bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Dynamic Properties of Carbon Black Loaded Natural Rubber Vulcanizates. Part II
Authors: Payne A. R. 
Published: February 2011

Abstract
The dynamic shear modulus at very high strains, (G∞), of carbon black filler loaded vulcanizates is regarded as due to the product of two factors : (a) a hydrodynamic interaction due to filler particles, and (b) a second factor for which evidence is given suggesting that it arises from a few strong linkages which are known to link filler particles to the matrix. Experimentally a measure of (a) has been obtained from model vulcanizates using glass spheres as the filler, and of (b) from equilibrium swelling measurements on rubber vulcanizates containing carbon black. Quantitatively, the difference between the shear modulus of the pure gum vulcanizate, Gpure gum, and G∞ can be explained by these measurements.
An Elution Chromatography Technique for cis-1,4-Polybutadiene
Authors: Hulme J. M. , McLeod L. A. 
Published: February 2011

Abstract
Experiments are described to show that cis-1,4-polybutadiene can be fractionated using the elution chromatography technique of Baker and Williams. Changes have been made to the equipment to give easier and more reliable operation. A method of selecting solvents and precipitants is described and it is shown that by proper selection of solvent and precipitant, the resolution of the higher molecular weight fractions may be improved. The influence on the fractionation of temperature, concentration of polymer in the eluant and column loading are investigated. It is concluded that column loading is the most important factor in explaining reversals of limiting viscosity number in the fractionation results.
Atmospheric Ozone in Helsinki and Its Effects on Rubber
Authors: Soininen Antti , Pehu-Lehtonon Anna-liisa , Auterinen Elli 
Published: February 2011

Abstract
Although the amount of ozone in the atmosphere is rather small compared with other gases its importance in several respects is rather great. This is mainly due to the high absorption and reacting capacities of ozone. The absorption capacity becomes apparent among other ways in the fact that the ozone layer of the atmosphere absorbs the excessive ultraviolet radiation coming from space as well as heat radiation from the earth. On the other hand, the reacting capacity can best be observed in numerous harmful oxidation phenomena, among which a typical example is the cracking of the surface of rubber products, caused by ozone. Generation and distribution of ozone in the atmosphere.—It is assumed that ozone is generated in the upper atmosphere photochemically under the influence of ultraviolet radiation. The shortwave ultraviolet radiation of a wavelength of about 2000 A breaks the oxygen molecules into atoms that combine with other oxygen molecules to form ozone. The ozone in turn absorbs ultraviolet radiation of a longer wavelength, which again breaks up the ozone thus maintaining an equilibrium in the concentration. This equilibrium is largely dependent upon temperature, the lower temperatures giving rise to a considerably higher concentration of ozone than the higher temperatures. The maximum concentration of ozone in the atmosphere is at an altitude of about 20 kilometers from the earth. The distance of this maximum from the surface of the earth, however, varies over different parts of the globe and according to the season. There is a constant movement of ozone from the actual ozone layer to the lower air regions near the surface of the earth. The major part of the ozone is destroyed near the earth's surface, as it comes into contact with oxidizable matter. Generally speaking, this movement of the ozone into the lower parts of the atmosphere is caused by turbulence, that is, by mixing of the air masses. In the atmosphere there is a regular circulation between the different regions. Near the equator the direction of the movement is upwards, from the troposphere to the stratosphere, while around the latitude 60 it is the other way around. This phenomenon explains, for example, the relatively large increase in radioactivity in polar districts and, in addition, it offers a partial explanation of the high ozone concentration near the surface of the earth in these parts compared with that in warmer regions.
Ozonation of Atactic Polypropylene
Authors: Lazar M. , Pavlinec I. , Manasek Z. , Micko M. , Berek D. 
Published: February 2011

Abstract
1. It is determined by study of the accumulation of peroxides in atactic polypropylene that ozone acts as an initiator of oxidation and considerably accelerates the course of the reaction even at room temperature. 2. The surface of the oxidized specimens is an important kinetic factor in the accumulation of the peroxides. 3. In addition to the formation of hydroperoxides in the initial phases of the process there takes place a crosslinking of the surface layer of the oxidized films by polymeric peroxides. These peroxides gradually decompose with the simultaneous formation of hydroperoxides. 4. The degradation of macromolecules under the action of ozone is less than in oxidation by the atmosphere.
The Compounding of Styrene—Butadiene Rubber with Shellac
Authors: Saxena K. K. , Banerjee S. 
Published: February 2011

Abstract
It has been possible to incorporate shellac up to 25 phr in OE-SBR without any difficulty on a roll mill by properly adjusting the temperature of rolls. Shellac acts as a lubricant and a processing aid at higher temperatures. A higher amount of shellac can be used safely as the stock becomes less and less scorchy. It improves tear resistance, tensile strength and hardness of the gum stock. Greater abrasion loss may restrict its use even though other properties are rather good. Due to the presence of lac dye in shellac stocks of different pastel shades may be obtained. From the present study it appears that shellac may be used as an extender and may replace rubber by 20 parts quite advantageously.
Vulcanization of Carboxylic Rubbers
Authors: Zakharov N. D. 
Published: February 2011

Abstract
1. A study of a series of substances contributing to structure formation was carried out. The most active of these materials were shown to be aluminum chloride, caustic soda, caustic potash, calcium oxide, magnesium oxide and calcium hydroxide. 2. It was shown that the quantity of chemical crosslinks in metal oxide vulcanizates of carboxylic rubbers was significantly less than in corresponding sulfur vulcanizates. 3. The number of crosslinks in the steric network of the vulcanizates depend on the form of the vulcanizing agent. Magnesium oxide gave the densest three dimensional structure. 4. It was shown that nonchemical intermolecular bonds play a significant role in the formation of structures of carboxylic rubbers. The assumption that these bonds could be of the hydrogen, van der Waals and coordination types was expressed.
Agglomeration and Reinforcement of Synthetic Latexes by Freezing
Authors: Talalay L. 
Published: February 2011

Abstract
For most applications rubber latexes must have high solids content. To achieve this, with reasonable fluidity, the latex particles must be large. Limitations in the kinetics of emulsion polymerization make it desirable to polymerize a small particle latex and postagglomerate to a larger size. This paper deals with the process of freezing and thawing a latex under controlled conditions which result in a substantial increase in particle size. The variables controlling the process such as soap coverage of the particles, pH, freeze duration, and freeze temperature are analyzed. The type of soap used is shown to affect the lower limit of usable freezing temperature. The polymer composition and hardness are shown to affect coagulum formation and the shape of the particles after freeze-agglomeration. Coagglomeration of a mixture of rubber and resin latexes by freezing is found to result in a reinforced polymer system analogous to that obtained by carbon black reinforcement of dry rubber. The effects of the particle size and the softening temperature of the reinforcing resin are demonstrated. An optical microscopic method for observing the freeze-agglomeration process is described and an attempt is made to elucidate the mechanism of the process.
Dilatometric Determination of Polymer Compatibility
Authors: Bartenev G. M. , Kongarov G. S. 
Published: February 2011

Abstract
1. The temperature contraction curves for rubbery polymer mixtures define the degree of compatibility of these polymers only when the glass temperatures are not close to the same. 2. Mixtures of obviously incompatible polymers display several glass temperatures (according to the number of polymers in the mixture). The values of these temperatures coincide with the glass temperatures of the pure polymers and do not depend on the ratio of the polymers in the mixture. 3. Mixtures of compatible polymers have a single glass temperature which changes linearly with the volume ratio of the polymers. 4. The coefficient of linear expansion (contraction) of all polymer mixtures follows the additivity law within the visible limits of experimental error from sample to sample.
Relaxation Processes in Vulcanized Rubber. III. Relaxation at Large Strains and the Effect of Fillers
Authors: Gent A. N. 
Published: February 2011

Abstract
Some experimental measurements are described of stress relaxation and creep at room temperatures in vulcanizates of natural rubber, butyl, and SBR. In an unfilled natural rubber vulcanizate the rate of stress relaxation is found to rise sharply for extensions of more than about 200%. Reasons are given for attributing this to the growth of a crystalline phase. Similar rates are observed at all extensions for a carbon black filled natural rubber vulcanizate. This is shown to be in satisfactory accord with the Mullins-Tobin model structure for filled vulcanizates, when the whole of the observed relaxation occurs in “softened” regions at rates appropriate to the high local deformations. The failure of rubber-carbon black associations with time does not appear to constitute a major relaxation process. In noncrystallizing unfilled vulcanizates the rate of relaxation is found to decrease somewhat with extension, possibly due to finite-extensibility effects. Preliminary measurements on a filled SBR vulcanizate suggest that a significant contribution to the observed relaxation arises from progressive failure of rubber-filler associations in this case. The relation derived previously between the rates of creep and stress relaxation at equivalent deformations is confirmed in all cases, within experimental error. Its validity in highly-irreversible systems is thus established experimentally.
Elastomeric Fibers Based on Polyurethanes
Authors: Rinke H. 
Published: February 2011

Abstract
Highly elastic polyurethanes suitable for fiber production can be obtained by various synthetic routes based on diisocyanate polyaddition processes. Macro-diisocyanates obtained from long chain diols and diisocyanates are allowed to react with polyamides during fiber formation (chemical spinning process) or the macrodiisocyanates are treated in solvents (e.g., dimethylformamide) with polyamines to give highly viscous, spinnable solutions of polymer. Both methods yield highly elastic polymers with wide-mesh network structures. The production of polyurethane fibers and their structures and physical properties are described.
Stresses at a Crack in an Elastomer
Authors: Andrews E. H. 
Published: February 2011

Abstract
A microscopical, photoelastic technique has been used to investigate the distributions of stress and strain around a crack in a highly elastic material, natural rubber. The finite strains encountered in such a material give rise to a distortion of the principal-stress map, an effect which has no parallel in classical elasticity and which leads to a complex dependence of the stresses upon the external constraint. The strain energy at a point is, however, simply related to the external constraint when the latter is expressed in terms of a stored energy parameter T, which is defined. The same parameter is shown to govern the distortion of the stress field. The decay of strain energy in a direction perpendicular to the crack axis is much more gradual when the strains are finite, but the rate of decay along the axis in the elastomer is similar, both in form and magnitude, to that predicted by infinitesimal-strain theory.
Preparation of Ultrathin Sections of Polymeric Materials
Authors: Razikov K. Kh. , Markova G. S. 
Published: February 2011

Abstract
Much importance attaches at the present time to the use of ultrathin sections for the investigation of the structure of polymeric materials by electron microscopy, electron diffraction and other methods. Extremely thin sections (down to hundredths of a micron) can be prepared by means of ultramicrotomes in which thermal regulation of the feed of the specimen is provided. The use of ultramicrotomes in various branches of sciences has given valuable information on the fine structure of many substances. In the present article we describe the use of the ultrathin section method for the investigation of the structure of polymers by means of an ultramicrotome of the “Sjostrand Ultra-microtome LKB-Producter” type. As a result of the elasticity of polymeric materials the preparation of thin sections is rendered difficult. Therefore the development of a method of producing ultrathin sections of polymeric materials is of considerable interest. We have developed such a method for the study of the structure of thin polymeric fibers (of diameter 15 to 20 µ) of thick monofilament (of diameter 0.5 mm and above) and also of films. The technique of preparation of ultrathin sections consists of the following stages: 1) embedding the specimens for investigation; 2) preparation of the specimen for cutting; 3) preparation of the knives; and 4) preparation of the apparatus and cutting.
Kinetics of Thiazole-Accelerated Sulfur Vulcanization of Natural Rubber
Authors: Russell R. , Smith D. A. , Welding G. N. 
Published: February 2011

Abstract
Thiazole-accelerated sulfur vulcanization of natural rubber gum stocks has been investigated at temperatures from 110° to 140° C for times over the range 1 to 104 min. Swelling measurements on the vulcanizates were used to estimate the contribution of chemical reactions to the network chain density, (ρMc−1)chem which was plotted against cure time. The kinetic graphs show clearly an induction period (t0), then fast crosslinking, a slow limited degradation, and finally a “long-time” crosslinking reaction. Apart from the induction period, each of the kinetic graphs is satisfactorily represented by a rate equation assuming three independent additive reactions: first order crosslinking, first order partial degradation, and a long-time reaction assumed to be zero order. The method has been used to compare MBT and MBTS at equal concentration. One consistent difference is the increase of induction period with MBTS in place of MBT, accompanied by a somewhat greater increase of time of cure to maximum network density. Also the completed contributions (Xand Δ) from the initial crosslinking reaction and the degradation reaction, respectively, are greater with MBTS than with MBT. Over the temperature range studied there is no difference between MBT and MBTS in the activation energies for crosslinking, or for t0−1 or for the long-time reaction, but MBTS has a higher activation energy for degradation than MBT. With rising temperature of cure, Δ increases towards X with each accelerator.
Fluid Bed Vulcanization
Authors: Hughes B. G. , Izod D. A. W. , Moakes R. C. W. , Soden A. L. , Watson W. F. 
Published: February 2011

Abstract
This paper describes the use of fluidized solid particles as heating medium for rubber vulcanization, with emphasis on the continuous vulcanization of unsupported extrusions. The relevant features of fluid beds for this purpose—density, pressure and flow of gas, particle size, viscosity, heat transfer, chemical inertness—are considered. The construction and experience in the use of a horizontal trough and vertical column fluid bed are outlined. Attendant problems, notably porosity of the vulcanizate, are dealt with.
Intrinsic Viscosity-Molecular Weight Relationship for cis-1,4-Polyisoprene
Authors: Beattie W. H. , Booth C. 
Published: February 2011

Abstract
The intrinsic viscosity-molecular weight relationship has been determined for synthetic cis-1,4-polyisoprene prepared with butyllithium initiator. The best representation of our results is the equation,[η]=2.00×10−4(Mv)0.728 for intrinsic viscosities determined in toluene at 30° C. This relationship agrees, within experimental error, with that obtained for natural rubber by Carter, Scott, and Magat.
Influence of Chemical Modification on the Oxidizability of Natural Rubber
Authors: de Merlier Jacqueline , Le Bras Jean 
Published: February 2011

Abstract
The rubber hydrocarbon, which presents two reactive sites for each isoprenic unit: the double bond and the α-methylenic carbon, is highly sensitive to the action of oxygen. It is known that different products can react with rubber, some by addition on the double bonds, others by combination to the α-methylenic carbons and we have attempted to determine the influence that these modifications might have on oxidizability. The reagents chosen were maleic anhydride to block the α-methylenic carbons and saligenol to saturate the double bonds. Modified rubbers containing varying proportions of these reagents were prepared and their oxidizabilities at 80° C were measured, using the manometric method. In both cases an important decrease of oxidizability was noted, which went far beyond what might have been expected from the small proportion of reactive groups combined; differences in the oxidation kinetics were also observed, according to the mode of combination to the rubber hydrocarbon of the two types of reagent used. These results show that it is possible, in this way, to improve the resistance of raw rubber to oxidation and that this will probably influence the behavior of vulcanizates.
Reaction Products of Chloral with cis-1,4-Polyisoprene
Authors: Pinazzi Christian , Pautrat Rene , Cheritat Roland 
Published: February 2011

Abstract
In an earlier note the fixation of chloral onto cis-1,4-polyisoprene (natural or synthetic) in the presence of a catalyst such as AlCl3 or BF3 was discussed. A similar combination with glyoxal has already been mentioned. The fixation of chloral produces macromolecular products with a level of fixation of not higher than n=30 (n, number of reagent molecules attached to a chain of 100 C5H8 units). These compounds contain hydroxyl groups, the infrared bands of which appear at 3,300–3,500 cm−1, while the chlorines are identified at 570, 620, 680, 730, and 1,080 cm−1; these bands can be attributed to side chains —CHOH—CCl3. Also, the band which is characteristic for the cis configuration remains in the spectrum, but has decreased in comparison with the blank; the broadening of the peak at 1,640 cm−1 and the presence of a band at 860 cm−1 indicate the appearance of vinylidene double bonds not located in the chain. This observation is in agreement with our earlier work. The presence of side chains —CHOH—CCl3 is confirmed by the reactivity inherent to these functional groups. The expected reactions take place but are limited by the formation of a three dimensional network resulting in insoluble compounds. Thus, a modified polyisoprene (n=15) loses only 60% of its chlorine by heating to 130° C in xylene solution in presence of finely dispersed sodium. It is difficult to eliminate the remaining chlorine because the radicals formed by the —CCl3 groups produce crosslinking. Phenyllithium produces similar effects to those of sodium, in addition a certain number of phenyl groups are added and result in bands found at 1,495–1,580 cm−1. The presence of hydroxyl groups is also verified by reaction with acetyl chloride. Bifunctional reagents such as adipoyl dichloride or hexamethylene diisocyanate produce crosslinking reactions which become evident by rapidly increasing insolubility.
Studies of the Hard Rubber Reaction. I. Heat of Reaction
Authors: Bhaumik M. L. , Banerjee D. , Sircar Anil K. 
Published: February 2011

Abstract
A method for the determination of the heat of the hard-rubber reaction by the application of differential thermal analysis is reported. The heat of reaction was determined with stocks containing different rubber/sulfur ratios and also with a 68/32 stock, preheated to contain different amounts of combined sulfur. Heat evolution is observed first with samples containing about 7 per cent sulfur and therefrom the amount of heat evolved shows a nearly linear increase up to 30 per cent sulfur. With increasing combined sulfur in the 68/32 stock, the quantity of exothermic heat gradually diminishes; so also does the temperature of initiation, i.e., the temperature at which heat evolution appears to begin. Initiation of the exothermic reaction appears to be a function of composition and temperature of the mass. An increase in the rate of reaction was observed when the composition reached 0.5 g-atom of sulfur per isoprene unit. An endothermic dehydrogenation reaction is observed at the end of the hard-rubber reaction. This, however, does not affect the determination of exothermic heat, because there is similar dehydrogenation taking place in the reference material (ebonite) which almost balances this heat loss. The final product has a lower sulfur content due to loss of sulfur as hydrogen sulfide.
A Molecular Theory of Filler Reinforcement Based upon the Conception of Internal Deformation (A Rough Approximation of the Internal Deformation)
Authors: Sato Yoshiyasu , Furukawa Junji 
Published: February 2011

Abstract
A molecular theory is presented in this paper which gives a method of analysis for the mechanical properties of filler-reinforced elastomers, based upon the concept of the internal deformation and the statistical theory of rubberlike elasticity. By using a suitable model and a few new concepts a proper analysis for such a heterogeneous system is obtained. From the theory the internal mechanism of filler reinforcement is understood. It is made clear that reinforcement consists of three effects: the volume effect, the surface effect, and the cavitation effect. From the theory, formulae for the tension, swelling tension, Young's moduli, local stress distribution, strain birefreingence, condition for swelling equilibrium, and so on are derived. It has long been recognized that rubbery substances and plastic materials are reinforced by incorporation of suitable powdery substances (reinforcing fillers) which improve their mechanical properties such as elastic modulus, hardness, stiffness, resilience, solvent resistance, plastic viscosity, tensile strength, tear resistance, etc. Although numerous attempts have been made to clarify and systematize the internal mechanism of filler reinforcement, there is at present no distinct picture of the mechanism, much less a satisfactory theoretical treatment of the phenomena.
Spectrophotometry and Chromatography for Identification of Antioxidants and Accelerators in Rubber Mixtures
Authors: Fiorenza A. , Bonomi G. , Piacentini R. 
Published: February 2011

Abstract
The difficulties encountered in the identification of antioxidants and accelerators in rubber mixtures are reviewed. A method of column chromatographic separation of components contained in the mixture extracts is discussed. The identification of the principal ingredients is achieved by means of ultraviolet and infrared spectrophotometry utilizing mixtures containing different antioxidants. Various spectra are presented, produced by both types of spectrophotometry, illustrating the efficiency of the method. The method could also be used to identify certain components of plastic material extracts.