bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wettability and surface chemistry of irradiated PTFE
Authors: Morra A. , Occhiello E. , Garbassi F. 
Published: April 2003

AbstractLow energy electron irradiation of PTFE induced fluorine depletion and introduction of oxygen on the surface. The effect on surface chemistry was shown to be dependent mostly on the amount of electrons reaching the sample, rather than on their energy.Changes in surface energy resulted in different wetting behaviors. The measurement of advancing water contact angles and the analysis of XPS C‐1s peak shapes showed that the least wettable portion of irradiated surfaces is made in most cases of CF2CF  units. When the treatment caused a nearly complete fluorine depletion, only isolated CF2 or CF groups are present. Receding angle values decreased linearly depending on the amount of oxygen introduced on the sample during the treatment, suggesting the formation of strongly oxidized polymer islets. The invariance of contact angles with aging time indicated very low macromolecular mobility, probably related to extensive surface crosslinking.
Neue polymer‐additive, 1. Füllstoffe auf basis von modifizierten siliciumdioxiden
Authors: Bräuer Leopold , Gruber Heinrich , Greber Gerd 
Published: April 2003

AbstractDurch Umsetzung von Siliciumdioxiden (SD) mit Methyldichlorsilan wurden HSi‐modifizierte SD (I) erhalten, aus denen durch Hydrosilylierungsreaktionen mit geeigneten CC‐ungesättigten Partnern neuartige (Reaktiv‐)Füllstoffe mit bspw. Harnstoff‐ oder Melamin‐Resten zugänglich sind, die methylolierbar und daher kovalent in Formaldehyd‐Harze einkondensierbar sind. Die Addition von I an Divinylbenzol (DVB) führte zu Styrol‐modifizierten SD VII, die mit beliebigen ungesättigten Monomeren copolymerisierbar sind. Die resultierenden SD‐Pfropfcopolymeren zeigten in Abhängigkeit vom verwendeten Monomeren entweder hydrophile (Acrylnitril) oder stark hydrophobe (Styrol, Acrylsäuremethylester) Eigenschaften, im letzteren Fall gute Verträglichkeit mit organischen Medien.
New resin system for low‐pressure moulding compounds with special properties
Authors: Hacker H. , Hauschildt K. , Huber J. , Laupenmühlen H. , Wilhelm D. 
Published: April 2003

AbstractMoulded materials produced from aromatic epoxide resins, aromatic polyamines with high‐temperature‐resistant structure units and powdered mineral fillers possess outstanding properties like high glass transition temperatures, high mechanical strength, low linear thermal expansion coefficient, and reduced flammability without the addition of flame retardants. An account is given of the synthesis of aromatic polyamines, the preparation and working of moulding materials and the properties of the finished products.
Synthesis, characterization and kinetics of thermal decomposition of various peroxycarbamates and their initiation of methyl methacrylate polymerization
Authors: Yildirim Hüseyin , Baysal Bahattin M. 
Published: April 2003

AbstractSeveral dimeric and polymeric peroxycarbamates were synthesized using various aliphatic diisocyanates and hydroperoxides. The products were characterized by IR spectroscopy, molecular weight measurements, isocyanate and peroxide analyses. Thermal decomposition kinetics of these peroxycarbamates were studied in 1,4‐dioxane or toluene solutions at 80, 90, and 100°C. All reactions were found to proceed according to a first‐order kinetics with activation energies in the range of 126–144 kJ/mol, depending on the structure of the peroxycarbamate. One of the polymeric products was used to initiate methyl methacrylate polymerization at 80°C in bulk. The initiating activity of this peroxycarbamate was found to be better than that of some hydroperoxides.
Interactions of some liquid chemicals with polyolefins
Authors: Iring Margit , Barabás Klára , Földes Enikő , Tüdős Ferenc , Ódor Lujza 
Published: April 2003

AbstractPolyolefins are known to be highly resistant towards chemicals. It is shown, however, that both chemical and physical interactions take place between them which lead to changes in the initial advantageous properties. The interactions are rather slight in the case of HCl and NH4OH solutions. At the same time several limitations must be considered in the storage of high purity organic liquid chemicals. Apart from electronic grade, however, the organic reagents used in this study except from Freon TF may be stored in vessels made of polyolefins.
An investigation of poly(tetrafluoroethylene) surfaces after etching with anion radicals by means of XPS photoelectron spectroscopy
Authors: Lukáš J. , Lochmann L. , Kálal J. 
Published: April 2003

AbstractThe layer of reaction products on the surface of poly(tetrafluoroethylene) etched with a solution of sodiumnaphthalene in tetrahydrofuran was investigated by means of XPS photoelectron spectroscopy. The etched surfaces were also examined after vigorous rinsing with water and tetrahydrofuran. Using the elementary compositions thus determined and chemical shifts in XPS spectra, information was obtained regarding the concentration gradient of the elements and the chemical composition at various depths of the etched layer.
Synthesis and properties of a new o‐cresol novolak epoxy resin containing oxyethylene units
Authors: Iijima Takao , Kabaya Hidekazu , Tomoi Masao 
Published: April 2003

AbstractA new o‐cresol novolak epoxy resin containing oxyethylene units was synthesized and characterized. The mechanical, thermal, and dynamic mechanical properties of resins cured with methyl hexahydrophthalic anhydride were examined and compared to those of a conventional o‐cresol novolak epoxy resin (EOCN 1020). This new epoxy resin gives a cured resin with higher flexibility, compared to the conventional one.
Graft copolymerization of methyl methacrylate onto modified plantain pulp in the presence of ceric ions
Authors: Okieimen Felix E. , Uroghide Isaiah N. 
Published: April 2003

AbstractPlantain pulp was modified by treatment with allyl chloride in diisopropyl ether at 60 °C which results in an average degree of substitution of 0.215 allyl chloride moieties per anhydroglucose unit (AGU). Graft copolymerization of methyl methacrylate onto modified and unmodified pulp was carried out at 29 °C using various concentrations of ceric ion initiator. It was found from the dependence of the extent of graft polymer formation on ceric ion concentration that termination of graft polymerization occurred mainly by the interaction of growing graft polymer chains with ceric ion and that the extent of graft polymer formation was markedly enhanced by the modification of the plantain pulp. The effect of isopropanol on the extent of graft polymer formation on the modified material was also examined.
Photooxidation of polyethylene films, 1. Experimental kinetics of functional group formation
Authors: Gugumus F. 
Published: April 2003

AbstractThe variation of the photooxidation of PE‐LD films as a function of film thickness depends heavily on the exposure device used for artificial weathering. Carbonyl development is practically proportional to film thickness if high UV intensity artificial exposure devices are used. With less accelerating devices and on outdoor exposure, only limited increase with film thickness is observed. Then, an appreciable part of total oxidation is restricted to the surface layers. The differences between exposure devices are attributed to the absence of chain reactions in polyethylene with high UV intensity devices. With other accelerating devices and on outdoor exposure, chain reactions occur especially in the surface layers of the films where they involve usually oxidation products.
Photooxidation of polyethylene films, 2. Mechanisms and kinetics of functional group formation
Authors: Gugumus F. 
Published: April 2003

AbstractVarious mechanisms are proposed to explain the formation of the photooxidation products of the PE‐LD films (ketones, carboxylic acids, vinyl groups). The kinetics of product formation are discussed in detail. The experimental results can be explained on the assumption that the rate of ketone formation increases linearly with exposure time. Possible explanations are proposed.
Models for photoinduced processes in polymeric materials
Authors: Blumen Alexander , Roy Apurba Kumar , Schnöurer Horst 
Published: April 2003

AbstractThe article focusses on energy transfer experiments and on photoconductivity measurements in polymeric materials. The results are interpreted in terms of scaling theories; fractals are used to describe the spatial and continuous‐time random walks (CTRW) the temporal disorder. We display some successful applications of scaling ideas and also draw attention to the limitations of the models.
Lichtinduzierte Umorientierung der optischen Achse in LC‐Farbstoff‐Copolymeren
Authors: Endres Bernhard , Krieg Manfred , Omeis Jürgen , Rau Norbert 
Published: April 2003

AbstractUntersucht wird der Einfluß von linear und zirkular polarisiertem Licht auf den Ordnungszustand von nematischen Farbstoff‐ Copolymeren. Am Beispiel eines Modellsystems wird gezeigt, daß mit linear polarisiertem Licht die optische Vorzugsachse dieser Systeme gezielt reorientiert werden kann. Die Untersuchungen zeigen, daß der Isomerisierungszyklus des Azofarbstoffes für diese Eigenschaft des Materials verantwortlich ist Nach Bestrahlen der Probe mit zirkular polarisiertem Licht wird für das Polymere das gleiche Transmissionsverhalten beobachtet. Wie es auch selektivreflektierende Materialien, z. B. cholesterische Flüssigkristalle, aufweisen.
HERSTELLUNG VON MIKROSTRUKTURPRODUKTEN DURCH TIEFENLITHOGRAFIE UND SPRITZGUSS
Authors: Götz F. , Ehrfeld W. 
Published: April 2003

AbstractFor fabricating microstructures with extreme structural heights a technology has been developed which is based on deep‐etch lithography and subsequent replication processes. A particularly high precision is achieved if the lithographic process is carried out by means of synchrotron radiation. Electroforming and molding processes are used for the replication of microstructures from a large variety of materials. The field of application comprises micromechanics, microoptics, electrical and optical microconnectors as well as sensors and actuators.
OPTISCHE UND ELEKTRO‐OPTISCHB SCHALTPROZESSB IN POLYMEREN FLÜSSIGKRISTALLEN
Authors: Birenheide R. , Wendorff J. H. 
Published: April 2003

AbstractLow molar mass and polymeric liquid crystals display extremely large electro‐optical and nonlinear optical responses, due to a combination of orientational long range order and fluidity. These responses are controlled on the one hand by the intrinsic anisotropic dielectric and optical properties of these phases and on the other hand by their peculiar curvature elastic and viscous properties.Polymeric liquid crystals, although having the disadvantage of longer response times, offer the advantage that the liquid crystalline state and any modulation imposed on it can be frozen in a glassy state. Polymeric liquid crystals can thus be used in various applications related to the control of light propagation, optical information storage and the manufacturing of holographic optical elements.
Blends of bismaleimide resins and bis(allyl phenyl) esters
Authors: Varma I. K. , Gupta S. P. , Varma D. S. 
Published: April 2003

AbstractThe effect of reactive diluents such as bis(4‐allyl 2‐methoxyphenyl) adipate (AEg), bis(4‐allyl 2‐methoxyphenyl) terephthalate (TEg), and bis(o‐allyl phenyl) sebacate (APS) on curing characteristics and thermal behaviour of bis(4‐maleimidophenyl) methane (BM) chain‐extended with 4,4′‐diaminodiphenyl methane (DADPM) is described. Samples containing 5, 10, 15, 20, 25, 35, and 45 wt.‐% of these reactive diluents and bismaleimide resin were prepared. Addition of APS, AEg, and TEg affected the curing exotherm of bismaleimides. The thermal stability of bismaleimide decreased on addition of APS or AEg, but in presence of TEg an improvement in char yield at 800°C was observed. Glass fibre reinforced laminates fabricated from bismaleimide resin containing 10% APS exhibited interlaminar shear strength of 20.8 N/mm2 and flexural strength of 541 N/mm2.
Composites of furfuryl alcohol‐formaldehyde resins and olive stones for production of activated carbons
Authors: Simitzis Johannis 
Published: April 2003

AbstractComposites based on resin of furfuryl alcohol‐formaldehyde or poly(furfuryl alcohol) and olive stones (pressed and extracted as received from industrial production) were cured as small cylinders and then pyrolyzed. The pyrolysis was studied by thermogravimetric analysis up to ∼︁ 1000°C and by FTIR‐spectroscopy for the initial composites and their pyrolysis residues up to 500°C. The specific surface areas of the carbonaceous residues and their discoloring ability for dyes of methylene blue and alizarin yellow were determined. The results are interpreted and discussed under the aspects of the pyrolysis process and the new carbonaceous materials produced. The usage of olive stones in mixture with resins based on furfuryl alcohol is more advantageous (e. g. leading to higher adsorption of the dyes) than the usage of the resin alone.
Application de l'impédancemétrie électrique à l'étude de la réticulation d'un adhésif en film. Cas d'un assemblage métal/métal
Authors: Bourahla Hamid , Lenoir Jeanine , Romand Maurice 
Published: April 2003

AbstractSous l'action d'un traitement thermique, la réticulation d'un adhésif en film s'accompagne d'une variation des propriétés rhéologiques et électriques de la résine. L'intérêt des mesures non destructives d'impédance électrique est de permettre de suivre en continu la réticulation, de déterminer en particulier le début et la fin du mouillage, le point de gélification et la fin de la réticulation du film d'adhésif (FM 96) utilisé en vue d'élaborer un joint collé métal/métal (acier inoxydable 22 CN 18‐10). L'influence de la température et de la durée de réticulation est également mise en évidence. Aprés un second balayage en température, les diagrammes d'impédance sont caractéristiques de l'existence d'un reéiculat polyphasé. Ces résultats sont confirmés par analyse thermique (DSC et DTMA).
Charakterisierung von vernetzten polymeren mittels verdampfungsanalyse, 8. Feinporige adsorberpolymere auf polystyrolbasis
Authors: Häusler Karl‐Georg , Bischof Gert Jürgen , Popov Georgi , Feistel Lothar , Schwachula Gerhard 
Published: April 2003

AbstractErgebnisse aus Verdampfungsanalyse und Quecksilberporosimetrie zeigen bei feinporigen Adsorberpolymeren auf Polystyrolbasis des Typs Wofatit Y 77 signifikante Unterschiede des Porenvolumens. Der Vergleich der beiden Werte ermöglicht die Bestimmung des Beitrages der Mikroporen zum Gesamtporenvolumen. Darüber hinaus ermöglicht diese einfache Methode die Bestimmung des Quellungsgrades der Polymermatrix.
Copolymerization of alkyl α‐chloroacrylates with methyl methacrylate
Authors: Pathak C. P. 
Published: April 2003

AbstractHexyl α‐chloroacrylate (HCA) and cyclohexyl α‐chloroacrylate (CCA) have been copolymerized with methyl methacrylate (MMA) in toluene at 55°C using azobisisobutyronitrile (AIBN) as initiator. Copolymer compositions have been determined both by 1H NMR and elemental analyses. For copolymerization of MMA (M1) with HCA (M2), the reactivity ratios (RR) are r1 = 0.47 ± 0.19 and r2 = 0.81 ± 0.51 and with CCA the values are r1 = 0.76 ± 0.31 and r2 = 2.30 ± 1.73. Thermal properties of these copolymers have also been investigated.
Effects of processing variables on the mechanical properties of compression molded polystyrene‐wood fiber composites
Authors: Sean Sy Trek , Sanschagrin Bernard , Kokta Bohuslav V. , Maldas Debesh 
Published: April 2003

AbstractOptimization of mixing and molding conditions (e.g. temperature, time and pressure) of aspen chemithermomechanical pulp (CTMP)‐polystyrene composites was carried out. Compounding conditions showed a substantial effect on the mechanical properties of the composites. The effect of fiber encapsulation with polystyrene on the mechanical properties of the composites was also evaluated. Compared to non‐encapsulated ones, the mechanical properties of composites showed superior results when encapsulated CTMP fibers were used. After encapsulation of wood fibers, and optimization of mixing and molding conditions, composites with up to 36% of fiber volume fraction could be incorporated in polystyrene with improved mechanical properties.
Charakterisierung der stabilität von modifizierten polypropylen‐glasfaser‐verbunden nach thermo‐ und photooxidation
Authors: Peter Ralf , Mäder Edith , Rätzsch Manfred , Kovářova Jana , Rotschová Jitka , Pospíšil Jan 
Published: April 2003

AbstractHomopolymerisat und verschieden chemisch modifiziertes Polypropylen wurden für die Compoundierung mit Glasfasern unter Anwendung verschiedener Stabilisierungsvarianten im Hinblick auf ihre thermo‐ und photooxidative Beständigkeit charakterisiert. Zur Untersuchung der thermooxidativen Stabilität der Polymer‐Compounds wurde die direkte Messung der Sauerstoffabsorption angewendet. Die durch die thermischen Oxidationsprozesse hervorgerufenen Veränderungen in der Zähigkeit und im Dehnungsverhalten wurden durch den Schlagbiege‐ und den Zugversuch charakterisiert. Die durch die Photoalterung hervorgerufenen Veränderungen wurden IR‐spektroskopisch verfolgt. Die Untersuchungsergebnisse werden hinsichtlich des Einflusses von Stabilisatorsystem, Modifikator und Glasfasern diskutiert.Demnach weisen die mit 0,10% BHT, 0,30% DSTP, 0,05% Irganox 1010 und 0,25% Tinuvin 770 stabilisierten Compounds im Ausgangszustand und nach kurzen Alterungszeiten die beste thermooxidative und mechanische Beständigkeit auf. Dieser Effekt verliert sich mit zunehmender Alterungsdauer. Bezüglich des Modifikators zeigen die mit einem Gemisch aus Acrylsäure und Maleinsäureanhydrid im Verhältnis 5:1 modifizierten Proben thermooxidativ und mechanisch das beste Verhalten, photooxidativ dagegen das schlechteste. Reiner Maleinsäureanhydrid‐Modifikator führt zu einer deutlichen Verschlechterung des thermooxidativen und mechanischen Verhaltens, die UV‐Beständigkeit wird im Vergleich zu unmodifizierten Proben nicht beeinflußt. Die Glasfasern bewirken eine deutliche Verbesserung der Verbundeigenschaften — vor allem bei Einsatz eines Modifikators —, eine signifikante Retardierung des Thermooxidationsverlaufes sowie eine Erniedrigung der Photostabilität, wobei der letztere Einfluß nicht eindeutig ist.
Heterogeneous functionalizing of polysulfone membranes
Authors: Breitbach Ludger , Hinke Ekkehard , Staude Eberhard 
Published: April 2003

AbstractIn recent years efforts have been increased to work with more intelligent membranes which render more than normal filtration properties. Thus, membranes have been prepared using chemically modified polymers or have been furnished with additives in order to increase their selectivity and/or special sorbing capabilities. In this paper, methods are described how commercially available polysulfone membranes can be functionalized by chemical reactions without disintegrating their mechanical properties. For this purpose, Sulfonation, chloromethylation, aminomethylation, and lithiation reactions were applied. A broad spectrum for further conversions modified membranes is opened by these chemical reactions which allow an individual fitting of the membranes with special substitutes. The chemical reactions and the analytical procedures are also described.
A DSC investigation on the stabilizer distribution in PVC blends
Authors: Braun Dietrich , Eidam Norbert , Kömmerling Stefan 
Published: April 2003

AbstractThe distribution of a liquid organotin stabilizer between the phases of heterogeneous poly(vinyl chloride) (PVC) blends has been studied by differential scanning calorimetry (DSC). This method can be used even at low stabilizer concentrations. At concentrations > 1 wt.‐% the stabilizer can be detected in both phases of a PVC/SAN (poly(vinyl chloride)/poly(styrene‐co‐acrylonitrile)) blend. At lower concentrations no stabilizer could be found in the SAN phase. Determination of the induction period of thermal degradation at 180°C under nitrogen atmosphere showed no loss of thermal stability for blends containing the stabilizer partly in the SAN phase. Kinetic measurements with the DSC indicate a migration of the stabilizer out of the SAN phase, PVC/PMA (poly(vinyl chloride)/poly(methyl acrylate)) blends showed no solubility of the stabilizer in the soft PMA phase.
Durch Matrixmodifizierung und Zusatzstoffe zu Polyesterverbunden mit speziellen Eigenschaften
Authors: Bledzki Andrzej K. , Jakobi Rolf 
Published: April 2003

AbstractUngesättigte Polyester ergeben durch Modifizierung der Harzkomponente oder durch Additive Werkstoffe mit einem breiten Eigenschaftsprofil. Die mechanischen Werte sind durch chemische Modifikation der Polymerkette oder durch kautschukartige Additive gezielt einstellbar. Antistatische Eigenschaften und elektrische Leitfahigkeit lassen sich durch Zugabe von Rußen, Graphit oder metallischen Füllstoffen erreichen. Gleichzeitig kann auch die Wärmeleitfähigkeit beeinflußt werden. Andere Füllstoffe verbessern das Reibungs‐ und Verschleißverhalten oder können bei Zugabe von Mikrohohlkugeln zu deutlicher Gewichtsverminderung führen. Die gezielte Veränderung der Eigenschaften trägt wesentlich zum Einhalten erhöhter Sicherheitsanforderungen bei.
NEUE VERARBEITUNGSMETHODEN FÜR RIESELFÄHIGE DUROPLASTE
Authors: Braun U. 
Published: April 2003

AbstractDuroplastische Formmassen werden nach konventionellen Verfahren der Kunststofformgebung wie Formpressen und Spritzgießen bzw. deren Varianten Spritzpressen und Spritzprägen verarbeitet. Wie in anderen Industriezweigen hat auch hier der wachsende Kostendruck zu einer steten Weiterentwicklung dieser Verfahren geführt. Über erfolgreiche Verfahrensverbesserungen zur Reduzierung der Herstellkosten wird im folgenden berichtet.Die Einführung der Spritzgießverarbeitung für Duroplaste in den 60er Jahren bedeutete gegenüber der bis dahin ausschließlich betriebenen Preßverarbeitung einen erheblichen Rationalisierungsschritt. Die Zykluszeiten ließen sich durch das Aufschmelzen der Formmasse in der Plastifiziereinheit sowie durch das Einbringen von Friktionswärme beim Einspritzvorgang erheblich reduzieren. Heute erlebt die Preßverarbeitung eine Renaissance insbesondere dann, wenn es gilt, hochpräzise Formteile mit minimaler Schwindung und geringstem Verzug herzustellen. Durch Rundtischautomaten, Vorplastifiziergeräte und Entnahmegeräte ließen sich die wirtschaftlichen Nachteile der klassischen Preßverarbeitung weitgehend kompensieren.
Radikalbildung aus Hydroperoxiden in Gegenwart starker Säuren
Authors: Dulog Lothar , Höfer Hans‐Joachim , Schober Hans‐Jörg 
Published: April 2003

AbstractThe polymerisation of styrene and methylacrylate initiated by hydroperoxides is accelerated in the presence of strong acids such as sulfuric acid, p‐toluene‐sulfonic acid or perchloric acid. By copolymerising styrene and methylmethacrylate and by phenolic type inhibitors the radical nature of the catalytic effect of the acid was proved. Kinetic experiments demonstrated the acid involvement in the starting reaction.
2H‐NMR relaxation studies of reactive intramolecularly crosslinked macromolecules
Authors: Bauer H. , Müller K. , Kothe G. , Funke W. 
Published: April 2003

AbstractSelectively deuterated intramolecularly crosslinked macromolecules were studied by dynamic 2H NMR spectroscopy. By performing various relaxation experiments detailed information about the molecular mobility of the various components of the polymer chains could be obtained. In particular, the NMR investigations revealed significant effects of molar mass or degree of isomerization on the motional characteristics.