bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Weight Dependence of Relaxation Spectra of Amorphous Polymers in the Rubbery Region. VII. Comparisons of Experimental Relaxation Spectra with Those Estimated from Molecular Weight Distributions
Authors: Yasuda G. , Maekawa E. , Homma T. , Ninomiya K. 
Published: February 2011

Abstract
In a previous paper, the relationship between the relaxation spectrum of an amorphous high polymer in the rubbery region and the molecular weight distribution function was studied by the phenomenological theory method. We found a simple, direct proportional relationship between them. The reliability of assumptions and approximations made for the theoretical study can be evaluated by comparison of calculated and experimental data. As reported previously, selection of values for the simplified method was optional in calculating molecular weight dependence of the relaxation spectrum of a sample with a homogeneous distribution. Therefore, the feasibility of selection has to be evaluated by comparison of calculated results with observed data. For the comparison, it is necessary to obtain experimental data for a sample having a homogeneous distribution and compare it with calculated results for the relaxation spectrum and molecular weight distribution of the previous paper. However, these data are scarce in the current literature. From available past literature, we selected polystyrene, poly(vinyl acetate) and polyisobutene as typical samples of amorphous high polymers. In addition, experimental data for two samples of polystyrene were included. Thus, data for a total of five samples were compared with calculated results of the previous paper.
Anomalous Flow of Polyisobutylene
Authors: Lund J. Kenneth 
Published: February 2011

Abstract
This work began as a study of shear degradation in a polymer melt subjected to a uniform shear field. A new type of biconical rotor rheometer was designed and constructed for it. Early in the investigation, however, phenomena were observed which led our efforts away from the original objectives. Viscosity data on a polyisobutylene melt have been obtained which indicate the presence of two flow regions, having significantly different flow activation energies. Normal entanglement flow is encountered in one, the other is apparently dominated by a different mechanism, which results in lower flow activation energies. A mechanism involving rotating flow units is proposed and applied to describe this region.
Analysis of Flow of Shear Thinning Colloidal and Polymeric Systems Which Exhibit Elastic Recovery or Rigidity
Authors: Gillespie T. 
Published: February 2011

Abstract
The hydrodynamic-structural theory of viscosity is extended to take into account the possibility of a distribution of relaxation times. A new equation is presented which is easily applied to experimental data. The effect of a distribution of lifetimes is to extend the range of shear rate over which shear thinning occurs. When the ratio of the largest relaxation time to the smallest relaxation time is greater than 1 but less than 10 the new equation gives results in agreement with the Willamson equation. When this ratio of maximum relaxation time to minimum relaxation time is 300 ± 100 the new equation agrees with an equation recently suggested by Cross. The utility of the new equation is discussed and is illustrated by using it to determine the relaxation time spectra in polystyrene melts.
Structure of Polybutadienes
Authors: Bahary W. S. , Sapper D. I. 
Published: February 2011

Abstract
Polybutadienes made with six different catalyst systems were examined: (1) butyllithium, (2) “nickel-based”, (3) alfin, (4) “titanium-based”, (5) “cobalt-based”, and (6) free radical emulsion. The microstructure and macrostructure of the polybutadienes have been determined and are compared to the results published in the literature. These polybutadienes may be considered to be random terpolymers of cis, trans, and vinyl addition of butadiene. The glass transition temperature is specified by the vinyl content. The crystalline melting points of the high trans and also the high cis polybutadienes obey to a high measure Flory's equation for melting point depression of a random terpolymer. The molecular weights of the polybutadienes have been determined by light scattering and osmometry and the degree of long chain branching has been determined by the branching index, 〈g′〉. The macro-structural features of the linear polymers are confirmed by fractionation. However, the polydispersities calculated from fractionation data do not agree with those determined from light scattering and osmometry for the branched samples. The discrepancy is attributed to the method of characterization of the fractions. A distinction is made between molecular weight distribution and molecular size distribution.
Chemistry and Technology of Elastomeric Polysulfide Polymers
Authors: Bertozzi Eugene R. 
Published: February 2011

Abstract
The first synthetic rubber manufactured in the United States was of the polysulfide type. In 1927 Patrick and Mnookin had obtained the first of a series of patents on the products from the reaction of organic dihalides and inorganic polysulfides. Production was started in Kansas City in 1929 with the first of the polysulfide elastomers, the ethylene tetrasulfide polymer, under the trademark name Thiokol A. Thus, the Thiokol Chemical Corporation started its long association with the polysulfide polymers. Interest developed in many countries because of the potential cheapness and availability of the raw materials required. In the case of Thiokol A, these were sulfur, caustic soda, and ethylene dichloride from ethylene and chlorine. The most interesting property of these polymers was the unusual inertness to solvents and hydrocarbon fuels in contrast to the easy swelling of natural rubber. In this respect, Thiokol A was more inert than the polysulfide polymers to follow, but it had also some less desirable properties. It was difficult to process, had a bad odor that remained to some extent even when fully cured, and gave off irritating fumes during processing. It was subsequently found that the polymers from bis (2-chloroethyl) ether were free of this problem, processed better and gave improved physical properties. Thiokol B and Thiokol D were respectively the tetrasulfide and disulfide elastomers derived from bis-2-chloroethyl ether. These resulted from a study of the effect of polymer structure on polymer odor and properties that indicated a reduction in odor when the polysulfide units were separated by an increasing number of atoms. However, the process for making these polymers gave a high byproduct yield of the six atom heterocycle, thioxane, which has a pungent odor and no economic value. Five and six membered monosulfide rings are formed readily with the corresponding 1, 4- and 1, 5-dichloro aliphatic compounds.
Viscous and Elastic Behavior Attributed to Polymer Entanglements
Authors: Porter Roger S. , MacKnight William J. , Johnson Julian F. 
Published: February 2011

Abstract
Polymer chains are separated and behave as individual hydrodynamic units in sufficiently dilute solutions. A minimum polymer molecular weight, dependent on concentration, is necessary to produce the characteristic rheological effects generally attributed to entanglements. The minimum polymer molecular weights and concentrations for which entanglement effects are observed are called the characteristic entanglement compositions. Undiluted polymers exhibit such effects only above some minimum molecular weight. The common observation of entanglement effects indicates that they are not due solely to chemical or structural inhomogeneities. Polymer composition, e.g., polarity and perhaps tacticity, can lead, however, to changes in frequency and strength of entanglements. Entanglements appear to govern many important polymer characteristics, thus providing a strong motivation for their study. Characteristic chain spacings between entanglements have been reported from various viscoelastic experiments, low shear viscometry, nonNewtonian flow, and from relaxation times measured by nuclear magnetic resonance. The different techniques generally give concordant values, although with a wide variation in precision. For a few polymers, e.g., polydimethylsiloxane, the characteristic entanglement spacing has been calculated by each of the four techniques. For others, e.g., polyisobutylene and polystyrene, entanglement spacings have been reported by all except NMR. Entanglement effects have been treated theoretically by analogy with theories of rubber elasticity. Other theories have been developed based on breakage and reformation of entanglements and on polymer chain slippage. Certain of these theories have been shown to have the same formalism and yield similar conclusions. In general, the entanglement hypothesis provides a consistent interpretation for a variety of rheological data on concentrated systems of amorphous polymers, this despite the fact that an entanglement has not as yet been directly “seen”. A discussion of entanglements and the first method of calculating entanglement spacings was given by Mark and Tobolsky. A review in the field of polymer viscosities for concentrated systems has been recently prepared. Experimental details and theoretical derivations are given in texts. The notations used are defined in the Appendix.
Determination of Copolymer Molecular Weight
Authors: Rempp Paul , Benoit Henri 
Published: February 2011

Abstract
From this brief review it appears that determinations of molecular weight averages, of molecular weight distributions, and of compositional inhomogeneity of binary copolymers, require care in the choice of techniques and methods. Some of the most commonly used techniques for molecular weight determinations on homopolymers of various kinds are inadequate for the same determinations on copolymers. Others are more sensitive to fluctuations in composition than in molecular weights. Osmotic methods are the only one which are really insensitive to inhomogeneity, and which yield molecular weights. Ultracentrifugation in a density gradient yields precise information only on fluctuations in composition. Viscosity determinations require calibration, but even so, they may lead to erroneous values of the molecular weight in the case of copolymers. GPC is less sensitive to compositional heterogeneity, but cannot be applied for nonlinear copolymers. Finally, light scattering is a very powerful tool for studies on copolymers, since it leads to molecular weight averages and its helps characterize polydispersity and fluctuations in composition.
Application of High Resolution Nuclear Magnetic Resonance Spectroscopy to Elastomers in Solution
Authors: Chen Hung Yu 
Published: February 2011

Abstract
Use of high resolution nuclear magnetic resonance for polymer studies started late in 1950. The pioneer article of Bovey, Tiers, and Filipovich called attention to the potential of high resolution NMR for studies of polymer chain configurations. Since then, extensive use has been reported of high resolution NMR for various problems involving polymer structures. This review was originally intended to cover only studies dealing with rubber or elastomers. As the work proceeded, it became more obvious that the division of elastomers and non-elastomers appeared invisible so far as polymers in solution are concerned. Thus, it seems more appropriate to treat the subject in terms of polymers in general rather than limiting it only to elastomers. The review includes four main parts: namely, tacticity of polymer chain, orientation variation, or head-to-head or head-to-tail type variation of polymer chain, chain sequence distributions, and analytical measurements of structure and ratio of monomer units in polymer chains. This division is merely for convenience of discussion, but because of interrelationships existing in actual polymer systems, this partitioning will frequently appear not to be so precise. Excellent review articles on the subject appeared previously elsewhere; general articles are also available. Main object of this review is to furnish an up-to-date broad view of usefulness of high resolution NMR in polymer research. A more qualitative description, rather than a rigorous quantitative treatment is given each subject. Those who wish to pursue the subject in more detail should consult original articles. Extensive reviews on application of wideline NMR to polymer studies, which is not included in this review, are also available. Application of the recently developed spin-echo NMR technique to polymer solutions is not included.
Stress Strain Isotherms for Poly-(Dimethylsiloxane) Networks
Authors: Mark J. E. , Flory P. J. 
Published: February 2011

Abstract
Stress strain isotherms are presented for poly (dimethylsiloxane) networks of different degrees of crosslinking, swollen to various extents by a diluent. Results are interpreted in terms of the equation f*v21/3V/(α−α−2)=2C1+2C2α−1, where ƒ* is the tension per unit initial area (unswollen) exhibited by a network when swollen to a polymer volume fraction v2 and elongated to the relative length α, 2C1 is a parameter of the network structure established by the molecular theory of rubber elasticity, and 2C2 is an additional parameter found to give a better representation of experimental data. Values of C2 obtained for networks are found to decrease as the degree of crosslinking is decreased, and the degree of swelling is increased.
Dynamic Properties of Pbna-Natural Rubber Vulcanizates
Authors: Payne A. R. 
Published: February 2011

Abstract
Some crystalline organic compounds containing a β-naphthyl group stiffen rubbers considerably. This paper discusses the dynamic behavior of these systems when subjected to oscillatory strain of increasing amplitude. Modulus strain amplitude plots similar to that in carbon black-natural rubber systems are obtained. The implication of these results to reinforcement theory is discussed.
Investigation of Carbon Chains in Rubber Vulcanizates by Means of Dynamic Electrical Conductivity
Authors: Voet Andries , Cook F. Russell 
Published: February 2011

Abstract
Previously obtained dynamic shear modulus data over a wide amplitude range of rubber vulcanizates loaded with carbon blacks of widely varying structure as well as graphitized black were augmented with dynamic conductivity data at 30° C and at 100° C. Results confirm the existence of reversible transient and irreversible persistent carbon structures, the former being nearly completely destroyed at moderate shear amplitudes (50% strain), but effectively restored at lower amplitudes in a dynamic equilibrium between chain destruction and reformation. Higher structure blacks are characterized by a higher rate of chain rebuilding than lower structure blacks and by marked persistent chain alignment at higher amplitudes. Conductivity as a function of strain and time shows carbon chain behavior during stressing. The rates of destruction and rebuilding of the transient chains and the exact point at which the transient structure effects balance the chain alignment effects on conductivity have been established. The unusual behavior of vulcanizates loaded with graphitized black is explained.
Lower Critical Solution Temperatures of Polybutadiene Solutions
Authors: Vanzo Ed 
Published: February 2011

Abstract
The lower critical solution temperature (LCST) is observed in polymer solvent systems as a rather high temperature above which the solution separates into two phases. This is a relatively recently discovered phenomenon, since it normally occurs above the boiling point of the solvent. Freeman and Rowlinson were apparently the first to report a LCST for hydrocarbon polymers in hydrocarbon solvents.
Role of Silicas and Silicates in Rubber Adhesion
Authors: Creasey J. R. , Russell D. B. , Wagner M. P. 
Published: February 2011

Abstract
The addition of resoreinol plus hexamethylenetetramine and/or hydrated silicas to rubber compounds can result in increased adhesion to textiles, wire, and other rubber compounds. Silica prevents loss of adhesion on aging or at elevated temperatures. The increase in adhesion is due, depending on the system, to improved wetting and hydrogen-bonding between the rubber compound and the substrate to which it adheres.
Fundamental Theory of Polymer Processing
Authors: Torner R. V. , Godkova L. S. 
Published: February 2011

Abstract
The theory of polymer processing is essentially a part of solid state mechanics. It basically consists of the theoretical and experimental investigation of motion and different physical-chemical processes in deformable viscoelastic systems. With this approach we could regard the great variety of known processing methods as a complex of separate problems the solution of each of which could be regarded as a particular example of the integration of a closed system of differential equations of motion under suitably specified initial and boundary conditions. This approach would enable us to examine in theoretical terms, and from a quite general viewpoint, the wide variety of phenomena which occur in processing machines including phase changes and chemical reactions.
Application of Differential Thermal Analysis and Thermogravimetric Analysis to Elastomer Systems
Authors: Maurer J. J. 
Published: February 2011

Abstract
Judging by the increasing number of articles appearing in the literature, it appears safe to say that Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA) are gaining acceptance and finding ever increasing use in the field of chemistry. The fact that this acceptance and increased interest is comparatively recent is really quite remarkable when one considers the comparative ease with which the techniques can be performed, and the many areas of applicability for them. This recent interest in two old techniques is probably related to two facts. First, the need for time-consuming construction of elaborate, precise equipment apparently previously presented too great an obstacle to all except the serious student or practitioner. Therefore, it was not possible for most workers to use routinely, or to investigate the utility of these thermal methods. This problem has been solved by the development and commercial availability of reliable, high-sensitivity equipment. Second, the polymer chemist has discovered the utility of these techniques and is beginning to exploit them. Because of the great size and scope of the field of polymer chemistry, this area may soon become the largest contributor to the thermal analysis literature. As one reviews the available literature on the application of DTA and TGA to polymers it becomes apparent that most of the articles, including reviews, are concerned with plastics—and that investigations of elastomers are actually few in number and relatively recent. One possible reason for this is that many of the plastics applications for DTA are concerned with the measurement of various aspects of crystallinity in polymers of high degree of crystallinity, especially polyolefins.
Radioisotope Methods of Analysis and Characterization of Elastomers
Authors: Campbell D. R. , Warner W. C. 
Published: February 2011

Abstract
Radioactivity applied to rubber technology encompasses such diverse areas as the effect of radiation on elastomers, use of strong gamma and beta sources for process control, and isotope methods to measure tire tread wear. These applications of radioisotopes have received considerable attention in recent years and the principles and techniques have been discussed extensively in both reviews and original papers. Significant contributions, however, have also been made in advancing elastomer technology through analytical use of radioisotopes of carbon, hydrogen, sulfur, and other beta-emitters, as well as by special radioisotope techniques. This survey discusses recent advances achieved with beta-emitters in vulcanization, diffusion, dispersion, adsorption, coagulation, and determination of functional groups in polymers. In addition, the value of activation analysis and other radioisotope investigative methods for characterization of elastomers is shown.
Course of the Terpolymerization of Ethylene, Proylene, and Dicyclopentadiene. I. Single Initial Addition of Dicyclopentadiene
Authors: Cunningham Robert E. 
Published: February 2011

Abstract
Detailed studies were made of the course of the terpolymerization of ethylene, propylene, and dicyclopentadiene to form unsaturated elastomers. All the dicyclopentadiene was added at the start of a polymerization, but the monoolefins were added continuously throughout the run. Under these conditions, unsaturation of the initial polymer is fairly high but decreases steadily as the reaction progresses. From analyses of the initial samples from each run, the catalyst of VCl4 (with A12Et3Cl3 cocatalyst), with heptane as the polymerization solvent, was most efficient for introducing unsaturation into terpolymer. This system also produces gel in the terpolymer in the latter stages of reaction, however. Catalysts of VCl4, VOCl2, or V(C5H7O2)3, with Al2Et3Cl3 cocatalyst, in benzene solvent gave terpolymers of quite similar unsaturations. With all systems, terpolymer yield increases very rapidly in the first few minutes of reaction, then very slowly for the remainder of the 30-min reaction time, reflecting the rapid loss of activity of the vanadium catalysts. Molecular weight growth of the terpolymer prepared in heptane was extremely rapid, reaching a high value in a few minutes. When prepared in benzene, the terpolymers showed a steady increase in molecular weight throughout the reaction but reached only a moderate final value (as expressed by inherent viscosity).
Configuration of Isoprene Structure in Butyl Rubber by Time-Averaging High Resolution Nuclear Magnetic Resonance
Authors: Chen Hung Yu , Field J. E. 
Published: February 2011

Abstract
In making butyl rubber, a small amount of isoprene is usually copolymerized with the isobutylene to facilitate vulcanization. The isoprene component thus incorporated in the butyl rubber can be present in three possible configurations, i.e., 1,4-, 1,2-, and 3,4-. The question concerning which of these configurations was the prevalent one in butyl rubber was investigated by Rehner in 1944. His chemical method was based on the fact that only butyl rubber with isoprene units in 1,2- or/and 3,4-configurations would yield formaldehyde and formic acid on ozonization. Since these compounds were not detected in this reaction product, he concluded, indirectly, that the isoprene segment in the butyl rubber was essentially in the 1,4-configuration. In this communication, we would like to report that, by means of a time-averaging high resolution nuclear magnetic resonance method, we are able to observe the absorption peak due to the 1,4-isoprene unit in a typical commercial grade butyl rubber. Since the IR has failed to detect such low concentrations of isoprene in the butyl rubber, the present NMR result seems to be the only direct observation of this structural component. We would also like to point out that such measurements may be useful in determining quantitatively the isoprene unit in butyl rubber as well as other polymers with minor constituents such as the third monomer unit in ethylene propylene terpolymer.