bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relaxation Response of Polyurethan Elastomers
Authors: Theocaris P. S. 
Published: February 2011

Abstract
The transient extension relaxation modulus E(t) and the lateral contraction ratio vr(t) for a polyurcthan elastomer have been measured simultaneously in the transition region from glass to rubber. The differential moiré method was used in these measurements and yielded simultaneous values of the longitudinal extension and the lateral contraction principal strains of the tension specimen. Composite curves of E(t) and vr(t) reduced to a standard temperature were obtained by applying the method of reduced variables. The time factors KT in both curves coincided, and followed the WLF equation. The shear and bulk modulus characteristic functions were determined from the extension modulus and lateral contraction ratio functions. The values of the lateral contraction ratio in relaxation were determined by using data of the extension relaxation modulus along the whole viscoelastic range and the initial value of the lateral contraction ratio at the rubbery state and applying an indirect method. The results obtained by the indirect method coincided with the experimental values. The shear modulus function was evaluated from the extension relaxation modulus and the lateral contraction ratio functions and compared with the shear dynamic compliance determined by Landel. The experimental data indicated that a linear relationship holds between the lateral contraction ratio in relaxation and the bulk modulus along the whole response spectrum. The same relationship was previously shown to hold for a series of various polymeric substances.
Viscoelastic Behavior of Open Cell Foams
Authors: Gent A. N. , Rusch K. C. 
Published: February 2011

Abstract
Open-cell foams show abnormally large mechanical damping due to the energy dissipated in forcing air in and out of the foam during a deformation cycle. This pneumatic damping has recently been treated theoretically and experimentally. The dependence upon the test-piece dimensions, the frequency of deformation and the viscosity of the fluid has been shown to be in good agreement with the theoretical predictions. The dominant property of the foam structure is its permeability to fluids. This has also been measured for a number of different foams and related to their structural features by means of a simple model. A review is given of these developments.
Compliance-Time-Temperature Relationships from Indentation Measurements on a Pure-Gum Rubber Vulcanizate
Authors: Roth Frank L. , Bullman George W. , Wood Lawrence A. 
Published: February 2011

Abstract
Previous work on the calculation of shear compliance J (limit of the ratio of strain to stress at zero deformation) from observations of the indentation of a flat natural rubber surface by a rigid sphere has been extended over greater ranges of time, temperature, and state of vulcanization. The extreme ranges of time were 5 sec to 23.5 hr and of temperature −67 to +100° C. The curves of JT against log t−60 (where t−60 is the equivalent time at −60° C and T is in °K) were sigmoid with a region of maximum slope and continuing through a region of minimum slope extending over about 7 decades. In contrast with predictions of the Williams, Landel, and Ferry equation, the empirically determined shift of abscissa necessary to give a single JT curve was found to be a linear function of T−1 with a slope corresponding to an “apparent activation energy” of 36.9 kcal (°K)− (mole)−1 (154.5 k.J (°K)−(mole)−1).
Pressures and Flow Rates in Extruders with Axially-Variable Geometry
Authors: Tangorra G. 
Published: February 2011

Abstract
The problem of predicting pressures and flow rates for extruders, with geometrical parameters arbitrarily variable along the axis is considered for isothermal, Newtonian conditions. A graphical method is applied to an actual case of a truncated, cone-shaped extruder. Experimental results are reported. The same general procedure, but with further simplified formulas, is applied subsequently to cases of extruders having diameter, pitch, and thread depth linearly variable along the axis.
Butadiene and Isoprene Rubber in Giant Tire Treads
Authors: Krol L. H. 
Published: February 2011

Abstract
The lower abrasion found for IR in comparison with NR in an identical formulation could well be counterbalanced by proper modification of the formulation. In spite of the increased black level the heat build-up can still be kept within the limits set by the NR reference. Also, for ternary blends the reduced abrasion resistance of IR can be offset by increasing the black content, without sacrificing loss properties.
Stereoregular Polymerization of Butadiene with Alkylaluminum Chlorides and Cobalt Octoate
Authors: Gippin Morris 
Published: February 2011

Abstract
The requirement of water or oxygen to activate the diethylaluminum chloride co-catalyst used with a cobalt compound to produce 98 per cent cis-1,4 poly-butadiene was reported previously. Activation is considered to form two alkylaluminum compounds differing in Lewis acidity. Several reactions presumed to lead to the formation of the higher acid were carried out with a minor proportion of the diethylaluminum chloride by partial dealkylation with organic hydroperoxide, halogen, tertiary alcohol, organic halide or aluminum. Water is neither necessary nor desirable in the ethylaluminum sesquichloride-cobalt octoate catalyst system. Polar solvents do not appreciably alter the cis-1,4 catalysis with diethylaluminum chloride/water/cobalt octoate, but do decrease the rate or extent of polymerization with increasing dielectric constant of the solvent. A mechanism of cobalt catalysis of butadiene polymerization is proposed.
Relaxation of Disulfide and Tetrasulfide Polymers
Authors: Tobolsky A. V. , MacKnight W. J. , Takahashi M. 
Published: February 2011

Abstract
The chemorheology of crosslinked polyethylene disulfide, polyethylene tetrasulfide, and mixtures of these polymers with elemental sulfur is investigated. It is shown that stress decay in the disulfide polymer occurs by scission of the small quantities of higher polysulfide linkages present in the network. It is also shown that elemental sulfur decreases the chemical relaxation time in crosslinked polyethylene disulfide in a predictable manner.
Oxidative Scission of Natural Polyisoprenes in Solution
Authors: Bell C. L. M. 
Published: February 2011

Abstract
Polyisoprenes are oxidized by a chain reaction in which a large number of oxygen molecules are absorbed for each reaction chain started. During the oxidation, scission of the polymer backbone takes place. Using solutions of natural rubber and gutta percha, measurements of the relative amounts of oxygen absorbed and scission produced indicate that most scission occurs during propagation of the oxidation chain. However, more detailed analysis of the data indicates that scission also occurs nearly every time an oxidation chain is terminated.
Solution Masterbatching Studies
Authors: Scott C. E. , Eckert F. J. 
Published: February 2011

Abstract
Hydrosolution masterbatching (HSMB) imparts excellent dispersion and improved pigment-to-polymer adhesion to carbon and oil masterbatches of poly-butadiene, SBR and blends of these rubbers. Tire tests show HSMB stocks to resist wear slightly better than like stocks mixed in a conventional manner. The HSMB process can be used to produce fully compounded vulcanizable tread stocks in which the stock is discharged continuously from a drying extruder. The dispersion and adhesion advantages of HSMB stocks are also noted in complete masterbatches. HSMB oil, black, and polymer masterbatches usually have higher viscosity, tensile strength, hardness, and dynamic modulus but lower resilience and reduced scorch safety, in comparison with conventionally mixed stock. Carbon black dispersion as revealed by light and electron microscope analysis is excellent. Experiments characterizing carbon gel and development of carbon black dispersion on HSMB stocks (vacuum dried), indicate the total effective molecular contact between elastomer and pigment to be increased, so that, in effect, surface area is increased.
Statistical Variability of Ultimate Properties of SBR Gum Vulcanizates
Authors: Fedors R. F. , Landel R. F. 
Published: February 2011

Abstract
The statistical variability of ultimate properties for 8 samples of SBR-sulfur gum vulcanizates differing in crosslink density by a factor of about 25 was studied. It is shown that these variability data, determined at one rate and one temperature, can be correlated when plotted as a reduced failure envelope. The envelope obtained in this manner agrees reasonably well with the reduced envelope previously reported which was constructed from break data obtained by testing (a) single specimens of constant crosslink density at varying rate and temperature and (b) single specimens at constant rate and temperature but varying crosslink density. It is also shown that the statistical variability data for all samples, including a benzene-soluble one, can be represented by a double exponential cumulative distribution function. It is also shown, in agreement with previous work, that the most probable values of σb when plotted as a function of νe exhibit a maximum in σb at a low value of νe.
Relation of Water Vapor Permeability of Elastomers to Molecular Structure
Authors: Iyengar Y. 
Published: February 2011

Abstract
This communication is a quantitative correlation of water vapor permeability of nonpolar elastomers with molecular structure. Permeability of physical blends and of composite layers of elastomers are also discussed. Permeability—Elastomer Structure.—Steric hindrance and unsaturation influence water vapor permeability of elastomers. The low permeability of isobutylene—isoprene (butyl) rubber is attributed to the presence of bulky methyl groups in its isobutylene component. The high unsaturation in isoprene and butadiene is blamed for the high permeability of natural rubber and styrene butadiene rubber. Hence, permeability should be correlated quantitatively with a factor which can evaluate and combine these two structural parameters. Defining the factors A and B to express the relative molar concentrations of unsaturated and steric groups in the average monomer unit of elastomers as (unsaturation) A=1+x/X (steric groups) B=1+y/Y
High Quality Foams from NIR Latex
Authors: Angove S. N. , Graham E. S. , Hilditch G. , Stewart R. A. , White F. L. 
Published: February 2011

Abstract
Foam rubber properties have been measured for NIR latexes as a function of acrylonitrile content of the copolymer and as a function of ratio of NIR latex to NR latex and high modulus SBR latex. Foam rubber made from NIR latex had good aging and oil resistance, combined with the desirable high tensile strength and elongation characteristic of natural rubber foam. Resilience and low temperature flexibility of NIR foams were found to be lower than that achieved with foams of either SBR or NR latexes. Although compression modulus of NIR foam was lower than that of a high modulus SBR foam and approximately equivalent to that of NR foam, it was effectively increased by the addition of either such SBR latex or a high-styrene resin latex.
Studies of the Compounding of Nitrile Rubber with Shellac
Authors: Jose K. A. , Baneejee S. 
Published: February 2011

Abstract
Shellac is highly compatible with nitrile rubber and can be incorporated in this rubber on a roll mill up to 50 phr without any difficulty. It acts as an antiscorching agent and plasticizer at processing temperatures. To a small extent, it retards cure increasing the cure time from 30 to 40 minutes at higher concentrations of shellac. This is not harmful in industrial applications. Shellac improves physical properties like modulus, tensile strength, tear resistance, hardness, swelling in hydrocarbon oils to a considerable extent. Resilience remains the same. Abrasion resistance is reduced. Heat generation is more with higher percentage of shellac. It can be seen that the optimum concentration of shellac for the best physical properties is 20 to 30 phr.
Thermal Degradation of Aged Chloroprene Rubber Studied by Thermogravimetric Analysis
Authors: Denardin Elton L. G. , Samios Dimitrios , Janissek Paulo R. , de Souza Gabriel P. 
Published: February 2011

Abstract
The thermal degradation of original and aged chloroprene rubber was studied using thermogravimetric analysis. Thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTG) techniques were used to detect the mass loss during the temperature elevation. By the analysis of the mass loss curves through usual kinetic methods, it was possible to evaluate the different degradation processes present in the overall degradation. The activation energies of the degradation processes were obtained using the dynamic, non-isothermal Kissinger and Osawa methods and the half-width at half-high technique (HWHH). The results obtained demonstrate clearly the differences between original and aged chloroprene rubber as well as the influence of the air and N2 in TGA.
New Generation Carbon-Silica Dual Phase Filler Part I. Characterization and Application to Passenger Tire
Authors: Wang Meng-Jiao , Kutsovsky Yakov , Zhang Ping , Murphy Lawrence J. , Laube Steven , Mahmud Khaled 
Published: February 2011

Abstract
A new carbon-silica dual phase filler (CSDPF) 4000 has been developed for passenger tire application. Analytically, this filler is featured by higher levels of silica at the surface of the aggregate and higher silanol contents compared with the CSDPF 2000 family of products introduced previously. From the compounding point of view, this new dual phase filler shows higher polymer-filler interaction on the carbon domains and lower filler-filler interaction relative to the conventional fillers used in tire tread compounds. The new filler shows significant improvement in wet skid resistance over the earlier products. When this filler is employed in passenger tire tread compounds, the tradeoff among rolling resistance, wear resistance and wet skid resistance of the tire can be significantly improved compared with conventional fillers.
Emulsion Rubbers Copolymerized with Monomeric Antioxidants
Authors: Meyer G. E. , Kavchok R. W. , Naples F. J. 
Published: February 2011

Abstract
It has been shown that dual functional compounds bearing antioxidant and polymerizable functions can be copolymerized with numerous monomers in emulsion systems. Somewhat higher initiator levels and/or increased temperature appear to be required for normal polymerization rates in the presence of these monomers. The only incompatible initiator—monomer combinations found are those of persulfate and benzoyl peroxide with amine antioxidants. The dual functional monomers retain their normal antioxidant characteristics in the copolymerized form and are not removed by solvent extraction nor volatilization except under conditions that destroy the polymer. The amine antioxidants, in the copolymerized state, cause comparatively little discoloration on aging and cause no migratory stain while providing antioxidant protection equivalent to high-quality, conventional amine antioxidants.
Liquid Carboxyl-Terminated Poly(Butadiene)
Authors: Hoffman R. F. , Gobran R. H. 
Published: February 2011

Abstract
In general HC-434 is a relatively homogeneous, difunctional polymer that can be readily chain extended through a variety of cure reactions. To date most of the work has been done with epoxide and aziridinyl curing agents, and a moderate amount of work has been done to improve the rates of cure by means of catalysts. Both aromatic amines and chromium salt complexes have proven to be effective catalysts. The physical properties of the chain-extended polymer with reinforcing fillers approach those of SBR vulcanizates, but improvement is still needed to achieve the properties required for tire formulations. The liquid polymer systems are suitable for belting, hose, and molding applications. However, additional work is required to develop the optimum cure systems for physical properties, faster catalysts, and alternative chain-extension reactions with other reactive curing agents.
Processing and Properties of Liquid Rubbers
Authors: Humpidge R. T. , Matthews D. , Morrell S. H. , Pyne J. R. 
Published: February 2011

Abstract
Difficulties of compounding liquid rubbers are discussed and detailed descriptions are given of mixers for the adequate continuous dispersion of carbon black and of light-weight injection molding machines suitable for the pastes which result; some of the problems of injection molding are outlined and suggested solutions given. The reinforcement of liquid rubbers with textile fibers is discussed and suggestions proposed for the layout of a factory suitable for the processing of liquid rubbers.
Specific Shape Characterization of Carbon Black Primary Units
Authors: Hess W. M. , McDonald G. C. , Urban E. 
Published: February 2011

Abstract
A full field feature specific image analysis system has been developed for direct morphological characterization of carbon black in the electron microscope. The system provides quantitative size and non-dimensional shape information, as well as qualitative classification into specific shape categories using pattern recognition programming methods. Data on samplings of 500–1000 primary black units can be recorded on magnetic tape in less than 10 minutes. Although not yet tested on a full range of rubber grade blacks, the new system has demonstrated good sensitivity in resolving morphological differences among a series of four HAF blacks of varied DBP absorption. The blacks exhibited large frequency variations across nine specific shape categories which range from spheroidal to fibrous types. Within each category, the unit size and non-dimensional shape factors were similar for all four blacks. On a composite average basis, however, large differences in unit size (longest dimension or projected area), anisometry (length/width ratio), and irregularity (perimeter/area ratio) were observed. The new image analysis system also has the capability of volume measurements based on microdensitometry. Although data is limited at this time, such measurements should provide more three-dimensional approximations of carbon black unit size. It is also anticipated that microdensitometry will aid in the determination of domain (particle) size.
Chlorobutyl Covulcanization Chemistry and Interfacial Elastomer Bonding
Authors: Zapp R. L. 
Published: February 2011

Abstract
A new analytical and diagnostic technique has been developed and applied to covulcanized Chlorobutyl—polydiene rubber blends that indicates the existence or absence of interfacial bonds. This technique of differential solvent swelling is based upon solvent—elastomer interaction parameters and draws upon the analogy to filler-adhesion analysis of vulcanized networks. Interfacial bonds between dispersed Chlorobutyl and polydiene rubber phases are first obtained with very active thiuram and thiuram tetrasulfide curative systems. Subsequently less active curatives utilizing bis-alkylphenol polysulfides as sulfur donors were also found to promote interfacial bonds. By means of mercaptan probes it was established that strong evidence of interfacial bonds in covulcanized networks was associated with a preponderance of monosulfidic crosslinks. Prolonged heating, which matures polysulfidic links to more thermally stable monosulfidic links, did not produce strong interfacial bonds where none existed after the initial vulcanization cycle. Thus, interfacial bonds must be formed with more thermally stable monosulfide links during the initial stages of vulcanization. Reinforcing carbon black has a minimal effect upon the acquisition of interfacial bonds or the sulfur-bond chemistry. The curative formulation remains the factor which governs production of the monosulfidic links required for strong interfacial bonding. A definite correlation was found between interfacial bonding and physical strength of fully compounded Chlorobutyl—SBR covulcanized blends. Carbon-black reinforced systems covulcanized with a sulfur donor, such as bis-alkylphenol polysulfide, as the sole source of sulfur, displayed tensile strengths and rupture energies considerably greater than the equivalent systems containing elemental sulfur.
The Compression Set Behavior of Nitrile Rubber
Authors: Jahn H-J. , Bertram H-H. 
Published: February 2011

Abstract
The compression set (C.S.) of a vulcanizate depends on the formulation, processing, and conditions of cure. The following factors are the most important: (a) the type of elastomer, (b) the curing system, (c) the type and amount of filler, (d) the type and amount of plasticizer, (e) the type and amount of antioxidant, (f) the type of cure (press, steam, or hot air), and (g) the cure time and temperature. The present paper is intended, as far as possible, to describe these relationships quantitatively. Most tests will refer to nitrile rubber. We have modified the C.S. method described in ASTM D-395. The deviations are as follows : (1) When C.S. is plotted as a function of the duration of compression, the resulting curves rise steeply for roughly the first seven days, afterwards becoming flatter. The higher the test temperature, the steeper the curve. The ordinary compression times of 22 and 70 h still correspond to the steep part of the C.S. curve; here relatively small inaccuracies in the compression time and test temperature bring large errors in the C.S. readings. Therefore, to improve the correlation between C.S. readings and field behavior the test was extended to seven days in most cases. Longer test times would have been experimentally impractical. (2) As a rule, only C.S. figures relating to 20°, 70°, and 100° C are found in the literature, so test temperatures were extended to include practical conditions. Generally, therefore, C.S. readings were taken at twelve different temperatures ranging from −60° C to +160° C. (3) According to the standards the test pieces should be cooled to room temperature after removal of the load and before the recovery measurement is carried out. Only ASTM D-1229-62 requires the remeasurement to be taken at the load temperature. This ensures accurate measurements of the C.S. at low temperatures. In our tests this was done in every case because at high temperature the C.S. readings are lower since (1) many elastomers recover better at elevated temperatures than at room temperature and (2) the thermal expansion of the test piece can be measured in addition to the recovery. Nevertheless, the differences between remeasurements taken at room temperature and the test temperature are small if the test temperature is fairly high. Where lower test temperatures are used, the remeasurement should always be taken at test temperature if useful results are to be obtained. In all the tests the time allowed for recovery between removal of the load and the remeasurement was thirty min.