bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zur thermodynamischen Charakterisierung von Polymer Blends mit der inversen Gas‐Flüssig‐Chromatographie. I. Poly(vinylacetat) + Poly(n‐butylmethacrylat)
Authors: Wohlfarth Ch. 
Published: April 2003

AbstractDie χ‐Werte von 13 verschiedenen Lösungsmitteln mit Poly(n‐butylmethacrylat) beziehungsweise Poly(vinylacetat) werden über einen Temperaturbereich von 343 bis 423 K beziehungsweise 403 bis 473 K mit der inversen Gas‐Flüssig‐Chromatographie ermittelt. Untersuchungen am 1:1‐Blend beider Polymere ergeben den χBC‐Wert des Polymer‐Polymer‐Systems. Gegenüber einer früheren Arbeit beobachten wir eine deutlich geringere Abhängigkeit der χBC‐Werte von den Lösungsmittelproben.
Semicontinuous emulsion polymerization of vinyl acetate IX. Decomposition of the initiator
Authors: Donescu D. , Fusulan L. 
Published: April 2003

AbstractThe way in which the decomposition reaction of a persulfate initiator is influenced by the nature of reactants of the polymerization medium and by the working conditions during the semicontinuous polymerization and copolymerization of vinyl acetate is studied. The rate of the splitting reaction of potassium persulfate is higher in the aqueous phase containing a protective colloid and surfactant. The splitting rate is smaller in the presence of vinyl acetate. The presence of hydrophobic commonomers decreases the rate of initiator decomposition. An increase of the addition rate of monomers leads to an increase of the obtained polymer and of the splitting rate of the initiator.
Adsorptive surface modification of a manganiferous ore and its effect on the radical polymerization of methyl methacrylate
Authors: Moustafa A. B. , Radwan F. M. , Emam A. 
Published: April 2003

AbstractThe surface unmodified manganiferous ore catalyzed the radical polymerization of methyl methacrylate initiated by sodium bisulphite. An adsorptive surface modification of the ore with stearic acid was carried out to various extents. The influence of the surface coverage on the reaction parameters was investigated. The surface modification effectively retarded the catalytic action of the manganiferous ore and caused a drop of the viscosity average molecular weights of the polymers.
Infrared spectroscopy of oligoethyleneterephthalate‐oligooxyethylene block copolymers
Authors: Bogdanov B. , Mihailov M. , Gavrailova G. 
Published: April 2003

AbstractThe temperature dependence of structure sensitive absorption bands in the infrared spectra of oligoethyleneterephthalate‐oligooxyethylene (OETP‐OOE) block copolymers is investigated. Informations on the crystalline structures formed by the OETP and OOE blocks are obtained. A measurable mutual influence between these structures when crystallizing from solution or from melt has been established.
The phase behavior of polymer blends – Effects of thermodynamics and rheology
Authors: Kammer H. W. 
Published: April 2003

AbstractPart one of the paper is devoted to the thermodynamics of the phase behaviour of polymer blends. According to an equation‐of‐sate theory the phase behaviour is directed by the interplay of three effects: the interaction between the segments, the free‐volume effect, and the size‐effect. When the size‐effect is negligible only lower critical solution temperature (LCST) behaviour occurs. Phase separation at elevated temperatures is an entropy driven process whereas at an upper critical solution temperature (UCST) an unfavourable enthalpic effect associated with the size‐effect acts as driving force for phase separation. Also positive volumes of mixing can be related to the size‐effect. In the second part the phase behaviour of blends exposed to shear is discussed. For blends it has been found experimentally that shear flow elevates phase‐separation temperatures. Obviously, shear‐induced phase changes depend on the stored elastic excess energy. A negative stored excess energy corresponds to an additional attraction between the different segments, hence, the miscibility region of the system is enlarged theoretical and experimental reuslts agree qualitatively.
Sphärolithwachstum bei der isothermen Kristallisation von Poly(ethylenterephthalat)
Authors: Fabry F. , Dobbert P. 
Published: April 2003

AbstractAnhand von Messungen zur Zeitabhängigkeit des Kristallinitätsgrades und der Kleinwinkellichtstreuung von kristallisierten Poly(ethylenterephthalat)‐Proben wird ein Auswerteverfahren vorgestellt, das es gestattet, Aussagen zur Sphärolithform und deren Änderung im Verlauf der isothermen Kristallisation zu machen. Ausgehend von einer modifizierten Avrami‐Gleichung läßt sich ein Formparameter berechnen, der die Abweichung von der Kugelgestalt angibt. Die Ergebnisse zeigen, daß sich mit wachsender Kristallisationszeit die Garbenform immer stärker ausprägt, die Kugelform wird jedoch nicht erreicht.
Einfluß der Morphologie bei Polypropylen mit Propylen/Ethylen‐Copolymerisaten auf Tieftemperaturschlagzähigkeit und Weißbruch
Authors: Ramsteiner F. 
Published: April 2003

AbstractDie reduzierte Schlagzähigkeit von Polypropylen unterhalb dessen Glasübergangstempertur kann durch Einmischen einer dispersen Phase verbessert werden. Mit dieser Zähigkeitsverbesserung geht aber durch die so erhöhte Craze‐Verformung die Bildung von Hohlräumen einher, an denen Licht gestreut wird; der aus optischen Gründen unerwünschte Weißbruch entsteht. Der Einfluß der Größe der dispergierten Teilchen auf die Tieftemperaturzähigkeit und die parallel laufende unerwünschte Neigung zum Weißbruch wird aufgezeigt.
Polyelectrolyte behaviour of poly(vinyl alcohol)‐boric acid complexes
Authors: Moneva‐Andonova L. 
Published: April 2003

AbstractThe polyelectrolyte behaviour of poly(vinyl alcohol)‐boric acid complexes is investigated. A plateau is observed in the dependence of pKa on the degree of neutralization, while the HENDERSON‐HASSELBACH plots show two linear regions with different slope related to two different macroconformations. The complexes undergo a transition to an extended rigid conformation when neutralized in aqueous solution determined by decreased flexibility of the chain and charge acquisition.
Organische Elektronenleiter und Vorstufen. XIII. Untersuchungen zum thermischen Verhalten von Poly(bis‐alkylthio‐acetylen)en
Authors: Richter A. M. , Laube U. , Moniak F. , Fanghänel E. , Hempel G. , Goldenberg S. , Scheler G. 
Published: April 2003

AbstractDas thermische Verhalten der Poly(bis‐alkylthio‐acetylen)e wurde im Temperaturbereich von 30°C bis 600°C untersucht. Aus den Ergebnissen der thermischen Analyse, aus 13C‐Festkörper‐NMR‐ und ESR‐Messungen an den festen Thermolyserückständen und der Untersuchung der flüchtigen Pyrolyseprodukte werden mögliche Abbaureaktionen abgeleitet. Für einen weiten Zeit‐ und Temperaturbereich wird für Poly(bis‐methylthio‐acetylen) ein einfaches kinetisches Modell formuliert.
Determination of molecular weight of poly(acrylic acid) using ultrasonic technique
Authors: Hassun S. K. , Hussain F. M. A. , Al‐Mehdi H. A. H. 
Published: April 2003

AbstractUltrasonic velocity and isentropic compressibility of aqueous solutions of poly(acrylic acid) of various molecular weights and concentrations have been measured. The results are discussed on base of the interactions between polymer and water molecules. An equation correlating the isentropic compressibility and molecular weight of the polymer is suggested.
Solvent‐induced phase separation in ternary solutions of poly(methyl methacrylate), poly(styrene‐co‐acrylonitrile) and toluene
Authors: Reichelt K. , Kummerlöwe C. , Kammer H. W. 
Published: April 2003

AbstractMorphology evolution in ternary polymer solutions consisting of poly(methyl methacrylate), poly(styrene‐co‐acrylonitrile) having different AN‐contents and toluene was studied by optical microscopy and light scattering. The solutions subjected to different isothermal demixing conditions displayed regularly or irregularly phase separated structures. Effects of the AN‐content of the SAN, the blending ratio and the annealing conditions on the arising morphologies are presented. A criterion for conservation of the periodic bicontinuous structure developed in the unmixing process can be established.
The effects of surfactants on the miscibility of polymers
Authors: Funke Z. , Starke L. 
Published: April 2003

AbstractThe surface tension of molten LDPE can be determined with the help of the pendent drop method, depending on the temperature and on the surfactant added. The critical micelle concentration was reached on addition of 1% of the surfactant. A four‐component mixture consisting of HDPE, LDPE, PVC, and PS, whose composition corresponded to that of collected waste plastics, was used to study the effects of the addition of surfactants on the applicational properties.
The sorption of ethyl xanthogenate on polyester fibres. I. Electrokinetic properties
Authors: Espinosa‐Jiménez M. , Cano Suárez A. 
Published: April 2003

AbstractAn experimental investigation on the streaming potential and adsorption of ethyl xanthogenate ions on polyester fibres at various temperatures has been carried out. The results reveal that the uptake of ethyl xanthogenate ions by the polyester fibres in the tested temperature interval takes place with the establishment of strong chemical bonds. The results are interpreted on the basis of nucleophilic attack of the negatively charged oxygen in the carbonyl group of the polyester on the thiocarbonyl group of the xanthogenate ion.
Ultrasonic investigation of thermostabilized poly(acrylonitrile) fibres
Authors: Lyubcheva M. 
Published: April 2003

AbstractThermostabilized poly(acrylonitrile) fibres obtained under different conditions have been investigated by means of ultrasonic measurements. The correlations between ultrasonic velocity, density, and some properties of the fibres are studied. The possibility of using ultrasonic velocity as a parameter for the control of the oxidation process of poly(acrylonitrile) fibres is discussed.
The synergetic effect of the catalytic system di(tributyltin) carbodiimide + triethylene diamine in reactions of 2,4‐tolylene diisocyanate with macrodiols at various temperatures
Authors: Sojecki R. 
Published: April 2003

AbstractThe influence of temperature on the magnitude of the synergetic effect of the catalytic system di(tributyltin)carbodiimide + triethylene diamine in reactions of 2,4‐tolylene diisocyanate with macrodiols has been studied. For calculations of the reaction rate constants a differential‐integral method based on the consequent‐parallel reaction scheme was applied. A proportional increase of the maximal synergetic effect with increase of temperature has been established. A qualitative interpretation of the observation is presented.
Catalytic degradation of polyolefines under the action of friedel‐crafts catalysts in solution. 2. Investigation of structural pecularities of degraded poly(isobutene) by low‐temperature calorimetry and 13C‐NMR
Authors: Khalafov F. R. , Novrusova F. A. , Krentsel B. A. , Agaeva E. A. , Yafarov O. I. , Mekhtiev S. A. , Kuliev A. M. , Nurullaev G. G. 
Published: April 2003

AbstractThe temperature dependence of specific heat of poly(isobutene) degraded under the action of strong Lewis acids has been investigated. From the calculated thermodynamic parameters have been drawn conclusions on the structural conversions of the macromolecules in the process of catalytic degradation. By means of 13C‐NMR the formation of branched macromolecules was shown. On the basis of the results a degradation mechanism for poly(isobutene) is suggested.
Treatment of celluloses in nonaqueous solution of sodium hydroxide
Authors: Pašteka M. 
Published: April 2003

AbstractTreatment of cellulose with solution of sodium hydroxide in isopropyl alcohol leads to formation of sodium cellulosate, which is destroyed in water medium to the starting substances. The degree of alkalization of the cellulosates depends on the pretreatment of the cellulose materials. It is assumed that the degree of alkalization is connected with the acceptibility of cellulose for sodium hydroxide or sodium isopropylate.
Poly(ethylene terephthalate) fibres with improved mechanical properties
Authors: Evstatiev M. , Sarkisova M. , Petrovich S. , Fakirov S. 
Published: April 2003

AbstractCold drawn poly(ethylene terephthalate) (PETP) fibres are subjected to zone annealing or isothermal annealing with fixed ends. The morphological changes taking place during both types of thermal treatment are followed by means of SAXS, WAXS, birefringence and density measurements, DSC, and mechanical tests. Differences in the supermolecular structure of the samples subjected to zone annealing and those annealed with fixed ends are established. Zone annealing results in better definition of the basic structural elements, higher orientation and larger number of taut tie molecules which in turn predetermine the higher performance of the zone annealed material.
Effect of the type of divinyl monomers on the structure and properties of their copolymers with 4‐n‐amyl styrene
Authors: Solovskaya N. A. , Zakharov S. K. , Asinovskaya D. N. , Lukyashina V. A. , Andreev D. N. 
Published: April 2003

AbstractCopolymers of 4‐n‐amylstyrene with dimethylsilyldiacrylate and diacrylmethylmethane were synthesized. The physicochemical, thermomechanical and elastic properties of the copolymers have been studied. The structure of the divinyl monomer affects the crosslinking and the mechanical properties of the materials.
Concentration dependent diffusion of water in polyamide 6
Authors: Hanspach J. , Pinno F. 
Published: April 2003

AbstractThe dependence of water diffusion in polyamide 6 on water concentration can be described by the equation D(c) = D(0) + βc2. The mean value D̄ correlates with the diffusion coefficient defined by Fick's law and depends exponentially on temperature with the activation energy Es = 0.49 eV. The diffusion process can be described by the thermally activated exchange of water molecules in cooperation with free volume. On the other hand free volume is generated by the water itself which affects the concentration dependence of the diffusion coefficient.
Structural changes of LODP cellulose in the original and mercerized state during enzymatic hydrolysis
Authors: Fink H.‐P. , Philipp B. , Zschunke C. , Hayn M. 
Published: April 2003

AbstractThe structural changes during enzymatic hydrolysis of cellulose substrates were studied by SAXS, WAXS, water retention values, and degree of polymerization. LODP cellulose samples in original (cellulose I) and mercerized (cellulose II) form were hydrolyzed using a commercial cellulase preparation produced by the fungus Trichoderma reesei. The mercerization of the LODP‐cellulose I powder results in a remarkable increase in degradability due to a more finely dispersed void structure with a distinct higher specific inner surface of the cellulose II. Based on the course of the degree of crystallinity, lateral and longitudinal crystallite sizes, and the DP at different stages of degradation a supermolecular mechanism of the “all or nothing” type was found for the chains in LOPD‐cellulose I, whereas for cellulose II an endwise degradation of ordered regions has been concluded.
Dielectric relaxation in liquid crystalline siloxane copolymers
Authors: Novotna E. , Kresse H. , Krücke B. 
Published: April 2003

AbstractDielectric relaxation measurements have been carried out in the frequency range from 1 Hz to 100 kHz on copolymers with different molar ratios of two liquid crystalline parts. Two dielectric relaxation ranges were detected which are related to the two respective parts. The copolymers show an increasing molecular mobility with respect to the homopolymers. The results are discussed in relation to the phase diagram and to dielectric data on low molecular liquid crystals.
Side chain liquid crystalline polymethacrylates with three‐ring azobenzene groups
Authors: Krüger H. , Wolff D. , Zschuppe V. 
Published: April 2003

AbstractThe influence of three aromatic rings in the azobenzene mesogenic moities on the LC character of side chain polymethacrylates is described. The three‐ring azobenzene groups exhibit some retardation and inhibition effect during the radical methacrylate polymerization. Therefore the polymerization conditions had to be modified. Dimethylformamide was found to be a solvent realizing high polymer yields and satisfactory molar masses. The phase behaviour of the obtained SCLC polymethacrylates and of their monomers is characterized by X‐ray, DSC and polarizing microscopy in dependence of spacer length. The polymethacrylates with three‐ring azobenzene mesogens show significant higher glass transition and clearing temperatures than two‐ring analogues. The change in the liquid crystalline phase arrangement from smectic C to smectic B with increasing spacer length is explained by the better movability of the mesogens.
Comparative characterization of solvent spun cellulose and high wet modulus viscose fibres by their long periods
Authors: Lenz J. , Schurz J. , Wrentschur E. 
Published: April 2003

AbstractThe evaluation of the long periods and crystallite lengths of original and pretreated solvent spun cellulose fibres revealed that they consist of about 90% crystalline cellulose in the direction of the fibre axis. In the case of high wet modulus viscose fibres this percentage is only 50–60%. The intensity of the long period of solvent spun fibres is lower than that of the high wet modulus viscose fibres corresponding to a smaller difference between their crystalline and amorphous orientation factors. There is existing a significant correlation between this difference and the intensity of the long period.
Characterization of the cationic polyelectrolyte poly(diallyl dimethyl ammonium chloride) by ultracentrifugation methods
Authors: Wandrey C h. , Görnitz E. 
Published: April 2003

AbstractThe characterization of polyelectrolytes is demonstrated by combination of different ultracentrifuge methods with laboratory as well as technical poly(diallyl dimethyl ammonium chloride) samples. Low speed sedimentation equilibrium in an analytical ultracentrifuge was used to determine the molecular weight averages Mw and Mz. The method was shown to be applicable even in case of partly aggregated solutions and the amount of aggregates was established. Equilibrium sedimentation in a density gradient of a preparative ultracentrifuge allows to separate linear and branched parts. While structural uniform polymers are distributed in a Gaussian band, nonuniformities lead to deformations of distribution curves. With mathematical curve analysis structural portions can be determined.
Orientation dynamics of side chain polymers subject to electric fields. Part I. Steady state
Authors: Hoffmann C. L. , Man H.‐T. , Fuller G. G. 
Published: April 2003

AbstractMany polymeric glasses must be orientationally ordered for the materials to exhibit useful characteristics. The objective of this work was to understand the dynamics of the orientation and relaxation processes and to relate these behaviours to the structural characteristics of the polymeric material. In this study we considered materials suitable for nonlinear optical applications. In particular, thin polymer films, either doped with nonlinear optical chromophores or films with the chromophores covalently bonded to side groups were studied. Orientation of these chromophores was achieved by the application of an external electric field. Ellipsometry was used to measure the birefringence resulting from chromophore orientation and the steady state and transient behaviours were studied. Materials characteristics studied included method of chromophore incorporation, chromophore concentration, spacer length, and molecular weight. Our results showed that the polymer structure, specifically the tacticity, was the dominant factor determining the steady state and transient behaviours. The relationship between monomer and polymer structure and the resulting effect on the orientation dynamics is discussed. Qualitative agreement with theoretical predictions was obtained for the simpler guest/host system, but the model was shown to be inadequate to explain the behaviours of the more complex systems studied. The results reported here have provided valuable insight into the molecular processes that occur during the chromophore orientation and relaxation, and the effects of structural characteristics of the polymers on these mechanisms.
Palladium and nickel catalyzed polycondensation ‐ The key to structurally defined polyarylenes and other aromatic polymers
Authors: Schlüter A.‐D. , Wegner G. 
Published: April 2003

AbstractThis article provides an overview on a new and easy to perform Ni‐and Pd‐catalyzed polycondensation of various kinds of homo‐ and heteroaromatic monomers. It allows the regiospecific coupling of these monomers at predetermined positions to furnish the corresponding structurally perfect polyarylenes, which up to now have only been known as ill‐defined, generally insoluble and infusible materials. The compatibility of this method towards functional groups is excellent. The achievable degrees of polymerization range from 20 to 60. The solubility and characterizability of the polymers is ensured, if necessary, by the attachment of flexible alkyl, tert.‐butyl, or alkoxy chains to the monomers. Results of initial physicochemical measurements with some of the polymers and their respective model compounds are briefly discussed. They do not only give vital clues to the intrinsic properties of poly‐ and oligoarylenes but also disclose exciting, unprecedented properties of these materials.
Determination of the pore size distribution of membranes by gel permeation chromatography
Authors: Weigel Th. , Albrecht W. , Paul D. 
Published: April 2003

AbstractPolyacrylonitrile membranes with different separation ranges are prepared and characterized by gel permeation chromatography. The determination of the pore size distribution of the ultrafiltration flat membrane (upper ultrafiltration range) and of the microfiltration hollow fiber membrane (lower microfiltration range) is affected by different measuring procedures. A comparison of the parameters of separation performance is obtained by making use of aqueous poly(ethylene glycol) (PEG) mixtures with broad molecular weight distribution, or the application of single PEG test substances is performed. The obtained results are discussed in connection with the separation range of membranes and the molecular weight of test solutions.
Study of the crystallization kinetics of a thermotropic liquid crystalline polymer
Authors: Zhao S. R. , Schaper A. , Ruland W. 
Published: April 2003

AbstractThe isothermal crystallization kinetics of a thermotropic liquid crystalline (LC) polymer has been studied using the integral intensity of a selected X‐ray reflection as a measure of the crystallinity. The starting conditions for the crystallization have been varied by isothermal annealing of the polymer in the LC state during various time intervals. Using the Avrami equation to interpret the crystallization kinetics, Avrami exponents increasing from 0.66 to 2.1 have been obtained with increasing annealing time. This observation can be explained by simultaneous heterogeneous nucleation from ID (centers of disclinations) and 2D (domain walls) nuclei. Using a modified form of the Avrami equation, the contributions of the two types of nuclei can be separated. Avrami exponents smaller than 1 appear to be related to the finite size of the domains. Time resolved studies of the crystallization process using a polarization microscope and bright field transmission electron microscopy observations corroborate the interpretation of the Avrami plots.