bluuebunny/crossref_metadata_2025_split huggingface dataset:
Etude des proprietes du polystyrene en solution en fonction des conditions de polymerisation
Authors: Ahad Elie , Sicotte Yvon 
Published: June 2010

AbstractEn caractérisant, par diffusion de la lumière en solvant thèta, des fractions fines de polystyrène provenant d'échantillons obtenus sous différentes conditions de polymérisation, radicalaire et anionique, on a mis en évidence que le rapport du carré moyen du rayon de giration sur la masse moléculaire varie avec les conditions de polymérisation. Il s'agit vraisemblablement d'une variation de tacticité en fonction des conditions de polymérisation. Cette variation de tacticité se reflète également dans la loi de viscosité en solution qui varie d'un échantillon à l'autre. Ces effets expliquent, en partie du moins, la dispersion très grande des paramètres structuraux rapportés pour le polystyrène atactique. Ce travail a permis par ailleurs de vérifier que la polydispersiteé des échantillons de polystyrène obtenus par polymérisation radicalaire ne montre pas de variations significatives entre 0°C et 60°C comme température de polymérisation.
Induced changes in the molecular weight of polybutadiene using alkyllithium‐alkyl halide complexes
Authors: Halasa A. F. , Adams H. E. 
Published: June 2010

AbstractIt has been demonstrated that gel permeation chromatography is useful in studying the reaction of aliphatic chloride, such as CCl4 and secondary‐butyl chloride, with polybutadiene. These materials produce an increase in average molecular weight of the polymer and the concomitant change in distribution assists in verification of the proposed mechanism of reaction. Reaction is assumed to proceed through intermediate formation of radicals. If live polymer is used, both allyl and alkyl radicals are produced. Allyl radicals readily dimerize while alkyl radicals attack double bonds in the backbone of the chain to produce crosslinking. Quite different distributions result from these two reactions. Molecular weight distributions of polymers produced by reacting either CCl4 or secondary‐butyl chloride with live polymer indicate the predominant reaction to be dimerization of allyl radicals. On the other hand, the crosslinking reaction occurs exclusively if dead polymer is reacted with secondary butyl chloride. In this case, it is necessary to add a strong base, such as n‐butyllithium, to obtain the molecular weight increase.
Conductivite des polymers: Influence de l'etat hygrometrique et de l'etat acide‐base sur la conductivite de l'ovalbumine et de la polyvinyl 4 pyridine
Authors: Petit Michel , Haas Hubert , Debionne Jean Louis , Jozefowicz Mircel 
Published: June 2010

AbstractEn vue de généraliser les résultats obtenus lors des études de la conductivité des polyamides et des polyanilines, l'étude des propriétés de conductivité de l'ovalbumine, de la polyvinyl 4 pyridine et des perchlorates de polyvinyl 4 pyridinium a été effectueé, ces matériaux étant choisis comme substances modèles. Ces études ont été effectuées sur les Polymères pulvérulents pastillés par compression. Les déterminations de la conductivité ont été faites en utilisant des électrodes de mercure, selon une méthode décrite antérieurement. L'influence de l'état hygrométrique, de l'état acide‐base et de la température sur la conductivité de ces polymères a donné lieu à un examen approfondi. Les résultats obtenus montrent que, en fonction de ces paramètres, les échantillons prèsentent trois régimes de conductivité:
— un régime transitoire de basses températures.
— un régime transitoire de hautes températures qui semble ětre ionique.
— un régime permanent de conductivite. Dans le domaine de températures étudié, et quel que soit l'état acide‐base ou le degré hygrométrique, la variation de la conductivité en fonction de la température obéit à une loi d'Arrhénius. Les lois de variation de la conductivité en fonction de la teneur en eau pour ce qui concerne l'ovalbumine, la polyvinyl 4 pyridine et les différents perchlorates de polyvinyl 4 pyridinium étudiés présentent une grande analogie avec celles qui ont été déterminées dans le cas des polyanilines et des polyamides. L'étude de la variation de la conductivité avec l'état acide‐base a permis d'établir dans le cas de la polyvinyl 4 pyridine, une corrélation entre celle‐ci et la variation du potentiel chimique ou électrochimique des ions H+ dans le polymère. Dans tous ces cas, il a été possible de montrer que les températures critiques de transition entre les différents régimes de conductivité varient de manière simple en fonction des paramètres qui définissent l'état physicochimique des échantillons étudiés.
Morphology and kinetics studies of spherulitization of polyethylene terephthalate
Authors: Baranov V. G. , Kenarov A. V. , Volkov T. I. 
Published: June 2010

AbstractA modified method of registration of small‐angle scattering of polarized light using the principles of the Fraunhofer diffraction permits the study of fast processes of spherulitization with averaging from a large amount of the scattering elements (several million). With the aid of this method the dependencies on temperature of the growth rate of the spherulites and the lag time have been studied for isothermal crystallization from the melt and from the glassy state. It has been shown that the maximum growth rate of spherulites in the course of the crystallization from the melt is observed at 155°C, and that from the glassy state is observed at 190°C. The thermodynamic parameters of the secondary nucleation determining the spherulite growth have been established. The energies of the formation of the lateral surfaces of cylindrical nucleus in the crystallization from the glassy state, and from the melt were found, to be equal, (σu = 5.75 erg/cm2) and those for the end ones were different (in the first case σe is 5.5 erg/c2 and in the second one σe is 14 erg/cm2). The morphology of spherulites depends strongly on the initial state of the system and the crystallization temperature. Spherulites are observed to have polarizability ellipsoids oriented along the radius and at an angle of 45° to it; in the course of the growth of spherulites changes in ellipsoid orientation are possible.
Orientation of polymer single crystals in an electric field; a kerr effect and light‐scattering study
Authors: Picot C. , Hornick C. , Weill G. , Benoit H. 
Published: June 2010

AbstractOrientation properties of polymer single‐crystal suspensions in an electric field are studied by Kerr effect and light scattering. It is shown that all the crystals are fully oriented in direction parallel to the electric field for relatively weak field strength (400 V/cm). Kerr‐effect measurements carried out in a.c. electric field indicate the existence of an “electrical” relaxation time (10−2 – 10−3 sec) which is very different from the rotationnal relaxation time (0.1 – 0.5 sec). The orientation property of the polymer crystals is explained by the assumption of the presence of electric charges possessing a certain mobility inside the crystal. The use of Kerr effect measurements is proposed for determination of crystal concentration in suspensions of polymer single crystals.
Structure and thermal properties of crosslinked polymers containing isocyanuric rings
Authors: Alaminov H. , Proynova Z. , Michailov M. , Manjova N. 
Published: June 2010

AbstractStudies were carried out on crosslinked polymers prepared by radical polymerization of new types of oligoestermaleinates containing isocyanuric rings and allyl groups. It was found by infrared spectroscopy, that during polymerization of oligoestermaleinates a great number of the maleic groupings were isomerized to fumaric. It was also found by electronic microscopy, that cured isocyanuric oligoestermaleinates are microheterogenous and have a globular fibrillar structure. The dependence of the thermostability and other properties of the polymers on their chemical composition was studied by differential and thermogravimetric analysis. They have a better thermostability than the crosslinked polyestermaleinates, which do not contain isocyanuric rings.
Corona induced bonding of synthetic polymers to cellulose
Authors: Kim C. Y. , Suranyi G. , Goring D. A. I. 
Published: June 2010

AbstractCorona treatment improved bonding between sheets of cellulose and synthetic polymers. The bond strength increased at higher temperatures of pressing. Physical changes in the surface were detected microscopically after corona treatment in air. Sheets treated in pure nitrogen made strong bonds although the surface treated in nitrogen was indistinguishable from the untreated surface.
Method of determining the relative stability of different conformational states of biological macromolecules
Authors: Ptitsyn O. B. 
Published: June 2010

AbstractA general approach is suggested for the determination of the degree of stability of the native structure of macromolecules and the difference of free energies of different conformations of macromolecules. The idea of the approach is that in case a direct measurement of free energy of transition is impossible, use may be made of the effect of the “transforming agent” for the estimation of the difference of free energies of two conformational states evaluating the derivative from the difference of free energies by the external parameter (such as temperature, solvent constituents). This approach is illustrated by the determination of the degree of stability of the helix state of polypeptide chains in water, water‐organic mixtures and in organic solvents, as well as by the determination of the stability of DNA double helices in aqueous medium at different pH and ionic strength including physiological conditions.
Development in polymer statistics
Authors: Staverman A. J. 
Published: June 2010

AbstractA short survey is given of recent developments in polymer statistics. Through the many years since the original conception of the entropy derived from the large number of configurations of macromolecules by Mark and Guth the basic idea has never been subjected to doubt but not much progress has been made in the way of confirmation of quantitative theoretical relations.In quantitative relations quantities appear such as the effective number of chains in a network and also the energy differences between more and less elongated configurations which cannot be determined easily and have to be treated as adaptable parameters.On the other hand the theory of networks has been further developed so as to establish the exact physical meaning of the effective number of chains in a network. The theory of networks has also been extended to entanglement networks in which the entanglements have a finite life time. Based upon the Rouse‐Zimm treatment of viscoelastic dilute solutions on one hand and upon the generalized network model of Duiser and Chömff on the other hand, van Wiechen and Booy have developed a general theory of time dependent elasticity in concentrated polymer systems. This theory is briefly reviewed.
Recent developments in the statistical mechanics of polymers
Authors: Guth Eugene 
Published: June 2010

AbstractIn a previous paper I discussed the statistical mechanics of polymers, particularly the theory of rubber elasticity. The present continuation of that paper emphasizes that the resolution of the stress into internal energy and entropy contributions at constant volume may alternatively also be done at constant pressure yielding a resolution of the stress into internal energy, entropy and pressure contributions. The network theory of rubber elasticity, as developed by James and Guth starting in 1939, presents a framework comparable to the van der Waals equation for real gases and Weiss' theory of ferromagnetism and is compatible with an internal energy contribution at constant volume due to intramolecular forces and thus independent of extension. Until very recently, experimental data did not exhibit this independence. However in 1969 work in extension by Shen on natural rubber and by Price et al. on butyl rubber and polydimethyl siloxane and by Boyce and Treloar on natural rubber in torsion clearly showed this independence. I also stress that our theory does not imply a universal “front factor.” On the contrary, its value will depend, among other factors, on the degree of both segment dispersion and randomness of crosslinking. The experimental situation with regard to the “front factor” urgently needs further clarification.
Ein Graphisches Verfahren zur Ermittlung der Dehnungen bei Langzeitigen Nicht‐Isothermen Kriechversuchen
Authors: Binder K. , Tschamler H. 
Published: June 2010

AbstractResults of studies of creep in low‐pressure polyethylene carried out by two procedures, involving a precise (nonisothermal) temperature program and alternatively with outdoor exposures of up to 2 3/4 years, are reported and discussed. On the basis of the results, some generally valid characteristics of nonisothermal creep processes are demonstrated. It is shown that the elongation values equivalent to those obtained by the two nonisothermal methods may be graphically ascertained or calculated from the much more easily obtained isothermal tensile creep data. The laboratory data and the graphically determined elongation values show almost complete agreement, and the results of outdoor exposure studies and the calculated elongation values are in sufficient agreement for most practical purposes.
The role of network orientation and microstructure in fracture initiation
Authors: Kausch H. H. 
Published: June 2010

AbstractThree approaches towards a fracture theory are discussed, namely the statistical, the continuum‐mechanical, and the micro‐morphological approach. The latter recognizes that (amorphous or semicrystalline) high‐polymer solids are composed of chain molecules which show a close range order and/or a superstructure. Information from morphological and spectroscopic investigations is utilized to characterize the different elementary molecular processes (slip of chains, segment rotation, chain scission, crystal deformation) which may lead to fracture initiation, crack growth, or yielding.The statistical variability of the elementary processes and the correlation of these processes with each other determine the statistical variability of the cumulative process, e.g., time to failure or fracture strength. Thus, a relation between the results of the micro‐morphological approach and the terms of the statistical approach (underlying distribution) is obtained. A mathematical study of the effect of these processes (network degradation, stress relaxation) on the expectation values of strength or time to failure is carried out for networks of different degrees of orientation.The results obtained for one‐phase networks are applied to critically stressed regions of heterogeneous polymers (amorphous regions in oriented fibers, plastically deformed zone at tip of growing crack). Thus, a correlation between continuum‐mechanical terms (stress intensity factor, surface energy) and molecular terms (network properties, activation energies) is attempted. A failure criterion is derived.
The yield behavior of polymers
Authors: Ward I. M. 
Published: June 2010

AbstractStarting from a review of recent research on yield behavior, the author emphasizes the need to extend classical yield criteria in two ways. First, for iso‐tropic polymers, inclusion of a term allowing for the hydrostatic component of stress. Second, for oriented polymers, allowance for differences of behavior in tension and compression. The causes for these differences and progress in defining yield criteria by classical plasticity and by regarding yield behavior as an extension of nonlinear viscoelastic behavior are discussed.
Cleavage fracture of oriented poly(vinyl chloride)
Authors: Miller L. E. , Puttick K. E. , Rider J. G. 
Published: June 2010

AbstractPoly(vinyl chloride) (Cobex) sheet was oriented by hot drawing. Double cantilever beam cleavage specimens were then cut out parallel to the direction of molecular alignment. The fracture surface energy and fracture surface features were then investigated as a function of the birefringence, a measure of the degree of molecular alignment. Two different modes of crack propagation were observed. The first mode was by local plastic deformation at the crack tip coalescing voids present in the material and giving a dimpled fracture surface. This occurred up to a birefringence of 2.55 × 10−3 and was accompanied by a sharp fall in fracture surface energy with increasing birefringence. The second fracture mode was by smooth cleavage, this occurred above a birefringence of 2.13 × 10−3 and was accompanied by a slight decrease in fracture surface energy with increasing birefringence. There was a transition region at intermediate birefringence values where both modes of fracture were found.
Molecular weight distribution of poly(vinyl chloride)
Authors: Lyngaae‐Jørgensen J. 
Published: June 2010

AbstractUnder the assumption that poly (vinyl chloride) (PVC) contains a negligible amount of long branches, simple kinetic considerations lead to the result that the molecular weight distribution (MWD) function resulting from a heterogeneous polymerization will be in accordance with the functional expression for the most probable distribution (mpd). A comparison between the experimental MWD curves determined by gel permeation chromatography (GPC) and the mpd supports this hypothesis and it is shown that the form of the MWD of PVC is very close to or identical with the mpd. Furthermore, it is found that PVC samples prepared by heterogeneous polymerization in the temperature interval 25–55°C have approximately identical distributions when normalized molecular weights are used. The degree of long chain branching is estimated to be equal to or less than 2 × 10−4 long branches per repetition unit.
Particle size of poly (vinyl chloride) latices and rheology of poly (vinyl chloride) pastes
Authors: Rangnes P. , Palmgren O. 
Published: June 2010

AbstractAn anlytical centrifuge for the determination of particles in the micron and submicron range is described. The sedimentation of particles is visualized on an oscilloscope, where light‐absorption curves give an apparent size distribution. The true size distribution can be calculated from the oscilloscope curve. The centrifuge has been especially applied for analysis of PVC latex particles. Sedimentation time is about 10 min. On a later model, four samples can be compared directly on the oscilloscope. A comparison between the centrifuge and electron microscope is given.The particle size of PVC latex is strongly dependent on type and concentration of the emulsifier used. Sodium octyl sulphate gives large particles. A short description of some fundamental characteristics of PVC paste rheology is given. Viscosity curves for PVC made from mixtures of latices of four different particle sizes show that the viscosity can be altered by altering the proportions between small and large particles. Examples of high and low viscous PVC pastes are given.
Zur Radikalkinetik im Vakuumbestrahlten Polyvinylchlorid
Authors: Bartl A. 
Published: June 2010

AbstractIn the course of the formation of radicals in vacuum irradiated polyvinyl chloride, a limiting concentration occurs within the temperature range from −196°C to +20°C if a high irradiation dose is applied. The value of the limiting concentration decreases with the increasing temperature. This temperature dependence was investigated in detail by using the electron‐spin resonance method. When the formerly described results referring to the recombination of radicals within the temperature range from 40°C to 90°C are taken into consideration, the occurrence of a temperature‐dependent limiting concentration in the course of the formation of radicals can be explained satisfactorily.
Simulation of degradation processes: Influence of degradation on molecular weight distribution: First approach. I. Random crosslinking and chain scission
Authors: Maláč J. 
Published: June 2010

AbstractThe properties of polymers are changed by the influence of degradation processes. Easy to notice are changes in color caused by the formation of chemical groups absorbing the light spectrum in the visible region. The changes in color can, therefore, be determined and measured by sufficiently sensitive photometers, especially because the changes in the visible region are preceded very often by changes in the UV‐region.Mechanical properties, as well as rheological properties (and consequently the processa‐bility of polymers), depend on the relaxation spectrum which is sensitive to changes in the molecular weight distribution of the polymers.The molecular weight distribution is changed by the influence of degradation as a consequence of crosslinking, chain scission, and depolymerization.The questions concerning the influence of degradation processes on the molecular weight distribution of the polymers have hitherto been given less attention than the question regarding the color changes, although these, too, are of considerable importance.The determination of the gel content and the limit viscosity numbers which are usually employed as a measure for successive degradation processes is less suitable than the determination of the molecular weight distribution, as it gives less information especially in the initial stage of degradation and its interpretation is often difficult.The aim of this paper is to create a simple model suitable for a computer which would make possible the simulation of the influence of degradation processes on the molecular weight distribution. The results thus obtained should serve as a basic material for a detailed study of these questions.
Poly(vinyl chloride) compositions in medicine
Authors: Buadze O. P. , Gegeshidze G. A. , Nazin A. N. , Shmyreva T. A. 
Published: June 2010

AbstractThe aim of this work has been to obtain a biologically harmless composition on the basis of suspension polyvinyl chloride resin. The authors were trying to select adequate plastifiers and stabilizers and to determine their optimum quantitative relations. Of various types of plastifiers, esters and polyesters of the selected acids were tested. Metallic soaps and organotin compounds were investigated as stabilizers. The polyvinyl chloride composition was first investigated under laboratory conditions and then tested on living animals. About 20 compositions were subjected to experimental tests on 250 dogs in all. On the basis of the results obtained a polyvinyl chloride composition was selected, the implantation of which causes a minimum reaction of the organism.
Monolayer characteristics of alternating block copolymers of dimethylsiloxane and bisphenol‐a carbonate
Authors: Gaines G. L. 
Published: June 2010

AbstractDimethylsiloxane (DMS)‐bisphenol‐A carbonate (BPAC) alternating block copolymers having overall compositions ranging from 25 to 83 wt‐% siloxane have been examined as films spread at the air‐water interface. At low surface pressure, the siloxane blocks appear to spread completely, while the BPAC segments are not located in the interface; the area occupied at low pressure is directly proportional to the siloxane content. At π = 6–8 dynes/cm, a rearrangement substantially identical to that observed with homopoly‐DMS films occurs. At areas of 0.2–0.4 m2/mg, fairly stable films persist (π up to > 12 dynes/cm), and the area requirement for these films depends on the overall composition, but we do not yet know the molecular configurations involved in this region. The mono‐layer properties may provide useful characterization data for copolymers of this type, as well as providing insight into their behavior at other interfaces.