bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystallization under Stress and Non-Gaussian Behavior of Macromolecular Networks
Authors: Smith K. J. , Greene A. , Ciferri A. 
Published: February 2011

Abstract
(a) Shape of the isotherm.—The appearance of a “first” upturn in the conventional isotherm is associated with non-gaussian behavior. Crystallization takes place, under usual conditions, in a range of elongation where non-gaussian behavior prevails and tends, initially, to reduce the stress below the value expected for the amorphous non-gaussian network. On further stretching a “second”, steeper up turn may be observed which is associated with a substantial reduction of amorphous content and, therefore, with crystallization. This interpretation, which is coherent with most of the experimental observations (particularly the lack of correspondence between the first upturn and the downturn of the energy component, the swelling behavior and the independence of the first upturn upon the mode of obtaining the isotherm and upon temperature) is satisfactorly fitted in the present picture of behavior of the network under stress. (b) Energy component.—Extensive measurements and theoretical analysis indicate that the ratio fe/f is essentially unaffected by swelling with n-hexadecane and by elongation, even in the elongation range following the gaussian region. The best value, i.e., 0.18, which is affected bya large error (± 0.05) confirms that the unperturbed dimensions of natural rubber molecules increase with temperature, an effect for which molecular description is lacking. Values of fe/f≦0.10, as they may occur for stretched natural rubber networks, are indicative of crystallization. (c) Crystallization under stress.—The following differences between experiments and Flory's approximate theory were noticed: (1) the value of ΔH is about one half the value to be expected on the basis of independent measurements. This indicates that the experimental variation of Tm with α is steeper than predicted; 2) Tm at α=1 appears to be some 30° below the actual isotropic melting temperature; 3) most serious differences between theory and experiments are found in the smooth change of slope of τ vs T curves at constant length in the region immediately following Tm. The part played in these effects by failure to obtain true equilibrium may not be essential judging from the fact that the best attempt made to reach equilibrium conditions did not reveal significant effects. Improved attempts to obtain equilibrium for the present system and using the present experimental technique are precluded by the occurrence of chemical degradation. Further experiments, on different polymer systems focusing attention on the region of incipient crystallization (or, preferably, “final melting”), are suggested.
Elongation at Break as a Measure of Cross-Link Density in Vulcanized Elastomers
Authors: DiGiulio E. , Bellini G. , Giandinoto G. V. 
Published: February 2011

Abstract
After recalling the reaction mechanism suggested for the crosslinking of ethylene propylene copolymers with organic peroxides, the authors consider the relation between concentration of curing agent and crosslink density. It is experimentally found that, as a first approximation, the elongation ratio at break of vulcanizates (unfilled or filled with small quantities of carbon black) is a function of molar concentration of peroxide only: αR=K/P1/2 This relation can be theoretically justified on the basis of the extensibility of polymer chain segments and of the criterion for rupture originally put forward by Taylor and Darin. By applying the above relation to ethylene propylene copolymers it is possible to evaluate the influence of the chain-splitting reaction during cross-linking. The reciprocal of the square of elongation ratio at break (1/αR2) measures the total degree of crosslinking.
Occurrence of Wave Effects in Rubber Antivibration Mountings
Authors: Snowdon J. C. 
Published: February 2011

Abstract
An approximate theory of rod vibration given by Love has been extended to describe the occurrence of wave effects, or wave resonances, in rubber antivibration mountings. Thus, the longitudinal vibration of a mass-loaded rubber mount of significant lateral dimensions and uniform cross section has been determined with the assumption that the elastic modulus and damping factor of the rubber are frequency-dependent quantities. Knowledge of the manner in which the elastic modulus and damping factor of natural rubber, natural rubber filled with carbon black, and a high-damping synthetic rubber depend upon frequency has enabled realistic computations of transmissibility. These computations have been contrasted with results obtained, for the same rubbers, from the simple one-degree-of-freedom theory in which the occurrence of wave effects is disregarded. Effectiveness of the natural-rubber mountings, which have relatively small damping, is overestimated by the simple theory at high frequencies, although transmissibility will normally remain a small quantity. In the case of the high-damping rubber considered, the results of the simple and Love theories are in relatively close agreement.
Filler Reinforcement of Liquid Elastomers
Authors: Rivin D. , True R. G. 
Published: February 2011

Abstract
To realize the potential processing benefits of liquid rubbers, methods must be developed for producing acceptable reinforced compounds which retain the inherent rheological advantages of the uncured polymer. The most promising commercially available liquid rubbers are functionally terminated low molecular weight analogs of common general-purpose elastomers such as poly-(butadiene) or butadiene copolymers. In principle, these low molecular weight polymers can be vulcanized by a combination of chain extension and cross-linking to yield vulcanizates comparable to those from solid elastomers. Both cure reactions can be carried out simultaneously with a chemically specific polyfunctional coupling agent, or alternatively, chain extension with a difunctional reactant can be followed by use of accelerated sulfur or equivalent crosslinking agents. In contrast to certain polar polymers, liquid hydrocarbon rubbers yield relatively weak vulcanizates which are unsuitable for mechanical and tire applications. Physical properties are greatly improved by addition of up to 60 phr of reinforcing fillers such as carbon black or precipitated silica, but at the expense of flow behavior. Important filler-dependent properties of representative liquid rubbers will be described, with emphasis on the rheology of reinforced compounds.
Carbon Black Transfer in Blends of Cis-Poly(Butadiene) with Other Elastomers
Authors: Sircar A. K. , Lamond T. G. 
Published: February 2011

Abstract
The study of carbon black transfer by BR crystallization, elastic modulus, and electrical conductivity provides convincing evidence that carbon black does not transfer from SBR, BR, and NR—all highly unsaturated polymers— when compounds are made by conventional Banbury and mixing procedures. This agrees with the electron micrographic studies of Marsh and coworkers as well as the latest publication of Hess and coworkers. It was shown, however, that a change in the carbon black distribution occurs when a solution BR masterbatch is mixed with fresh BR, providing the former is not premasticated. Black migration also takes place from a low unsaturation polymer (chlorobutyl) toward a high unsaturation polymer (BR) in chlorobutyl—BR blends, irrespective of how the black is added. Electron micrographs reveal that even in this case black does not actually transfer, but migrates to the interface, in agreement with the observation of Marsh and coworkers for NR—CR blend. Black migration in chlorobutyl—BR blends can be reduced by increasing the chlorobutyl—black interaction by heat treating and by using a promoter. The advantages of the above techniques are that these methods are suitable for highly compatible SBR—BR blends as well as for highly loaded systems, which are difficult to examine by micrographical methods. Also, an idea of the degree of compatibility of the different elastomers with BR can be obtained from crystallization studies. The disadvantage of the crystallization method is that it depends on the melting endotherm of BR and is, therefore, unsuitable for combinations that do not include BR. It is evident from the work reported that the sequence of addition of elastomers and carbon black is of paramount importance to the properties of the finished compounds since carbon black migration is the exception rather than the rule: migration takes place only in limited cases and under well-defined conditions.
A Comparison of Methods for Determining Surface Areas of Carbon Black
Authors: Klyne R. A. , Simpson B. D. , Studebaker M. L. 
Published: February 2011

Abstract
1. The various tint tests correlate with each other—it does not make much difference which of the three procedures is used. The discrimination between similar blacks is comparable. Specific surface areas obtained by the three methods are comparable and differences appear to be due to experimental errors. (Compare Figures 5–7). 2. Surface areas larger than some 90 to 100 m2/g cannot be reliably determined from tint strength measurements alone. 3. Structure exerts a pronounced effect on tint strength of furnace blacks, especially above 90 to 100 m2/g. Porosity and/or composition are apparently also variables which affect tinting strength. 4. Densichron reflectance on the dry carbon black can be used to estimate specific surface areas up to about 140 m2/g; but, since theabsoluteerrorincreases as the specific surface area increases, this method loses some of its reliability at values above about 110 m2/g. The relative error in reflectance determinations does not vary greatly over the furnace-black range. Densichron reflectance is influenced by composition, evidently due to composition-related differences in optical properties of the carbons. 5. In CTAB adsorption measurements, titration errors and handling errors tend to be rather constant for blacks of different surface area. Hence, CTAB permits better discrimination among blacks of small particle size. 6. The errors in Densichron reflectance surface area increase with specific surface area. Hence, the deviations between CTAB and reflectance surface area which are due to experimental error increase with the surface area of the sample.
Estimation of Glass Transition Temperatures from Gas Chromatographic Studies on Polymers
Authors: Lavoie A. , Guillet J. E. 
Published: February 2011

Abstract
In a recent communication, Smidsrød and Guillet showed that thermodynamic data on the interactions between poly (isopropylacrylamide) and various gaseous solutes could be obtained by making the polymer the stationary phase in a gas Chromatograph. It was also shown that if a solute was used which was a nonsolvent for the polymer, a plot of the logarithm of the specific retention volume as a function of reciprocal temperature showed a marked inflection at a temperature close to the glass transition temperature for the polymer. We wish to report similar data on several additional polymers which lead us to believe that the phenomenon is a general one and may be used to obtain an estimate of transition temperatures for a variety of polymeric materials.
NMR Study of the Crystallization Kinetics of Cis-Poly(Isoprene)s
Authors: Hirst R. C. , Chen H. Y. 
Published: February 2011

Abstract
The satisfactory agreement between our NMR results and X-ray diffraction results for the crystallinity in stark rubber at room temperature lead us to conclude that the NMR rigid lattice fraction, PRL, may be taken as equal to the fractional crystallinity obtained by other methods. Similarly, the good agreement between the time dependence of PRL at low temperature and the theoretical curve shape strongly suggest that the NMR crystallinity method works well down to at least −25° C for natural rubber and synthetic cis-poly (isoprene). It would be desirable to compare carefully the NMR crystallinity found for rubber crystallized at −25° C with X-ray diffraction results, but we have been unable to find any such X-ray diffraction studies at −25° C. Maximum values of ΔV/V≅0.025 from dilatometric studies appear to imply somewhat smaller crystallinities than those found by NMR, but an accurate comparison is not possible without having X-ray diffraction densities at −25° C. While the present experiments were carried out on unfilled, unstretched, unvulcanized samples, the NMR crystallinity method is equally applicable to samples which are filled, stretched, and vulcanized. Naturally any additive or impurity containing hydrogen is a possible source of interference, but there should be no difficulty in correcting for such interferences.
The Determination of Rubber in Atmospheric Dusts
Authors: Cardina J. A. 
Published: February 2011

Abstract
Samples of airborne dusts were collected near heavily traveled highways and analyzed for rubber by pyrolysis gas chromatography. Dust samples obtained in truck traffic gave pyrolysis chromatograms markedly different from those obtained in passenger car traffic, and which correspond with those derived from known tire tread compounds. The distinction was based on the presence of styrene or dipentene in the pyrolyzates. Quantitative determination of dusts from the Pittsburgh Liberty Tunnel and the Akron Expressway Interchange show the presence of 1.5 to 2.5 per cent rubber, whereas dust from a residential area shows about 0.25 per cent. Methods were developed for sampling atmospheric dusts and preparing small amounts in a form suitable for pyrolysis.
Sequence Length and Crystallinity in Alpha-Olefin Terpolymers
Authors: Davison S. , Taylor G. L. 
Published: February 2011

Abstract
The minimum sequence length for crystallization in a polymer was determined by a novel kinetic approach using sequence analysis of a series of blocky terpolymers. Copolymers and terpolymers of ethylene, propylene, and but-1-ene were prepared with a Ziegler—Natta catalyst system. Compositions of feeds and polymers were analyzed, and kinetic reactivity parameters were calculated using both the Fine—Ross and Alfrey—Goldfinger approaches. The parameters were then applied to determine the sequence length distribution of each component in the terpolymers. Also, deliberate control of sequence lengths enabled synthesis of heptane-soluble, rubbery polymers even using a catalyst system which normally produced blocky materials. Crystalline contents of the terpolymers were determined experimentally by nitric acid digestion. A critical comparison of the measured crystallinities with the calculated sequence length distributions was thereby made possible. From this comparison a minimum sequence length of monomer below which crystallization did not occur was estimated; this length was approximately 20 backbone carbon atoms.
Scorch Control of Carboxylic Elastomers
Authors: Hallenbeck V. L. 
Published: February 2011

Abstract
Carboxylic elastomers can be cured by standard compounding recipes utilizing sulfur and zinc oxide. The zinc oxide, besides aiding the sulfur cure, also gives a secondary cure through an ionic bond with the carboxyl groups. However, because of the affinity of the zinc oxide for the carboxyl group, the stocks tend to have an excessive scorch and a short shelf life. To prevent this excessive scorch the zinc oxide must be isolated from the carboxyl group until the desired cure temperature is reached. Three materials may be used to isolate the zinc oxide : 1) zinc sulfide coated zinc oxide, 2) zinc phosphate coated zinc oxide and 3) metallic alkoxide combined with the zinc oxide. The use of any of these gives scorch control without affecting final physical properties. The amount of zinc sulfide coating, zinc phosphate coating, and metallic alkoxide varies with the type of carboxylic elastomer.
Rubber Microscopy
Authors: Kruse Julius 
Published: February 2011

Abstract
Rubber microscopy was limited in its beginning primarily to the study of the filler materials dispersed in the rubber, to a surveillance of the fineness of these materials, as well as to the investigation of articles made of rubber for the purpose of elucidating technological questions which had to do with structure and preparation or manufacture. In the last few decades considerable improvement in techniques of microscopical investigations have given a new impetus to rubber microscopy so that, in addition to the above named applications, new goals have become possible. Thus today with the aid of electron microscopy, interference microscopy, and also spectrophotometric and polarization optical measurement procedures applied to microscopic objects one can designate rubber microscopy as a valuable aid in the investigation of the microstructure of rubber materials of all kinds. The technology of preparing specimens for electron microscopy has been particularly helpful to produce knowledge concerning the flow phenomena in colloidal situations which take place when carbon black is mixed into the rubber and which lead to the formation of a special network consisting of carbon black and rubber. In addition to this, there was derived from the logical and practical application of the above mentioned investigative procedures an improvement in analytical methods whereby only small amounts of materials are needed for the investigation of mixes or compounds and vulcanizates. Thus today one can name three principal application areas for rubber microscopy: 1. The study of the microstructure of rubber compounds and vulcanizates; 2. The analytical investigation of compounds and vulcanizates; 3. The examination of articles made of rubber in order to clarify their structure as well as to solve technological problems.
Gas—Liquid Chromatography on Polymers. I. Polyisobutylene—Hydrocarbons at 25°C
Authors: Leung Yu-Kwan , Eichinger B. E. 
Published: February 2011

Abstract
The Flory—Huggins mixing parameters χ, obtained by glc agree closely with those derived by extrapolation of results from static vapor sorption and osmometry for the systems PIB—n-pentane and PIB—n-octane. Substantial discrepancies between the two are observed for the systems PIB—benzene and PIB—cyclohexane. It is not clear at this early stage whether this indicates specific interactions between solvent and polymer, including surface adsorption, or if there are large inaccuracies in the sorption data at low concentrations of solvent. As we noted above, and from consideration of the vapor sorption measurements, it does not seem likely that the latter possibility is cause for great concern. Instead, we are inclined to the view that specific interactions, or more general geometrical contraints on cavity formation, are operating in these highly concentrated solutions. Since X12 values from enthalpies of mixing and from glc agree so closely for n-alkanes, we have further evidence for the remarkable accuracy of Flory's solution theory. However, the peculiar discrepancies between the various experimental determinations of χ and between theory and experiment for benzene and cyclohexane suggest possible secondary influences on such systems that have not yet been comprehended. We are hopeful that the temperature coefficient of χ will provide further insight into the nature of such influences that appears to be manifest in the data reported here.
Mechanism of Smoke Inhibition by Hydrated Fillers
Authors: Lawson D. F. , Kay E. L. , Roberts D. T. 
Published: February 2011

Abstract
The smoke inhibitory activity of hydrated fillers in SBR is centered primarily in condensed-phase processes and is analogous to the generally accepted mechanism of flame retardation by the hydrates. Dissipation of heat, which disfavors pyrolysis and favors competing crosslinking reactions is probably involved. These reactions should occur chiefly among polybutadiene segments of the polymers. In addition, the smoke-suppressant efficiency of hydrated fillers should depend upon the crosslinking efficiency of the rubber. Finally, although smoke generation in latex rubber goods presents a challenge, substantial practical reductions in visible smoke can be achieved through the selection of proper hydrated fillers.
Using the SI System of Units
Authors: Conant F. S. 
Published: February 2011

Abstract
SI surpasses previous metric systems in coherence, simplicity, distinction between force and mass, choice of units, and uniformity of usage. Coherence eliminates conversion factors, other than powers of ten, within the system. Through simplification, only seven base units, two supplementary units, fifteen named derived units, and fourteen prefixes are needed to describe the entire system. Introduction of the newton as a unit of force and retention of the kilogram for mass clarifies the difference between the two quantities. Other new units are: pascal for pressure, Siemens for electric conductance and mole for amount of a substance. International agreement minimizes proliferation of specialized units or usage. Adopted conventions include spelling, abbreviations, style, and usage, as well as definitions for the units. Tolerances, rounding of numbers, and elimination of the comma in multidigit numbers assume new significance. Conversion to SI offers a unique opportunity to reduce the number of sizes of many products. Several schemes for metric modularism have been developed for this purpose. In changing from conventional to SI units the key idea is “think metric” rather than use dual dimensioning.
Thermoanalytical Methods in Vulcanizate Analysis I. Differential Scanning Calorimetry and the Heat of Vulcanization
Authors: Brazier D. W. , Nickel G. H. 
Published: February 2011

Abstract
Our objective has been to demonstrate that DSC is a convenient and rapid technique for the study of elastomer vulcanization characteristics. Although we have been concerned only with NR and NR-BR blends, the observation of exothermicity in sulfur vulcanization is quite general. Similar observations on sulfur vulcanization of IIR, SBR, EPDM, CSM, and NBR rubbers have been made in our laboratory. In non-sulfur vulcanization systems, we have found the diurethane cure of natural rubber to be exothermic and amenable to DSC study. As reported by Bruce et al., the magnesium oxide cure of chloroprenes is exothermic, but magnesium oxide-diamine vulcanization of fluoroelastomers is characterized by very low exothermicity. Future studies of the effect of various additives on soft rubber cure could make a significant contribution to our understanding of the complex cure mechanism. Successful kinetic analysis of DSC scans is perhaps the major hurdle to be overcome before the DSC technique can be meaningfully applied to such problems.
Chemical Stress-Relaxation of Filled Vulcanizates under Large Cyclic-Deformation
Authors: Kusano T. , Murakami K. 
Published: February 2011

Abstract
The stress relaxation under cyclic deformation was used to elucidate the fatigue mechanism of carbon-black filled natural-rubber vulcanizates. Below 70°C the rate of stress relaxation of the filled vulcanizates depended on both extension ratio and frequency. Above 70°C it depended on the extension ratio only. The stress relaxation above 70°C is caused by the scission of both the primary bonds of polymer chains and bonds between polymer and carbon black. Below 70°C it is caused by the scission of the bonds between polymer chain and carbon black. However, at very small deformation above 70°C the mechanism of the stress relaxation of the filled system was the same as that of the unfilled system. The failure of the chemical bonds of polymer chains is involved, but not the failure of bonds between polymer and filler. The same relaxation mechanism may be operating in both air and nitrogen under the large deformation, because the amplitude dependence was the same.