bluuebunny/crossref_metadata_2025 huggingface dataset:
The Proöxygenic Role of Iron in the Oxidizability of Rubber
Authors: Dufraisse Charles , Vieillefosse Roger
Published: February 2011

The influence of iron on the oxidizability of rubber, though not as a matter of fact neglected in the past, has perhaps not received sufficient attention. However, the various ways in which this metal and its derivatives have caused contamination are certainly too obvious to imagine that they have passed unobserved. As is known, traces of iron can be detected in latex at the time it is tapped, and regardless of the method of treatment which it undergoes later, the rubber has an opportunity at every step in its preparation to become further contaminated with iron. Milling, calendering, and molding are carried out with iron equipment, and the ingredients used in rubber compounding may contain more or lees iron, at least as impurities, even when they are not primarily iron compounds, as is the case of certain pigments. In short, manufacturing processes, contamination by iron from ingredients, adventious causes such as iron containers for latex, dust and various other causes which need not be enumerated, all contribute to the presence of iron in rubber. Certainly then iron cannot be a very dangerous element under ordinary conditions, for otherwise its harmful effects would have been recognized long ago, and would have led to the avoidance of iron in practice, as has happened in the case of copper. Nevertheless experiments of the authors to determine why vulcanization increases the oxidizability of rubber have led to the suspicion that iron may be harmful, and a desire to ascertain the role it plays in deterioration prompted the authors to carry out the experiments which are described in the present paper. The object of the work was thus limited, and it aimed not to settle the problem of the influence of iron on rubber, but rather to investigate in a simple manner in what way iron gets into a rubber mixture, in what form it exists, and what are its harmful effects. Incidental to this, some of the observations may perhaps be of some value in current practice.
Investigation of the Aging Processes in Rubber. I. The Effect of Irradiation with Ultra-violet Light or the Surface Tension of Rubber Solutions
Authors: Dogadkin B. , Pantschenkow G.
Published: February 2011

1. Irradiation of rubber solutions in the presence of air with ultra-violet light brings about a pronounced lowering of their surface tensions at the boundary of solution and water. This lowering is connected with the formation of oxidation products of rubber, which are surface-active. 2. The kinetics of the changes in the surface tension are similar to those of the changes in viscosity brought about by irradiation of the solutions. 3. Irradiation of solutions of purified rubber in an atmosphere of nitrogen does not bring about any change in their surface tensions, as judged by the values of the minima of their isotherms. 4. These facts show that, in the absence of oxygen, light may exert an independent effect on rubber by causing depolarization of the rubber molecules and disaggregation of the micelles, which is closely related to this depolarization. In a general way, the nature of the action of light on rubber and the conditions necessary for the light to be effective are explained by the present work. In conclusion, the authors wish to express their appreciation to Professor A. A. Seide for his kindness in furnishing the samples necessary for the work.
The Russell Effect with Rubber
Authors: Rossem Avan , Hessels J. H. E.
Published: February 2011

(1) The Russell effect from raw rubber, after exposure to light and air, depends on three factors: (a) smoke components: smoked sheet shows a strong Russell effect owing to the presence of these components; Para does not because it is prepared with a different kind of smoke; (b) tackiness: most crepes show little Russell effect, but prolonged exposure after acetone extraction causes concurrent increases in both the Russell effect and tackiness; (c) acetone extract: the extract shows a strong Russell effect, but this is scarcely apparent when it is present in the rubber. (2) The gaseous products that cause the Russell effect are decomposed or driven off at 80° C. (3) These gaseous products are not the same as those formed by treatment with ozone. (4) Antioxidants for raw rubber do not affect the Russell effect, but sodium bisulfite weakens it. (5) Mastication or mixing with sulfur alone has little effect, but mixing with diphenylguanidine, triphenylguanidine or hexamethylenetetramine plus sulfur, or with mercaptobenzothiazole alone, considerably weakens the Russell effect. (6) Vulcanized rubber (normally or overcured, or oxidized by aging) shows a very weak Russell effect; this effect therefore will not detect incipient oxidation or a tendency to oxidation. (7) Quartz mercury vapor lamps are not suitable for experiments on the Russell effect, because the results are complicated by the ozone formed around them. (8) Ozone, even in very low concentrations (0.01 per cent or less), causes a strong Russell effect in both raw and vulcanized rubber.
The Electro-Deposition of Rubber on a Zinc Anode
Authors: Dogadkin B. , Sandomirsky D.
Published: February 2011

1. During the electrophoresis of rubber on a zinc anode in a weakly alkaline latex (concentration of ammonia less than 2 per cent), there is a sudden drop in the current, and as a result a diminution in the rate of deposition of the rubber. In a strongly alkaline bath, the rate of deposition remains practically constant. 2. The addition to the latex of salts the anions of which give soluble compounds with zinc diminishes to a marked degree the drop in the current strength. 3. The action of salts and alkalies is explained by the nature of the phenomenon at the anode and the structure of the film of rubber deposited. 4. The electrolytic deposition of rubber on zinc electrodes surrounded by a diaphragm of plaster or of glass takes place at a practically constant rate, irrespective of the concentration of the alkalinity in the latex. A diminution in the rapidity of the deposition of rubber still takes place upon the addition to the bath of salts the anions of which form insoluble compounds with zinc. In conclusion the authors wish to express their very deep gratitude to the Director of the Institute, Dr. L. G. Landau, for the interest which he has taken in their work.
Textile Finishes Research
Authors: Stevens H. P.
Published: February 2011

The investigation was initiated with the object of using latex or rubber dispersions as a component of the sizes used for calico printing, dyeing, and stiffening, particularly as regards retention of stiffening ingredients and fillers. Dr. Stevens had, as collaborator, in the investigation, Dr. R. Gaunt, of Manchester, and facilities placed at the disposal of the Association by a firm of Textile Manufacturers. The research assistant who worked under Dr. Gaunt's supervision also availed himself of facilities afforded by the College of Technology, Manchester. The present report summarizes experimental work carried out by the research assistant, and the following are the more important matters dealt with: The microscopic examination of latex impregnated threads is of importance in showing that latex merely penetrates between the fibers but does not penetrate the fiber itself, and that modification of the fiber surface such as by mercerization or xanthation does not result in a closer union of fiber and rubber. The basic conditions under which fabrics take up latex have been investigated and it has been shown that the method of “padding” adopted considerably modifies the results. Under some conditions latex serum appears to be preferentially absorbed so that there is a deficiency of rubber in the cloth. The loss of rubber on soaping padded cloths is a mystery which has not been solved. Much of the work has been devoted to preventing the stickiness or damp feel of latex-treated fabrics. This defect can be eliminated to a great extent by soaking the finished fabric in warm water, but such treatment would not be practicable on a large scale. A satisfactory method of eliminating stickiness has not yet been found. In some cases when tackiness had disappeared the improvement had resulted from the oxidation of the rubber. The cause of the tackiness is not known except that it is probably due to a component in the latex. Attempts to remove this from the latex as by dialysis or the use of centrifuged latex were unsuccessful. A new material made by impregnating stockinette with latex is of interest. The stretch is greatly reduced, but a strip returns after stretching and maintains a tension when stretched like elastic webbing, though to a much less extent. This product may prove useful for bandaging and similar purposes. Also the use of latex as an adhesive for joining lengths of cloth in finishing processes is under trial. Preliminary work on the treatment of cloth with colored latex has been done. This mode of producing colored finishes will require further investigation. The full report is as follows.
Effect of Temperature and Frequency on the Dielectric Constant, Power Factor, and Conductivity of Compounds of Purified Rubber and Sulfur
Authors: Scott A. H. , McPherson A. T. , Curtis Harvey L.
Published: February 2011

The electrical measurements given in this paper differ from those previously reported by the authors and by other investigators in that they were made on specimens prepared from purified rubber. The purification, which involved the removal of proteins, resins, and water-soluble salts, affected all the electrical properties to some extent, but did not alter the general character of the variation in electrical properties with composition, temperature, or frequency. The results of the present investigation afford comprehensive data on the electrical properties of rubber-sulfur compounds, and may form a basis for designing rubber compounds for specific electrical uses. They also demonstrate the inadequacy of the simple numerical coefficients that are sometimes employed to evaluate the changes in the electrical properties with temperature and frequency. A discussion of the results from the standpoint of modern dielectric theory is not included in the present paper, but is contemplated for a separate paper.
Effect of Temperature on Tensile Properties of Vulcanized Rubber
Authors: Somerville A. A. , Russell W. F.
Published: February 2011

The tensile properties and tear resistance of a large number of commercial inner tubes, before and after aging by different methods, are studied at 0°, 25°, and 100° C. A number of uncured bus-truck tube stocks are also studied from the point of view of their capacity to withstand high temperatures. The effect of testing rubber at 100° C. as compared with room temperature is discussed; how some compounds collapse at 100° C., while others have tensile properties equal to, or better than those at 25°, is shown. The effect of testing artificially aged specimens at 100° C., as well as at 25° C., is discussed; the high-temperature test may reveal conditions of deterioration and overcure that are not noticeable in the 25° tests. The compounding and curing conditions that lead to high tensile properties at 100° C., as well as those which cause inferior quality, are discussed.
Physical Properties of DuPrene Compounds
Authors: Bridgwater E. R.
Published: February 2011

Although DuPrene differs chemically from natural rubber, it bears a closer physical resemblance to rubber than any of the previously known synthetic rubbers. It differs from natural rubber in many respects which makes it more suitable for certain purposes and less suitable for others. Its physical properties are susceptible of wide variation depending on the nature and amounts of vulcanizing agents, reënforcing pigments, etc., that are compounded with it, and it tills the need for a rubber-like material having greater resistance to the action of oils and solvents and greater resistance to the deteriorating influences of heat and oxidation than natural rubber.
Research on Modified Rubbers. Part III. Adhesive Latex (b) Characteristics of and Tests on Sticky Latex
Authors: Schidrowitz P.
Published: February 2011

In the course of an investigation on the oxidation products of dry rubber and of latex, the reaction of latex with hydrogen peroxide was studied. One result of this work was that a latex possessing distinctive adhesive or sticky qualities was prepared, and it is believed that the so modified latex may prove to be of commercial interest. It is proposed, for the sake of brevity, to refer to this product as “sticky” latex. Attention was first drawn to the apparent advantage of “sticky” latex as a result of difficulties which arose in connection with the problem of making a good joint between leather and a certain type of rubbered fabric. The latter was coated with rubber cement, according to the well-known practice, and the leather treated with latex. Using “ordinary” 36 per cent latex, 60 per cent concentrated (by centrifugation) latex, ditto diluted to 36 per cent, 70 per cent concentrated (by evaporation) latex, and ditto diluted to 36 per cent, the results were not as satisfactory as was desired. “Sticky” latex was then tried and found to give distinctly better results. The process of handling was facilitated and a joint was obtained which could not be broken without tearing the fabric, and which, moreover, resisted the action of fresh and sea-water acting over a period of several days. When using a self-curing rubber cement on the fabric, it was found that whereas the joints made with the standard varieties of latex mentioned tended to open up (unless constant pressure was applied prior to the completion of the vulcanization stage), this undesirable effect did not take place when “sticky” latex was employed. The readiness with which surfaces treated with “sticky” latex adhere to one another, and the fact that prolonged pressure is not necessary to obtain good results, should be of considerable practical importance in certain classes of work. Another advantage is that if a piece of material has been applied in a wrong position, making an adjustment necessary, the broken joint may readily be remade when “sticky” latex has been used. The other fabrics tried do not possess this property to the same degree, and if a joint made with these is pulled apart, the surfaces do not readily adhere again.
Research on Modified Rubbers. Part IV. The Oxidation of Rubber with Aqueous Hydrogen Peroxide-Acetic Acid Mixtures
Authors: Bloomfield G. F. , Farmer E. H.
Published: February 2011

Mair and Todd (J. Chem. Soc., 1932,, 386), in extending the earlier work of Robertson and Mair (J. Soc. Chem. Ind., 46, 41T (1927)), studied the interaction of a chloroform solution of purified rubber with concentrated hydrogen peroxide (100 vols.) dissolved in glacial acetic acid; by this means they obtained a non-acidic substance of the empirical formula C50H92O16, which was unsaturated toward bromine and permanganate, and was considered to have all its oxygen present in the form of hydroxyl groups. Other workers have reported that when peracetic acid dissolved in glacial acetic acid is used in place of the hydrogen peroxide—acetic acid mixture, the products of reaction are acetylated derivatives of rubber (British Patent 369,716). These acetylated derivatives are stated to be obtainable either from solid rubber or from solutions of rubber, but no evidence as to their constitution has been advanced. Now the oxidative degradation of rubber is of considerable interest from two points of view: first, with regard to the light which it may throw on the size, structure, homogeneity, and normality of chemical behavior of the molecules of rubber; and, second, with regard to its efficacy as a means of transforming rubber into derivatives of similar or smaller molecular weight, capable of useful application in industry. The very careful work of Mair and Todd has gone far to show that hydrogen peroxide under the conditions of their experiments attacks the unsaturated centers of the rubber molecule and effects more or less complete hydroxylation of the carbon chain; at the same time it brings about a considerable degree of degradation of the molecule. The product of Mair and Todd, however, is produced under rather restricted conditions of reaction and the reagents employed are costly; consequently the extent to which the character of the product can be modified (i. e., by controlling the degree of degradation, hydroxylation, and acetylation) is left undetermined, and the possibility of producing useful materials at a reasonably low cost by modifying the conditions of reaction and the form of reactants is left unexplored. On the other hand, the employment of peracetic acid as an oxidizing agent, though offering a theoretically elegant way of effecting hydroxylation or acetoxylation at the unsaturated centers of the rubber molecule, is not without drawbacks: the preparation of the reagent is expensive and on a large scale dangerous; moreover, in spite of the fact that it is claimed to be employable either with solutions of rubber or with solid rubber, its reaction with rubber is so vigorous that the prospect of exercising any effective control over the extent of degradation or degree of hydroxylation (acetoxylation) is greatly diminished.
Isoprene and Rubber. Part 41. The Hydrogenation of Rubber and Balata
Authors: Staudinger H. , Leupold E. O.
Published: February 2011

Viscosity measurements of dilute solutions of rubber and of balata led to the following values for the size and form of the molecules of these hydrocarbons. It is therefore not a question of definition whether the particle sizes shown above are to be regarded as the molecular or the micellar weights of these substances, for here the concept of molecular weight has the same significance as in the case of lower molecular substances, i. e., the molecule comprises the sum of all atoms combined by normal, i. e., homopolar atoms. The only difference between low and high molecular substances is that low molecular substances are composed of molecules of uniform size, whereas high molecular substances are a mixture of homologous polymers, so that the values above refer to average molecular weights. These results, which explain the nature of colloidal solutions of rubber, are at variance with the views of most investigators of colloids, who ascribe a micellar structure to the rubber particles, and in this way explain the property which rubber has of forming colloidal solutions. This makes clear why until very recently explanations of the constitution of rubber have been open to question among these particular investigators themselves. In order to lend further support to our opinion, the reduction of rubber and balata and low molecular homologous polymeric hydrocarbons was undertaken from certain points of view, as shown in the work which follows.
Natural and Synthetic Rubber. XII. Reversible Vulcanization, by Organo-Metallic Derivatives
Authors: Midgley Thomas , Henne Albert L. , Shepard Alvin F.
Published: February 2011

Rubber has been vulcanized with organo-metallic compounds; this vulcanization has been reversed, then repeated. An interpretation of the experiments is proposed and the bearing on sulfur vulcanization is pointed out.
Natural and Synthetic Rubber. XIV. A Structural Formula for Ebonite
Authors: Midgley Thomas , Henne Albert L. , Shepard A. F.
Published: February 2011

A formula for ebonite has been proposed, where sulfur is linked to a carbon atom bearing a methyl group on the one side and to the next third carbon atom of the rubber chain on the other side This formula is based on a consideration of the pyrolysis products of ebonite.
Plantation Studies of Crude Rubber Variation
Authors: Sackett George A.
Published: February 2011

1. A comparison of the results of the present work with that of previous investigators shows that certain natural and processing variations have the same effect on a Captax-accelerated stock as they have on a rubber-sulfur stock. 2. In attempting to produce a uniform sheet on a plantation the following points should be remembered: Latex should be blended so that the effect of the tapping system is minimized. Latex should be brought to a standard dry rubber content before coagulation. The anticoagulant and coagulant must be carefully controlled as to quality and quantity. The length of time between acid addition and rolling should be carefully standardized. The rolling equipment should be sturdily constructed and the rolls so fixed that they cannot be easily changed. The temperature of drying should be so fixed that it is always the same and at such a point that fuel consumption is at a minimum. 3. The causes of variation are so many that unless everything is held absolutely constant, the product may vary in rate of cure as much as if nothing is done in the way of standardization. 4. While it is conceivable that a plantation may produce a uniform product for a short space of time through careful supervision, no amount of care in processing can entirely overcome the seasonal variation, or the variations due to rainfall and wind. It is not probable, however, that all plantations will be able to produce a material with the same rate of cure as all the others, for they must overcome variations caused by climate and geographical location as well as those caused by different types of all the manufacturing equipment of all kinds. The consumer of crude rubber must bear the burden of eliminating most of these variables by blending the crude rubber just prior to use, for only at that time does the rubber accumulate in such a way that blending is economical.
Iodine Value of Rubber and Gutta-Percha Hydrocarbons As Determined by Iodine Chloride
Authors: Kemp A. R. , Mueller G. S.
Published: February 2011

HALOGEN absorption methods employing solutions of bromine, iodine bromide, or iodine chloride are widely used for determining the unsaturation of organic compounds. In the use of these methods the choice of halogen reagent, the amount employed, and the time and temperature for the reaction are all important factors which must be given careful consideration in order that the best results may be obtained. Certain structural differences in unsaturated organic compounds may have a decided influence on the reactivity of these substances toward halogens. For example, the presence of negative groups on one or both of the unsaturated carbon atoms protects against halogen addition; thus maleic or fumaric acids do not add iodine chloride (7). Styrene adds iodine chloride quantitatively, but in the case of cinnamic acid only a slight reaction takes place (4). No addition of iodine chloride occurs with dichloroethylene and very little with vinyl bromide (3). The authors have found that polyvinyl chloride (DuPrene) adds iodine chloride to only 30 per cent of theory. A triple-bonded compound, such as diphenylacetylene (4), shows only partial addition of iodine chloride, as would be expected from the negative effect of the first additive halogen. The unsaturated terpenes vary widely in their reactivity with halogens, extensive substitution occurring along with addition (5), particularly in the case of pinene. Aside from these complications, however, numerous investigators have shown that one or more of the halogens add quantitatively to a wide range of unsaturated hydrocarbons, acids, glycerides, alcohols, esters, etc. Of the many methods proposed the well-known Wijs procedure involving the use of 0.2 N iodine chloride in glacial acetic acid has been widely used and accepted.
Rubber. XVIth Communication. The Method of A. R. Kemp for the Determination of the Iodine Number of Rubber
Authors: Pummerer Rudolf , Stark Hermann
Published: February 2011

In a communication of Pummerer and Mann in 1929 on the determination of the iodine number of rubber by means of iodine chloride in chloroform solution, Fisher and Gray were erroneously mentioned as the originators of the method, because of the fact that these authors were the first to publish the method in accessible form. The fact was overlooked that Fisher and Gray state in a footnote that the method was not their own but was that of A. R. Kemp of the Bell Telephone Laboratories. We are greatly indebted to Kemp for calling to our attention the error, which also appears in our XIVth Communication. The first paper of Kemp on the subject appeared a year later, and contains precise information. Kemp worked with a solution of iodine chloride in glacial acetic acid and a solution of rubber in carbon disulfide at 0° C., and as long ago as 1927 he showed that rubber obtained by extraction of crepe with petroleum ether (b. p. 35–60° C.), and precipitation with alcohol according to the method of Weber, Caspari and Feuchter, gave very satisfactory iodine numbers of 99.43–99.76 per cent of the theoretical value. At 15–20° C. disturbing effects of substitution occurred.
The Impact Resiliometer
Authors: Lüpke Paul
Published: February 2011

Original Purpose The writer's first conception of an instrument for quickly measuring the resilience of rubber samples arose in connection with the basic idea for and development of the present A.S.T.M. hardness tester, in an endeavor to provide a reproducible means of measuring and expressing those properties of rubber compounds superficially apparent to the average user. It seemed that if the resistance to pressure (indenting or flexing) and the pressure, or force, of recovery, of a sample were duplicated, the article produced would “feel” the same as the sample, and under normal conditions of use would act mechanically the same. Nature of Problem This problem of measurement, as is generally known, is complicated by the time-hysteresis characteristic of vulcanized rubber compounds, arising through a dual nature, and causing them to manifest both elastic and plastic properties. Any instrument which applies load momentarily measures the almost purely elastic properties, while one which applies a more or less sustained load measures elastic properties modified by the material's partially plastic nature. These ideas are expressed from commercial and industrial viewpoints without regard to their possible deviations from the strict definitions accepted in physical science.
The Degradation of Rubber Solutions
Authors: Bary P. , Fleurent B.
Published: February 2011

From the beginning of our experiments we have called attention to the fact that the character of the degradation varies nit only with the prevailing temperature but also with the solvent used. In particular, if one compares the solutions obtained by the degradation of a given rubber (pale crepe) at a concentration of 0.02 in aromatic hydrocarbons, it is found that the color of the solution changes in the following way: In benzene at 80° the degraded solution remains colorless. In toluene at 93° the degraded solution becomes golden yellow. In xylene at 138–140° the degraded solution becomes dark brown. In cumene at 150–155° the degraded solution becomes brown-yellow. The temperature takes part in these changes through a pyrogenic action which in the case of xylene, can easily be detected by the odor, but this is not the only cause since cumene, used like xylene at the boiling temperature, gives a much lighter solution than would have been expected, and there is no pyrogenation or only a very slight one. Moreover, it is observed that when the degradation has reached a sufficiently high point, coagulation of rubber by the addition of alcohol or of acetone becomes impossible, and sometimes a very stable emulsion is formed, but the part emulsified does not represent anywhere nearly the total quantity of rubber, since the latter has been converted to a great extent into a form soluble in acetone. If the solution is evaporated by a method which makes possible a determination of the rubber it contained when it was not degraded, the quantity found after evaporation is very much less than that which should be present, and furthermore the product obtained is in a pasty state, almost liquid and gluey, as rubber would be if it had turned to a fatty condition.
The Formation of Sulfur from Hydrogen Sulfide and Sulfur Dioxide. A Contribution to the Vulcanization Process of Peachey
Authors: Hock Lothar , Schmidt Hans
Published: February 2011

In the reduction of sulfur dioxide by hydrogen sulfide, the course of the reaction depends wholly upon whether water is present or the gases are dry. With water present, there is a ready separation of sulfur, even at room temperature, according to the general reaction: SO2+2H2S→3S+2H2O, though accompanied by more complicated reactions involving the formation of polythionic acids. On the contrary at room temperature the dried gases do not react, and only at elevated temperatures do they give rise to sulfur and water vapor, in which case because the reaction is exothermic the equilibrium is displaced more and more toward the original sulfur dioxide and hydrogen sulfide. Conversely then, the formation of free sulfur is favored by lowering the temperature. The heat of activation of the reaction is however so great, even at room temperature, that the rate of the reaction is imperceptibly small, and accordingly no reaction is observable. In the presence of rubber, on the other hand, conditions are extremely favorable for activation, because the rubber hydrocarbon plays the part of an acceptor of the liberated sulfur and is vulcanized by it, as Peachey and Skipsey were able to show in their well-known work. The question then arises whether, in this form of vulcanization, the water which is already present or which is formed plays a decisive role in starting and continuing the reaction (in which case the formation of polythionic acids might also play a part), or whether the essential reaction takes place between the two gases in the dry state, in which case the reaction progresses in a much more unrestrained way than in the absence of substances which activate the reaction. In view of this, two series of experiments were planned with the object of obtaining a better insight into the reaction. In one series the rate of the reaction with both gases in the dry state was studied by some trial measurements only; in the other series the part played by moisture in vulcanization by the Peachey process and in the vulcanization of rubber swollen in benzene was investigated.
The Testing of Rubber and Rubber-Like Materials for Oil-Resistance
Authors: Hayden O. M.
Published: February 2011

The technic of testing the oil-resistance of rubber and rubber-like materials is less accurate than that for many other qualities. It is impossible to obtain exact measurements of the most significant changes that occur during immersion in a swelling medium. The problems facing testing engineers are to develop observation and manual tests which will supplement machine tests, to develop accelerated tests that can be correlated with service conditions, and to interpret test results in values which will demonstrate the performance of these products in oil or solvent service.
Selection and Use of Age Resistors in Rubber Compounds
Authors: Crawford Richard A.
Published: February 2011

THE early development of the rubber industry was handicapped by two serious defects in rubber articles. They were not stable to temperature changes, and they deteriorated rapidly with age. Although the process of vulcanization corrected the first difficulty, rapid deterioration with age was common until the discovery of certain organic accelerators, such as p-aminodimethylaniline, the aldehydeamines, and mercaptobenzothiazole. Prior to these discoveries a number of materials had been patented for the purpose of improving the age-resisting properties of rubber, but many of them were of little merit and most of the others possessed some accelerating value, a fact which was not appreciated at the time. Typical of the more useful early patents for age-resisting materials are American patents by Murphy in 1870 (15), Moore in 1901 (14), and Martin in 1922 (12), and the German and English patents of the Ostwalds in 1908 and 1910 (19, 20). Murphy patented phenol, cresol, and cresylic acid, either added to the uncured stock or as dipping solutions for vulcanized articles for the purpose of improving their resistance to aging. Moore used reducing agents, including hydroquinone, pyrogallol, and p-aminophenol hydrochloride, to preserve the adhesive properties of rubber cements. Martin suggested aniline and other organic bases as a surface treatment for vulcanized articles. The Ostwalds also recognized the beneficial effects of aniline on rubber and stated that it could be added at any convenient stage of manufacture. (It is interesting to note that these inventors considered that addition of aniline to uncured stock or dipping the cured article in aniline were equivalent, and they, therefore, evidently did not recognize the accelerating effect of aniline.)
Relation of Volume Change to the Mechanism of Rubber Vulcanization
Authors: Williams Ira
Published: February 2011

The present investigation shows that no direct relation exists between either combined sulfur or density and the degree of vulcanization. It is not probable that the various changes in physical properties of the rubber during vulcanization are due to changes in the polymeric state involving a change in primary valence forces. Neither is it apparent in what manner combination of sulfur has contributed directly to the change in physical properties of the rubber. It is probable that the change in physical state is due to a change in manner or degree of aggregation of the rubber molecules.
Measurement of Quality in Rubber Goods by Physical Tests
Authors: Carpenter Arthur W.
Published: February 2011

THE expression “measurement of quality” as applied to rubber goods seems at first thought to be quite definite; unfortunately, it conveys to different persons widely divergent ideas. Engineers in dealing with various materials often interpret the word “quality” as being synonymous with strength. Such usage is quite common in the rubber industry, and stocks possessing high tensile strength may be designated as high quality. A rubber compounder, on the other hand, may consider the quality of a rubber compound to be related to the percentage of pure rubber contained in the mixture. Thus, compounds having only small amounts of other materials added to the rubber would be considered high grade though they might be inferior in strength. Purchasers of rubber products have in the past shared both of these viewpoints, but today the more enlightened consumers understand the expression “high quality” to indicate the relative excellence of an article in performance of the intended service. This seems a more rational interpretation since, in the last analysis, satisfactory service is the prime objective and may or may not be affected by either great strength or high rubber content.
Thermal Properties of Rubber Compounds. II. Heat Generation of Pigmented Rubber Compounds
Authors: Barnett C. E. , Mathews W. C.
Published: February 2011

THE first paper (1) of this series discussed thermal conductivity of rubber and a number of compounding ingredients which were measured using the electric current as the source of heat. In this article the fundamental factors controlling the generation of heat and the variations possible by pigmentation are being studied. Results obtained for pigmented rubber in the pendulum and flexometer will be discussed and correlated. In the writers' laboratory two machines have been used extensively in studying the temperature developed in rubber compounds subjected to distortion by compressive forces. The first of these is a flexometer described by Cooper (2), and the second a compression machine in which a rubber block 14 cm. (5.5 inches) in diameter and 9.53 cm. (3.75 inches) high is pounded with a definite load a specified number of times per minute. The laboratory test block used in the flexometer is in the shape of a frustrum of a rectangular pyramid, of which the base is 5.4 × 2.86 cm. (2.126 × 1.125 inches), the top 5.08 × 2.54 cm. (2 × 1 inches), and the altitude 3.81 cm. (1.5 inches). This block of rubber is compressed between two plates under definite load, one of the plates being stationary while the other travels in a circular motion of definite magnitude. After the sample has been placed in the machine, the moving plate is set to one side of the center. Both the loading and the amount of offset may be varied within wide limits. With this machine one may study either the temperature developed over a period of flexing or the time required to compress the sample a predetermined amount.
The Structure of Unstretched Rubber Based on Studies with Electron Rays
Authors: Bruni G. , Natta G.
Published: February 2011

It is known that the x-ray examination of rubber at the ordinary temperature and in the unstretched state gives photographs which are similar to those of liquids, while a crystalline structure is obtained only if the rubber is stretched or frozen. In the first case, in order for a fibrous structure to be visible, it is necessary to stretch the sample to elongations corresponding to different multiples of the initial length (up to 9). The presence in rubber of filiform molecules of extremely high molecular weight has already been demonstrated by Staudinger as a result of studies on the properties of solutions of some of its soluble derivatives, and it was likewise proved that the linking of the isoprene groups into chains takes place through bonds corresponding to the principal valences. X-ray analysis has confirmed these hypotheses. The identity period along the axis of the fibers of stretched rubber, first determined by Katz and by Hauser and confirmed by measurements of Mark and Susich on highly oriented preparations, is in fact 8.1 A. U., a length which corresponds to that predicted for a chain of two isoprene groups with cis-configuration.
Heats of Combustion of Rubber and of Rubber-Sulfur Compounds
Authors: Jessup R. S. , Cummings A. D.
Published: February 2011

The work described in this paper is part of a series of investigations at the National Bureau of Standards to determine the properties of purified rubber and of compounds of purified rubber and sulfur. Values of the heat of combustion of rubber have been reported by a number of observers, and values of the heat of combination of rubber and sulfur, determined as the difference in the heats of combustion of vulcanized and unvulcanized rubber-sulfur mixtures, have been reported by several observers. The results obtained by the various investigators are not in satisfactory agreement. The values reported in the literature for the heat of combustion of rubber vary over a range of about 4.5 per cent, and the two recent sets of data on the heat of combination of rubber and sulfur differ radically, as may be seen from Fig. 2. It was thought that these differences might be due, in part at least, to differences in the composition of the rubber, and that more consistent results might be obtained by using purified rubber. The data presented in this paper were obtained on samples of purified rubber and on compounds of purified rubber and sulfur prepared in connection with an investigation of the electrical properties of rubber and rubber-sulfur compounds by Scott, McPherson, and Curtis.
Studies on the Nature of the Action of Organic Accelerators for Rubber Vulcanization. X. The Action of Organic Acids on Rubber Sols
Authors: Shimada Keiichi
Published: February 2011

In continuation of the previous communication, the author has examined the influence of small amounts of organic acids, such as butyric, valeric, propionic, chloroacetic, bromoacetic, p-bromobenzoic, and o-iodobenzoic acids, on the viscosity of dilute benzene-rubber sols. The results are briefly summarized as follows:
Adsorptive Properties of Carbon Black. A New Angle
Authors: Barron H.
Published: February 2011

(1) A new method has been developed for quantitatively determining the adsorptive properties of finely divided fillers, whereby advantage is taken of the partition coefficient of solutes between immiscible solvents. If carbon black is shaken with a mixture of polar and non-polar solvents (e. g., benzene and water) the carbon black is always retained in the non-polar layer after separation. The behavior with other fillers has been investigated. This phenomenon has made it possible rapidly to determine the amount of iodine, benzoic acid, or phenol adsorbed by carbon black from the two phase liquid system by titration of the aqueous layer after equilibrium has been reached. A knowledge of the partition coefficient then enables the adsorption from the non-polar liquid to be readily calculated. (2) The adsorption isotherms for carbon black, degassed carbon black and heat-treated carbon black have been investigated, employing this technic. (3) Since the partition coefficient of a solute between immiscible liquids is unaffected by the presence in either liquid of a substance insoluble in the other phase, the method developed can be used to investigate the effect of dispersed rubber, sulfur, etc., upon the adsorptive properties of the filler. Sulfur and stearic acid were found to have a negligible effect upon the absorptive power of carbon black for phenol benzoic acid, and iodine; whereas the presence of 1 per cent rubber in the benzene phase greatly reduced the ability of carbon black to adsorb the first two of these substances. This action of rubber in depressing adsorption also occurred in the presence of sulfur and stearic acid, and suggests powerful adsorption of rubber upon the surface of carbon black.
Bioreactors for Bone Tissue Engineering
Authors: Carpentier Benoît , Layrolle Pierre , Legallais Cécile
Published: February 2011

Bone tissue engineering is a promising solution for patients with bone defects that require reconstruction. This regenerative therapy consists in culturing osteogenic cells on a biodegradable substrate to obtain a bio-hybrid construct that will stimulate bone healing after implantation. This multidisciplinary technology nevertheless requires further development before it can become routine clinical practice. One challenge is to achieve three-dimensional seeding and osteogenic commitment of mesenchymal stem cells on biomaterials under sterile and reproducible conditions. For this purpose, different dynamic culture systems have been developed. This paper reviews recent advances in the field of bioreactors for bone tissue engineering. The purpose of such systems is to improve nutrient delivery to the cells and generate shear stress that may promote cell differentiation into osteoblastic phenotypes. A brief overview of the value of computational fluid dynamics for understanding the cell environment is also provided. Finally, some proposals are made regarding the use of bioreactors as safe and controllable devices that will help commit cells and biomaterials for the regeneration of bone tissue.
Industrial Hygiene: Retrospect and Prospect—Hippocrates to Nanotechnology
Authors: Pendergrass John A.
Published: February 2011

Industrial hygiene has been acknowledged as the art that control the conditions, which arise in or out of the work place and may adversely affect the health and well being of workers or the environment. In the past fifty years many scientific societies have been established and Hippocrates to nanotechnology represents great deal of concern for developing the direction of the future of industrial hygiene. In just the past seventy years industrial hygiene has, in the public mind and the future for the profession is found to be very promising. The present study addresses that contribution of the industrial hygienists is continue to be challenging, exciting and a very useful for the mankind.
Man‐Made Mineral Fibers
Authors: Singh Jaswant , Wagner Andreas
Published: February 2011

Man‐made mineral fiber (MMMF) asbestos substitutes are mineral fibrous materials such as fibrous glass, rock wool, slag wool, and refractory (ceramic) fibers. It has been reported that the chemical composition and morphology of these substitute fibrous materials are similar to those of asbestos and, therefore, serious questions have been raised about their health hazards. The man‐made mineral fibers have found wide applications in commerce and in the building industry. Evidence from epidemiological studies have shown that exposure to MMMF has moderately increased mortality rates and much less carcinogenic risk when compared to asbestos. It is prudent for industrial hygienists to treat these materials with the same precautions as asbestos and minimize the exposure among workers.
Ionizing Radiation
Authors: Cember Herman , Johnson Thomas E.
Published: February 2011

The discovery of radiations has opened new fields of scientific investigation and uses of radiation. Many sources of information have been used to analyze the harmful effects of radiation and this lead to the formation of the scientific basis for radiation safety standards. Occupational exposures that are within the radiation safety guidelines have not resulted in harmful effects. Ionizing radiation and radioisotopes are used safely today in industry, science, and medicine because of the vast amount of knowledge about radiation physics and biology. This vast amount of dose–response data has enabled health physicists and industrial hygienists to control the radiation environment in the workplace so that no harmful radiation effects are seen. This chapter focuses on sources of radiation and safety assessment.
Control of Biohazards
Authors: Heinsohn Patricia A.
Published: February 2011

The present study addresses the need for industrial hygienists and other health and safety professionals to recognize that specific occupational biohazards across a variety of work settings are coupled with the need to effectively control occupational exposure to biohazards. Because various guidelines and regulations for biosafety apply to laboratory and health care settings, control techniques in these settings have been presented. However it has been found that the typical industrial hygiene approach to evaluating an airborne chemical hazard by air sampling for the contaminant during an industrial process is generally not applicable to evaluating a potentially infectious biohazard.
The History and Biological Basis of Occupational Exposure Limits for Chemical Agents
Authors: Paustenbach Dennis J. , Cowan Dallas M. , Sahmel Jennifer
Published: February 2011

The history and biological basis of occupational exposure limits (OELs) for chemical agents and various mathematical formulae or models for adjusting OELs have been discussed in the present study. Over the past 60 years, many organizations in numerous countries have proposed occupational exposure limits (OEL) for airborne contaminants. Cook has reported that the earliest efforts to set an OEL are directed at carbon monoxide (CO) and Kobert published one of the earlier tables of acute exposure limits. Baetjer has reported that the rst list of standards for chemical exposures in industry in the U.S. is known as Maximum Allowable Concentrations (MAC) and these have been prepared in 1939 and 1940. The American National Standards Institute (ANSI) has developed its rst Standard‐carbon monoxide, with an acceptable concentration of 100 parts per million (ppm). Cook has published a list of 132 industrial atmospheric contaminants with MACs. The airborne concentrations in major corporations in the United States have been reported to be further lowered to mirror the anticipated changes in either the ACGIH TLVs or the OSHA Permissable Exposure Limits (PELs).
Biological Monitoring of Exposure to Industrial Chemicals
Authors: Berode Michèle , Droz Pierre‐Olivier , Guillemin Michel P.
Published: February 2011

Human biological monitoring is becoming a powerful tool for scientists and policy makers to assess and manage the risk of exposure to chemicals both in the general population and at the workplace. Absorption, distribution, metabolism and excretion of chemicals constitute the fundamental bases to derive relevant biomarkers. This chapter will focus on the occupational environment keeping in mind that biological monitoring in humans is a very actual issue in public health politics, in environmental medicine and in science in general.