bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strain Energy as a Criterion for Stress Softening in Carbon-Black-Filled Vulcanizates
Authors: Dannenberg E. M. , Brennan J. J. 
Published: February 2011

Abstract
Stress softening of vulcanizates of SBR 1500 containing different blacks possessing the same “structure” but varying in surface activity, and effects of different black loadings, of black structure levels, and of particle size, were investigated. It was concluded: 1. Strain-energy loss can be used as a quantitative measure of stress softening, and initial strain-energy input as a measure of prestress severity. 2. The effects of carbon black and polymer variables can be normalized in a single general relationship by plotting per cent strain-energy loss as a function of initial strain-energy input for filled vulcanizates. 3. With the exception of natural rubber, gum vulcanizates studied showed no stress softening. The stress softening of natural rubber gum vulcanizates is attributed mainly to stress-crystallization. 4. Stress-softening of filled vulcanizates is not a completely reversible process. Rates of stress recovery are reasonably rapid. 5. The degree of stress softening can be predicted from the initial stress—strain curve, the prestress severity desired, and the general correlation based on strain-energy considerations found in this study. 6. Prestressing reduces abrasion resistance as measured in the laboratory.
Sedimentation Analysis of Styrene Butadiene Copolymer Rubber
Authors: Homma Terutake , Fujita Hiroshi 
Published: February 2011

Abstract
Methods are presented by which the limiting viscosity number [η]Θ and the limiting sedimentation coefficient s0 of a monodisperse linear polymer in its theta solvent as functions of the molecular weight M may be deduced from data taken with a series of polydisperse samples of the polymer. The necessary data are the limiting viscosity numbers and the distribution functions of s0 of the chosen samples in the theta solvent, plus their number-average molecular weights. The methods are applied to unfractionated and fractionated samples of a styrene-butadiene co-polymer rubber (SBR) having 24 weight per cent bound styrene in a theta solvent, 2-pentanone, at 21.0° C. The following relations are deduced for monodisperse unbranched SBR in this theta solvent: [η]Θ=1.73×10−3M21 and s0=0.83×10−15M21, where [η]Θ is expressed in deciliters/gram and s0 in seconds. Besides these, the viscosity—molecular weight relations for this cold rubber in toluene and in cyclohexane, both at 30° C, are established. The new relation for the toluene system does not accord with the French-Ewart relation for “hot” rubber in the same solvent. The integral distribution of molecular weight in an unfractionated SBR is calculated from its distribution function of s0 in 2-pentanone at 21.0° C by using the derived s0 versus M relationship, and is found to coincide well with the mass distribution obtained from fractionation data if the new viscosity—molecular weight relation is used for the molecular weight of each fraction.
Upturn Effect in the Non-Newtonian Viscosity of Polymer Solutions
Authors: Burow S. P. , Peterlin A. , Turner D. T. 
Published: February 2011

Abstract
Previously consideration of the hydrodynamic consequences of the separation of the segments of a macromolecule in laminar flow has led to the prediction that a very long polymer molecule in an extremely viscous solvent should have a limiting viscosity number which increases with the gradient G or, more precisely, with the parameter β=M[η]0η0G=NkT which is defined below. Experiments in Cannon—Fenske and Single-Pass capillary viscometers reveal such upturns of viscosity in solutions of polymethylmethacrylate in Aroclor and polyisobutene in polybutene oligomers which, as predicted, are very sensitive to molecular weight (1 to 7×106) and solvent viscosity (η0 =1 to 100 poise). A satisfactory comparison with theory is presented using values of [η]=ηsp/c, extrapolated to c=0, for solutions of polymethylmethacrylate in Aroclor-in the concentration range 0.125 to 2.0×10−3 g/cm3.
Effect of Temperature on Ozone Cracking of Rubbers
Authors: Gent A. N. , McGrath J. E. 
Published: February 2011

Abstract
The rates of growth of single ozone cracks have been measured for vulcanizates of a series of butadiene—styrene copolymers, over a temperature range from − 5° C to 95° C. The rates appear to be determined by two mechanisms. At low temperatures, near the glass transition temperature, they are quantitatively related to the segmental mobility of the polymer. The principal rate-controlling step in this case is concluded to be movement of the polymer chains after scission to yield new surface. At high temperatures the rate approaches a limiting value of 10−3 cm/sec/mg of ozone/1. This is about 1/1000 of the maximum possible value when instantaneous reaction of one incident ozone molecule causes scission of one network chain.
Thermodynamics of Swelling. I. Thermodynamic Properties of Crosslinked Binary Systems
Authors: Rehage Günther 
Published: February 2011

Abstract
Part I of this article was devoted to the thermodynamic properties of binary-mixed phases, in which one component was a low-molecular-weight liquid and the other a polymer crosslinked by primary-valence bonds. Special attention was paid to the case where the macromolecular material is in a glassy state at the measurement temperature. When solvent concentrations are low, the mixed phases are also in the glassy state. If the freezing concentration is exceeded during isothermal absorption of liquid, elastic materials appear, stable as to form when swelled, which are designated gels. Like liquids, gels are in a state of internal equilibrium. When polymer components have primary-valence crosslinks, liquid take-up always leads to an equilibrium state (swelling maximum, saturated gel). The enthalpy-concentration diagram was investigated rather thoroughly. If the polymer is in internal equilibrium at the measurement temperature, then the heat of mixing (heat of swelling) arises only from interaction between molecules. On the other hand, if the pure polymer component is frozen, the negative heat of freezing is superposed upon the “genuine” heat of swelling, resulting from interaction. Even when the enthalpy of the mixed phase is an additive function of the values for the pure components, a heat of mixing appears which originates only from liberation of the heat of freezing. The sign of the limiting heat of dilution, i.e., the differential heat of dilution at the swelling maximum, determines the temperature dependence of the swelling equilibrium. In athermic systems, maximum swelling is independent of temperature. The osmotic swelling equilibrium was investigated thermodynamically. It was shown that swelling pressure in crosslinked systems corresponds to osmotic pressure in solutions. A survey of results from the statistical theory of crosslinked systems is presented using, as a basis, Flory's theory for an ideal-athermal gel. As with the thermodynamic treatment of low-molecular-weight systems, excess functions were also introduced here. For low-molecular-weight, liquid mixtures, the excess functions have reference to formulas for an ideal solution. For polymeric, crosslinked systems, however, the reference values suggested are the statistical equations for an ideal-athermal gel. Finally, limiting laws for infinite dilution are derived for a crosslinked, mixed phase.
Anisotropy of Thermal Conductivity in Stretched Elastomers
Authors: Hennig J. 
Published: February 2011

Abstract
Thermal conductivity, η⊥, of some crosslinked, stretched elastomers and of stretched, plasticized PVC was determined, normal to the direction of elongation ε, as a function of temperature, between − 10° C and +45° C. Elongation was kept constant during measurement. η⊥ is smaller than heat conductivity of the unstretched (isotropic) material and decreases as elongation is increased. Anisotropy of thermal conductivity is particularly marked (η⊥=λ0≅0.8 to 0.9 for ε=200 per cent)—assuming equal elongation—in the case of polymers whose chain molecules contain polar side groups (e.g., butadiene-acrylonitrile copolymers, polychloroprene, chlorosulfonated polyethylene) whereas in those with molecular chains which possess only non-polar side groups (such as natural rubber and polyisobutylene), hardly any anisotropy appears. As far as plasticized PVC is concerned, anisotropy decreases, at the same elongation, with the plasticizer content and disappears almost entirely when the plasticizer concentration is higher than 60% by weight, i.e., the ratio η⊥=λ0 approaches 1, and in fact all the more rapidly, the more effective the plasticizer. Dependence of anisotropy on time was not observed.
Vulcanization of Elastomers. 47. Vulcanization of Natural Rubber and Polybutadiene with Benzoyl Peroxide
Authors: Scheele Walter , Rohde Ernst 
Published: February 2011

Abstract
The present article reports experiments intended to elucidate the kinetics of benzoyl peroxide decompositions in natural rubber and polybutadiene, and of consequent reactions. Both in natural rubber and in polybutadiene and at all temperatures, peroxide decomposition is first order with respect to concentration as well as time. The decomposition rate is substantially higher in natural rubber than in polybutadiene, and independent of the constitution of the polymer chains of the polybutadiene (tacticity, vinyl side groups, and the like). A somewhat higher activation energy of peroxide decomposition was derived for polybutadiene than for natural rubber. Formation of benzoic acid and crosslinking both follow a first order time law; the rates for peroxide decomposition, formation of benzoic acid, and crosslinking are the same in natural rubber and polybutadiene. It seems probable that peroxide decomposition in polybutadiene is purely homolytic. Interaction between peroxide and natural rubber is assumed, resulting in an increase in the rate of decomposition. The benzoic acid yield is considerably higher in natural rubber than in polybutadiene, and diminishes in the latter with the increase in vinyl side groups. In natural rubber this yield is a function of temperature, but in polybutadiene it shows practically no temperature dependence. Benzoyloxy radicals are incorporated into the elastomers as benzoate groups, as confirmed by infrared spectroscopic determinations with cis-1,4 polybutadiene. An interpretation of the formal kinetics of the vulcanization of 1,5-polyenes is proposed, which, together with the experimental results, may be used as a basis for consideration of the reaction mechanism.
Effect of Curing Systems on Fatigue of Natural Rubber Vulcanizates
Authors: Cox W. L. , Parks C. R. 
Published: February 2011

Abstract
The fatigue life of natural rubber-HAF black vulcanizates showed maxima when plotted as a function of crosslink concentration as did other properties related to a tearing process such as tensile strength, crack growth, and tear strength. Accelerated-sulfur vulcanizates were superior to peroxide and nonelemental-sulfur cures; this can be attributed to an exchange of polysulfide crosslinks under stress. An effective antioxidant was essential for maximum fatigue resistance. Accelerated-sulfur systems, although having a higher original fatigue life than peroxide or nonelemental-sulfur cures, showed a rapid loss on accelerated aging in air. This would indicate that an oxidative effect was involved. Sulfur group analyses of the flexed samples showed an increase in the concentration of RSSxSR linkages but a decrease in the total polysulfide sulfur, Sx, with no change in the crosslink densities. This suggests that the polysulfide linkages not only underwent exchange during the fatigue process but also homolytic cleavage to polythiyl radicals. These radicals can add to double bonds and in the presence of oxygen initiate oxidation chains which would lead to main chain scission.
Comparison of Number—Average Molecular Weights Calculated by GPC and Membrane Osmometry
Authors: Ambler M. R. , Mate R. D. 
Published: February 2011

Abstract
Data are presented which show that when a polymer contains an appreciable amount of low molecular weight species below the diffusion limit of the osmometer membrane, the osmotic molecular weight, Mn, is generally higher than the Mn calculated from gel-permeation chromatography (GPC). Experiments were performed on samples of poly(vinylchloride) (PVC) and high-cis poly (butadiene) polymers. Osmotic data were obtained in the usual manner, while GPC data were obtained using the universal calibration approach. It was found that when all polymer species below approximately 10,000 molecular weight were excluded from the calculation of Mn by GPC, agreement in Mn was obtained between membrane osmometry and GPC. The data obtained suggest that the choice of Mn as measured by membrane osmometry in the calibration of the GPC should not be done casually, as the measured Mn may not reflect the “true” value of that sample, especially when the polymer sample contains an appreciable amount of low molecular weight material.
Effect of the Reference Chain Dimensions in the Molecular Theory of Viscoelastic Behavior of Polymer Networks
Authors: Ilavský M. , Hasa J. , Havlíček I. 
Published: February 2011

Abstract
Mooney's version of the molecular theory of polymer networks has been generalized to the case when the external strain applied in the isotropic state is different from that at network formation. As in the theory of equilibrium behavior of the polymer networks, this generalization allows inclusion in the viscoelastic functions of effects connected with the temperature dependence of internal energy of the chains and with the strain effect of the solvent. From viscoelastic functions thus generalized, it is possible to derive a relation for calculation of the monomeric friction coefficient. It also suggests the possibility of superposing data obtained at various temperatures, degrees of swelling, and condition of network formation.
The Application of the Molecular Probe Technique to a Study of Polymer Crystallization Rates
Authors: Gray D. G. , Guillet J. E. 
Published: February 2011

Abstract
Most experimental methods for following the changes in crystallinity of polymeric systems have involved measurement of volume changes, changes in absorption spectra, and changes in optical properties. The basis of the novel method reported here is that the bulk interaction between small concentrations of a “probe” molecule and a polymer substrate depends in a simple manner on the degree of crystallinity of the polymer sample. In a recent paper from this laboratory it was suggested that this bulk interaction may be measured by a gas chromatographic method. In this paper, the method is extended to measuring the rate of polymer crystallization; a linear and a branched chain polyethylene) were studied using decane as the “molecular probe”.
Temperature Dependence of Ultimate Strength and Elongation of Vulcanized Rubber
Authors: Furukawa Junji 
Published: February 2011

Abstract
The ultimate elongation of vulcanized rubbers attains its maximum at a temperature Tmax, which was found to be sensitively increasing with increasing sequence regularity of alternating BD-AN copolymers and with increasing length of hard block of BD-ST block copolymers. Two kinds of rupture are proposed: a brittle rupture at low temperature occurs when the chain is extended fully and a plastic rupture occurs when the loosening of the chain caused by bond scission becomes faster than elongation. In the former case αb ∝ 1/αη˙, whereas in the latter αb ∝ 1/ατ˙, η and τ being resistance to viscous slippage and bond scission, respectively. It is estimated that Tmax decreases with increasing the crosslinks as well as the amorphous part, similar to a melting point.
1,2-Polybutadiene Resin Co-Agents for Peroxide Cure of Rubber Compounds
Authors: Martin J. W. 
Published: February 2011

Abstract
It is clear that low MW 1,2-poly (butadiene) resins are useful components of a wide range of peroxide-cured rubber compounds because they can provide non-scorch plasticizing before cure and reinforcement after cure. The resins increase the crosslinking efficiency of EPDM and EPR compounds and provide properties consistent with high crosslink densities. In NBR the resins serve as plasticizers before cure and unextractable softeners after cure. Applications for the low MW 1,2-poly (butadiene) resins in rubber technology appear to include high-hardness compounds, easily processed compounds, electrical insulations, and mechanical goods. Because some of the favorable effects of the resin (viscosity and crosslinking) counteract some of the undesirable properties of low-cost fillers, highly extended rubber compounds may well benefit from the addition of these special resins.
Dependence of Compression Modulus on Poisson's Ratio
Authors: Moghe S. R. , Neff H. F. 
Published: February 2011

Abstract
The experimental results and the widely used empirical formula (E/EApp)=(1+βS2)−1+(E/B) for the compression modulus are compared with analytical solutions obtained by Moghe and Neff. It is shown that the empirical formula does not represent the data adequately, particularly for large and small shape factors. It is also shown that the variation in β in the empirical formula arises due to the inadequacy of the representation rather than the thixotropic behavior as claimed.
Pure Flexure of a Layered Orthotropic Shell-Elasticity Study of a Tire-Related Problem
Authors: Levinson M. , Demiray H. , Sheung S. C. 
Published: February 2011

Abstract
This paper presents the analysis of the plane strain, pure bending of a portion of a three-layered cylindrical shell which is taken as a simple model of a part of a belted pneumatic tire. The two inner layers, representing the body and belts, respectively, are modeled as orthotropic, incompressible materials whose properties can be found from the appropriate cord and matrix material propties in a manner given in an Appendix. The outer layer, representing the tread rubber, is considered to be an isotropic, incompressible material. We concern ourselves with the study of the stresses tending to separate the various layers. These stresses, for two particular cases, are found to be strongly dependent on the crown angles of the cords in the body and belt layers. The results are presented in graphical form with the separation stress as a function of the body crown angle and with the belt crown angle entering as a parameter.
Preparation and Activity of Polymerizable Antioxidants for Emulsion Rubbers
Authors: Kline R. H. , Miller J. P. 
Published: February 2011

Abstract
A number of compounds have been prepared which contain both an antioxidant function and a polymerizable function in the same molecule. These compounds, which include representatives of both amine and phenolic antioxidants, were designed to be used as comonomers in the preparation of emulsion rubbers. Oxygen absorption tests in SBR-1006 show that these compounds exhibit antioxidant activity typical of the class of antioxidant, i.e., amine or phenol, to which they belong.
Thermoelastic Properties of Rubberlike Networks and Their Thermodynamic and Molecular Interpretation
Authors: Mark J. E. 
Published: February 2011

Abstract
Thermoelastic measurements and their interpretation by means of rotational isomeric state theory provide a great deal of insight into both thermodynamic and molecular aspects of rubberlike elasticity. Furthermore, conformational energies obtained in part from thermoelastic studies can in turn be used in the interpretation and even prediction of a variety of configurationally dependent properties of chain molecules, as is shown in many of the theoretical investigations cited in Sections IV and VII of this review.
Fluoroelastomers
Authors: Arnold R. G. , Barney A. L. , Thompson D. C. 
Published: February 2011

Abstract
The importance of fluorine in polymer chemistry has been known since the discovery of poly (tetrafluoroethylene) in 1938. Highly fluorinated polymers are very stable and have remarkable resistance to oxidative attack, flame, chemicals, and solvents. This stability has been attributed to the strength of the carbon—fluorine bond compared to that of the carbon—carbon bond, to steric hindrance, and to strong Van der Waals forces. The synthesis of elastomeric polymers containing enough fluorine to impart a significant degree of stability was not achieved until the mid-1950's. Since then a multitude of fluoroelastomers have been reported, but, of these, only certain copolymers of vinylidene fluoride, and fluorosilicone polymers have become commercially important. Recently, however, perfluoroelastomers based on perfluoro (alkyl vinyl ethers) and tetrafluoroethylene have been shown to possess an even greater degree of high temperature stability than do the fluoroelastomers hitherto available. These perfluoroelastomers also are essentially inert to most chemicals and solvents. Copolymers of perfluoro (alkyl vinyl ethers) with partially fluorinated monomers also have been developed that give better flexibility at low temperature. These polymers, now at the developmental stage, appear to be the forerunners of a new generation of superior high-performance elastomers. The discussion that follows will concern firstly, the commercial fluoroelastomers; secondly, those that show commercial promise and might be considered semi-commercial or at the developmental stage but which are available only in limited developmental quantities; and thirdly, those reported in the literature that, so far at least, have been of research interest only. In this last category, polymers will not be included which contain so little fluorine that performance characteristics are not substantially enhanced. For example fluoroprene [poly(2-fluorobutadiene)] and copolymers with nonfluorinated, olefin monomers in which the latter predominate will not be included.
The Effect of Compounding Variables on the Rate of Heat and Smoke Release from Polychloroprene Foam
Authors: Stewart C. W. , Dawson R. L. , Johnson P. R. 
Published: February 2011

Abstract
The addition of certain hydrated fillers or char promoters to a neoprene latex foam recipe can result in significantly lower rates of heat and smoke release. The degree of improvement depends to some extent on the severity of the test conditions, with the greatest improvement being obtained for conditions which are encountered during the early stages of a fire.
The Preparation and Properties of meta-Carborane—Siloxane Elastomers
Authors: Peters E. N. , Hedaya E. , Kawakami J. H. , Kwiatkowski G. T. , McNeil D. W. , Tulis R. W. 
Published: February 2011

Abstract
A new synthesis of D2-carborane—siloxanes is described which overcomes many of the disadvantages of previous synthetic methods. Linear polymers with molecular weights up to 250,000 can now be prepared using silanol-silylurea condensation reactions. Elastomers with useful general properties and good retention of mechanical properties after heat aging in air at 315°C for 300 hr were produced. The property profile and ease of vulcanization suggest utility in high-performance sealant, gasket, O-ring, and coating applications.