bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modification of Carbon Black with Ionizing Radiations
Authors: Lezhnev N. N. , Nikitina T. S. , Kuzminskiĭ A. S. 
Published: February 2011

Abstract
It is well-known that the reinforcing properties of carbon blacks used as active fillers for rubber depend to a considerable extent upon the adsorption properties of the surface of the carbon black particles. The presence on this surface of atoms and groups of polar or apolar character chemically bound with it, the surface relief and the presence of atoms with unsatisfied valencies in the hydrocarbon framework of the elementary crystallites determine the specific adsorption properties of carbon black of various types. In the present investigation we demonstrate the possibility of modifying the surface of the carbon blacks by the action of ionizing irradiation and by the radiochemical “sewing-up” of various compounds on their surface. Such modified carbon blacks have a considerable influence upon the physico-chemical properties of the resulting vulcanizates, which may make is possible to create new materials. The investigation was devoted to: (1) Ukhta thermal black—a typical representative of the soft semireinforcing blacks (practically not oxidized) ; (2) channel black from the same works—a hard active black, having a markedly oxidized surface, capable of irreversible interaction with the surface of the rubber and with the compounding ingredients.
Recent Developments in Superior Processing Natural Rubber
Authors: Baker H. C. , Foden R. M. 
Published: February 2011

Abstract
SP rubbers give greater latitude in extrusion and calendering processes by extending the range of operating conditions and giving greater scope for compounding for good physical properties. Compounds based on SP rubbers extrude smoothly with lower die swell at lower temperatures and higher viscosities. Greater productivity is obtained through the faster screw speeds which are possible with SP rubbers in many types of compound. SP rubber compounds calender with greater conformity to gage, greater ease of handling and control of shrinkage of the calendered sheet, at temperatures 10° C lower than normal. The firmer stocks given by SP rubbers and their greater resistance to degradation on milling lead to reduced wastage of unvulcanized compound in the factory, while the stricter control of processing permitted by SP rubbers results in a lower percentage of rejected articles. Evaluation of an experimentally produced SP 90 crepe has indicated the potentialities of a concentrated form of SP rubber as a more efficient processing aid than crosslinked SBR 1009 with NR and SBR.
Polymerization of Vinyl Monomers in Rubber Latexes
Authors: Allen P. W. , Bell C. L. M. , Cockbain E. G. 
Published: February 2011

Abstract
In recent years numerous workers have reported on the polymerization of vinyl monomers, in the presence of polymers, in which graft copolymers and/or homopolymers are formed. Kinetic studies of such reactions have been relatively few, however, particularly for systems involving polymer latexes rather than solutions. In the present paper a kinetic study of the polymerization of styrene, methyl methacrylate, and homologous methacrylic esters in natural rubber latex is reported, and certain abnormal features of the polymerizations are discussed.
Vulcanization of Elastomers. 25. Natural Rubber and Synthetic Elastomers with Sulfur and Sulfenamides. I
Authors: Scheele Walter , Toussaint Horst-Eckart , Chai Yoan-Kun 
Published: February 2011

Abstract
The sulfur vulcanization of Perbunan N 2818 (acrylonitrile-butadiene) was investigated in the presence of N-cyclohexyl-2-benzothiazolylsulfenamide (CZ) at different temperatures and various concentrations of reactants. The following were found : 1. The decreasing sulfur concentration vs. time plot followed the 0.8th order under all experimental conditions and an activation energy of 28.2 kcal/mole was calculated. 2. When using the cyclohexylammonium salt of MBT as accelerator, sulfur decrease proceeds at the same rate as with CZ. 3. It was concluded from 1 and 2 that even in the presence of CZ, the ammonium salt was the actual accelerator, which forms during the scorch or induction period through reaction of CZ with the rubber. 4. In view of the discrepancy found in the relation of reaction order with respect to time and concentration of reactants, the formation of a reactive intermediate is postulated; the analogy between the kinetics of sulfenamide accelerated sulfur vulcanization, and those accelerated with MBT as well as DPG is pointed out. 5. In connection with 3 the dependence of starting rate as well as rate constant of 0.8th order of the decreasing sulfur concentration on the molar ratio of CZ/S8 and on the sulfur starting concentration is discussed.
The Role of Hysteresis in Tire Wear and Laboratory Abrasion
Authors: Schallamach A. 
Published: February 2011

Abstract
The simple theory outlined in this paper accounts for the wear of slipping wheels in their dependence on external parameters. In addition, it draws attention to the importance of the elastic properties and the unsuspected influence of mechanical hysteresis. The experimental evidence brought forward in support of this side of the theory stems mostly from laboratory work. When attempting to apply the theory to road wear, it must be kept in mind that the mechanical properties of tires are only in part determined by the tread, their elastic behavior being largely that of the pneumatic casing. Laboratory experiments carried out with solid wheels give therefore an exaggerated estimate of the influence exercised by the hysteresis of the tread on the rate of wear. Nevertheless, the relation between wear and hysteresis should be as valid for tires as for other slipping wheels, if the resilience pertaining to the tire as a whole is introduced into the calculations. There is another aspect of hysteresis which might usefully be mentioned here. In the foregoing, the rolling resistance of tires has been neglected. While rolling resistance has most probably little effect on the wear mechanism, it does increase with increasing hysteresis of the tire. Thus, lengthening the life of a tire by increasing its hysteresis has to be paid for by an increased fuel bill.
Power and Thrust Force of Mill Rolls during the Mastication of Rubber
Authors: Mikhalev M. F. 
Published: February 2011

Abstract
There is described the dependences of change in plasticity of rubber upon the time of mastication, the peripheral velocity of the rolls, the gap, and the friction ratio. Equations are recommended for practical use which make it possible to determine the magnitude of the power of the machine and of the thrust forces set up in the gap between the rolls during mastication of raw rubber as a function of grade and initial plasticity. In addition, the authors investigated the dependence of these values upon the recovery and softness of the rubbers, a characteristic feature being that the relationships of the alteration in P and N to the recovery and softness remain the same as in the case of plasticity, and differ only in respect of the values of the coefficients and indexes. The equations describing these relationships will be considered by the authors in subsequent articles.
Microhardness Testing, Its Possibilities and Limitations
Authors: Scott J. R. , Soden A. L. 
Published: February 2011

Abstract
The need to test small awkwardly shaped rubber articles, which cannot be tested by normal methods, has led to the development of a scaled-down micro test for hardness. Attention is drawn to the mechanical problems that arise in devising such a micro test, especially those associated with friction in the moving parts and with the measurement of the very small movements of the indentor; the various ways in which these problems have been solved are described. The results of experimental work are presented to show the substantial equivalence in readings between the micro and the normal (macro) test, the good reproducibility of micro test results, the influence of testpiece dimensions, and the advantage of using a foot on the instrument as specified in ISO Recommendation R48 for the normal hardness test. Attention is drawn in particular to the influence of the dimensions of the rubber tested, showing on the one hand that reliable hardness measurements can be made, as expected theoretically, on much thinner and smaller specimens than in the standard test, though on the other hand there are minimum dimensions below which even the micro test cannot be expected to give results agreeing strictly with those of the macro test.
Electron Paramagnetic Resonance Investigation of Vulcanization
Authors: Blokh G. A. 
Published: February 2011

Abstract
New and extensive prospects are being developed with the employment of electron paramagnetic resonance (radiospectroscopy) (EPR) for the investigation of the chemical reactions taking place in the vulcanization of rubber. It is well-known that molecules which are taking part in chemical reactions in the majority of cases pass through the state of forming chemically active free radicals in which there are electrons having unpaired spins, i.e., the radicals have magnetic moments. Observation of the occurrence and disappearance of free radicals in chemical processes may be effected by the investigation of the paramagnetic resonance absorption of these radicals. Measurement of the radio-frequency of any given compound makes it possible to determine the degree of dissociation into free radicals. Consequently it becomes exceptionally valuable to employ EPR to solve the question of the nature of the reactions which take place in vulcanization. If in point of fact vulcanization is a radical reaction, then we ought to be able to observe EPR spectra.
The Lability of Sulfur Atoms in Vulcanization
Authors: Blokh G. A. 
Published: February 2011

Abstract
The application of the isotope method to the investigation of the mechanism of the action of accelerator and vulcanizing agents has made it possible to look at this question in quite a new light. With the help of the isotope S it has been demonstrated that in the process of curing there takes place a continuous exchange of atoms of sulfur in the structure of the accelerators, and of elementary sulfur as a vulcanizing agent, with the formation of unstable intermediate compounds. The sulfur thus liberated undoubtedly has high energy, as a result of which it combines rapidly with the rubber. It must be remembered in this connection that the reacting elementary sulfur is an eight-membered S8 ring, while the sulfur liberated from the sulfur containing compounds has the open chain structure:
Diffusion of Sulfur in Rubber in Relation to Vulcanization
Authors: Ludwig Rudolf 
Published: February 2011

Abstract
The present work is a report concerning the diffusion of sulfur in rubber. Following a suggestion of Prof. W. Seith, it was originally planned to investigate only the diffusion of radioactive, bound sulfur. If such a diffusion took place at all, it would seem to be equivalent to a wandering of the sulfur bridges which crosslink the carbon chains of the polymerized isoprene molecules in the vulcanizate and impart elasticity to the rubber. However, since the sulfur bridges are not exactly defined, and other types of combined sulfur can be present in the rubber, such a conclusion is not quite justified. Before such measurements are undertaken, one should be familiar with the diffusion of free sulfur in the rubber. Furthermore, a possible thermodynamic equilibrium between the free and the bound sulfur might invalidate the measurements. It was thus necessary to first determine the possibility of the occurrence of this equilibrium as well as the rate at which it is established. The diffusion experiments made it mandatory that suitable analytical procedures be found. Because of the multiplicity of the procedures, methods, and results, it appeared to be desirable to subdivide the material to be presented into several sections. First there will be a compilation of literature dealing with the chemistry of vulcanization.
Radiation Crosslinking of Rubber. III. Chain Fracture
Authors: Mullins L. , Turner D. T. 
Published: February 2011

Abstract
Exposure of hydrocarbon polymer molecules to high energy radiation results either in a decrease in their molecular weight or else in an increase with the eventual formation of an insoluble network. The primary faetor determining the behavior is the relative incidence of fracture of the main chain of carbon atoms to crosslink formation. The ratio of fractures to crosslinks β has usually been estimated from studies of the solubility of irradiated polymers. Most of this work has been on polyethylenes, but even under comparable experimental conditions widely differing estimates of β have been reported. The use of stress-relaxation measurements to detect the fracture of network chains during irradiation has also been reported. A recent study of the elastic behavior of crosslinked networks has indicated that comparative estimates of the number-average molecular weights of both (1) the chain segments lying between adjacent crosslinks and (2) the molecular chains crosslinked into the network may be obtained from stress-strain measurements alone. In the present work an attempt has been made to apply all three methods in a study of chain fracture occurring during the irradiation of purified natural rubber in vacuo.
Effects of Type of Rubber, Temperature, and Degree of Crosslinking on the Friction Properties of Elastomers
Authors: Bartenev G. M. , Styran Z. E. 
Published: February 2011

Abstract
1. The data on the influence of temperature and rate of slip on the frictional action of elastomers confirms the results of Schallamach for compounds of natural rubber and indicates that the external friction of highly elastic materials is a molecular-kinetic process of transition of chains, which adhere to the other rubbing surface, over an energy barrier under the action of an external force and thermal motion. 2. The energy barrier, which is dependent on the force of adhesion of the rubbing materials (energy of activation), is changed only slightly by changing the temperature, load and crosslink density for compounds from the same rubber. A greater change in the activation energy occurs by going from one polymer to another (from 18 to 32 kcal/mole). It is higher for polar rubbers (SKN) than for nonpolar rubbers (NR, SKBM, SKS). 3. Independently of the nature of the rubbing pair, the friction of elastomers follows Formula (2) over the range of slip velocities of 0.001–10 mm/min. In spite of the use of extremely small slip velocities, such a limit was not reached which might be attributed to the existence of actual static friction with the highly elastic materials. On the contrary, the drop in the coefficient of friction with decreased rate of slip became sharper the smaller the rate. For all elastomers there is observered a drop in the force of friction up to 60–80°. Above this region is an anomolous portion of the curve, the more sharply expressed, the greater the polarity of the rubber. The anomolous change in the force of friction is connected with the increase in the effective area of contact resulting from the destruction of the secondary bonds in the three dimensional network and a decrease in the static modulus of the compound. 5. High modulus compounds give a linear relationship for the force of friction up to 100–120° while low modulus compounds have a deviation in their linearity which appears, the earlier, the lower the equilibrium modulus. The slope of the linear portion of these compounds is greater than that of the lower modulus compounds which is connected with the increase in the effective area of contact at the transition from a hard to a soft compound. 6. At small normal loads (to 3 kg/cm2) the properties of the law of friction may be described by Coulomb's law. The force of friction is a linear function of the effective area of contact.
The Influence of Polymers with Conjugated Bond Systems on the Stability of Polyvinylchloride
Authors: Berlin A. A. , Popova Z. V. , Yanovskiĭ D. M. 
Published: February 2011

Abstract
We may now consider thermal and light initiated oxidative degradation in halogen-containing carbon-based polymers to occur through a radical-chain mechanism. Obviously the process is initiated by radical products of degradation in macromolecules, particularly by alkoxyl and hydroxyl radicals originating in the breakdown in the polymer of hydroperoxides. The development of the chain process occurs with the splitting out of atoms of hydrogen and halogen, resulting in dehydrochlorination to form double bonds and breaking down of the macromolecule. Although until recently there has been no very well-defined indication of the mechanism of formation, development, and splitting of the chains through thermal and light-oxidative degradation of Polyvinylchloride (PVC) it may be asserted that the most effective inhibition of this process is possible only by using materials which have the ability to accept radicals. Naturally, the radical acceptors employed can only be those which on heating, and exposure to the presence of air will not form hydroperoxides capable of reinitiating the destructive processes. Of major theoretical and practical interest in this connection, there have been described investigations on the effect of thermoxidative degradation in PVC, by a certain type of recently synthesized polyphenylvinylene (PPV) also containing the conjugated bonds of the degradation products of some high polymers, in particular PVC.
Strength and Elastomeric Properties of Rubber Solutions and Their Vulcanizates at High Deformation Rates
Authors: Trapeznikov A. A. , Assonova T. V. 
Published: February 2011

Abstract
Investigations of the strength and elastic properties of rubber solutions and of vulcanizates are of interest in relation to studies of the formation and character of the structures in such solutions. We carried out determinations with the aid of an elastoviscometer for oscillographic recording of P(ε) curves at high values of ˙ε⋅2, and also an elastorelaxometer designed for direct measurements of elastic deformations in flowing systems at high values of ˙ε. P(ε) curves for 6% solution of rubber in decalin are given in Figure 1.
The Mechanochemical Modification of High Polymers
Authors: Ceresa R. J. 
Published: February 2011

Abstract
Degradation of natural rubber during mastication has been shown to proceed via two alternative mechanisms, oxidative scission at high temperatures and mechanical scission at lower temperatures. The low temperature process, cold mastication, has received the greater attention. The energy supplied to the extended rubber chains during mechanical deformation is sufficient to cause homolytic scission into polymeric free radicals. The degradation of high polymers by a rupture process via mechanical scission has been shown to occur during the cold mastication of synthetic elastomers and during the mechanical working of high molecular weight vinyl and acrylic polymers in the visco-elastic state. The application of shearing forces to certain polymers in the brittle glass state has provided evidence for both homolytic scission into polymeric free radicals and heterolytic scission into polymeric ions. Polymeric radicals, produced by mechanical chain scission, have been used as initiators of vinyl polymerization to give block copolymers of an essentially linear character. Thus the block copolymerizations of methyl methacrylate, styrene, vinyl acetate, acrylonitrile, and ethyl acrylate have been initiated by mechanically shearing natural rubber, polymethyl methacrylate, polystyrene, polyvinyl acetate, polyethylene, polyvinyl chloride and polyvinyl formal during the process of extrusion of the polymer plasticized to a viscoelastic state with the monomer. Many other polymer-monomer systems have yielded block copolymers by cold mastication. Cold mastication of elastomer blends, such as natural rubber and neoprene, also leads to block copolymer formation by both combinative and hydrogen abstractive processes between the different species of elastomer radicals present. If two polymers are completely compatible so that one continuous phase is present in the blend, and if the polymeric constituents have a common viscoelastic temperature range, then mechanical working during extrusion or internal mixing can lead to block copolymer formation. If the tendency of the polymeric radicals formed by mechanical rupture is to recombine rather than to disproportionate, then the chances of block copolymer formation are increased. The presence of sites for hydrogen or halogen abstraction upon one of the polymer constituents is also an aid to grafted block copolymer formation. Thus polyvinyl chloride-neoprene blends give grafted block copolymers on extrusion or internal mixing and polyethylene-polyvinyl acetate blends block copolymerize when masticated in the absence of oxygen. Block copolymerization is largely controlled by the viscoelastic properties of the systems chosen.
Mechanochemical Phenomena in Polymers. III. Strength of the Bond between Elements of Multiply Polymer Articles
Authors: Slonimskiĭ G. L. , Drugova G. P. 
Published: February 2011

Abstract
1. The basis of the process of ply separation of multiply rubber articles under repeated deformations is fatigue of the material in the region of the joint of the plies, which is a mechanochemical process, as previously studied, consisting of the development of chain chemical processes initiated by free radicals which are formed in the mechanical scission of chemical bonds in the molecules. 2. By the addition of substances inhibiting chain radical processes to the polymer it is possible to raise considerably the strength of the bond between elements of multiply vulcanized rubber articles.
Mechanochemical Phenomena in Polymers. IV. Modification of Raw and Vulcanized Rubbers
Authors: Slonimskiĭ G. L. , Kargin V. A. , Reztsova E. V. 
Published: February 2011

Abstract
1. Mechanical processing of polymers swollen in substances capable of polymerizing leads to the development of processes of radical polymerization initiated by mechanical scission of chain molecules. The new polymeric substances thus formed have a correspondingly altered set of properties. 2. Processes of manufacturing polymers which are closely connected with the development of mechanochemical processes may be used to improve the properties of the processed polymer.
Polymerization of Isoprene by Organomagnesium Compounds
Authors: Fo-shung Wang , Dolgoplosk B. A. , Erusalimskiĭ B. L. 
Published: February 2011

Abstract
1. It was established that ether-free organomagnesium compounds promote the polymerization of isoprene at elevated temperatures. 2. The polyisoprene so-formed is mainly 3,4 linked. The nature of the halogen and radicals in the organomagnesium material has no influence on the microstructure of the polymer chains. 3. The presence of complex-forming agents (ethyl ether and triethylamine) affect an appreciable reduction in the velocity of polymerization and a marked lowering in the content of 3,4 links in the chains.
Absence of 3,4-Structure in Natural Polyisoprenes
Authors: Fraga D. W. 
Published: February 2011

Abstract
The concentration of 3,4 structure in hevea and balata has been the subject of some controversy in the past few years. The controversy concerns the assignment given to an absorption band found at 11.25 µ in the spectra of hevea and balata. It is known from the spectra of simple compounds that the isopropenyl group gives an absorption band at 11.25 µ, and that an absorption occurs at 11.25 µ in the spectra of synthetic 3,4(isopropenyl)-type polyisoprene. Salomon and van der Schee, in 1954, stated that it was tempting to assign the 11.25 µ peak in hevea and balata to the 3,4-type structure; however, they found that the absorption at 11.25 µ survived ozonization of the polymer. This cast some doubt on the validity of the assignment. Binder, in 1957, assigned the absorption at 11.25 µ to 3,4 structure and calculated that hevea and balata contained 2.2 and 1.3 wt-% 3,4 structure, respectively.