bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vulcanizing Efficiency during the Scorch Period
Authors: Gerke Roscoe H. 
Published: February 2011

Abstract
Values of vulcanizing efficiency, Ci/Si for different rubber compounds have been determined by extrapolating curves of crosslinking (or stress) versus percentage combined sulfur to the combined sulfur axis. The values Ci/Si are corrected for sulfur content of the ingredients, rubber or carbon black. For Hevea vulcanizates determination of the ratio Ci/Si gave values of zero or infinity. SBR vulcanizates also gave values of zero or infinity. For a polybutadiene vulcanizate Ci/Si it was found to be zero. A TMTD Hevea stock showed neither detectable crosslinks nor combined sulfur during the first ten minutes of heating but when sulfur started to combine Ci/Si was found to be infinity.
Crosslinking Reactions of Carboxylic Elastomers
Authors: Brown H. P. 
Published: February 2011

Abstract
Carboxyl groups in elastomer molecules have been shown to contribute to the crosslinking or joining of these molecules through hydrogen bonding, salt formation, reaction with diepoxides or polyepoxides including epoxy resins, reaction with diamines or polyamines, esterification with di- or poly-hydric alcohols, reaction with carbodiimides, reaction with polyimines, and by reaction with polyisocyanates. Each of these reactions alone may produce useful crosslinkages. Or, they may be used in conjunction with crosslinking reactions operating in other parts of the molecule such as sulfur or peroxide vulcanization. This has been particularly true of salt formation, especially through the use of zinc oxide, with sulfur vulcanizarions. The carboxyl groups in some instances may be generated during the crosslinking reaction. Thus polyethylacrylate may be crosslinked with hexamethylene diamine, barium hydroxide and similar reagents. Many of the reactions of the carboxyl groups in elastomers are quite rapid. For some purposes such as surface toughening of elastomer films, this may be quite useful. For others such as the vulcanization of carboxylic elastomers with zinc oxide or with recipes containing zinc oxide, this may be objectionable because of the scorchiness of the stocks. The scorchiness of vulcanizates of carboxylic elastomers involving zinc oxide may be controlled with organic acid additives or by the use of zinc oxide coated with less reactive materials such as zinc sulfide or zinc phosphate. The speed of reaction of epoxides with carboxyl containing polymers is influenced by the structure of the epoxide. The ease with which carbodiimides induce crosslinkage is dependent upon the structure of the carbodiimide.
Vinylpyridine Rubber (PBR)-Filler Interactions. II.
Authors: Brucksch W. F. 
Published: February 2011

Abstract
This paper describes some reactions of vinylpyridine rubber with fillers. The work was done to learn if there is a chemical basis for the superior abrasion resistance of pyridine rubber treads. The results show that chemical factors are important when rubber-to-filler interaction is involved. The copolymerized pyridine groups of the rubber are absorbed readily onto the filler surface, especially when the pyridines are modified by complex formation with certain zinc salts or by conversion to pyridinium cation. Multiple adsorption generates a network. Those qualities associated with reinforcement are enhanced: viscosity (carbon black “stiffening”), “bound” rubber, electrical resistivity, modulus and resistance to tearing and to abrasion. The network bonds are, however, temperature dependent and can be erased by heating to 100° C. Adsorption of modified pyridines onto filler is like the mordant dyeing of fabrics. The pyridinium compound acts like a color “lake” adsorbed onto carbon black. Adsorption-bonding can be used to generate a portion of the modulus in sulfur-cured treads. For the same modulus, less sulfur is required, with a corresponding improvement in heat-aging.
Introduction to the Molecular Viscoelastic Theory of Polymers and Its Applications
Authors: Peticolas Warner L. 
Published: February 2011

Abstract
In summation, it can be said that the relation between the molecular characteristics of polymers, such as molecular weight, branching and their corresponding distribution, and the rheological properties of polymers can now be given with remarkable success, though much work remains to be done and refinements are badly needed. These relationships should help permit the design of polymers with exactly the right molecular weight and branching distribution to meet specific end-use requirements. It is hoped that the present review will be of use to rheologists seeking to design polymers for certain end-use specifications as well as to stimulate further research in this area.
Application of Finite Elastic Theory to the Behavior of Rubberlike Materials
Authors: Blatz Paul J. 
Published: February 2011

Abstract
A brief review of the theory of finite elasticity is presented. The theory is applied to the characterization of the mechanical response parameters of a polyurethan foam. The incorporation of compressibility and anisotropy effects into the strain energy function are discussed. An example of the behavior of a composite or filled foam is presented. Finally some of the problems associated with the molecular interpretation of mechanical parameters are discussed.
Polyolefin Elastomers
Authors: Natta G. , Crespi G. , Valvassori A. , Sartori G. 
Published: February 2011

Abstract
The new processes of anionic co-ordinated polymerization have permitted the synthesis of new polymers which are of interest as plastics, fibers, and elastomers. Among these last, the ethylene-propylene rubbers are particularly interesting for the future of the rubber industry. In fact these elastomers are prepared from low-cost raw materials (ethylene and propylene) and show good mechanical and elastic properties as well as excellent resistance to aging.
The Friction of Polymers on Ice
Authors: Gnüeich W. , Grosch K. A. 
Published: February 2011

Abstract
The paper describes friction experiments on smooth icy surfaces at various temperatures. Speed and temperature variations for NR gum rubber shows that in principle the WLF transformation can be applied to friction on ice, and friction—temperature curves may be interpreted as being part of the friction master curve on smooth solid surfaces. Very near the melting point the friction decreases rapidly for all polymers, and this appears to be associated with changes in the nature of the icy surface. At low temperatures, the friction—temperature curves do not only agree in shape with curves obtained on glass but reach similar values in magnitude also. Black and oil extension effects are also similar to those expected from friction experiments on other surfaces. The blending of polymers, either in the gum state or filled with carbon black, broadens the region of high friction, enveloping the friction curves of the two polymers making up the blend. Depending on the temperature region, either one of the constituents of the blend dominates the friction behavior. It is instructive to speculate on the relevance of these experiments to winter tire performance. It is obvious that the very clean polished smooth ice track obtained only under great difficulty even in the laboratory is not realizable in practice, so that the ice on which tires operate is in every case contaminated with either snow, water, or dirt. In this case the coefficient of friction drops drastically, as is demonstrated in Figure 11. Nevertheless it is easily shown that compound effects do exist in tire skid measurements on ice. It is generally observed that NR-based compounds have a higher skid resistance on ice than SBR-based ones. This ranking is also observed in all experiments described in this paper and is explainable because of the position of the friction master curve. Even if practical speeds, as they occur in tire usage, are considered, it is easily demonstrable that the shift of the master curve towards lower temperatures is insufficient to have a real impact on compound relations. It is in any case minimized by the fact that, at high sliding speeds, the simultaneously occurring temperature rise in the interface tends to cancel any velocity shift in the master curve. On ice the temperature rise cannot exceed 0°C, so that only a very small band of the master curve is in operation. In this band, NR is near its maximum, SBR has exceeded its maximum value, and BR has not reached it.
Influence of Carbon Black on Process-Ability of Rubber Stocks. I. Bound Rubber Formation
Authors: Cotten G. R. 
Published: February 2011

Abstract
1. A direct correlation between bound rubber content and molecular weight of soluble polymer was found for a wide range of carbon black samples and processing conditions in SBR. 2. No significant polymer degradation occurred during the ineorporation of carbon black into SBR rubber. 3. A theory was proposed to explain the observed changes in viscosity and extrusion shrinkage of rubber stocks. This theory is based on the concept of occluded rubber which is rich in high molecular weight polymer and behaves as a part of filler volume during viscous flow.
Reinforcement of Silicone Rubber by Particulate Silica
Authors: Boonstra B. B. , Cochrane H. , Dánnenberg E. M. 
Published: February 2011

Abstract
The interaction between fumed silica and silicone elastomer after various treatments of the silica surface has been investigated. The effect of the treatments was determined by measuring bound rubber, an interaction coefficient by means of the oscillating disk rheometer, the mechanical properties of the vulcanizates, the morphology of the silica aggregates, and the use of an hydroxyl-terminated silicone rubber. The results indicated that the interaction is much more intensive than in carbon black-hydrocarbon rubber systems. This is demonstrated by much higher bound rubber values (by a factor of 2–3) and a higher interaction coefficient. It is shown that the major effect on this interaction coefficient is the specific interaction by hydrogen bonding, between silica surface silanol groups and the polydimethylsiloxane chain. In this bonding the isolated hydroxyl groups should play the major part. Partial inactivation of these isolated silanol groups leads to improved strength but lower modulus. Maximum inactivation of the surface hydroxyl groups leads to soft compounds with lower tensile strengths and moduli, as well as very low bound rubber. Replacement of surface hydroxyl groups by vinyldimethylsilyl groups did not have the expected activating effect. Apparently the attached vinyldimethylsilyl groups do not form crosslinks with the elastomer chains, so that the overall result of the presence of these groups on the silica surface is a weakening of the interaction with the silicone rubber chains, although to a lesser degree than in the case of trimethylsilyl groups. The interaction between filler surface and polysiloxane can be maximizedby the use of a hydroxyl-terminated elastomer. The terminal groups will react with the silica surface so strongly that the particles act as crosslinks after proper heat treatment and a crosslinked polymer is obtained with a tensile strength of the same level as a peroxide-crosslinked vulcanizate but with higher compression set. At the temperature of the compression set test (175°C) the bonds apparently rearrange so that the permanent deformation is practically 100%. Quantitative data have been presented which prove that breakdown of silica aggregates does occur during mixing in silicone rubber on a two-roll mill.
Strain Dependence of the Glass Transition Point in Chlorinated Polyethylene Vulcanizates
Authors: Naoki M. , Nose T. 
Published: February 2011

Abstract
The experimental glass transition temperature observed as the inflection point in a certain physical quantity, Tgapp, changes not only with glass-forming conditions but also with the variables observed. Moreover the change of Tgapp with extension largely depends on the variables observed. These results indicate that Tgapp as determined by measurement of a certain physical quantity is not necessarily a direct reflection of the molecular mobility.
Mechanistic Studies on the Photooxidation of Commercial Polybutadiene
Authors: Beavan S. W. , Phillips D. 
Published: February 2011

Abstract
Products from both the thermal and photooxidation of polybutadiene have been studied using various analytical techniques such as infrared and ultraviolet spectroscopy, gas—liquid chromatography, phosphorescence emission, and phosphorescence excitation spectroscopy. Analyses have allowed a plausible mechanism to be formulated for the photooxidation of this polymer, consistent with all the observed physical and chemical changes. Both photo- and thermal oxidative polymer degradation initially result in the formation of α,β-unsaturated carbonyls which, under photo-degrading conditions, are subsequently photolysed to yield the observed final products.
Infrared Absorption Spectra of Alternating Copolymers of Butadiene with Acrylonitrile and Deuterated Analogs
Authors: Furukawa J. , Kobatashi E. , Uratani K. , Iseda Y. , Umemura J. , Takenaka T. 
Published: February 2011

Abstract
Random copolymers consisting of various amounts of butadiene and acrylonitrile have been prepared by conventional radical initiators or Ziegler—Natta catalysts. Recently, a novel alternating copolymer of butadiene with acrylonitrile was successfully prepared by the authors using a system of organoaluminum halide—transition metal compound as a catalyst. The NMR and x-ray analyses of the alternating copolymer indicated a high alternating regularity and trans regularity of the butadiene unit. Studies of mechanical properties of the copolymer suggested that the alternating copolymer was more flexible and stronger than the random copolymers. This report deals with a study of the ir spectra under stretching of the alternating copolymer influenced by the regularity of the molecular structure. The ir spectra of trans-1,4-polybutadiene have been studied by several authors and the assignments of the absorption bands of polyacrylonitrile have been given by Liang and Tadokoro et al. Tentative assignments of the absorption bands of the alternating copolymer were attempted on the basis of ir spectra and ir dichroism of partially deuterated copolymers and correlations with the results obtained on the above-mentioned homopolymers.
Modification of Emulsion Polymerization with Blends of Mercaptans
Authors: Uraneck C. A. , Burleigh J. E. 
Published: February 2011

Abstract
Although blends of modifiers have been used in the manufacture of SBR elastomers and similar polymers in emulsion systems for a long time, no studies of the kinetics of their reaction nor of their effect on molecular weights have been reported. This is such a study. Model equations for blends of modifiers are derived to predict modifier depletion and polymer molecular weight. These equations are used to serve as guides for preparing blends of modifiers in SBR-type polymerizations and for comparisons with experimental results.
Terpolymers of Ethylene, Propylene, and Tricyclo [5.2.1.0]Deca-2,5,8-Triene
Authors: Cesca S. , Arrighetti S. , Priola A. , Duranti P. V. , Bruzzone M. 
Published: February 2011

Abstract
Tricyclo[5.2.1.0]deca-2,5,8-triene (1) or a mixture of its methyl derivatives was used as termonomer to obtain ethylene—propylene—triene terpolymers (EPTM) having unusual properties in the curing process, even at low levels of triene (ca. 1 wt %). Three types of catalyst systems have been investigated, based on VCl4, VO[O(CH2)3CH3]3, or V(acac)3 and (C2H5)2AlCl. Several parameters of the terpolymerization process were studied (e.g. Al/V mole ratio; catalyst and termonomer concentration; polymerization time; presence of a Lewis base or chain transfer agent) and their influence on Mv and EPTM composition were evaluated. Fractionation data and the use of model compounds allow to conclude that 1 enters EPTM chains randomly and by selective opening of the norbornenic double bond, whereas the conjugated diene system is involved in side reactions if the catalyst has some acid character or the concentration of the triene is above some critical value.
Excluded-Volume Effects in Dilute Polymer Solutions. V. Butyl Rubber in Various Solvents
Authors: Tsuji T. , Fujita H. 
Published: February 2011

Abstract
It is a fundamental requirement of the two-parameter theory of linear homopolymers in dilute solution that the expansion factor α, and the interpenetration function Ψ depend only on the excluded-volume parameter z and that these functions are universal in the sense that their forms are independent of the chemical nature of the polymer and solvent as well as of the temperature. It follows immediately from the above requirement that the values of Ψ for different combinations of polymer, solvent, and temperature should form a single composite curve when plotted against αs.
Entanglement Networks of 1,2-Polybutadiene Crosslinked in States of Strain. II. Application of the Mooney-Rivlin Equation to Networks Crosslinked at 0°C
Authors: Kramer Ole , Ferry John D. 
Published: February 2011

Abstract
This paper gives the results of a recalculation of the data in Paper I of this series, with an expression for strain energy which is a special case of the Mooney-Rivlin theory, instead of the ideal theory based on Gaussian networks. It was shown in Paper I that the apparent concentration of elastically effective network strands terminated by entanglements, νN, can be estimated by crosslinking linear polymers in states of strain. The maximum value of νN found by this method was about one-half the value obtained from viscoelastic measurements in the rubbery plateau zone, νc=2.5×10−4 mol cm−3. The low value of νN was primarily attributed to the crosslinking temperature being too far (12°) above the glass-transition temperature, Tg. Crosslinking temperatures closer to Tg give values of νN close to νc, as will be shown in Paper III of this series. In addition, it was found that these networks behave slightly differently from the predictions of the ideal Gaussian composite network theory: ideal Gaussian composite networks are isotropic relative to the state of ease whereas these networks exhibit anisotropy of equilibrium swelling, relative to the state of ease, in n-heptane; and νN, instead of being a constant, was found to decrease with increasing extension ratio during crosslinking, λ0. The latter result is illustrated in Figure 1 for irradiation times from 3 to 5 h; here, νN is plotted against the extension ratio, λs, in the state of ease in which the retractive force of the entanglement network and the compressive force of the crosslink network are equal and opposite in direction. The experimental points can be fitted rather well by a curve (not the one shown) with the functional form of a constant divided by λs, like the C2 term in the Mooney-Rivlin equation.
Estimation of Long-Chain Branching in Ethylene-Propylene Terpolymers from Infinite-Dilution Viscoelastic Properties
Authors: Mitsuda Y. , Schrag J. L. , Ferry J. D. 
Published: February 2011

Abstract
A method is outlined for estimation of small degrees of long-chain branching in polymers with moderately narrow molecular weight distribution (Mw/Mn&lt;1.4). The storage and loss shear moduli, G′ and G″, are measured in dilute solution by the Birnboim-Schrag multiple-lumped resonator and extrapolated to infinite dilution, choosing a suitable solvent viscosity and frequency range such that the data lie in the terminal zone where G′ and G″ are proportional to the second and first powers of frequency, respectively. The intrinsic reduced steady-state shear compliance is determined from these data and corrected for moderate molecular weight heterogeneity (assuming a Gaussian distribution) from knowledge ofMw/Mn and the Mark-Houwink exponent a. The resulting value of S2/S12 (where S1=∑ τp/τ1, S2=∑ (τp/τ1)2, the τp's being the relaxation times and τ1 the longest one) is compared with values calculated by the Zimm-Kilb theory as evaluated by Osaki for comb polymers of regular geometry and different numbers of branch points. The method has been illustrated by measurements on four ethylene-propylene copolymers. One containing no termonomer and one containing a saturated termonomer appeared to be linear; two containing unsaturated termonomers showed small degrees of branching. The method appears to be promising for detecting from one to four branch points per molecule.
Carbon-13 Nuclear Magnetic Resonance Spectroscopy of Polymers. Part V. Monomer Sequence in Styrene-Butadiene Copolymers
Authors: Katritzky A. R. , Weiss D. E. 
Published: February 2011

Abstract
Future studies of styrene-butadiene copolymers will undoubtedly reveal much more information. Better resolution should be available with existing instrumentation, by using higher probe temperatures, smaller sweep widths, and longer accumulation times. More peaks could be resolved in the high-field region than the 17 we have assigned. The advent of higher-field 13C instruments will further improve resolution and, perhaps more important, relaxation-time studies will allow better assessment of peak intensities and reveal those diads of the copolymer which have greater mobility and hence facilitate precise correlation of the new structural information now reported with the mechanical properties of the copolymers.
The Use of Stable Free Radicals to Determine Motion in Polymeric Systems
Authors: Miller Wilmer G. , Veksli Zorica 
Published: February 2011

Abstract
The application of thermally and chemically stable nitroxide free radicals to a variety of motional problems in polymeric systems has been investigated. Solvents do not cause significant motion in glassy polymers until the glass transition is lowered to the temperature of measurement. With nonsolvents the results depend on the nature of the sample preparation as well as on the polymer-solvent pair. Molecular motion at the surface of a polymer immersed in a nonsolvent was investigated by means of surface-labeled latex spheres. The application of nitroxides as spin labels to the measurement of translational diffusion coefficients is explored and discussed. Finally, the application of the technique to adsorption and motion of surfactants and polymers onto surfaces is reported.
Reinforcement Studies—Effect of Silica Structure on Properties and Crosslink Density
Authors: Polmanteer K. E. , Lentz C. W. 
Published: February 2011

Abstract
This work was undertaken to study the effect of silica filler structure on the effective crosslink density and on mechanical properties. Vulcanizates of silicone, SBR, and EPM were included in the work. A compression modulus method was used for crosslink density determination. Samples were swollen prior to measurement in two environments : (a) toluene, (b) toluene in an NH8 atmosphere (designed to cleave polymer-filler linkages if they were present). The results showed that, in peroxide-cured silicone and EPM elastomers, the crosslink density increased with filler structure, but after cleavage of polymer-filler bonds by the NH3-modified swelling environment, there was very little change of crosslink density with filler structure increase. The effect of increasing filler structure on crosslink density in the SBR elastomers was very slight, showing a small increase in progressing from discrete particles to low structure and thereafter no change. The quanitative results of this study are important in that they provide excellent support for Medalia's theory of the role of occluded volume in reinforcement. The results show that polymer-filler bonds are required, in combination with occluded volume, in order to achieve a substantial increase in both 200% modulus and crosslink density.