bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selective modifications of PMMA for effective decay of electrostatic charges
Authors: Dave A. M. 
Published: April 2003

AbstractPoly(methyl methacrylate) (PMMA) modified with ion or metal containing monomers is found to exert no large improvement concerning electrostatic charging, but decreases discharge periods significantly depending upon the type and concentration of the modifying comonomer.The newer approach reported here aims at making a representative thermoplastic like PMMA an antistatic polymer through selective copolymerization safeguarding the mechanical and optical properties as usual. Moreover, unlike the conventional approach of incorporating surfactants, the antistatic effects are exerted immediately after the polymer is made.
Hardening reactions of epoxy‐phenol systems in the presence of imidazole type catalyst by DSC
Authors: Lázló‐Hedvig Zs. , Molnár I. , Váradi J. , Tüdős F. 
Published: April 2003

AbstractThe thermal features of polyaddition and crosslinking of epoxy‐novolac resin mixtures and that of epoxy and phenol model systems—diane (DIANE) and dianediglycidyl ether (DDGE) — were studied in the temperature range of 20–250°C by DSC in the presence and absence of imidazole type catalysts (imidazole and benzimidazole). In the DDGE‐DIANE (mole ratio 2:1) system the exothermae showed a characteristic bimodality when catalyzed by imidazoles. The bimodal character could be interpreted in terms of the mechanism of action of the imidazoles.
Modellierung der umsatzabhängigkeit ausgewählter technischer kennwerte von PVC‐S unter nutzung von vorstellungen zur morphogenesis
Authors: Henschel Ines , Platzer Bernd 
Published: April 2003

AbstractGegenstand dieses Artikels ist die Berechnung einiger Eigenschaften von PVC‐Pulver, das nach dem Suspensionspolymerisationsverfahren hergestellt wurde. Ausgehend von einer Analyse der Einflußfaktoren und von experimentellen Daten wird ein Modell für die spezifische Oberfläche und für die Porosität des Pulvers entwickelt. Das Modell nutzt Gleichungen für die Morphogenesis von PVC‐S, die kürzlich in dieser Zeitschrift vorgestellt wurden, und frühere Arbeiten über den Kornbildungsprozeß. Damit berücksichtigt das Modell die Abhängigkeit der Produkteigenschaften von Reaktionskinetik, Umsatz, Temperatur, Vermischung und Dispergatorsystem. Es zeigt sich, daß die spezifische Oberfläche nur von der inneren Morphologie abhängig ist. Die Porosität ist darüber hinaus von einer eventuellen Mehrzelligkeit des Korns abhängig. Die Ergebnisse für die spezifische Oberfläche korrespondieren mit Daten, die nach der BET‐Methode bestimmt wurden; die Daten der Porosität (Quecksilber‐Hochdruck‐Porosimetrie) stimmen ebenfalls mit den durch das Modell berechneten überein. Die Eigenschaften von im Großreaktor hergestellten Produkten korrespondieren gut mit dem Modell.
Oberflächenstrukturierung polymerer fasern durch UV‐laserbestrahlung. 5. Oberflächenstrukturierung und laserablation von seide
Authors: Knittel Dierk , Schäfer Karola , Schollmeyer Eckhard 
Published: April 2003

AbstractDurch Untersuchungen an Seide (Fibroin von Faltblattstruktur des β‐Keratintyps) wird untermauert, daß neben von außen aufgebrachten Spannungen und neben internen Spannungsfeldern in Synthesefasern auch Spannungen in einer Polymerkette, die durch ihren chemischen Aufbau bedingt sind, in Zusammenwirken mit einem laserinduzierten Temperaturfeld zur Strukturierung der Faseroberfläche führen können.Die Bedeutung der erzielten regelmäßigen Rollenstruktur an Faseroberflächen für Anwendungsmöglichkeiten wird diskutiert.
Radiation induced grafting of methacrylic acid onto silk for the immobilization of antimicrobial drug for sustained delivery
Authors: Singh Harpal , Tyagi P. K. 
Published: April 2003

AbstractMedical grade black braided silk suture and pure mulberry silk twisted yarn were grafted with methacrylic acid (MAA) using 60Co gamma radiation. The effect of various synthesis conditions on the grafting was studied. The addition of methanol in water has a marked effect on the degree of grafting, maximum yield of grafting was obtained in an equivolume mixture of water‐methanol. The percent grafting increased with the increase in the monomer concentration and in total radiation. For a constant total dose, grafting was found to be higher at lower dose rates. The order of the dependence of the rate of grafting on the dose rate was found to be 0.53 and 0.56 for medical grade black braided silk suture samples and mulberry silk twisted yarn samples respectively. The immobilization of an antimicrobial drug, 8‐hydroxy quinoline (8‐HQ) hydrochloride on the grafted pure silk for sustained delivery, its release in vitro and its antimicrobial activity were also studied. The percentage of 8‐HQ immobilized onto various grafted silk samples increased with the increase in the degree of grafting. The release of the drug in distilled water was sustained for 32 days. 8‐HQ was found to be active against both gram‐positive and Gram‐negative bacteria.
Glass fiber reinforced composites of epoxy resin cured with different amines
Authors: Thakkar Jatin R. , Patel Ravji D. , Patel Ranjan G. , Patel Vithal S. 
Published: April 2003

AbstractDiglycidyl ether of bisphenol A (DGEBA), cured with six different curing agents, i.e. 4,4′‐diamino diphenyl sulfone (DDS), 4,4′‐diamino diphenyl methane (DDM), 4,4′‐diamino diphenyl ether (DDE), dicyandiamide (DICY), 4,4′‐diamino‐3,3′‐dichloro diphenyl methane (MOCA) and diethylene triamine (DETA), respectively, was studied for the kinetics of the thermal degradation. Such epoxy systems have been used to prepare the glass fiber reinforced laminates, which were evaluated for their properties such as heat distortion temperature (HDT) and resistance to chemical reagents. The mechanical properties like shore‐D hardness, flexural strength and interlaminar shear strength (ILSS) as well as dielectric properties like dielectric constant, tan δ, electrical resistance and breakdown voltage have also been estimated. The composition prepared using an epoxy fortifier showed improvement in flexural strength and interlaminar strength up to ≈33% and ≈36%, respectively.
Mischungen aus semiflexiblen, flüssigkristallinen polyestern und polystyrol
Authors: Braun Dietrich , Schülke Ulrike 
Published: April 2003

AbstractMischungen aus Polystyrol und einem semiflexiblen, flüssigkristallinen Polyester werden durch gemeinsames Ausfällen von Polymerlösungen hergestellt und differentialkalorimetrisch und polarisationsmikroskopisch untersucht.Des weiteren werden Mischungen der gleichen Komponenten durch radikalische in situ Polymerisation von Styrol in Anwesenheit des Polyesters hergestellt; das thermotrope Verhalten des flüssigkristallinen Polyesters in diesen Mischungen wird mit den oben genannten verglichen.Die Untersuchungen ergeben, daß nach der zweiten Methode Polystyrolpfropfäste am Polyester entstanden sind, was auch durch Extraktion des Homopolystyrols und nachfolgende IR‐spektroskopische Untersuchung des Rückstandes bewiesen wird. Aufgrund dieser Verträglichkeitsvermittler ist der Polyester feiner in der Polystyrolmatrix verteilt, und die Kristallisation tritt bei tieferen Temperaturen ein als beim reinen Polyester.Um die Bedingungen der Pfropfreaktion zu verbessern, wurden mit Styrol copolymerisationsfähige Doppelbindungen über 4,4′‐Fumaroyldioxydibenzoylchlorid in den Polyester eingebaut. Die anschließende Pfropfcopolymerisation mit Styrol führte aber nicht zu Produkten mit wesentlich veränderten Eigenschaften gegenüber der Pfropfung mit dem gesättigten Polyester.
Incorporation of a well‐defined polyether side‐chain into segmented poly(ether‐urethane urea) and examination for blood‐compatibility
Authors: Hashimoto Hisaho , Demachi Ayako , Nishimata Toyoki , Sasamura Yasuaki , Iida Kazutoshi , Kaneko Noriaki , Sakamoto Nagayoshi , Kakuchi Toyoji , Yokota Kazuaki 
Published: April 2003

AbstractA new method of introducing a hydrophilic polyether side chain into segmented polyurethane using a polypropylene oxide macromer with 1,3‐diol at one chain‐end, which behaves as chain extender, is described. In this procedure, a molecular‐designed side‐chain is incorporated quantitatively and directly into polyurethane biomedical elastomer. The design is also of interest to biomaterials in artificial organs.
Curing of epoxides. Reaction of dicyanodiamide with phenylglycidyl ether
Authors: Zeppenfeld Gisela , Matějka Libor , Špaček Pavel , Schmidt Pavel , Dušek Karel 
Published: April 2003

AbstractCuring of epoxy resins with the latent hardener 1‐cyanoguanidine (dicyanodiamide) was studied using a model system. Phenylglycidyl ether was reacted with 1‐cyanoguanidine in the presence of benzyldimethylamine as a catalyst in a solution in 2‐methoxyethanol. The reaction kinetics was followed by means of HPLC and IR spectroscopy. Some of the reaction products were isolated by semipreparative HPLC and identified.The influence of temperature and of the initial ratio of reaction components on the reaction mechanism was studied. Three partial reactions were found: a) addition of the amino groups of 1‐cyanoguanidine to the epoxide, which then initiates the reaction of OH groups of the addition products, b) with the C≡N group, or c) with the epoxide (etherification). The relative extents of the latter two reactions increase with conversion. The reaction of the nitrile group is preferred at high temperatures but depressed in the presence of excess epoxide in the reaction mixture when etherification prevails.
Bigraft copolymer EVA‐g‐AA‐g‐HEMA from peracid type polymeric initiator
Authors: Hsiue Ging‐Ho , Chu Hsiao‐Lung 
Published: April 2003

AbstractIn this study a poly(ethylene‐co‐vinylacetate) grafted with acrylic acid (EVA‐g‐AA) film was used as a substrate, whose carboxyl groups can be oxidized to form a highly reactive polymer initiator. The activation energy for its decomposition is 13.41 kcal/mol. The peracid type membrane has a high reactivity and 2‐hydroxyethyl methacrylate (HEMA) can be easily grafted on to form a bigraft copolymer EVA‐g‐AA‐g‐HEMA. The properties and morphology of the bigraft copolymer were discussed.
Etude de polymères thermostables en vue de leurs applications en electronique
Authors: Boiteux G. , Oraison J. M. , Seytre G. , Vallet G. , Davenas J. , Mariaggi P. , Senneron M. , Sillion B. 
Published: April 2003

AbstractHeat resistant polymer are more and more needed for structural applications in aerospace and for electrical applications in electronics.Thermostable dielectric coatings are used as intermetallic layers in wafer fabrication or for interconnection processes and dielectric films find their main applications for the production of flexible circuits. On the other hand, for the development of surface mount technology, heat resistant films are required, due to the severe thermal stresses encountered by the components during the wave soldering.Among the heat resistant polymers, polyimides are the most popular. In spite of all the works performed on polyimides, these materials still exhibit certain shortcomings such as good processability. An approach to improve the processability involves the synthesis of fully cyclized linear polymers with a good solubility. For this we can introduce in the main chain flexible linkages (ether, carbonyl, sulfone), lateral groups with large steric hindrance or polar groups giving strong interactions with solvent.We will discuss in this paper the synthesis and the thermal and dielectric properties of various heterocyclic polymers fully cyclized and soluble.Additionally, new applications of polyimides can be relevant regarding the properties which are obtained under irradiation with ion‐beams. We will present some results on the effect of irradiation and the induced conductive character of such materials.
Influence de la température sur i'écoulement des polymères. Correlation pratique et mathématique de i'énergie d'activation de i'écoulement pour le polyéthylène basse‐densité, polyéthylène haute‐densité, polystyrène et d'autres polyoléfines
Authors: Déri Fawaz , Aldeyab Salem , Majid Balkhi Abdel 
Published: April 2003

AbstractNous avons étudié les propriétés rhéologiques des matériaux à l'état fondu au moyen d'un viscosimètre à capillaire.Nous avons essayé de relier les valeurs des énergies d'activation, à vitesse et tension de cisaillement constantes, avec les valeurs de l'indice d'écoulement.Les valeurs de l'indice d'écoulement obtenues selon l'approche mathématique ne coincident pas avec les valeurs obtenues expérimentalement. L'énergie d'activation de LDPE est supérieure à celle du HDPE en raison du volume libre de LDPE qui est plus grand.
Changes in structure of PA fibres during mass colouration
Authors: Wlochowicz A. , Broda J. , Ślusarczyk C. 
Published: April 2003

AbstractThe effect of organic pigments on the supermolecular structure of mass coloured PA fibres has been investigated by means of small‐angle and wide‐angle X‐ray scattering methods. It has been found that the dye molecules introduced in polymer melt before the fibre is formed take part in the formation of the supermolecular structure of the fibres. The presence of these molecules causes changes of the weight fractions of the polymorphic forms of the polyamide, the increase of the crystallinity index of the fibres and the increase of the thickness of the transition layers between crystalline and amorphous regions. Changes which have been observed are dependent both on the content of pigments and on their chemical nature.
Salicylic acid‐biuret‐trioxane terpolymer resins and their ion‐exchange properties
Authors: Pal T. K. , Kharat R. B. 
Published: April 2003

AbstractTerpolymer resins (SBT) were synthesized by the condensation of salicylic acid and biuret with trioxane in the presence of acid catalyst and using varied molar ratios of reacting monomers. Terpolymer resin compositions have been determined on the basis of their elemental analysis and the number average molecular weights of these resins were determined by conductometric titration in non‐aqueous medium. The viscosity measurements carried out in DMF indicate normal behaviour. IR spectra were studied to elucidate the structure. TGA data were analysed to estimate the characteristic thermal parameters. The terpolymer resins have been further characterized by reflectance spectra in solid state, absorption spectra in non‐aqueous medium, X‐ray diffraction and electrical conductivity. Chelation ion‐exchange properties have also been studied employing the batch equilibration method.
Ammoniakdiffusion in Polymerfilmen
Authors: Müller F. W. , Schiller K. , Jänchen U. , Marx J. 
Published: April 2003

AbstractMit Hilfe einer neuartigen Untersuchungsmethode wurden die Diffusionskoeffizienten von Ammoniak (NH3) in 22 transparenten filmbildenden Polymeren bei Raumtemperatur bestimmt. Die Methode beruht auf der UV‐VIS‐spektroskopisch verfolgbaren reversiblen Reaktion von Ammoniak mit 4‐Nitrophenol zu einem 4‐Nitrophenolat‐Ammoniak‐Meisenheimer‐Komplex.Die Farbbildungsreaktion im Polymerfilm wurde untersucht und anhand einer einfachen Näherung der Diffusionsgleichung ausgewertet. Die erhaltenen Diffusionskoeffizienten stimmen sehr gut mit den wenigen verfügbaren Literaturwerten überein.Die Abhängigkeit der NH3‐Diffusionskoeffizienten von der Polymerstruktur ist weitgehend der für permanente Gase bekannten analog.Die beschriebene Methode erlaubt problemlos, Diffusionskoeffizienten zu messen, die sich bis zu drei Größenordnungen unterscheiden (Ethylcellulose: 1,07 · 10‐7 cm2 · s‐1; Polyvinylalkohol: 0,9 · 10−10 cm2 · s−1).
The mechanism of orientation in cold‐drawn polyoxymethylene as revealed by crystallographic pole figures
Authors: Schweizer Thomas , Vancso Gyula 
Published: April 2003

AbstractThe orientation mechanism of cold‐drawn, partially crystalline polyoxymethylene (ULTRAFORM) samples was studied by performing wide angle X‐ray scattering (WAXS) measurements. The anisotropic samples were prepared in uniaxial tensile tests around 130°C, in a temperature range between the glass transition and the melting point. The process of the plastic deformation is discussed for different degrees of anisotropy. The orientation distribution of the crystalline lamellae was qualitatively characterized by performing pole figure intensity calculations from the measured WAXS intensities. The degree of orientation was quantitatively described by calculating the orientation factors for the [100] normal vector of the unit cell. The texture of the necked samples with high orientation degrees was a mixture of axial and uniplanar‐axial textures. An explanation for the formation of this kind of orientation is proposed assuming an influence of the sample geometry on the orientation process.
The interactions between wood components and formaldehyde‐based resins. I. Monofunctional resin model compounds
Authors: Mora F. , Pla F. , Gandini A. 
Published: April 2003

AbstractResults are presented on the chemical interactions occurring when some monofunctional model compounds simulating the structure and reactivity of thermosetting phenol‐ and urea‐formaldehyde resins are mixed with wood components (hemicelluloses, cellulose, and lignins). Whereas hemicelluloses clearly show a propensity to give condensation products with these model compounds, lignins can react less readily in some instances depending on the delignification procedure used to isolate them and on the type of model compound. Cellulose did not react under the conditions chosen, mostly because of its crystalline character.
Bigraft copolymer EVA‐g‐AA‐g‐HEMA for biomaterial usage
Authors: Hsiue Ging‐ho , Chu Hsiao‐lung 
Published: April 2003

AbstractThe preparation of a bigraft copolymer of EVA‐g‐AA‐g‐HEMA which is a good biocompatible material from a peracid type polymeric initiator, EVA‐g‐AA peracid, is described. The peracid type membrane has high reactivity and HEMA can be easily grafted onto the film. The biocompatibility test showed that the blood clotting time of the HEMA grafted membrane could be as high as 60 min. The wettability of a grafted membrane decreased as the degree of grafting increased. The grafted membranes have high oxygen and water permeabilities as well as high selectivity for solutes.
Conventional crosslinking studies on low density polyethylene monofilaments
Authors: Mukherjee A. K. , Tyagi P. K. , Gupta B. D. 
Published: April 2003

AbstractConventional crosslinking of low density polyethylene (LDPE) was carried out using dicumyl peroxide (DCP) as crosslinking agent. DCP in various concentrations was mixed with LDPE chips in an extruder at 135 – 145°C. Monofilaments were drawn on a laboratory drawing machine at 110°C. It was found that tensile properties, percent shrinkage and density were improved with the increase in the concentration of DCP and in the heating period, whereas, however, the percent swelling decreased.
Kationisierung von Zellstoff unter homogenen reaktionsbedingungen
Authors: Ott Gerhard , Schempp Walter , Krause Thomas 
Published: April 2003

AbstractEs wurde der Versuch unternommen, durch Umsetzung von Zellstoffen mit Glycidyltrimethylammoniumchlorid im Lösungsmittelsystem Dimethylacetamid/Lithiumchlorid kationische Cellulosederivate mit möglichst hohen Substitutionsgraden zu erhalten. Hierzu wurden Temperaturabhängigkeit, Reaktionsdauer und Molverhältnis der Reaktanden untersucht. Als optimal erwies sich eine Reaktionsdauer von 8 h bei einer Reaktionstemperatur von 70°C. Der Cellulosegehalt in Lösung und das Molverhältnis der Reaktanden müssen dem verwendeten Zellstoff angepaßt werden.
Synthese und Charakterisierung von Epoxidharzen aus Bisphenol A, Cyanursäuure und Epichlorhydrin
Authors: Braun Dietrich , Vargha Viktoria 
Published: April 2003

AbstractAus Bisphenol A, Cyanursäure und deren Mischungen wurden mit Epichlorhydrin Epoxidharze hergestellt. Die entstandenen Produkte wurden durch Gelpermeationschromatographie, FT‐IR‐, 1H‐NMR‐, 13C‐NMR‐Spektroskopie und DSC‐Analyse charakterisiert. Bei den Synthesen entstehen außer den Glycidylderivaten von Bisphenol A und Cyanursäure Spaltprodukte des Isocyanuratringes bzw. deren Glycidylderivate. Die erzeugten Mischharze lassen sich ohne Härtungsmittel in der Wärme vernetzen.
Einfluß der molekularstruktur auf die dauerfestigkeit teilkristalliner kunststoffe
Authors: Goldman A. J. , Kestelman V. N. 
Published: April 2003

AbstractDer Zusammenhang zwischen der Molekularstruktur eines linearen teilkristallinen Polymeren (HDPE) und seiner Dauerfestigkeit wurde untersucht. Durch die Untersuchung einer größeren Zahl von HDPE‐Proben mit unterschiedlichem Molekulargewicht konnte ein Zusammenhang zwischen der Lebensdauer und dem Viskositätsmittel des Molekulargewichts gefunden werden, der eine quantitative Voraussage der Lebensdauer ermöglicht.
Polymer composites with radical salts of 1‐methyl‐3‐alkylimidazolium‐7,7,8,8‐tetracyano‐p‐quinodimethane and their electric conductivity
Authors: Šorm Miloslav , Nešpůrek Stanislav , Koropecký Igor , Kubánek Vladimír 
Published: April 2003

AbstractThe polymer composites were prepared by reticulate doping of polystyrene and poly(γ‐methyl‐L‐glutamate)(PMGA) with 1‐methyl‐3‐alkylimidazolium‐7,7,8,8‐tetracyano‐p‐quinodimethane simple salts I and complex salts II. The electric conductivity strongly depends on the chemical structure of the donor, on the stoichiometry and concentration of the radical salts, on the type of the polymer, and on the preparation conditions of the films. A high conductivity, even higher than that of pure radical salts measured in pressed pellets, was obtained in the PMGA doped films, and is most probably due to the α‐helical conformation. This high order conformation of molecules forces microcrystals of charge transfer salts to grow in long hair‐like shapes distributed regularly in the bulk of the polymer film.
Eine neue methode zur herstellung von hydroxyterminierten polydienen
Authors: Trathnigg B. , Krause D. , Dworczak R. , Maier B. , Junek H. , Schmidt A. 
Published: April 2003

AbstractEs wird gezeigt, daß hydroxyterminierte Polydiene mit guter Mikrostruktur und Funktionalität sowie enger Molekulargewichtsverteilung unter Verwendung von Azobis‐isobuttersäure‐di‐hydroxyethylamid hergestellt werden können. Die Aktivierungsenergie des Initiatorzerfalls wurde durch volumetrische Messung des bei dieser Reaktion freiwerdenden Strickstoffs bestimmt.
Durability of radiation‐sterilized polymers, XIII. The effects of nucleating agent on the oxidative degradation of poly(propylene‐co‐ethylene)
Authors: Kadir Zahrah Abdul , Yoshii Fumio , Makuuchi Keizo , Ishigaki Isao 
Published: April 2003

AbstractThe radiation stability of the random and block poly(propylene‐co‐ethylene) (CP, copolymer with 6% ethylene units) with and without nucleating agent (NA) was compared in relation to radiation sterilization of medical supplies. In both cases, it was found that the radiation stability of CP in the presence of NA was lower than that of CP without NA.Addition of NA to CP did not improve the transparency but the crystallization occurred at higher temperature. Thus, adding NA to CP has the advantage of shorter moulding time in the production of medical supplies.The radiation instability of the CP with NA was due to a different crystal structure, because the spherulite shape differs from that of CP without NA. Furthermore, by the chemiluminescence analysis, a higher oxidative degradation was observed in the sample with NA.