bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultimate Tensile Properties of Elastomers. IV. Dependence of the Failure Envelope, Maximum Extensibility, and Equilibrium Stress Strain Curve on Network Characteristics
Authors: Smith Thor L. , Frederick J. E. 
Published: February 2011

Abstract
Uniaxial tensile data from tests at different rates of extension over a wide temperature range are considered for butyl, silicone, Viton B, SBR, and natural rubber vulcanizates (series A) and for six Viton A-HV vulcanizates (series B) of differing crosslink densities. For series A and for A-6 in series B, equilibrium stress-strain data were obtained at large deformations by an indirect method. The ultimate tensile properties of all vulcanizates were previously characterized by a time- and temperature-independent failure envelope. The failure envelope's maximum extension ratio, (λb)max, to be equal to or less than (λ∞)max, the maximum extension ratio (hypothetical) in the absence of rupture and also the maximum extension ratio of network models. Failure and equilibrium data for series A vulcanizates are represented by a specific function of the equilibrium modulus and the maximum extensibility; except for SBR and possibly Viton B, equilibrium and failure data are sensibly identical; thus, (λb)max≅ (λ∞)max. For series B vulcanizates, qualitative considerations indicate that (λ∞)max/(λb)max is greater than unity and possibly dependent on crosslink density. Consideration of network models suggests that (λ∞)max should be directly proportional to Mc1/2 and inversely proportional to (〈r2〉0/M)1/2. For series A, no correlation between (λb)max and (〈r2〉0/M)1/2 was found. For series B, it that (λb)max ∝ Mcβ, where β is a constant in the neighborhood of 0.7. For all vulcanizates, (σb)max≅ 104 (λb)max−1, where (σb)max is the stress in psi (based on the undeformed cross section) at (λb)max.
Failure of Polymeric Materials under Biaxial Stress Fields
Authors: Sharma M. G. 
Published: February 2011

Abstract
Failure behavior of polymeric materials depends considerably on which of the three material states (glassy, transition, and rubbery states) occurs. Failure behavior of polymeric materials can be described by the concept of failure surfaces in principal stress or principal strain space. For a Hycar elastomer, octahedral shear stress criterion described failure very well for stress states corresponding to the first quadrant of the stress space. For cellulose acetate butyrate, maximum shear stress criterion characterized failure reasonably well for stress states corresponding to the first and the fourth quadrants of stress space. It appears that it is possible to predict triaxial failure behavior from known biaxial failure properties.
Streaming Birefringence as a Rheological Research Tool
Authors: Wayland Harold 
Published: February 2011

Abstract
This paper reviews theoretical and experimental evidence currently available to establish criteria “to aid the experimenter who wishes to use streaming birefringence as a tool for studying fluid flow. Instrumental techniques are reviewed, and the possibilities for both qualitative and quantitative flow visualization by streaming birefringence in pure Newtonian liquids, colloidal suspensions, and dilute and concentrated polymer solutions are discussed. Methods of reconstruction of the velocity and stress fields from birefringence data are outlined.
Verification of the Flory Theory of Random Reorganization of Molecular Weight Distribution. Kinetics of Methylsiloxane Polymerization
Authors: Carmichael Jack B. , Heffel James 
Published: February 2011

Abstract
Distributions of linear and cyclic methylsiloxanes were determined by gas liquid chromatography during acid clay catalyzed reactions of equal molar amounts of D4[D= (CH3)2SiO] and MM[M= (CH3)3SiO1/2 at 80° C. Theoretical and experimental distributions of the linear siloxanes are compared as a function of time. The relatively large amounts of MD4M and MD8M present after 0.5 h indicate that D4 initially enters the linear chains as a unit. Sufficient reorganization has occurred after 0.5 h that the distribution of MD10M through MD13M is approximately random. The distribution of shorter chains becomes increasingly random as the reaction proceeds toward equilibrium. A corollary to the above conclusions is that the rate constant for propagation of dimethylsiloxanes appears to be approximately independent of molecular size.
Orientation Induced Nucleation in Polymer Crystallization
Authors: Binsbergen F. L. 
Published: February 2011

Abstract
Crystallization kinetics of polymers crystallizing from the melt are influenced by the mechanical history of the sample. Strain free samples show a larger crystallization half time than samples in which the strain has not been completely removed by relaxation at a suitable temperature. A larger number of nuclei has been assumed to be present in strained samples than in strain free ones. This has been called “orientation induced” or “stress induced” nucleation. This communication presents a morphological description of the phenomenon and of the underlying type of nucleation. My observations were made with a microscope (Reichert ‘Zetopan-Pol’) equipped with a hot stage and 24-mm camera, and mainly with the polarizers crossed. For most of my experiments I used polypropylene, but similar phenomena were also observed with several other polymers.
Breaking Energy of Rubbers
Authors: Grosch K. , Harwood J. A. C. , Payne A. R. 
Published: February 2011

Abstract
Recent investigations of failure of rubbers and plastics have indicated that hysteresial losses in a polymer are an important factor in fracture. This communication reports experimental evidence that the energy density at break of a polymer is amply related to the hysteresis loss in the polymer. A previously unstrained sample is stressed at a constant extension rate to rupture and the mean value of the rupture load is determined from a number of these measurements. A fresh rubber test piece is then extended under the same conditions until just before rupture, and then retracted at the same rate as was used for extending the rubber. The energy at or near break is determined by measuring the area under the load extension curve, and the hysteresis loss determined from the area between the extension and the retraction curves.
Structural Characterization of Filled Vulcanizates Part 1. Determination of the Concentration of Chemical Crosslinks in Natural Rubber Vulcanizates Containing High Abrasion Furnace Black
Authors: Porter M. 
Published: February 2011

Abstract
The degree to which HAF black restricts the swelling of natural rubber vulcanizates in n-decane has been determined using a vulcanizing system in which the stoichiometry of crosslinking is unaffected by the carbon black. The dependence of the degree of restriction, as measured by the ratio of the volume fractions of rubber in the filled and unfilled vulcanizates swollen to equilibrium, on the concentration of carbon black follows an exponential relationship previously proposed by Lorenz and Parks. This is found to be equivalent to a simple linear relationship between the apparent and actual crosslink concentrations: napparent/nactual=1+Kϕ, where K is a constant characteristic of the filler and φ is its volume fraction in the vulcanizate. The relation has been used to determine actual crosslink concentrations in filled natural rubber vulcanizates. HAF black is found to cause increases of up to 25 per cent in the yield of polymer to polymer crosslinks in conventional sulfur vulcanizing systems, accompanied by changes in rate of cure and of crosslink reversion. All these are small compared with the effect of the filler on many physical properties.
Cis-trans Isomerization in Polyisoprenes. Part VII. Double Bond Movement During Isomerization of Natural Rubber and Related Olefins
Authors: Cunneen J. I. , Higgins G. M. C. , Wilkes R. A. 
Published: February 2011

Abstract
When trans-3-methyl-2-pentene or trans-3-methyl-3-hexene is treated with butadiene sulfone, thiolbenzoic acid, and dibenzoyl disulfide under anaerobic conditions, the olefin undergoes only cis-trans isomerization. However, similar reactions in the presence of oxygen or peroxides also cause changes in the position of the double bond. The latter structural modification is probably caused by acidic compounds formed by oxidation of the isomerization reagents. With natural rubber the nonrubber substances prevent movement of the double bond, and cis-trans isomerization is the sole change, even when the reaction with sulfur dioxide is carried out under aerobic conditions.
Silicone Rubber: A New Diffusion Property Useful for General Anesthesia
Authors: Folkman Judah , Long David M. , Rosenbaum Richard 
Published: February 2011

Abstract
Ether, nitrous oxide, halothane, and cyclopropane diffuse through silicone rubber. General anesthesia can be produced in dogs by passing the vapors of any of these anesthetic agents through a coil of silicone rubber tubing, each end of which is placed in an artery and vein. Potential applications include a new method for general anesthesia and a simple accurate vaporizer for halothane.
Organized Amorphous Copolymers. Polystyrene and Polyisoprene System
Authors: Gallot Bernard , Mayer Roger , Sadron Charles 
Published: February 2011

Abstract
We have described a systematic study of block copolymers of the type AB in which one component is crystalline polyoxyethylene, following an observation in these laboratories that block copolymers adopt a regular structure in the presence of a preferential solvent for one block component of the system at appropriate concentrations. We have recently extended this study to the case of amorphous block copolymers of polyisoprene (block A) and polystyrene (block B) in the presence of a preferential solvent S for one or the other. The systems studied have been principally of the kind AB/S (two-block copolymers) and less thoroughly of the type BAB/S (three-block copolymers).
Two Network Model for Vulcanizates Crosslinked under Strain
Authors: Yanai H. Steve 
Published: February 2011

Abstract
The two network model of Berry, Scanlan, and Watson has been generalized by utilizing the simplified non-Gaussian, three-chain model of Treloar. The generalized two network model provides : (1) the relationship between effective stretch and applied stretch with a given precrosslink level, (2) the stress strain relationship of stretched, crosslinked elastomer, and (3) the relationship between anisotropic swelling behavior and the stretch-crosslinking conditions. Experimental results are in fair agreement with theory. However, due mainly to premature failure of specimens during the tensile test, the results are not quite enough to test the present theory adequately. Therefore additional experimental data are desirable, preferably from specimens with a wider range of the variables.
Viscoelastic Behavior of Segmented Elastomers
Authors: Cooper Stuart L. , Tobolsky Arthur V. 
Published: February 2011

Abstract
Viscoelastic behavior of linear segmented elastomers was examined. The unusual properties found in spandex systems are also observable in hydrocarbon block co-polymers, indicating that hydrogen bonding interactions are perhaps not essential. Low temperature properties of segmented systems are governed by the structural nature of the associated flexible segments, which determines the value of the major glass transition temperature (Tg). It appears that an association of the hard segments provides a broad temperature range of enhanced rubbery modulus. This occurs between the major Tg and a secondary high temperature transition.
Constitutive Equations for Viscoelastic Fluids for Short Deformation Periods and for Rapidly Changing Flows: Significance of the Deborah Number
Authors: Metzner A. B. , White J. L. , Denn M. M. 
Published: February 2011

Abstract
The proper forms and asymptotic characteristics of constitutive equations which may be useful for the description of viscoelastic fluids in flow fields of engineering interest are considered. It is seen that the Deborah number emerges as a natural ordering parameter which determines, on the one hand, whether simple approximations explicit in stress may suffice to describe the fluid properties or, on the other hand, whether implicit or integral equations are required. Methods of scale up are discussed.
Milling Behavior of Gum Elastomers: Experiment and Theory
Authors: Tokita Noboru , White James L. 
Published: February 2011

Abstract
When an uncompounded elastomer is processed on a two roll mill, four different regions of mechanical behavior are observed, depending upon the temperature and the severity of the nip deformation. This behavior is observed on materials with a wide variety in chemical composition, though the severity varies. The flow at high temperatures is typical of melt or polymer solution behavior. At lower temperatures unstable flow and elastic solidlike regions are observed. By presuming the elastomer to be an isotropic viscoelastic medium, stress and velocity fields were computed in the polymer melt region. The unstable regime was found to correspond to a critical value of the ratio of viscoelastic to viscous forces. The mathematical analysis, done in terms of the Green-Rivlin-Noll theory of viscoelastic media, extends earlier studies of deformation in this geometry by Gaskell and Bergen.
Viscoelasticity and Flatspotting
Authors: Howard William H. , Williams Malcolm L. 
Published: February 2011

Abstract
Flatspotting involves delayed elasticity, so conventional principles of polymer viscoelasticity should be applicable. The strain behavior of the tire cord material during the complex stress and thermal history of the tire is idealized in a model, assuming flatspotting is caused mainly by the tire cord material and that the strains in the cord in the footprint area are less than the strains in the cords elsewhere in the tread. A flatspot index based on this model is empirically correlated with tire performance. It is shown here that this commonly used empirical index can be quantitatively interpreted in terms of a viscoelastic property of the tire cord material, in this case, creep compliance of nylon 66. Flatspotting depends on the shape of the viscoelasticity function, which is governed by chemical composition, stress differences in the tire, and the effect of environmental variables on the time scale. The most important environmental variables are temperature and moisture content. Certain qualitative predictions of tire behavior can be made on this basis.
Quantitative Measurement of Tire Flatspotting
Authors: Brownlee J. L. , Perry Eli 
Published: February 2011

Abstract
Equipment was developed to measure the flatspotting of tires quantitatively on an indoor wheel. It provides close control over all of the important variables and has the virtue of simulating driving conditions for all seasons of the year. Good correlations between quantitative values from the indoor wheel and subjective jury tests on the road are obtained when wheel speeds are adjusted to give the same maximum tire temperature as in the road test for a given ambient temperature. The tire cord was of primary importance in controlling the depth of flatspot. Other variables exerted their influence via their effect on cord properties. For nylon 66 cord, flatspot depth was decreased by high ambient temperatures, high tire air pressure, low loads, and moderate run-in conditions. Change in the moisture content of the nylon cord improved or worsened flatspot depending on the ambient temperature of test. Factors such as cord processing conditions, cord twist, tire bias angle, number of plies, building drum width, postinflation conditions, and temperature of cure had minor effects on the flatspot. A nylon 66 copolymer (Monsanto 88N) showed a large reduction in tire flatspotting.
Heats of Transport of the Rare Gases in a Rubber Membrane
Authors: Bearman Mirion Y. , Bearman Richard J. 
Published: February 2011

Abstract
Revised values for heats of transport, Q*, of the rare gases He, Ne, Ar, Kr, and Xe in rubber are presented. In the case of helium, it is shown that, within experimental error, there is no pressure dependence of heat of transport in the pressure range 25-65 cm. The apparent Q* varies slightly with temperature difference across the membrane. Nevertheless, departures from linearity in the local phenomenological equations seem to be negligible even though the temperature gradients range up to 900°/ni.
Electron Microscope Investigation of States of Distribution in Elastomer Blends
Authors: Kiyek H. , Schoon Th G. P. 
Published: February 2011

Abstract
High polymers that possess high elastic deformability are referred to as elastomers. They have a glass transition between —40° and —70° C. Uberreiter1 has appropriately described their aggregate state as “liquid with fixed structure”, since within the temperature range of elastic deformability individual chain segments of a macromolecule do describe, to be sure, a disordered temperature motion, corresponding to that found in liquids. Yet the macromolecule as a whole is not mobile, because of strong intermolecular forces. When elastomer blends are prepared by mixing the components on a mill or in an internal mixer, technical interest is mainly limited to technological properties, such as softening point, shear modulus, abrasion, etc. But it also seems important to obtain information about the distribution of the components in the blends, in order to evaluate more accurately the basic miscibility of elastomers in general, as well as the intrinsic strength of such multi-phase systems. A solution to the problem may best be obtained by electron microscope investigations since they permit observation of very minute structures representing constant and characteristic values for a given polymer, and can thus serve as a means of identifying a given polymer, even in mixtures. Schoon and Kretschmer have already found that a relation exists between microstructure (observed with an electron microscope) and molecular weight of high polymers.
Theoretical Consideration of Interfacial Forces Involved in Coalescence of Latex Particles
Authors: Vanderhoff J. W. , Tarkowski H. L. , Jenkins M. C. , Bradford E. B. 
Published: February 2011

Abstract
The Dillon, Matheson, and Bradford and the Brown hypotheses for the mechanism of film formation of latexes are extended, two latex particles in a drop of water being given as a model. As the water evaporates, the particles are brought together, so that their stabilizing layers are in contact and their further approach is hindered. The pressure forcing the particles together is increased by the further evaporation of water (that is, by the forces arising from the water air interfacial tension), until the stabilizing layers are ruptured and a polymer polymer contact is formed. Once this occurs, the pressure exerted upon the particles is increased further by the forces arising from the polymer water interfacial tension. Numerical values for the pressure exerted upon the particles are calculated as a function of latex particle size, degree of coalescence, and interfacial tensions both of water against air and polymer against water. Similar calculations with a latex particle coalescing against a flat surface (for example, a substrate) as a model demonstrate the importance of the contact angle between the polymer and the flat surface. The hypotheses developed are used to explain various experimental observations.
Porous Sprayed Sheets and Coatings
Authors: Satas D. 
Published: February 2011

Abstract
In the past few years, porous plastic films have been actively extended into a wide variety of uses, both in sheeting and in coatings. Some porous films, especially films of poly (vinyl chloride), have been used for quite some time in such specialized applications as battery separators. At present, the use of porous plastics in the apparel and footwear industries is of special importance. Large amounts of elastomers in sheet and film form, including coated textiles, are consumed by these industries. Nonporous products are not entireiy satisfactory for uses in which breathability or ability to transmit water vapor is required for comfort. Porous plastic materials in these areas not only improve the suitability and the functioning of plastic sheeting already used, but also replace some of the established materials used for apparel and footwear. It is not surprising, therefore, that a considerable activity is noticeable in this area, particularly in regard to processes for introducing porosity into polymeric films and coatings.
Determination of Carbon Black Particle Size by Reflectance
Authors: Studebaker Merton L. , Nabors Lester G. 
Published: February 2011

Abstract
A simple technique of sample preparation using dry carbon black samples has been developed which gives a carbon black surface of reasonably reproducible reflectance, using a commercially available and reasonably priced reflectance meter. The reflectance values were calibrated against particle size determined by Kraus and Rollmann using the calorimetric procedure of Harkins and Jura.
Effect of Temperature on Stress-Optical Properties of Styrene Butadiene Block Copolymers
Authors: Fischer E. , Henderson J. F. 
Published: February 2011

Abstract
Stress, strain, and optical properties of three elastomeric styrene butadiene block copolymers containing 31, 40 and 49 wt per cent styrene were studied as a function of temperature. Mechanical and optical properties indicate that these materials are two phase systems in which the polybutadiene chains form an elastomeric phase and the polystyrene a glassy phase with the latter providing physical crosslinks. Birefringence measurements indicate that decreases in modulus and strength of these materials are associated with decrease in concentration of elastically effective network chains. Independence of stress-optical coefficient of temperature suggests that the decrease in concentration of elastically effective chains is not due to onset of rubberlike behavior or flow within the polystyrene regions themselves, at least for temperatures below about 70° C. Rather, the decrease seems to be associated with increased mobility of the polybutadiene chains at higher temperatures, which also leads to an increase in the rate of stress relaxation. Birefringence measured during extension and retraction showed that stress strain hysteresis is due to restricted mobility of polybutadiene chain segments rather than to permanent viscous flow or to change in the effective network structure of the block copolymers. The ultimate properties of these rubbers were well correlated with the effective network structure in undeformed specimens.
Isothermal Permeabilities from Thermoosmosis Experiments
Authors: Bearman Mirion Y. , Bearman Richard J. 
Published: February 2011

Abstract
With the use of strain gauge pressure transducers, an improved constant volume apparatus has been constructed for measurement of isothermal permeabilities of gases from thermoosmosis experiments. Permeabilities are reproducible to about ±5% accuracy and compare favorably with those obtained by alternative techniques. Revised values are presented for permeability coefficients of the noble gases in rubber.
Behavior of Viscoelastic Materials in Short-Time Processes
Authors: Metzner A. B. , White J. L. , Denn M. M. 
Published: February 2011

Abstract
It is seen that great care is required in choosing constitutive equations which will correctly describe the behavior of viscoelastic fluids in processing equipment. The choices available, and their advantages and limitations, are considered through solution of a number of example problems. These considerations serve to develop scale-up criteria directly. The importance of the Deborah, Weissenberg, and Reynolds numbers in such problems is noted.