bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glass fibers in industrial applications
Authors: Marzocchi A. , Rooney M. J. 
Published: June 2010

AbstractIn the past thirty years, glass fibers have progressed from the realm of decorative curiosities to a basic commercial product with many decorative and industrial applications. Their thermal endurance, dimensional stability, resistance to environmental effects, high strength, and low cost have resulted in a variety of uses such as reinforced plastics, high temperature filter media, thermal insulation, distillation media, paper reinforcement, etc. Recent developments in fiber surface treatments, glass composition, fiber diameters, and product forms have contributed greatly to an ever‐increasing pace of new product developments. This paper will consider the properties of some of our newer glasses, fiber sizes, and chemical treatments. Physical properties and application of the concepts involved in glass and organic fiber combinations will be discussed, as will the recent work which has led to the use of glass fibers in rubber reinforcements, the first application of glass fibers to a dynamic use.
Optical diffraction techniques for interpreting X‐ray diffraction photographs of fiber structures
Authors: Taylor C. A. 
Published: June 2010

AbstractThe classical interpretation of x‐ray diffraction patterns of single crystals is through Bragg's law and it leads to the notion that each “reflection” is a separate entity in a list of data. The adoption of the optical diffraction, or transform, approach leads to a much more physical view of the diffraction process in which the pattern is assessed as a whole. Studies of the Fraunhofer diffraction pattern in visible light of masks representing the unit crystal cell provide a means of testing the validity of trial structures. The particular value of this approach in fiber studies is that masks can be made to represent extremely complicated atomic arrangements and their patterns can be observed instantaneously. The key problem, is, of course, the preparation of the masks. The most versatile procedure would be to build a semi‐automated machine controlled by punched tape prepared on a computer. Design studies are in progress. Several interim methods, including photographic etching, are in use at the moment and various aspects of the interpretation of fiber photographs will be illustrated with diffraction patterns prepared from masks made in this way. Interpreting fiber photographs from the standpoint of their diffraction aspects rather than from a structural model may provide valuable complementary evidence to that produced in the more conventional way.
Application of histochemical techniques in electron microscopy as applied to high polymers
Authors: Kassenbeck P. 
Published: June 2010

AbstractStaining reactions are necessary to reveal the fine structure of fibrous polymers in electron microscopical investigations. Reactions of heavy metal salts with organic compounds yield different results depending on pretreatment of the fibers, the nature of the heavy metal employed, and the conditions of treatment. In the case of keratin fibers, the structure as revealed by the electron microscope depends mainly on the conditions of treatment. For example, wool, after carboxymethylation, shows a complete reversion in contrast compared with untreated material. It is thus possible to reveal the sulfur‐rich fraction of keratin with a staining reactive which normally reveals the low‐sulfur fraction. The quantitative analysis is, in both cases, in good agreement with the electron‐microscopical results. Further examples of staining reactions are discussed, especially the reactions of keratin and cellulose fibers with silver salts.
Fiber length changes and their relation to fiber structure
Authors: Bosley D. E. 
Published: June 2010

AbstractDeformation processes in polymers are reviewed within the framework of rubber elasticity theory. The effect of hindered rotation on imposed and spontaneous length changes of polymeric fibers is discussed, leading to a new definition of crystallinity as a localized region of hindered rotation. This concept, together with a fringed‐micelle model, is used to relate length changes to molecular fine structure of polymers. The details of this model are described and compared with lamellar and paracrystalline models.
Gel permeation chromatography. II. Molecular size separability and the determination of polymer polydispersity
Authors: Osterhoudt H. W. , Ray L. N. 
Published: June 2010

AbstractAn equation describing the relationship between the GPC determined breadth of the molecular weight distribution, (σn/Mn)G, the true breadth of the distribution, σn/Mn, zone spreading or tailing ΔVe, and the separability employed, K(M), has been derived:magnified image.Here K(M) is the absolute value of the derivative dVe/dM, in which Ve is elution volume and M is molecular weight. The validity of this equation was established through GPC fractionations of blends of narrow molecular weight distribution polystyrenes. Application of the equation to experimental data shows that ΔVe increases with increasing M. The equation indicates that GPC molecular weight data are less in error with polymers of broader molecular weight distributions and with larger values of K(M). The importance of the experimental variable K(M) is that it defines the degree of fractionation, higher values of K(M) denoting more complete fractionation.
A method of solving Tung's axial‐diffusion equation for gel permeation chromatography
Authors: Pierce P. E. , Armonas J. E. 
Published: June 2010

AbstractA new method of solving Tung's diffusion equation for gel permeation chromatography is presented. The method is based on the Fourier transform method for solving integral equations. Three examples (narrow, bimodal, and broad distributions) are used for illustrating the method of solution. A simple means of estimating the resolution factor h for a multicolumn system, based on a knowledge of the resolution factors h, for the individual columns and the gel permeation chromatograph piping system, is described and tested.
Polymer reactors and molecular weight distribution. Part III. Gel permeation chromatography, methods of correcting for imperfect resolution
Authors: Duerksen J. H. , Hamielec A. E. 
Published: June 2010

AbstractThis paper reports a preliminary evaluation of four methods of correcting for imperfect resolution in gel permeation chromatography. These are methods of Tung, Smith, Hess and Kratz, and Pickett. To evaluate the methods over a range of resolutions, many broad‐ and narrow‐distribution polystyrene samples covering the molecular weight range 1000–500,000 were analyzed with three different column combinations having residence times from 20 to 150 min. The results show the increasing importance of the resolution correction with increasing molecular weight and decreasing residence times. For Tung's method the correction to molecular weight averages ranged from about 4% for 150 min. of residence time to about 12% for 20 min. Residence times as short as 10 or 15 min. should be possible without serious loss of accuracy. Inconsistencies in the high molecular weight results for the methods of Tung and Smith indicate inadequacies in the assumed chromatogram shapes for single molecular species, due to effects of column overloading and species interaction. These effects can be reduced by decreasing the sample concentration. When these effects are not prominent, the methods of Tung and Smith appear to be adequate. Smith's modified method permits the use of various chromatogram shapes for single species to account for overloading and interaction. Computational difficulties at present limit the use of the method of Hess and Kratz. Pickett's method looks promising, especially if concentration dependence can be included in the chromatograms representing the single species. Further evaluation needs to be done to determine which method best handles the region where overloading and species interaction occur.
The molecular weight distribution of polypropylene
Authors: Ouano Augustus C. , Mercier Philip L. 
Published: June 2010

AbstractThe Gel Permeation Chromatograph has been used for obtaining values of weight‐average and number‐average molecular sizes Aw and An and the heterogeneity indices Aw/An for a series of polypropylenes. Absolute values of Mw and Mn, the weight‐average and number‐average molecular weights, have also been obtained from the same samples with light‐scattering and osmotic pressure methods. Comparisons of the data from the gel permeation chromatograph with the data from the absolute measurements have been used for calculating Q, the constant used for converting Aw and An to the corresponding Mw and Mn values. Other correlations of interest, such as intrinsic viscosity versus weight‐average molecular weight and melt flow, and Newtonian viscosity versus weight‐average molecular weight, are also given.
The electrochemical polymerization of 4‐vinylpyridine in liquid ammonia
Authors: Laurin D. , Parravano G. 
Published: June 2010

AbstractThe polymerization of 4‐vinylpyridine (4VP) in an electrochemical cell in liquid NH3 solutions was studied. With monomer concentrations of 5 to 25 vol.‐% in the temperature range −33 to −78°C. rapid polymerization takes place when current is passed through the cell. Polymer yields of 80 to 90% are easily obtained in a few hours with NaN3 or NaCl as electrolyte and smooth Pt electrodes in a stirred three‐compartment cell. Current densities of 1 × 10−2 to 10 ma./cm.2 and applied voltages of 2.5 to 50 v. were employed. Different anodic materials were used, including Pt and pyrolitic graphite. The electrochemical yield is about 1 mole of polymer per faraday for current densities of ⩽ 1 × 10−2 ma./cm.2, and it becomes 0.5 and lower at higher current densities. The rate of polymerization was found to increase, and the molecular weight of the polymer to decrease, with increasing current density. It is concluded that the initiation step consists of electron transfer between the cathode and the monomer. Depending on the amount of polymer deposited on the cathode and on the current density, initiation may occur on the cathode surface or within the polymer deposit on the cathode or in the free liquid solvent. The consequence of the electron transfer to monomer is the formation of radical anions. Electrochemical yields of about 1.0 mole of polymer per faraday suggest that radical anion dimerization does not take place extensively, while dimerization may predominate when electrochemical yields are about 0.5. Subsequent chain growth occurs through an anionic mechanism, as evidenced by the nonterminating nature of the polymerization, the presistent red color of the polymer formed, and the sensitivity of the polymerization to the addition of protic substances. Polymer molecular weights were in the range of 10,000 to 360,000. Molecular weight distributions with Mw/Mn ratios of 1.21 or larger were found. Softening points, solubility characteristics, and infrared spectra of the electrochemical polymer are presented and discussed in comparison with those of poly(4‐vinylpyridine) prepared with chemical initiators.
Polymerization of isobutylene catalyzed by the Binary system TiCl4‐AlBr3
Authors: Chmelir̃ M. , Marek M. 
Published: June 2010

AbstractIn the course of a study of the influence of some Friedel‐Crafts halides on isobutylene polymerization catalyzed by aluminum bromide it was found that the most active catalytic complex is formed in the reaction of titanium chloride with aluminum bromide. The conversion and the molecular weight of the polymer depend on the aluminum bromide concentration but are practically independent of the TiCl4 concentration. The polymerization mechanism has been solved by means of the nonstationary‐state theory, by means of which values have been obtained for the rate constants of the individual partial elementary reactions (growth, monomer transfer, spontaneous transfer, and termination).
Correlations between the structure of some soluble catalytic complexes and their activity in the polymerization of acetylene. III
Authors: Angelescu Emilian , Nicolescu I. V. 
Published: June 2010

AbstractIn this work are described studies of the correlations between the catalytic activities and some physical‐structural properties of soluble complex catalysts of the type Al(C2H5)3‐Me(C5H7O2)n, where Me is V, Cr, or Co. These catalysts were used as active phases in the process of stereoregular polymerization of the acetylene. It was established that the catalytic activity varies as a function of the molar ratio of Al(C2H5)3 to Me(C5H7O2)n. On the basis of EPR determinations of the values of the electrical conductivity of the catalyst solutions and of the gas‐volumetric data there were established correlations between the optimal catalytic activity and the physical‐structural characteristics of the catalysts. These correlations throw light on the chemical nature of the catalytic complexes and on the interaction between catalyst and solvent.
Specific preparation of diolefin homopolymers with equimolecular binary microstructures
Authors: Teyssie Ph. , Dawans F. , Durand J. P. 
Published: June 2010

AbstractDuring an investigation of some structural features in the stereospecific polymerization of conjugated diolefins evidence was obtained that some catalytic species are able to yield high molecular weight polymers containing selectively two of the several possible geometric isomers; moreover, the two isomers involved are present in equimolecular amounts, in a nonsequential arrangement. Up to now equimolecular (cis‐1,4‐3,4)‐polyisoprene, (1,2‐3,4)‐polyisoprene, and (cis‐1,4‐trans‐1,4)‐polybutadiene were obtained with different catalytic systems (among which, monometallic complexes). The preliminary results suggest an alternating propagation mechanism, similar to the one already proposed by several authors for Ziegler‐type catalysts. Further work is in progress to prepare new binary polymers of this type, with different microstructures.
Effet de la Tacticité de l'Acide Polyméthacrylique sur la Vitesse de Formation de Chelates avec les Ions Cu2+
Authors: David C. , De Pauw A. , Geuskens G. 
Published: June 2010

AbstractA kinetic study of chelate formation between polymethacrylic acid (PMA) and Cu2+ ions has been done to determine the influence of tacticity on reactivity. The metallic‐ion concentration was kept very low and constant during the reaction by means of an ion‐exchange resin. The experimental results show that isotactic PMA is about 1.5 times more reactive than syndiotactic PMA. The activation energies are respectively 6 ± 1 and 7 ± 1 kcal./mole.
Préparation et Caractérisation d'Hétéropolymères Greffés
Authors: Gallot Yves , Grubisic Zlatka , Rempp Paul , Benoit Henri 
Published: June 2010

AbstractAn anionic grafting process that operates by means of a reaction between a carbanionic endgroup of a living polymer and an electrophilic grouping located on another polymer chain has been applied to the synthesis of graft copolymers of extremely high molecular weights. The polymers obtained have been characterized and fractionated. Their radii of gyration are small compared with those of linear macromolecules of the same molecular weight but higher than those of the backbone chain from which they derive. The same method has been applied to the synthesis of heterograft polymers; in that case a three‐block copolymer is chosen as backbone, the two outer blocks bearing electrophilic groupings. The grafting degrees which were reached here are higher than those obtained in the case of homopolymeric backbones. Nevertheless, fluctuations in composition and polydispersities remain of the same order of magnitude. The highly branched structure of the macromolecules obtained is shown by viscosimetric measurements and by the retention times of gel permeation chromatography. The “viscosimetric volumes” of the solvated particles are correctly located on the GPC calibration curve.
Polymerization by Visible Light
Authors: Bleha M. , Lím D. 
Published: June 2010

AbstractPhotopolymerization of methyl methacrylate initiated by labile azo compounds absorbing in the range of visible light was studied. The activation energy of the decomposition of the initiators used is much lower than the energy corresponding to the light absorbed. The results were compared with diacetyl‐initiated polymerization and made possible the conclusion concerning the relation between the structure and the initiation capability.
Molecular changes in the high‐temperature degradation of gelatin
Authors: Donnelly T. H. , Kauffman F. L. , Arendovich P. 
Published: June 2010

AbstractIn a search for a correlation of commercial gelatin test results (Bloom jelly strength and viscosity) with molecular properties, molecular weight distributions were estimated and related to intrinsic viscosities on separate gelatin solutions heated at 95°C. and pH 3.9 for graded periods of up to 48 hr. Number‐average molecular weights based on the estimated distributions were used for estimating the number of groups available for formol titration as a check on the procedure, while solution viscosities were compared with those calculated from the distributions. The need for further work and also the necessity of recognizing the essential polyelectrolyte character of much commercially tested gelatin is apparent.
Thermal degradation of poly(α‐methyl styrene) in a closed system
Authors: Jellinek H. H. G. , Kachi H. 
Published: June 2010

AbstractPoly(α‐methyl styrene), produced in various ways, was degraded in a closed system over a range of temperatures from 260 to 320°C. in the absence of air. Except for the initial parts of the degradation reaction (up to about 20% conversion to monomer), all samples had a random initiation reaction, followed by a depropagation step with a number‐average kinetic chain length larger than the number‐average polymer chain length. The energies of activation, after the initial part of the degradation, were all of similar magnitude (ca. 63 kcal./mole) and agreed with values found by previous workers. A few samples showed distinct maxima during the first 20% conversion in their curves of rate of monomer versus conversion, whereas others showed only constant rates or slowly decreasing rates during the initial periods of the reaction. The latter rates can be accounted for by chain‐end initiation (kinetic chain length ≫ polymer chains) or by a random initiation process followed by depropagation and disproportionation as termination reaction. The initial maxima found in some samples could be accounted for by a theory of random initiation in conjunction with a number‐average kinetic chain length larger than the polymer chains, which is inhibited by a reaction of polymer radicals with catalyst fragments. The inhibitor is consumed during the reaction.
The role of anomalous addition reactions in copolymerization processes
Authors: Lyubetzky S. , Goldenberg A. , Duntoff F. , Erussalimsky B. 
Published: June 2010

AbstractThe presence of anomalous sequences of the type CH2CHXCH2CH2CHXCH2 in copolymers of ethylene with vinyl chloride, vinyl acetate, and trifluoropropylene is established. A kinetic scheme is proposed, which takes into account the propagation reactions of anomalous growing chains. With the use of this scheme an equation for the copolymer composition is obtained and compared with the Mayo equation. The concentrations of single CH2 groups and of the sequences (CH2)2 and (CH2)3, found by infrared spectra, are used for calculating the constants of the above‐mentioned equation. The calculated values are in satisfactory agreement with the experimental ones.
Copolymerization of ε‐caprolactam with C‐methylcaprolactams
Authors: Čefelín P. , Schmidt P. , Šebenda J. 
Published: June 2010

AbstractIn polymerizations ε‐caprolactam and C‐methylcaprolactams differ by their equilibrium parameters. In the copolymerization of caprolactam with α‐methylcaprolactam in the amorphous phase the equilibrium concentrations of monomers do not change proportionally to the composition of the initial mixture and show a wide minimum. If in copolymerization the respective monomer were in equilibrium with the corresponding structural unit, this finding could be explained by a change of the number of structural units forming the average unit of the macro‐Brownian motion (segment). In the composition range where block grouping of the same structural units does not occur in random copolymer, the segment concentration acquires a characteristic constant value.
Polymerization of p‐methacrylyloxybenzoic acid in mesomorphic and in liquid states
Authors: Amerik Yu. B. , Konstantinov I. I. , Krentsel B. A. 
Published: June 2010

AbstractThe polymerization of p‐methacrylyloxybenzoic acid in the liquid crystalline state (dissolved in p‐cetyloxybenzoic acid) and in the liquid state (solution in dimethylformamide) was studied. The polymerization of p‐methacrylyloxybenzoic acid in the liquid phase is characterized by regularities usual in the radical homogeneous polymerization of vinyl monomers in isotropic mediums. At temperatures above 100°C. incomplete conversion is observed, which is explained by polymerization–depolymerization equilibrium. The polymerization of p‐methacrylyloxybenzoic acid in the liquid crystalline phase is characterized by a considerable increase in polymerization rate and polymer molecular weight (Mw = 6 × 105) over the liquid‐phase polymerization in DMFA (Mw = 5 × 104). The polymerization rate in liquid crystalline state does not depend on conversion degree and remains constant up to 70–75% conversion. The rate of polymer formation depends only slightly on the initial monomer concentration at the change of [M0] from 1.3 to 3 moles/l. The molecular structure of the mesomorphic phase also creates favorable thermodynamic conditions for the formation of macromolecules. At all T < Tceiling practically complete conversion of monomer into polymer is observed, which is impossible with homogeneous polymerization in solution.
Photochemical synthesis of block copolymers
Authors: Dhanraj J. , Guillet J. E. 
Published: June 2010

AbstractA new photochemical synthesis of block copolymers is described. Polyesters are prepared containing γ‐keto pimelic acid. This provides ketone carbonyl functions along the backbone of the polymer chain. When irradiated with ultraviolet light in the presence of a vinyl monomer such as methyl methacrylate, free radicals are formed by the scission of the main chain of the polyester at the ketone groups. These radicals initiate the polymerization of the vinyl monomer to form a block copolymer. If light is used which is absorbed by the ketone group but not the vinyl monomer, and no transfer occurs, only block polymer is formed. The quantum efficiency for initiation (2.4 × 10−4) is low compared with that for chain breaking (4.0 × 10−3) indicating the possibility that the addition of polymer radicals to the vinyl monomers may be a relatively inefficient process. The activation energy for the block copolymerization of methyl methacrylate is 3.7 kcal./mole which is very similar to that observed in the photopolymerization of this monomer with conventional sensitizers.