a week. Thus the rubber-like state of silk is a temporary state; but the high elasticity of rubber itself is also not everlasting. Evidently in both these cases there exists only a great quantitative difference in the duration of the existence of the highly elastic state under consideration. The ultramicroscopic study of the structure of separate threads of silk in different stages of their swelling, i.e., in different stages of elasticity, has led me to the conclusion that in principle it is possible to obtain in a rubber-like state such disperse systems, the component parts of which are substances quite different in their chemical composition from rubber-hydrocarbons. May the rubber-like state, under certain conditions, be a state universally possible for disperse systems composed of any substances, or not? I answer this question in the negative, because for the imparting to a system of the rubber-like state, the substances composing such a disperse system must possess special properties.
The Vulcanization of Rubber
Authors: Bacon Nicholas
Published: February 2011

Naturally it could not be expected that a work, even as important as that under discussion, would completely satisfy all opinions and objections concerning the complicated problem of vulcanization. The chief point for which there is evidence is that the sulfuration of rubber is a chemical phenomenon, and that in this reaction adsorption plays only a secondary part, or perhaps no part at all if by adsorption is meant a solution of sulfur in rubber. The work of Bacon devotes some attention to unworkable theories based on the existence of two distinct phases in vulcanized rubber, one the sulfurated compound, the other pure rubber. It is only to be regretted that the experiments do not take into account the more modern theories which have been developed and which are based on colloidal properties. It is interesting to note that the observations are not at variance with these more recent theories.
Methods of Determining Abrasion. With Particular Reference to the Relation between Road Performances and Laboratory Tests
Authors: Lambourn L. J.
Published: February 2011

Many previous papers have included descriptions of abrasion machines, but few have dealt particularly with the correlation of road performance and laboratory tests. It must be admitted in the first place that no abrasion machine, however good it may be, has yet been designed to replace road tests. None of the abrasion machines of the small laboratory type takes pattern into account, for example. Of course, there are one or two abrasion testing machines in which a complete tire is used, but they are not in favor, in view of the expense and time involved in obtaining results. Variation in Relative Road Results.—Relative road results on tread wear may be considerably influenced by external factors such as speed, road surface, front or rear wheel service, tire design, etc. In view of this possible variation in relative wear it is obviously necessary to eliminate as many of the causes as possible when comparing two tread compounds on the road. Probably the best way is to make a tire tread in two halves, i.e., one-half of the tread circumference of one mixing and the other half of another mixing; these halves joined together before curing form a perfectly sound tire. If the compounds cure at different rates, and this method cannot be employed, the best plan is to make a pair of tires of the same design and fit them, say, to the rear wheels of a car, and interchange them from near to off wheels every 500 miles. Even so, it is useless to rely on one or two tires to give the relative road results on tread wear; at least four distinct comparisons are necessary. It is not uncommon for the relative abrasion of two mixings to change during the actual course of the road test.
The Effect of Temperature on the Stress-Strain Properties of Vulcanized Rubber
Authors: Somerville A. A. , Cope W. H.
Published: February 2011

A method has been devised for testing rubber at various temperatures by putting a simple attachment onto a commercial testing machine. Wide variations have been found in the stress-strain curves on the same stock at different temperatures. The stress-strain properties at different temperatures vary for different rubbers. The state of cure causes a wide variation in tests at various temperatures. The amount of sulphur used is a factor in the stress-strain relationship at different temperatures. Successive stresses on the same piece of rubber show large decreases after the first or second stress. Stripping tests on frictions show much lower strength at 100° C. than at 0° C. Overcures are indicated prominently when stocks are tested at 100° C. Artificially aged rubber tested under these conditions shows a very marked deterioration which may be offset by anti-oxidants.
Heat Transfer in the Vulcanization of Rubber
Authors: Sherwood T. K.
Published: February 2011

Temperature lag in the heating of rubber articles is found to cause marked non-uniformity of cure in the product. The theory of “unsteady state” heat flow is discussed, and a method described for analyzing data on temperatures in rubber being heated. From data on the temperatures at different times during the heating process and on the relation between the rate of cure and the temperature, it is shown how the resulting curing effect at different points in a solid rubber object may be calculated. A new water cure process for tires is described which is very effective in reducing the non-uniformity of cure caused by the temperature lag effect, and at the same time appreciably reduces the necessary curing time.
Accurate Method for Comparison of Scorching Qualities of Accelerators
Authors: Thies H. R.
Published: February 2011

The determination of critical point curves for accelerators is of value in ascertaining their scorching tendencies. Also, the index number, defined as that increment of time at which the set-up crosses the 140 mm. “height of column” ordinate, is of value in comparing the scorching qualities of various accelerators. For accurate work the cures on the accelerators compared should be balanced at the temperature of use, and control obscuration readings should be fairly close together in their value. Stocks should be milled in as nearly the same manner as possible. For the complete history of an accelerator's behavior, critical point determinations should be made at at least two and perhaps three, temperatures, one corresponding to the milling temperature, another to the warm storing temperature of stock after it has left the mill or calender, and a third to room temperature, although the experimental results on the last named are not complete at this time. If these determinations are made, the scorching tendencies of an accelerator under actual factory use can be predicted with accuracy.
A Comparison of the Rate of Combination of Sulfur with Rubber and the Rate of Vulcanization
Authors: Bridgwater E. R.
Published: February 2011

The following general conclusions can be drawn from these experiments: 1—The low combined sulfur at correct cure which is, in general, characteristic of fast curing compounds is due both to the stiffening or polymerizing action of the accelerator and to the fact that fast curing compounds suffer less heat degradation during the cure. Some accelerators have a greater physical stiffening or polymerizing effect than others, that being the only way one can account for the difference in the rate of sulfur combination between Vulcanol and mercaptobenzothiazole, since Vulcanol which causes the combination of sulfur at a lower rate causes physical vulcanization or stiffening of the rubber at a higher rate. 2—The differences in the combined sulfur required to produce correct cure between one accelerator and another are not large as compared to the differences which result from changing the percentage of any given accelerator. 3—Accelerators differ among themselves in the benzol absorption which they impart to compounds. Neither the stress-strain curve nor the combined sulfur gives any information as to what the benzol absorption may be. The benzol absorption at any given state of physical cure depends even more upon the rate of cure of the compound than upon the accelerator used. In general, the higher the percentage of accelerator the lower is the benzol absorption. The effect of high sulfur is apparently due to the rate of cure and not to the sulfur itself because the high sulfur compounds which swell relatively little in benzol have low combined sulfur. It is indicated that oil resisting stocks should be highly accelerated but not overcured. In no case has curing beyond the point of maximum stiffness of the stress-strain curve caused a decrease in the benzol absorption. Referring to Table I, there is but little difference between the benzol absorption between 90 and 45 minute cures of either of the first three stocks. To state it another way, benzol absorption depends nearly as much upon the rate of cure as upon the state of cure. These facts should be borne in mind in compounding oil resisting stocks.
A Thermodynamic Theory of Rubber Fillers
Authors: Hock Lothar
Published: February 2011

Purely thermal measurements indicate that the physical reënforcement of rubber, i. e., the increase in the work expended in rupturing, brought about by the admixture of active fillers, depends upon the free surface energy between rubber and filler, besides a work of friction, and can be measured in absolute units. Experience has shown that the addition of so-called active fillers to rubber improves the physical properties of the latter, the work expended in breaking the rubber mixture being considerably greater than that expended in breaking the pure rubber. Furthermore, it has been found that the finer the active filler, e. g., carbon black or zinc oxide, the greater is the reenforcing effect. Obviously then the wetting of rubber and filler is the cause of the reenforcing action. In developing from these basic principles a theory of the action of fillers, the free surface energy between rubber and filler must be considered responsible for the increased work of breaking the loaded rubber. It is desirable, therefore, to find a way to determine this free surface energy. Now if a rubber-zinc oxide mixture is swollen in benzine, the rubber component swells and the zinc oxide is wet. This process is accompanied by a heat tone which can be measured calorimetrically, and which is not the sum of the heat of swelling of the same quantity of rubber and the heat of wetting of the zinc oxide when these are measured separately, but shows a distinctly different value. This difference represents the heat of adhesion of the filler and rubber. It also represents the total surface energy, and therefore is not a measure of the free surface energy to which is attributed the increase in the work of rupture.
Practical Method for Obtaining Dry Air for Humidity Control in a Rubber Laboratory
Authors: Conover F. S.
Published: February 2011

THE effect of relative humidity on rubber-testing has been the subject of much recent investigation. String-field and Conover and Depew have published papers on this subject. The last-named authors recommended that the rubber be stored in dry cabinets before milling, between milling and vulcanization, and between vulcanization and testing, at a temperature of 75° ±5° F. A short time later the Physical Testing Committee of the Rubber Division of the American Chemical Society recommended that all laboratory testing be carried out at 45 per cent relative humidity and 82° ±5°F. While both methods have undoubted merit, it was believed that for physical testing laboratories, particularly such as this one, zero humidity was both more conducive to reliable results and easier to maintain. Accordingly, equipment was installed for maintaining zero humidity and its performance has been consistently good. Since several of the larger rubber laboratories have shown interest in the equipment, it has been decided to present this description of the installation and its operation.
An Attempt at a Rational Classification of the Principal Accelerators of Vulcanization
Authors: Martin G. , Thiollet R.
Published: February 2011

AT the present time there are many accelerators on the market for the vulcanization of rubber, but it is often difficult to choose among them those best suited for a required purpose. Accelerators are often classed as slow medium, rapid and ultra rapid. These brief terms are entirely unsatisfactory for characterizing clearly the properties of these properties, and it frequently happens that two accelerators which have been placed together in one class behave in reality in very different ways and are not entirely replaceable one by the other. The object of this study is to establish a rational classification of the principal accelerators of vulcanization, which is based not only on their activity but also on their other important characteristics. The following points will be considered in their order: (1) The time required for the fixation of mixtures at different temperatures. (2) The time required to bring about vulcanization giving the maxima mechanical properties at different temperatures. (3) Aging. (4) These three points of view will be completed by a study of the plasticizing power and of the influence of different charges on the action of the accelerators.
Determination of the Iodine Number of Raw Rubber
Authors: Gorgas Adolf
Published: February 2011

In the course of an investigation dealing with the nature of the state of unsaturation of raw rubber, it became necessary to have available a precise and convenient method for determining the iodine number of raw rubber. Though iodine reacts only slowly with unsaturated compounds, chlorine and bromine form both addition and substitution products. In the substitution reactions, the hydrogen halide is evolved, and by addition of potassium iodate, e.g., in the method of MacIlhiney, it is possible to determine the hydroden halide formed and thus the quantity of halogen substituted. In all methods, however, where extensive substitution as well as addition take place, the results are variable and uncertain. Accordingly in the chemistry of fats where the iodine number is of the greatest importance, iodine halides have been used for determining the iodine number, for under certain conditions there is very little substitution. Thus Hübl, Waller and Wijs solutions contain iodine chloride and Hanus solution contains iodine bromine. The Hanus method has in fact to a great extent replaced all other methods For determining the iodine number of rubber, the Wijs method in the form in which it was modified by Kemp is probably used more than any other. In the Kemp method about 0.1 gram of rubber is swollen in 75 cc. of carbon disulfide, and is then allowed to react for 2 hours at 0° C. with 25 cc. of Wijs solution, i.e., 0.5 N iodine chloride in acetic acid.