bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical Testing of Synthetic-Rubber Products
Authors: Cooper L. V.
Published: February 2011

Evaluation that will predict with a high degree of accuracy the suitability for service of any product is the object of all physical testing. Over a comparatively short period of about twenty-five years, rubber technologists have evolved a series of tests which have evaluated natural rubber compounds reasonably well. When it became necessary to evaluate rubber substitutes, it was only natural that the same tests would be applied. The results obtained convinced everyone that these materials were definitely not equivalent substitutes, and to use them involved more than just replacement. Although the background is not so extensive as might be desired, the A.S.T.M. Committee D-11 on Rubber Products has learned enough about these materials to be able to present certain facts and recommendations to industry in general with regard to specifications covering synthetic rubbers and products made from them. The entire field of physical testing is quite extensive, as it covers not only finished products but the component raw materials from the time they are received until they emerge as final products ready to be put into service. Also, in this large field, not everyone is interested in the same phase of testing synthetic rubber products. Tire development engineers are not interested in load deflection figures, which are so essential to automobile design engineers, and the latter have no concern with adhesion to fabric which must be considered by the pneumatic tire technologists and those concerned with hose and belting. This paper is intended to deal primarily with some of the physical properties which affect the service of finished products.
Cure of GR-S in Thick Articles
Authors: Morris Ross E. , Hollister Joseph W. , Mallard Paul A.
Published: February 2011

Information on the relative rates of cure of GR-S stocks and similar Hevea stocks in thick sections is of interest to many rubber manufacturers. Since curing conditions for thick articles from Hevea stocks have been established, they would like to know how these conditions must be altered when GR-S stocks are used in the same applications. They could develop a GR-S stock with the same rate of cure as the Hevea stock which it replaces according to laboratory tests on comparatively thin sheets, but this agreement does not mean necessarily that thick sections cure at the same rate. The respective rates of heat flow through the rubbers must be considered. Only if the rates of heat flow as well as the curing rates of thin sections are in agreement, will the curing rates of the thick sections be equal. Juve and Garvey found that GR-S tread stocks cure faster in the center of thick sections than similar Hevea tread stocks. They were unable to explain this behavior because, according to their measurements, the thermal conductivity of the GR-S tread stock was less, and its specific heat greater than, the corresponding values for the Hevea tread stock. They concluded that the difference mav be due to an exothermic reaction.
The Du Pont Modified Williams Plastometer
Authors: Keen W. Newlin
Published: February 2011

Webster defines plasticity as “the ability to retain a shape attained by pressure deformation”. Plasticity measurements are made by rubber technologists for one or more of the following reasons: (1) to measure the workability of rubber or synthetic elastomers; (2) to determine the effect of natural or accelerated aging on the processability of compounded rubber or synthetic elastomers; (3) to determine to what extent softeners or compounding ingredients may have affected the workability of rubber or synthetic elastomers; (4) to serve as a control test in the manufacture of synthetic elastomers. The Williams Plastometer has been widely used in the rubber industry for a number of years. Since its introduction in 1924 by Williams it has undergone a number of refinements which have improved its mechanical efficiency and simplified its operation. However, the fundamental operating principles of this machine have been retained. This article discusses the modifications that have been incorporated into the instrument now in use at the du Pont rubber laboratories.
The Thermodynamics of Rubber at Small Extensions
Authors: Elliott D. R. , Lippmann S. A.
Published: February 2011

On analyzing their own data, Meyer and Ferri have concluded that, at small extensions, rubber is an ideal elastomer according to the definition that (∂E/∂L)P,T=0. Further analysis of Meyer and Ferri's data does not sustain their conclusion. If, however, (∂E/∂L)V,T=0 is taken as a new criterion for an ideal elastomer, Meyer and Ferri's data do indicate that rubber is ideal, at least for extensions up to 166 per cent. The new criterion implies that the valence angles do not store an appreciable amount of energy when the rubber is stretched. However, both the molecular orientation and the interatomic displacements do influence the energy required for extension.
Photo Vulcanization. A Study of the Products of the Action of Light on Rubber Under Conditions Precluding or Restricting Oxidative Degradation
Authors: Stevens Henry P.
Published: February 2011

Milled sheeted rubber in evacuated sealed tubes or tubes filled with inert gas becomes vulcanized on exposure to sunlight or ultraviolet radiation. Stress-strain curves and also swelling and solubility data are given in confirmation. The vulcanizing effect is enhanced by treating the surface, preferably the under-surface, of the rubber with sensitizers, which may be regarded as photovulcanizing agents. These usually are also photogelling agents, and comprise aldehydes, ketones, quinones and chlorinated quinones. Sulfur is also active, and to a lesser extent other substances, including some thermalvulcanization accelerators, although these latter do not act as photovuleanization accelerators. Some photovulcanizing agents protect rubber from oxidation during insolation, so with them a vulcanizing effect is obtainable in the presence of air. The nature of the photovulcanizing effect and its relation to modern theories of vulcanization are discussed.
Molecular Requirements for Synthetic Rubbers
Authors: Baker W. O.
Published: February 2011

Rubbery substances consist basically of long chains of atoms to which other atoms may be attached in small groups that occur repeatedly, and often regularly, like the links along a chain. There are hundreds of atoms in one of these “macro” molecules. It is the particular arrangement and the active forces between these molecules that are responsible for the elastic properties of many substances. The structure of the molecules of most synthetic rubbers as well as that of natural rubber is so complex, however, that efforts to determine, by direct study of the commercial products, what produces their rubbery characteristics have yielded results that are difficult to interpret. Progress in solving the puzzle has recently been made by starting with simple chain compounds and forming from them, by known chemical modifications, substances which have some of the properties that are found in natural rubber. Studies of these “model” chain compounds indicate that the long-chain molecules of rubbery substances must have forces between atomic groups which are small enough to permit twisting and kinking of the chains. There must also be lateral forces to hold adjacent molecules together, like a bundle of sticks, especially when the substance is stretched. Moreover, the molecules must have side groups to avoid the close packing, when unstretched, that is characteristic of crystals.
The Structure of Polyisoprenes. III. Ultraviolet Absorption Spectra
Authors: Bateman L. , Koch H. P.
Published: February 2011

The quartz ultraviolet absorption spectra of highly purified polyisoprenes correspond closely to those of simple ethylenes having the same degree of alkyl substitution at the double bond. This is also true of geranylamine hydrochloride, which shows no obvious characteristic that can be identified with the structural anomaly revealed by x-ray crystal analysis. The extent to which spectral variations are a measure of the electronic properties of groups and molecules of this type is therefore discussed—with the conclusion that for formally saturated substituents the correlation is still obscure. Evidence is presented to show that inductive influence is slight, and that interpretations hitherto advanced on the basis of hyperconjugation are unsound.
Determination of Total Sulfur in Rubber
Authors: Luke C. L.
Published: February 2011

The range of the hydriodic acid reduction-iodometric titration method for the determination of sulfur in semimicrosamples of rubber has been extended to provide for the analysis of macrosamples containing as much as 100 mg. of sulfur.
Inverse Correlation between Rubber Hydrocarbon and a Crystalline Fraction Isolated from Latex of Cryptostegia Grandiflora
Authors: Stewart William S. , Hummer Richard W.
Published: February 2011

1. Analysis of 157 samples of dried latex from above-ground portions of Cryptostegia grandiflora indicated a linear inverse correlation between the percentage of rubber hydrocarbons and the insolubles. 2. By extraction of the latex “insolubles” with absolute ethanol and fractional precipitation of the extract, an unidentified crystalline fraction was obtained which was inversely correlated with rubber hydrocarbons. It is possible that this crystalline fraction is the only one in the insolubles and latex inversely correlated with the rubber hydrocarbons.
Recent Advances in the Physics and Chemistry of Rubber. II. The Kinetic Theory of Rubber Elasticity
Authors: Treloar L. R. G.
Published: February 2011

In Part I, the nature of the rubber molecule was discussed, and it was shown to consist essentially of a single chain of relatively very great length. Many of the characteristics of rubber, such as the high viscosity of rubber solutions, the high elasticity, and the capacity for swelling in solvents, are directly connected with this fundamental molecular structure. The present Part II is concerned with the elasticity of rubber, and discusses the origin of the remarkable difference between the elastic properties of rubber and ordinary hard solids. The typical solid, e.g., a rock salt crystal, is represented by a structure in which each atom is held in an equilibrium position by strong forces. The application of a deforming force disturbs the equilibrium positions of the atoms very slightly, in such a way that internal stresses which balance the externally applied force are brought into play. The value of Young's modulus for a crystal is of the order 1011, and the maximum extension before breakage occurs is generally about 1 per cent. Rubbers on the other hand can be deformed by 700 per cent or more by comparatively small forces, corresponding to Young's moduli of the order 107. These enormous differences point to a different elastic mechanism in the two cases. When we look at the range of materials which show rubberlike elasticity, we find in all cases the same fundamental pattern of molecular structure. The atomic constituents of the molecule may vary, but the molecule invariably takes the form of a very long chain, generally, but not necessarily of carbon atoms. It is this basic similarity which provides the clue to the understanding of the phenomenon of high elasticity.
The Chemical Constitution of Butadiene Rubbers, Based on the Formic Acid and Formaldehyde in the Decomposition Products of Their Ozonides
Authors: Yakubchik A. I. , Vasiliev A. A. , Zhabina V. M.
Published: February 2011

A rapid method has been developed, with the aid of several types of synthetic rubber, for determining the characteristic chemical structure of butadiene rubbers by means of the formic acid and formaldehyde recovered when their ozonides are decomposed.
The Interaction of Plasticizers and Polymers
Authors: Frith Elizabeth M.
Published: February 2011

The general problem of plasticizer compatibility is discussed, and it is suggested that a comparative measure of compatibility can be obtained from experiments which measure polymer-plasticizer interactions (w). Experiments are described which measure the viscosity of dilute polymer solutions in suitable mixed solvents containing the plasticizer in question. The slope of the ηsp/c−c curve is shown to be related to the equilibrium extent of swelling of the polymer in the pure plasticizer and, in general, the slope of the curve is a good comparative measure of the plasticizer's compatibility. The effects of temperature and composition of the mixed solvent are also discussed. The experiments are considered in the light of a previous theory of the effect of solvent on the ηsp/c ratio: the results do not support the suggested view that the slope of the ηsp/c−c curve is a simple linear function of w/kT.
Rubber Photogelling Agents
Authors: Stevens Henry P.
Published: February 2011

This paper details an evaluation of a number of rubber photogelling agents or activators under insolation, particularly oxygen and sulfur. Contrary to previous statements, both elements are shown to be activators, and sulfur combines with rubber as in thermal vulcanization. Molecular oxygen, after allowing for degradative oxidation, is an extremely powerful gelling agent, comparable with quinonic or peroxidic oxygen.
Coagulation Studies of the Latex of Cryptostegia Grandiflora, R. Br. A Wartime Source of Vegetable Rubber. I
Authors: Siddiqui Rafat Husain , Warsi S. A. , Sastri V. V. K.
Published: February 2011

1. Coagulation can be brought about by methods which are physical and chemical in nature. The chemical methods are suitable for the coagulation of latex on a large scale. 2. The latex coagulates at a pH range of 4.2–7.5. 3. The range toward pH 4.2 is reached by acids and acid salts. 4. Coagulation when effected by chemical reagents, by autocoagulation or by passage of an electric current is always accompanied by a change in the hydrogen-ion concentration of the latex. 5. Dilute solutions of alkalies, acids and of some salts give very good results. 6. If the quantity of the coagulant exceeds the minimum amount required for the coagulation of latex, no coagulation occurs, and the latex passes into a second phase or zone. 7. When coagulation is effected by shaking, centrifuging, the application of dry heat, or adding alcohol and acetone, the pH value of the latex remains unchanged. 8. Coagulation is brought about also by reagents used for hydration and dehydration and for precipitating proteins, and by microörganisms and enzymes.
Carbon Blacks in GR-S
Authors: Parkinson D.
Published: February 2011

The importance of different types of colloidal carbon as reinforcing agents for the butadiene-styrene copolymer, GR-S, has been stressed in recent papers. It has been shown that, to a first approximation, the effect of carbon blacks in this type of synthetic rubber is similar to that in natural rubber, but it has been shown also that the extremely low tensile strength and poor tearing properties of uncompounded vulcanized GR-S necessitates the addition of some form of carbon black to almost all types of compounds. The present paper considers the influence of carbon blacks in vulcanized GR-S compounds. Earlier papers have discussed the effect of carbon blacks in natural rubber.
The Structure of Polyisoprenes. IV. Double-Bond Interaction in Certain Carbalkoxy-Substituted 1,5-Dienes
Authors: Bateman L. , Jeffrey G. A.
Published: February 2011

A peculiar lack of olefinic reactivity, combined with a facility for cyclization of methyl and ethyl Δ1,5-hexadiene-1, 1, 3, 3, 4, 4, 6, 6-octacarboxylates, has been attributed by Ingold, Parekh, and Shoppee to ring-chain mesomerism. A reinvestigation of these and related compounds has now been made by using x-ray methods, and it is shown that the crystal structure of the methyl ester is incompatible with the cis-configuration required for such interspatial double-bond saturation. A radical disruption of a mesomeric system by crystallization from solution is improbable and, an earlier formulation incorporating a bicyclobutane nucleus being rejected on chemical grounds, it is necessary to seek a new interpretation of the anomalous reactivity. We suggest that the determinative condition is hyperconjugation throughout the carbon framework of the molecule, and discuss this in relation to 1,5-dienes generally.
The Cold-Compression sets of Natural and Synthetic Vulcanizates
Authors: Morris Ross E. , Hollister Joseph W. , Mallard Paul A.
Published: February 2011

The behavior of certain large synthetic rubber gaskets on naval vessels during the past winter points to the necessity for a cold compression-set test in the specifications for these gaskets. It has been found, for example, that Neoprene gaskets on large valves, which perform satisfactorily at temperatures of 60° F and above, are not usable at temperatures of 40° F and below. They take a cold compression-set, while the valves are closed, so that when the valves are opened and then again closed, the leading edge or surface of the valve does not seat properly. This cold compression-set is not permanent; when the gaskets which exhibit cold compression-set are removed to a warm atmosphere (about 80° F), they slowly regain their original shape. A survey of the literature dealing with the effects of low temperatures on rubber compounds yielded no information on cold compression set. The set test proposed by Morris, James, and Evans in connection with their low temperature stiffness test is not directly applicable to the present problem because it is conducted in tension. Therefore to investigate cold compression-set, it was necessary to devise a new testing procedure.
Procedure for Determining Physical Properties of Films from GR-S Latices
Authors: Peaker C. R.
Published: February 2011

This article describes a new procedure for determining the physical properties of films from GR-S type of synthetic rubber latices. To obtain satisfactory films for testing, the latex solids should be above 30 per cent. A suitable formulation which will reach the optimum cure in from 30 to 60 minutes at 100° C is as follows: Polymer 100.0 Sulfur 2.0 Zinc oxide 3.0 Zinc mercaptobenzothiazole 1.5 Zinc dibutyldithiocarbamate 0.5 If zinc mercaptobenzothiazole is to be omitted, it is desirable to increase the dithiocarbamate to about 1.0 part. If the dithiocarbamate is not used, vulcanization should be carried out at higher temperatures, e.g., 120° C. These vulcanizing ingredients may be used as a composite dispersion by ball-milling the accelerator, sulfur and zinc oxide with 0.5 parts dispersing agent, such as Daxad-11, Vultramine, etc., to give a 45 to 50 per cent dispersion. It is recommended that freshly prepared pastes be used, since experience has shown that erratic results may be obtained when old pastes are used, particularly those containing zinc oxide. Additional stabilizers, such as soap, may be used with this compound if required in some cases. Films should be prepared promptly after the compound is made, for prevulcanization may occur in the final films and produce erratic results.
The Interaction between Rubber and Liquids. VII. The Heats and Entropies of Dilution of Natural Rubber by Various Liquids
Authors: Ferry J. , Gee Geoffrey , Treloar L. R. G.
Published: February 2011

Calorimetric measurements of the heats of mixing of seven liquids with dihydromyrcene are used to estimate the heats of dilution of rubber by these liquids. Combining the results with free energies calculated from vapor pressure gives entropies of dilution which show significant deviations from the present statistical theory. A thermodynamic study of rubber + methyl alcohol shows similar but larger deviations. This work forms part of a program of fundamental research on rubber undertaken by the Board of the British Rubber Producers' Research Association.
Cooling Facilities of Rubber Equipment
Authors: Taylor T. M.
Published: February 2011

Proper maintenance of rubber processing equipment is a necessary and important phase of production. If management is to maintain maximum overall production it must allow the engineering and maintenance organization sufficient authority, time and money to keep equipment operating at top efficiency. When the pressure of production jobs that have to be completed “yesterday” interferes repeatedly with repairs that should have been made last week, the chances are very good that a condition will soon exist where the rush job can not be completed until next month. The first rule, then, in maintenance work is, “Do it now.” A small repair job today may prevent a costly shutdown tomorrow. In addition to the mechanical difficulties regularly occurring, there are a number of little things that frequently cause production delays and hidden extra costs. One of the most important of these concerns the cooling of mills, Banbury mixers, calender rolls and tubing machines. Early in the history of the rubber industry it was learned that some means of carrying off heat occasioned by friction of the stock working on the equipment was necessary. It was learned later that the same facilities could be used to control temperatures within the ranges suited best for a given stock or processing operation. The methods in use today have altered little since the first installations were made, but it is doubtful that full use is always made of the facilities available. In ordinary times this was foolish and expensive. Today it approaches sabotage by interfering with production, increasing the percentage of seconds, and wasting vital raw materials. Most causes of inadequately cooled processing equipment are obvious, and their correction is generally inexpensive and elementary. However, as is often the case, the obvious little things are all too frequently overlooked and unsatisfactory conditions tolerated. It is hoped that, by pointing out potential trouble spots and emphasizing both the processing difficulties due to poor cooling and the ease with which they may be corrected, much future trouble may be avoided.
The Single-Cord Compression Adhesion Test for Evaluating the Adhesion of Vulcanized Rubber to Cord
Authors: Lessig E. T. , Compton Jack
Published: February 2011

The replacement of natural rubber by synthetic rubberlike materials (elastomers) in the construction of mechanical goods has led to considerable emphasis being placed on the problem of strongly bonding the cord reinforcing member to these new materials. The introduction of continuous filament rayon cord as the reinforcing member in natural rubber tires had earlier given the rubber industry the opportunity to determine the importance of cord adhesion in the performance of tires. Now with the advent of synthetic, continuous filament, high polymeric materials as superior reinforcing members, the problem of adhering synthetic and natural rubber to these materials to produce satisfactory working units becomes increasingly complex. It is evident that before very much can be accomplished with a problem of this scope a versatile test must be devised for evaluating the adhesion of synthetic and natural rubber to the various filamentary materials. Over a period of time there has been developed in this laboratory a single-cord compression adhesion test which may be adapted to the study of the adhesion of all types of synthetic and natural vulcanized rubber to continuous or staple filamentary materials in the form of plied yarns or cord. This test is based on the fact that the apparent adhesion of cord to vulcanized rubber or rubberlike material is greatly enhanced when stripped under compression, and differences in the apparent bonding forces between different cords and different elastomers are thereby greatly magnified. The test is unique in that the cord in the cylindrical adhesion test-pieces lies on a diameter at the mid-section which is stripped from the vulcanized elastomer as the ends of the test-piece are subjected to compression. In addition, the test may be performed at elevated temperatures, and is easily adaptable to routine control testing. This test seems to fill the need for a versatile, rapid and reliable adhesion test for evaluating the relative adhesion of vulcanized elastomers to cord.
Reactivity of Isoprenic and Analogous Hydrocarbons towards Thiocyanic Acid and Dithiocyanogen
Authors: Naylor Ralph F.
Published: February 2011

By analogy with hydrogen halides and hydrogen sulfide it is reasonable to expect thiocyanic acid to react with olefins, and it has been reported by Kharasch, May, and Mayo that it will add to isobutylene at room temperature to give a mixture of tert.-butyl thiocyanate and isothiocyanate. Under similar conditions in the present work, the only product that was obtained from cyclohexene and thiocyanic acid was a small quantity of an amorphous powder, probably mainly a perthiocyanic acid, formed by elimination of hydrogen cyanide from three molecules of thiocyanic acid. This tendency towards decomposition of the reagent prevented the use of elevated temperatures, and when methyl thiocyanate (a potential source of SCN and Me radicals by thermal decomposition) was heated at 170° with 1-methylcyclohexene and a little benzoyl peroxide (as catalyst), it underwent but slight reaction, the drop or two of product giving analytical values which suggested that it might be an impure adduct. Attempts to catalyze the addition of thiocyanic acid to, rubber included the use of ultraviolet irradiation, and of aluminum chloride or ferric chloride as catalyst. The most successful of these attempts was with ultraviolet light, but even then the product contained only 1.95% of sulfur, which represented 6% addition to the double bonds of rubber.
The Study of the Mechanism of Polymerization Reactions by Means of Size-Distribution Curves
Authors: Herington E. F. G.
Published: February 2011

Some of the experimental complications which may attend the study of size-distribution curves are indicated. To obtain information on the mechanism from distribution curves, the degree of polymerization must be known. Most information can be obtained if the fraction polymerized is small (say up to 10 per cent polymerized) and if the rate of initiation is kept constant during this reaction period. Fortunately, those conditions which are best suited for the mathematical treatment of the process are also those which avoid many of the experimental complications. Three main types of distribution curves may be distinguished; these are discussed in terms of the mechanism terminating the life of an active growing radical. Such distribution curves, taken in conjunction with other considerations, can greatly extend our knowledge of polymerization reactions.
Some Infrared Studies on the Vulcanization of Rubber
Authors: Sheppard N. , Sutherland G. B. B. M.
Published: February 2011

The two most effective ways of altering the physical and mechanical properties of natural rubber are vulcanization and the addition of carbon black. There is, however, little understanding of the structural changes brought about by these processes, in spite of extensive research by chemical and physical methods. For instance, in vulcanization it is not yet decided how the sulfur atoms are incorporated in the rubber polymer, what proportion are in bridges formed between the isoprene chains, whether such bridges are formed by —C—S—S—C— or —C—S—C— links, whether one double bond is broken for each sulfur atom incorporated, and so on. An ancillary problem is the effect of certain “accelerators” on the speed of vulcanization, about which even less is known. Again in the case of reinforcement of rubber by materials such as carbon black, there is controversy on the structural relationship of the carbon black and the rubber. Until such structural problems have been solved on the molecular scale there is little hope of controlling the macroscopic properties of rubber compounds in a truly scientific manner. This paper gives a preliminary account of the application of infrared spectroscopy to some of these problems.
Oxidative Breakdown of Rubber
Authors: Farmer E. H.
Published: February 2011

Scope of Survey.—The autoöxidation of vegetable and animal drying oils causes solidification, hardening, and toughening of the original olefinic material, whereas absorption of oxygen by natural rubber normally causes softening, with loss of strength and elasticity. Various synthetic rubbers appear to take an intermediate position between drying oils and natural rubber, but with none of the rubbers does autoöxidation represent a simple phenomenon, leading uniformly to softening as opposed to toughening. The peroxidation process which forms the basis of autoöxidation leads in general to two opposite effects, viz., to oxidative chain-scission (degradation) and to molecule-linking (polymerization or oxygen-vulcanization), and it seems logical to associate the former with the softening of olefinic materials and the latter with their toughening or oxygen-vulcanization. What, however, is far from clear is the cause of onset under given conditions of softening on the one hand or oxygen-vulcanization on the other, and the precise nature of the molecular changes which underlie the two phenomena. At present even qualitative information concerning the intricate course of autoöxidative reactions among olefinic substances is far from abundant, and the necessary kinetic evidence which must both set the final seal of credibility on those chemical explanations which careful experimentation indicates to be sound, and in difficult cases discriminate between alternative possible explanations, is only beginning to become available. The most useful contribution, therefore, which can be made at the moment is to clarify in terms of organic structure and reactions the basic issues involved, and to show how far existing chemical information provides certain or possible explanations of the broad lines of autoöxidative molecular breakdown (and its converse) as it is encountered among rubbers.
Photochemical Breakdown of Rubber
Authors: Bateman L.
Published: February 2011

A notable property of rubber and related olefins is their marked photochemical response to weakly absorbed light of wave-length greater than 3000 A. Although, as in photoinduced halogenation and oxidation, for example, photoactivation of the olefins cannot be generally inferred since the active absorbing entity is or may be the added reagent or a primary reaction product, the photogelling of rubber in a nonabsorbing solvent such as cyclohexane seems free from this ambiguity and points to direct photodecomposition of the rubber molecule. Some authors attribute the cross-linking of the gel state to C—C bonds between ethylenic centers and thereby explain the slightly reduced unsaturation of the gels and their resistance to rubber peptizing agents. Naunton, on the other hand directs attention to the remarkable gelling and reversion powers of minute traces of oxygen, and suggests that the few oxygenated centers which appear to remain even in highly purified rubber provide the sites for intermolecular condensation. This latter hypothesis undoubtedly expresses an important mode of cross-linking under certain conditions, but a possible inference that the oxygenated groups are regarded as specifically absorptive and as alone possessing photochemical activity is not in accord with existing evidence. The residual oxygen has been located analytically in hydroxyl groups and foreign chromophores are absent in the ultraviolet absorption spectrum of purified rubber. It is therefore difficult to see why the oxygenated fragments should be preferentially activated by irradiation rather than the much more numerous and more absorptive ethylenic units. However, a necessary prelude to further conjecture is fuller knowledge of the basic photochemistry of rigorously isolated rubber. In the work now described, scrupulous care has been taken to free the purified rubber from gaseous contaminants, and chemical changes have been followed directly and not deduced from vague gelation characteristics.
Rubber Photogelling Agents. II
Authors: Stevens Henry P.
Published: February 2011

A previous paper detailed the evaluation of oxygen and other photogelling agents under insolation. This paper deals similarly with various pro- and antioxygens, and it is shown that in small proportions all these act as mild photogelling agents, the effect being rather abruptly reversed when the proportion exceeds the optimum. The relevant factors are discussed.
Electrostatic and Tensile Properties of Rubber and GR-S at Elevated Temperatures
Authors: Havenhill R. S. , O'Brien H. C. , Rankin J. J.
Published: February 2011

A new apparatus has been described for measuring contact potentials of rubber and GR-S compounds at elevated temperatures. In this apparatus, the electrostatic charge, acquired by rolling a steel ball down the surface of a rubber test-specimen on a heated inclined plane, is measured when the ball drops into the cup of an electrostatic modulator. This potential, although not the actual contact potential, is nevertheless, proportional to it. With this apparatus, the contact potential of GR-S at elevated temperatures was found to increase much more (become more negative) than that of rubber. The release of electrons (increase in negative contact-potential) and consequent disruption of electrostatic attractive forces within the material at elevated temperature probably partly accounts for the much greater decrease in tensile strength of GR-S over rubber, and is further confirmation of the electrostatic contact potential theory of reinforcement. By the further application of this theory, highly positive materials, such as certain proteins, finely divided silica, and sodium silicate, which retain their positive charges at elevated temperatures and make the stocks more positive, have been found to more than double the hot tensile strengths of compounds made from GR-S latex and highly loaded with zinc oxide.
Differentiation of Rubber and Gutta Hydrocarbons in Plant Materials
Authors: Hendricks S. B. , Wildman S. G. , Jones E. J.
Published: February 2011

Hydrocarbons of the rubber (r) or gutta (g) types isolated from Hevea brasiliensis (r), Mimusops balata (g), Asclepias erosa (milkweed (r)), A. syriaca (milkweed (r)), Oenothera biennis (Evening primrose (r)), Solidago leavenworthii (goldenrod (r)), Eucommia ulmoides (g), Euonymus japonicus (g), and Jatropha sp. (chiite (r)) were positively identified by their light absorptions near 12 µ. Mixed cis- and trans-isomers were absent in all cases, even though the plants examined were selected as giving hydrocarbon polymers of questionable types.
Complement-4 Deficiency in a Child with Systemic Lupus Erythematosus Presenting with Standard Treatment-Resistant Severe Skin Lesion
Authors: Sozeri Betul , Mir Sevgi , Berdeli Afig
Published: February 2011

The complement system is of great importance in systemic lupus erythematosus. Complete genetically determined deficiencies are with few exceptions reported for the various complement proteins, and most of the deficiency states are rare. Deficiencies of the factors in the classical pathway are also associated with development SLE and SLE-like disorders. Most of the patients with lupus present skin involvement. Approximately, 75–95% of patients with cutaneous lupus erythematosus respond to antimalarial therapy and/or topical glucocorticosteroids. Immunosuppressive agents are usually considered a second-line approach in patients with resistant disease. In this study, we present the clinical features and determine the molecular basis responsible for the complete C4A and C4B deficiencies in a lupus patient presented subacute cutaneous lupus erythematosus and resistance to treatment.
Role of Integrative Signaling Through Gap Junctions in Toxicology
Authors: Upham Brad L.
Published: February 2011

Gap junctional intercellular communication (GJIC) plays a central role in coordinating signal‐transduction pathways that control gene expression inside of cells with those of neighboring cells in maintaining the homeostasis of a tissue. The normal homeostatic set point of gap junctions within tissues is in an open state, and although transient closure of gap junctions in response to mitogenic effectors is normal, chronic closure of channels by continuous exposure to environmental and food‐borne contaminants can result in adverse health effects such as cancer, teratogenesis, reproductive dysfunction, neuropathies, and cardiac arrhythmias. GJIC is the primary means of integrating signal transduction pathways controlling gene expression between contiguous cells. Thus, bioassay systems that can measure GJIC offer a central, more biosystems approach to assessing the potential for toxicants to epigenetically alter gene expression.Curr. Protoc. Toxicol. 47:2.18.1‐2.18.18. © 2011 by John Wiley & Sons, Inc.
Serum free light chains as biomarkers for systemic lupus erythematosus disease activity
Authors: Aggarwal Rohit , Sequeira Winston , Kokebie Rediet , Mikolaitis Rachel A. , Fogg Lewis , Finnegan Alison , Plaas Anna , Block Joel A. , Jolly Meenakshi
Published: February 2011

Objective

To evaluate serum free light chains (FLC) as a putative biomarker of systemic lupus erythematosus (SLE) activity.

Methods

Seventy‐five SLE patients and 41 age‐ and sex‐matched rheumatoid arthritis (RA) controls were enrolled. Disease activity was assessed using the Safety of Estrogens in Lupus Erythematosus: National Assessment version of the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) definition and physician global assessments for SLE and the Disease Activity Score in 28 joints for RA. Serum FLC levels were compared against other biomarkers (IgG, C3, C4, double‐stranded DNA [dsDNA] antibody). Nonparametric tests were used to compare 1) FLC and IgG in SLE versus RA and healthy controls, 2) FLC and IgG among different levels of activity in SLE, and 3) FLC in active versus nonactive RA. Correlation of FLC, C3, C4, dsDNA antibody, and IgG with the SLEDAI and modified SLEDAI (M‐SLEDAI) were obtained.

Results

FLC was higher in SLE than in RA; both were higher than referent healthy controls. Total FLC was significantly higher in subjects with greater SLE disease activity than lower/no activity. There were no significant differences in IgG, C4, or dsDNA antibody stratified by disease activity. Total FLC and C3 showed moderate to strong correlation with the SLEDAI and M‐SLEDAI. In RA, no differences were seen in FLC levels for different levels of disease activity. Similar results were seen after controlling for renal function, age, and sex. In multiple linear regression, FLC significantly explained 50% variance of the SLEDAI after adjusting for renal function, age, and sex.

Conclusion

Serum FLC levels correlate strongly with disease activity in SLE, but not in RA. Serum FLC may be used as a biomarker of SLE disease activity.
Toward Flexible Polymer and Paper‐Based Energy Storage Devices
Authors: Nyholm Leif , Nyström Gustav , Mihranyan Albert , Strømme Maria
Published: February 2011

All‐polymer and paper‐based energy storage devices have significant inherent advantages in comparison with many currently employed batteries and supercapacitors regarding environmental friendliness, flexibility, cost and versatility. The research within this field is currently undergoing an exciting development as new polymers, composites and paper‐based devices are being developed. In this report, we review recent progress concerning the development of flexible energy storage devices based on electronically conducting polymers and cellulose containing composites with particular emphasis on paper‐based batteries and supercapacitors. We discuss recent progress in the development of the most commonly used electronically conducting polymers used in flexible device prototypes, the advantages and disadvantages of this type of energy storage devices, as well as the two main approaches used in the manufacturing of paper‐based charge storage devices.
New Insights to Self‐Aggregation in Ionic Liquid Electrolytes for High‐Energy Electrochemical Devices
Authors: Kunze Miriam , Jeong Sangsik , Paillard Elie , Schönhoff Monika , Winter Martin , Passerini Stefano
Published: February 2011

Some cations of ionic liquids (ILs) of interest for high‐energy electrochemical storage devices, such as lithium batteries and supercapacitors, have a structure similar to that of surfactants. For such, it is very important to understand if these IL cations tend to aggregate like surfactants since this would affect the ion mobility and thus the ionic conductivity. The aggregation behaviour of ILs consisting of the bis(trifluoromethanesulfonyl)imide anion and different N‐alkyl‐N‐methyl‐pyrrolidinium cations, with the alkyl chain varied from C3H7 to C8H17, was extensively studied with NMR and Raman methods, also in the presence of Li+ cations. 2H NMR spin‐lattice and spin‐spin relaxation rates were analyzed by applying the “two step” model of surfactant dynamics. Here we show that, indeed, the cations in these ILs tend to form aggregates surrounded by the anions. The effect is even more pronounced in the presence of dissolved lithium cations.
Multistage rotor‐stator spinning disc reactor
Authors: Meeuwse Marco , van der Schaaf John , Schouten Jaap C.
Published: February 2011

The scale up of a rotor‐stator spinning disc reactor by stacking single stage rotor‐stator units in series is demonstrated. The gas‐liquid mass transfer per stage is equal to the mass transfer in a single stage spinning disc reactor. The pressure drop per stage increases with increasing rotational disc speed and liquid flow rate. The pressure drop is more than a factor 2 higher for gas‐liquid flow than for liquid flow only, and is up to 0.64 bar at 459 rad s−1. The high mass and heat transfer coefficients in the (multistage) rotor‐stator spinning disc reactor make it especially suitable for reactions with dangerous reactants, highly exothermic reactions and reactions where selectivity issues can be solved by high mass transfer rates. Additionally, the multistage rotor‐stator spinning disc reactor mimics plug flow behavior, which is beneficial for most processes. © 2011 American Institute of Chemical Engineers AIChE J, 2012
Kinetic mobility and connectivity in nanopore networks
Authors: Wang Fu Yang , Zhu Zhong Hua , Massarotto Paul , Rudolph Victor
Published: February 2011

Experimental results for methane and carbon dioxide diffusion in coal, as reported in the literature, often lead to diffusion rates of CO2 appearing to be much greater than that of CH4. The interpretation sometimes offered that the diffusion coefficient for CO2 is 1–2 orders of magnitude higher than that of CH4, violates fundamental principles. Nevertheless, the experimental observations require explanation. In this article, we: (a) Develop simplified models for the fast estimation of transport coefficients. These are compared with comprehensive grand canonical Monte Carlo (GCMC) and molecular dynamic (MD) simulations, collectively defined as molecular simulations (MS), which provide theoretical adsorption isotherms and various transport coefficients based on multicenter potential energy equations. The simplified models are shown to have acceptable accuracies. (b) Use the simplified models to compare diffusivities of CO2 and CH4 in carbon nanopores. For all cases examined, the diffusivity of CH4 is always larger than that of CO2. (c) Offer two explanations for the apparently contradictory experimental observations (that CO2 sometimes appears to diffuse much faster than the CH4 molecule, even though CH4 is lighter and has smaller adsorption affinity): (i) CH4 mobility could be significantly reduced by directional forces resulting from irregular pore geometries; and (ii) if pores contain throats with sizes close to the CH4 molecular diameter, the energy barrier that the methane molecules must overcome to proceed through is much larger than that required for CO2. (d) Demonstrate that both mobility and connectivity issues can be addressed using kinetic theory in association with percolation analysis. Furthermore, this method of understanding pore networks provides a number of important quantitative measures including percolation threshold, size of largest cluster, shortest path and tortuosity. Separating different transport mechanisms, as we propose here, provides improved insights into the complex transport phenomena that occur in carbonaceous porous media. In many cases, diffusivities reported in the literature with mixed mechanisms are better named “apparent transport coefficients,” because they lump in other unrelated phenomena, violating the fundamental basis of, or mathematical assumptions imposed on, the definition of diffusion. © 2011 American Institute of Chemical Engineers AIChE J, 2012
Argininosuccinate lyase deficiency—Argininosuccinic aciduria and beyond
Authors: Erez Ayelet , Nagamani Sandesh C. Sreenath , Lee Brendan
Published: February 2011

The urea cycle consists of six consecutive enzymatic reactions that convert waste nitrogen into urea. Deficiencies of any of these enzymes of the cycle result in urea cycle disorders (UCD), a group of inborn errors of hepatic metabolism that often result in life threatening hyperammonemia. Argininosuccinate lyase (ASL) is a cytosolic enzyme which catalyzes the fourth reaction in the cycle and the first degradative step, that is, the breakdown of argininosuccinic acid to arginine and fumarate. Deficiency of ASL results in an accumulation of argininosuccinic acid in tissues, and excretion of argininosuccinic acid in urine leading to the condition argininosuccinic aciduria (ASA). ASA is an autosomal recessive disorder and is the second most common UCD. In addition to the accumulation of argininosuccinic acid, ASL deficiency results in decreased synthesis of arginine, a feature common to all UCDs except argininemia. Arginine is not only the precursor for the synthesis of urea and ornithine as part of the urea cycle but it is also the substrate for the synthesis of nitric oxide, polyamines, proline, glutamate, creatine, and agmatine. Hence, while ASL is the only enzyme in the body able to generate arginine, at least four enzymes use arginine as substrate: arginine decarboxylase, arginase, nitric oxide synthetase (NOS) and arginine/glycine aminotransferase. In the liver, the main function of ASL is ureagenesis, and hence, there is no net synthesis of arginine. In contrast, in most other tissues, its role is to generate arginine that is designated for the specific cell's needs. While patients with ASA share the acute clinical phenotype of hyperammonemia, encephalopathy, and respiratory alkalosis common to other UCD, they also present with unique chronic complications most probably caused by a combination of tissue specific deficiency of arginine and/or elevation of argininosuccinic acid. This review article summarizes the clinical characterization, biochemical, enzymatic, and molecular features of this disorder. Current treatment, prenatal diagnosis, diagnosis through the newborn screening as well as hypothesis driven future treatment modalities are discussed. © 2011 Wiley‐Liss, Inc.