bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theory of Bound Rubber
Authors: Meissner B. 
Published: February 2011

Abstract
A theory of bound rubber formation has been developed which treats the effect as random adsorption of structural units of polymer on reactive sites which are assumed to exist on the surface of filler particles. Equations are derived for the fraction of bound rubber and for the molecular weight distribution of free (unbound) rubber. The theory contains only one adjustable parameter, the filler surface area per reactive site, A0. It is shown for the case of the Schulz distribution that the amount of bound rubber depends but slightly on the dispersion parameter of the polymer and is determined essentially by the adsorption index MwcP/A0NA, where c is the filler concentration, P is its specific surface area, and NA is the Avogadro number. All of the experimentally observed features of the bound rubber effect, including preferential adsorption of large molecules, are correctly predicted, the quantitative agreement of the theoretical equations with available experimental data being satisfactory. This supports the underlying assumption that the processes involved in the polymer-filler interaction may be approximated by a random-process model.
Particulate Reinforcement of Polyacrylate Elastomers. I. Introduction and Preparation of Materials
Authors: Blackley D. C. , Sheikh M. W. 
Published: February 2011

Abstract
The series of papers, of which this is the first, aims to demonstrate the importance of chemical reactions between filler particles and elastomer matrix in determining the physical properties of filled elastomers. A model system comprising small glass beads as the filler and crosslinked poly (ethyl acrylate) as the elastomer has been used. The beads themselves are inert towards the matrix during polymerization, but the reactivity of the surfaces of the beads can be varied by suitable treatments. This paper describes techniques for fractionating the beads to give narrow particle-size distribution, for preparing unfilled and filled elastomer sheets, and for preparing composites in which an elastomer sheet is polymerized in contact with a glass plate which may or may not have been previously subjected to surface treatment.
Recent Chemorheological Studies on Rubber Vulcanizates
Authors: Murakami K. 
Published: February 2011

Abstract
The structural changes of materials caused by chemical reactions are reflected in the viscoelastic behavior of these substances. Such viscoelastic behavior induced by chemical reaction was termed “chemorheology” by Tobolsky. This phenomenon is not readily observed in linear polymers since molecular flow, because of diffusion or chemical reaction, is generally much more rapid than relaxation. It has become possible, however, to establish chemorheology of linear polymers, by taking physical flow into consideration. As there is no mechanism for flow in crosslinked polymers, the rheological behavior at sufficiently high temperatures is almost always determined by chemical reactions. A significant problem in the degradation of crosslinked polymers is the determination of whether the scission of the crosslinked polymer occurs along the main chains or at crosslink sites. Both extreme cases have been studied theoretically and experimentally by A. V. Tobolsky and coworkers, while the case in which both types of scission occur simultaneously was suggested by Horikx. However, because of the difficulty of analysis for the case of simultaneous occurrence of both types of scission, there is as yet nothing in the literature. This paper deals with the theoretical and experimental results of the chemorheological treatment of crosslinked polymers concerning their scission mechanisms.
Accelerated Heat-Aging Studies on Fluorosilicone Rubber
Authors: Kalfayan S. H. , Silver R. H. , Mazzeo A. A. 
Published: February 2011

Abstract
The accelerated aging of a vulcanizate of fluorosilicone rubber was studied by four methods: infrared spectroscopy, GPC, weight loss, and stress relaxation, with the object of gathering information pertinent to understanding the basic mechanism of its aging. No changes were observed in infrared spectra of the rubber aged in air up to 315°C although severe degradation took place, as evidenced by high weight loss and drastic change in the physical condition of the test samples. It was concluded that although the polymer degrades, there is no change detectable within the precision of the analytical methods in the structure of the repeat unit of the elastomer. The gel-permeation chromatogram of unheated rubber showed peaks at MW 450 000 (95%) and 630 (5%). The low-molecular-weight component is very likely the cyclic tetramer of λ,λ′,λ″-trifluoropropylmethylsiloxane, the principal monomer of the FVMQ used. Heat aging increased the concentration of the 630 MW component, but rate studies were prevented by complications resulting from solvent-induced rubber degradation. Rapid decrease in the MW of FVMQ, as found by GPC, indicated random scission in the polymer backbone, as opposed to ordered unzipping of the repeat unit. The same conclusion was reached from the effects of crosslink density on stress relaxation. Activation energies obtained from weight-loss measurements (104 kJ/mol) were lower than those obtained from stress-relaxation measurements, (150–155 kJ/mol), suggesting that the processes being measured in each case may not be the same. Chemical stress relaxation takes place more rapidly in the presence of air than in an inert atmosphere, and intermittent stress-relaxation measurements indicate that crosslinks form during thermal aging in air, their rate first increasing and then decreasing.
Recycling Scrap Crosslinked Urethane Polymers
Authors: Gerkin R. M. , Critchfield F. E. , Miller W. A. , Roberts R. , Seefried C. G. 
Published: February 2011

Abstract
A. Scrap LRM polymers can be ground to powder on the Banbury operating at ambient temperature with cooling of the rotors and jacket. Particle size reduction can be accomplished in 5 min at 180 rpm. B. Powdered LRM polymer can be blended with TPU up to 50 wt.% and the composite compression molded to give the same properties as the TPU. C. Powdered LRM polymer can be blended with nitrile, chloroprene, and EPDM rubbers to give incompatible composites. The powdered LRM polymer acts in a manner similar to typical nonreinforcing fillers. D. It is possible to degrade powdered LRM polymers to a tacky mass at 180°C, which behaves much like a typical extender oil, when blended with nitrile and chloroprene rubbers. It is speculated that the degraded urethane should show a high degree of permanency in such blends. E. Addition of the urethane polymer to the rubber stocks does not interfere with the standard sulfur-curing mechanisms. F. Scrap HR foam can be ground to a powder in the Banbury in a manner similar to LRM scrap. G. A blend of 5 phr of powdered foam with a new HR foam formulation was machine processable. Addition of the powder had only a minor effect on the properties of the new foam.
Structure-Property Relationships of N,N′-Dinitroso-P-Phenylene-Bis (Hydroxylamine) Salts. Vulcanization of Nonhalogenated Elastomers
Authors: Martel Rock F. , Smith David E. 
Published: February 2011

Abstract
In a previous report the vulcanization activity of N,N′-dinitroso-p-phenylene-bis(hydroxylamine) salts in Neoprene WRT was discussed. The vulcanization was catalyzed by addition of stoichiometric amounts of aluminum or zinc powder (based upon percentage of allylic chloride), very possibly via the metal halide formed in situ. Natural rubber could not be vulcanized with these materials, however, differential thermal analysis indicated that amine-treated neoprene undergoes a crosslinking reaction at above normal curing temperatures. This evidence led us to propose that bisalkylation (α and/or β) at the allylic position is responsible for the formation of crosslinks. The mechanistic path is shown in Equations 1 and 2, and the analogy with the SN2′ activity of diamines in neoprene is quite apparent. The crosslinks III and/or IV are shown as the β form and one of the possible a structures. A number of structures for the α form have been proposed. The β structure has been known for some time. Our primary interest at this point was to extend the activity of N,N′-dinitroso-p-phenylene-bis(hydroxylamine) salts to elastomers which do not contain halogen. Any hope of achieving this goal depended, for the most part, upon whether or not certain of these materials would produce p-dinitrosobenzene, a known crosslinking agent, during the vulcanization cycle. The silver salt of phenylnitrosohydroxylamine, the monosubstituted counterpart of the bis(hydroxylamine) structure, decomposes readily to nitrosobenzene, nitric oxide and metallic silver. Accordingly, we prepared the di-silver salt of N,N′-dinitroso-p-phenylene-bis(hydroxylamine). The maximum rate of decomposition of this material was determined by differential thermal analysis, and occurred at 295° F. When 1.0 g of the di-silver salt was heated [see Reaction (3)] at 200° F for 2 hours, 0.3 g of a yellow solid sublimate was collected on a cold finger. The infrared spectrum of the yellow solid was identical with that of an authentic sample of p-dinitrosobenzene. Oxides of nitrogen were also visible in the reaction vapors (brown coloration).
Sorption and Diffusion in Crystalline Elastomers. I. Solubility of Isomeric Hydrocarbons in Stretched Rubber
Authors: Barrie J. A. , Platt B. 
Published: February 2011

Abstract
An important property of a polymer matrix which has a marked effect on the diffusion and sorption of vapors in polymer films is the degree of crystallinity. It is well established that the presence of crystallites leads to a decrease in both vapor solubility and permeability. Even so it is only recently that attempts have been made to relate these properties quantitatively with the degree of crystallinity. Most of this work was conducted with unstrained crystalline material, and relatively few data are available for stretched polymers either crystalline or noncrystalline. It was the main object of this work to investigate in more detail interrelations of vapor solubility, vapor permeability, and degree of crystallinity or orientation. The system hydrocarbon vapor-vulcanized natural rubber has been extensively characterized with respect to vapor permeability and solubility for regions of low penetrant concentration in the temperature range 30–60° C. As such it affords a useful reference state for studying the effect on either of these properties of a given degree of crystallinity or of orientation induced by subjecting the rubber to a simple elongation. Further, compared with unstretched semicrystalline polymers, the morphology of stretched rubber is comparatively straightforward, complex spherulitic growths being absent. In Part I of this paper we present and discuss solubility data obtained for isomeric hydrocarbons in stretched vulcanized natural rubber. The corresponding diffusion data are dealt with in Part II (following article, this issue). Throughout the investigation the degree of crosslinking was maintained constant.
Sorption and Diffusion in Crystalline Elastomers. II. Permeation of Isomeric Hydrocarbons in Stretched Rubber
Authors: Barrie J. A. , Platt B. 
Published: February 2011

Abstract
Part I of this series was concerned with the solubility data for the hydrocarbons n-butane and isobutane in stretched peroxide-cured natural rubber. The corresponding permeation data for these vapors and, in addition, for propane, as obtained by the experimental procedure described in Part I, are now presented and discussed, particularly with reference to the effect of crystallinity or orientation on the diffusion properties of the rubber.
The Mechanics of Ozone Cracking
Authors: Braden M. , Gent A. N. 
Published: February 2011

Abstract
Experimental measurements are described of the growth of a cut in a stretched rubber sheet under the action of an atmosphere containing ozone. A well-defined rate of crack growth is obtained, substantially independent of the applied tensile stress when this exceeds a critical value necessary for growth to occur at all. The rate of growth is found to be similar for a number of polymers and principally determined by the ozone concentration when the mobility of the polymer molecules is sufficiently high. When the molecular mobility is inadequate, crack growth is retarded. The critical condition is found to be similar for all the polymers examined, and largely independent of the conditions of exposure; it appears to reflect an energy requirement for growth of about 40 ergs/cm2 of newly-formed surface. The effect of the degree of vulcanization and the presence of additives, including antiozonants, on these two factors has also been examined. The dialkyl-p-phenylene diamines are found to confer protection by raising the critical energy required for growth to occur, in contrast to other protective agents which affect only the rate of crack propagation.
Temperature Coefficient of Vulcanization for Present-Day Tire Compounds
Authors: Ambelang J. C. , Beach K. C. , O'Sullivan D. F. 
Published: February 2011

Abstract
The temperature coefficient of vulcanization was measured for tread type compounds of present-day polymers, carbon blacks and accelerators. The state of cure was judged by modulus and crosslinking (from swell); the temperature coefficient was measured at 80% of the maximum reached at a standard cure temperature. An expeditious and precise method was developed for calculating the vulcanization coefficient.
Viscoelastic Properties of Rubberlike Composite Propellants and Filled Elastomers
Authors: Landel Robert F. , Smith Thor L. 
Published: February 2011

Abstract
The mechanical properties of rubberlike composite propellants and similar filled elastomers are determined largely by the volume fraction of filler, the visco-elastic properties of the binder, and the interactions between the binder and filler particles. The ratio of the quasi-equilibrium modulus of the composite to that for the unfilled elastomer increases with the volume fraction of the filler, apparently according to an equation of the form proposed by Eilers and Van Dyck. However, the same ratio for the dynamic storage modulus decreases as the frequency is increased or the temperature is decreased. The time-dependent tensile properties can be characterized by stress-strain curves measured at different strain rates and temperatures. Both the small deformation and ultimate properties can be represented by master curves, which are functions only of the experimental time scale, along with a temperature function which is a near-universal function of the glass temperature. Propellants under constant loads initially exhibit creep which is qualitatively similar to that of unfilled elastomers, but subsequently dewetting of the filler particles may begin and this causes the deformation to increase exponentially with time. A discussion is given of the use of Poisson's ratio, defined in terms of Hencky strain and measured as a function of extension, to indicate the initiation of dewetting and the subsequent volume increase.
Adsorption Properties and Infrared Spectra of Oxidized Carbon Blacks
Authors: Lygin V. I. , Kovaleva N. V. , Kavtaradze N. N. , Kiselev A. V. 
Published: February 2011

Abstract
Chemical analysis and adsorption of water indicate that strongly oxidized carbon blacks contain various oxygen compounds which greatly influence adsorption of water. Infrared spectra give indications of the nature of these compounds and of their mutual interaction.
Effect of Elongation on the Electrical Anisotropy of Natural Rubber and SBR Vulcanizates Containing ISAF Carbon Black
Authors: Chasset R. , Thirion P. 
Published: February 2011

Abstract
The electrical resistivity of testpieces under different elongations, both parallel and at right-angles to the axis of elongation, was measured for two vulcanizates, i.e. one of natural rubber and the other of SBR, compounded with 20 volume per cent of ISAF black (Vulcan 6). Within the range of validity of Ohm's law, the main results of this study are as follows: a) the resistivities of both vulcanizates increase considerably with elongation, in both directions. b) on the whole, both vulcanizates are electrically anisotropic, since current flows more easily longitudinally than it does transversely. The anisotropy increases at the start with elongation, then becomes practically constant. However, the latter level is much higher with natural rubber, for which it corresponds to an anisotropy of about 1,000 and an elongation of around 150%. For SBR this level is only 20 to 30 and is reached at only 50% elongation. Owing to the complexity of the problem, no interpretation can yet be given for these differences. It will first be necessary to examine other elastomers and carbon blacks. For the time being, it may merely be stated that the electrical anisotropy of natural rubber and SBR reinforced vulcanizates differs as much as their mechanical properties, especially their tearing behavior.
A Towing Device for Estimating Road Wear
Authors: Gelinas L. P. , Storey E. B. 
Published: February 2011

Abstract
The towing device was designed to provide a rapid screening test that might be applied to measure the wear resistance of small quantities of experimental polymers. The reproducibility of the test has been found to depend to a large degree upon the care was taken to design measuring equipment that would provide a good estimate of this value. The nature of the road surface will produce a change in the rate of wear and, with certain polymers, excessive cutting has been encountered that affected the reproducibility of the measurement. This difficulty may be avoided by selecting a smoother road surface and longer test runs may be employed without increasing the duration of the test beyond 6 hours. A towing device has been developed that allows the wear resistance of a small quantity of polymer to be evaluated by towing a test wheel at a slight angle over the surface of a road at normal tire loads and speeds. Data from road wear tests of tires of various sizes showed that a log-log plot of the volume loss per unit width of tread of the experimental against the control vulcanizate gave a single correlation. The volume loss of the control vulcanizate may be taken as a measure of the severity of the test. Tests using the towing device at various angles of tow gave data that showed a correlation of wear values similar to that found in road tests. The towing device provides an adequate method for screening the wear qualities of small quantities of experimental polymer.
Dynamic Mechanical Properties of Stretched Natural Rubber
Authors: Fitzgerald Edwin R. 
Published: February 2011

Abstract
Dynamic shear compliance measurements on a natural rubber vulcanizate have been carried out from 50 to 5000 cps as a function of static elongation in the range 0–400%. Above 300% elongation several very large resonance dispersions appear in the region 1000–2000 cps, but at lower elongations no such resonances are observed. The appearance of mechanical resonance dispersion thus coincides with the development of oriented crystallinity in the stretched rubber as shown from x-ray diffraction data. On the other hand, the magnitudes of the dispersions decrease with increasing elongation above 300% whereas x-ray measurements indicate the amount or extent of crystallinity increases with stretching above 300% elongation. The resonances thus clearly decrease as the crystallinity becomes more perfect or more extensive and hence appear to reflect the imperfections of the crystalline regions formed by elongation rather than the crystallinity itself. Observed changes in the compliance spectrum with time at each elongation also favor this view. Broad retardation dispersions were observed when the rubber was allowed to contract back to elongations below 300% after long times above 300%. These are tentatively ascribed to an extended amorphous state in which the rubber molecules are kept partially extended by very small randomly oriented crystalline regions which persist for some time after retraction. Another interesting feature of the results is an apparent correlation between the percent crystallinity determined from x-ray diffraction and the reciprocal of the general level of storage compliance 1/J′ at frequencies well below or well above the dispersion region.
The Scorching of Rubber Mixes. II. Effect of Retarders on the Kinetics of Sulfur Combination
Authors: Dogadkin B. A. , Dobromyslova A. V. , Belyatskaya O. N. 
Published: February 2011

Abstract
1. Vulcanization retardera decrease the rate of interaction of sulfur with rubber. 2. N-Nitrosodiphenylamine (NDPA) retards the rate of addition of sulfur in the presence of all the investigated vulcanization accelerators: CBS, MBT, TMTD, DPG, N-oxydiethylene-2-benzothiazylsulfenamide, and the 2,4-dinitrophenyl ester of MBT, as well as in the absence of accelerators. 3. The rate of addition of the elements of accelerators CBS and TMTD increases in the presence of NDPA. 4. The effectiveness of NDPA as a retarder decreases with an increase of the vulcanization temperature. 5. The mechanism of the inhibiting action of NDPA is considered from the point of view of the influence that the products of its dissociation (nitric oxide and diphenylamino radicals) may have on the initial vulcanization processes.
Scorching of Rubber Mixes. I. Structural Changes in Unfilled and Filled Stocks
Authors: Dogadkin B. A. , Dobromyslova A. V. , Belyatskaya O. N. , Gyul'-Nazarova T. A. 
Published: February 2011

Abstract
1. In the process of scorching there takes place a combination of the sulfur with the rubber. The flow of unfilled stocks heated at 120° ceases at the instant of combination of ∼0.5% sulfur reckoned on the stock. 2. In carbon black filled stocks there is an increase in the rate of combination of sulfur with rubber and a decrease in the time for which the stock is in the flow state, as the pH value of the carbon black added to the stock increases. 3. In processing a stock on the mill in the presence of fine-particle carbon black there is formed a rubber-carbon black gel, the amount of which hardly changes in the process of heating the stock in the plastimeter at 120°; only at the instant of cessation of the flow of the stock does its solubility decrease perceptibly. 4. In filled stocks in which a rubber-carbon black gel is formed in the course of treatment on the mill, the limiting amount of bound sulfur combined at the instant of cessation of the flow of the stock is less than in stocks in which no rubber-carbon black gel is formed. 5. Alteration in the amount of oxygen-containing functional groups upon the surface of the carbon black does not cause any important influence upon the amount of rubber-carbon black gel, but significantly alters the rate of combination of sulfur with rubber and the tendency of the stock to premature vulcanization. 6. Thus the phenomenon of premature vulcanization is governed for the most part by the reaction of the rubber with the sulfur and the other vulcanizing agents. In stocks with fine-particle carbon blacks there is also a significant influence from the formation of the rubber-carbon black gel in the processing of the stock on the mill.
Crosslinking of Polymers with Dimaleimides. I.
Authors: Kovacic Peter , Hein Richard W. 
Published: February 2011

Abstract
From gelation and compounding studies, dimaleimides were found to crosslink a wide variety of polymers including unsaturated hydrocarbon types, polyethylene, polymers containing amino groups and a urethan polymer. Except for the amino-containing polymers, the presence of catalytic amounts of peroxide was necessary for effective crosslinking. The chemistry of the crosslinking processes is discussed.