bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modell zur beschreibung der glasübergangstemperaturen binärer und ternärer mischungen von poly(styrol‐co‐n‐butylmethacrylat)en
Authors: Schellenberg Jürgen 
Published: April 2003

AbstractDie Glasübergangstemperaturen binärer und ternärer Mischungen chemisch einheitlicher Poly(styrol‐co‐n‐butylmethacrylat)e mit einem mittleren n‐Butylmethacrylat‐Anteil von 30,8 Gew.‐% und unterschiedlichen zahlenmittleren Molmassen im Bereich von 4900 bis 67000 g/mol wurden in Abhängigkeit von der Zusammensetzung untersucht. Es wurden wesentliche Abweichungen vom idealen Verhalten bezüglich einer linearen Abhängigkeit zwischen Glasübergangstemperatur und Zusammensetzung festgestellt.Dieses Verhalten konnte mit einem mathematischen Modell dargestellt werden, wobei sich insbesondere Polynome zur Beschreibung der teilweise über den Werten der Ausgangskomponenten liegenden Glasübergangstemperaturen der Mischungen als geeignet erwiesen. Schließlich wurden verschiedene Ursachen für diese Abweichungen diskutiert, wobei offensichtlich energetische Wechselwirkungen verbunden mit einer Nichtadditivität der Volumina von wesentlicher Bedeutung sind.
Stabilizer consumption and lifetime prediction in ageing of crosslinked polyethylene
Authors: Audouin L. , Langlois V. , Verdu J. , Rouyer E. 
Published: April 2003

AbstractThe thermal oxidation of β ray‐crosslinked polyethylene (XLPE) was studied in temperatures ranging from 90 to 180°C. Various analytical methods were used for determination of an end of the induction period on bulk samples: gravimetry, ultimate tensile properties, density and color change. On microtome slices of ∼30 μm thickness the depth distribution of oxidation products, phenolic antioxidant, density and tensile ultimate properties were followed as a function of exposure time by respectively IR and UV spectrophotometry, densitometry and Microfoil Tensile Testing.Depending on the testing method different durations of induction period (DIP) were obtained. They increase in following order:Phenol depletion < Ultimate elongation < Density < Carbonyl build‐up ≤ Color change < Weight loss.The difference between phenol depletion DIP and carbonyl build‐up DIP can be considered as negligible at temperatures higher than the melting point (about 30%) but it reachs more than 100% at T< Tm.Different kinetic regimes of phenol consumption were observed depending on the exposure temperature. A mechanistic interpretation is proposed explaining the role of the stabilizer system in initially homogeneous and later heterogeneous oxidation of the bulk material.The Arrhenius law was applied to different durations of induction period. A discontinuity appeared in the melting point region (120–130°C) which is tentatively interpreted in terms of different stabilizer concentration in amorphous phase of semicrystalline material (T < Tm) and in melt material (T > Tm). On the basis of the presented complex study of polyethylene thermo‐oxidation, different aspects of lifetime predictions are discussed.
New trends in epr and epr kinetics studies in the stabilization mechanism by N‐oxyl radicals
Authors: Faucitano A. , Buttafava A. , Mongini G. , Martinotti F. , Berzero A. , Greci L. , Mar'in A. , Neri C. , Farris R. 
Published: April 2003

AbstractThe mechanism of the solid state oxidation of isotactic polypropylene films and the the mechanism of inhibition by HALS have been investigated by kinetic‐ESR and kinetic modelling with derivation of the rate constants for the sensitive steps in the reaction scheme. The results have shown the inadequacy of the Denisov cycle to account for the observed experimental kinetics of the intermediate nitroxyl radicals. The molecular dynamics associated with the oxidation inhibited by HALS in the polypropylene matrix has been investigated by applying the Liouville stochastic method to the analysis of the temperature effects of the ESR spectra of the intermediate nitroxyl radicals used as spin probes. The investigation on the nature and characteristics of the molecular motions available at the oxidation sites has also been carried out with nitroxyl spin labels bound to the PP chains. For this application a novel method of spin labelling was developed based on reactions with some of the oxidation products, namely the terminal and intrachain ketones (keana method), alcohols, peroxides and macroalkyl radicals.
Model studies on the mechanism of hals stabilization
Authors: Step Eugene N. , Turro Nicholas J. , Klemchuk Peter P. , Gande Matthew E. 
Published: April 2003

AbstractHindered Amine Light Stabilizers (HALS) are know to inhibit the photo‐oxidation of polymers. A key reaction in their stabilization mechanism is believed to be the conversion of a hindered aminoether into a nitroxyl radical. Several different possible mechanisms for this conversion were explored. One, the elimination of the aminoether to form an olefin and hydroxylamine (an intermediate in the formation of a nitroxyl), while possible at high temperatures, cannot account for the inhibitory activity we observed for secondary and primary aminoethers. Direct radical displacement by peroxy radicals was also considered. However, the products predicted by this reaction pathway were not observed. Finally, oxidation of the nitrogen by a peroxy radical, by either electron transfer or a radical attack on the nitrogen, was investigated. While electron transfer was shown to be unlikely, direct oxidation of the aminoether nitrogen was supported by our results. A detailed mechanism for the reaction of both alkyl‐ and acyl‐peroxy radicals with aminoethers is proposed.
FT‐IR emission studies of polymer oxidation
Authors: George G. A. , Vassallo A. M. , Cole‐Clarke P. A. , Celina M. 
Published: April 2003

AbstractThe theory and application of mid‐IR emission spectroscopy to the study of the oxidation of single reactor particles of unstabilized polypropylene (0.4 to 40μg) is described. The rate of formation of carbonyl and γ‐lactone oxidation products is followed by FT‐IR emission at 150°C and is interpreted within a heterogeneous model of solid state oxidation. The results are compared with the reported chemiluminescence from single polypropylene particles and evidence is presented for concerted oxidation when the particles are in close proximity.
Thermohydrolytic ageing of polynadimide IP960
Authors: Hilaire B. , Verdu J. 
Published: April 2003

AbstractThis study deals with the thermal ageing of a polynadimide matrix IP 960, developed for composite aircraft applications in the 250 −300°C temperature range. In a first chapter, it is tried to give a suitable representation of the network structure on the basis of literature data, analytical results and rubbery modulus measurements. Ageing in air at 300 −360°C is then studied. The role of diffusion control of degradation kinetics is shown from comparison of samples of various volume/surface ratios. The crucial role of sorbed water is put in evidence. Ageing in vacuum at 360°C allows to reveal the existence of at least three kinetics steps. The corresponding degradation mechanisms are discussed. Chemical (NMR, FTIR, UV) as physical (weight loss, water sorption or mechanical testing) are used to quantify the sample degradation.
Sulfonated polysulfone membranes with antifouling activity
Authors: Poźniak Gryzelda , Bryjak Marek , Trochimczuk Witold 
Published: April 2003

AbstractThe protein fouling phenomenon was investigated on modified polysulfone ultrafiltration membranes. The sulfonation degree was correlated to the extent of deposition of bovine serum albumin. It was shown that membranes prepared from modified polysulfone were less fouled than their off‐charge analogues. The fouling phenomenon was also investigated for membranes prepared from co‐cast blends. It was demonstrated that blends containing more than 50 wt.‐% of sulfonated derivative behaved like a membrane from pure sulfonated polysulfone. The effect was attributed to surface separation of polymers and formation of surfaces enriched with sulfonic groups.
Synthesis and characterization of UV curable acrylated urethane prepolymers, II. Effects of various diacrylates as diluents and relative humidity on mechanical properties of TDI/PEG/HEMA‐based polymeric films
Authors: Yildiz Emel , Güngör Atilla , Yildirim Hüseyin , Baysal Bahattin M. 
Published: April 2003

AbstractVarious UV‐curable acrylated urethane prepolymers based on tolylene‐2,4‐diisocyanate (TDI), poly(ethylene glycol) (PEG 400), and 2‐hydroxyethyl methacrylate (HEMA) were synthesized. The effects of reactive diluent types, the composition of the products and of different humidity conditions on mechanical properties of cured films were investigated. Effects of diethylene glycol diacrylate (DEGDA) and thiodiethylene glycol diacrylate (TDGDA) as reactive diluents on tensile strength, elongation and Young's modulus values of the UV cured films were examined systematically. The results show that the increase of relative humidity from 50 to 95% leads to a decrease in tensile strength and Young's modulus values of polymeric films. The decrease of these mechanical properties in high relative humidity is due to the formation of hydrogen bonding in the polymer chain caused by water molecules.
Photovieillissement d'un copolymère d'éthylène et d'acétate de vinyle en présence de sueur artificielle. I. Analyse de i'évolution chimique au voisinage des faces altérées
Authors: Rigny‐Bourgeois V. , Dubois C. , Mercier M.‐F. , Chambaudet A. 
Published: April 2003

AbstractUne cellule de photovieillissement artificiel et accéléré est aménagée pour étudier le comportement de polyméres, en présence de sueur artificielle. Un copolymére d'éthyléne et d'acétate de vinyle (EVA) est soumis à un photoviellissement dans cette cellule. Parallélement, le photovieillissement est réalisé sans sueur artificielle afin de comprendre le rôle de ce substrat. Des études similaires sont également conduites sur cet EVA contenant des stabilisants lumière.L'évolution chimique est suivie par spectrométrie IR‐ATR au voisinage des surfaces directement irradiées ou immergées. La comparaison des résultats obtenus selon les différentes voies fait principalement ressortir une combinaison des effets de la photooxydation et de l'hydrolyse, l'activation de l'hydrolyse par l'irradiation et l'action efficace des stabilisants lumière vis à vis de la photooxydation.
Unsaturated alcohols and glycols containing ionizable groups for synthesis of urethane acrylate graft copolymer latices
Authors: Saija Leo M. , Umiński Maciej 
Published: April 2003

AbstractUnsaturated alcohols and glycols bearing carboxylic groups were synthesized from maleic anhydride (MA) and alcohols with 2 or 3 hydroxy groups. The halfester monomers were characterized by IR and NMR spectroscopy and were used for the preparation of urethane macroionomers and urethane acrylate graft copolymer latices. Obtained polymers were characterized by solubility and mechanical tests.
Zur bildung von polyepoxid‐polyamid‐netzwerken. Modelluntersuchungen am system phenylglycidether‐ε‐caprolactam
Authors: Tänzer Wolfram , Ludwig Ina 
Published: April 2003

AbstractEs wurden Versuche zur Homopolymerisation von ε‐Caprolactam (CL) und Phenylglycidether (PGE) mit den Initiator/Beschleuniger‐Systemen Na‐Caprolactam/N‐Acetylcaprolactam (NaCL/AcCL) und Na‐Caprolactam/N‐Acetylimidazol (NaCL/AcImi) durchgeführt, um die für eine mögliche Copolymerisation von CL und PGE geeigneten Reaktionsbedingungen zu ermitteln. CL und PGE wurden in unterschiedlichen molaren Verhältnissen (CL : PGE = 1 : 5 bis 1 : 0,05) und bei Temperaturen zwischen 100°C und 140°C (max. 240°C) in einer Eintopfreaktion polymerisiert.Die löslichen Produkte wurden mittels HPLC getrennt und spektroskopisch identifiziert. Die in Aceton unlöslichen Produkte wurden mit IR‐ und NMR‐Spektroskopie, Massenspektrometrie (MS) und Elementaranalyse untersucht.
Characteristics of permeation and separation of aqueous alcoholic solutions through a poly[bis(2,2,2‐trifluoroethoxy)phosphazene] membrane by evapomeation and pervaporation
Authors: Uragami Tadashi , Morikawa Takeshi 
Published: April 2003

AbstractThe characteristics of permeation and separation for aqueous solutions of methanol and ethanol through a poly[bis(2,2,2‐trifluoroethoxy)phosphazene] (PBTFP) membrane were studied by pervaporation and evapomeation. In pervaporation technique, methanol was preferentially permeated in all of the feed solution compositions and ethanol was permeated in lower ethanol concentrations of the feed solution. Water was predominantly permeated from the feed solutions with higher ethanol concentration. In evapomeation technique, water was selectively permeated in both all of the feed vapor compositions for aqueous methanol and ethanol solutions. These different permselectivities depended on the feed composition and the membrane permeation technique and could be discussed by a difference in the mechanisms of permeation and separation. It was found that the permeation rate was influenced remarkably by the degree of swelling of the PBTFP membrane and the permselectivity for water of aqueous alcoholic solutions was enhanced by an increasing degree of swelling of the membrane. When the degree of swelling of the membrane with rising permeation temperature was small, both the permeation rate and permselectivity for alcohol in pervaporation and evapomeation increased with the permeation temperature. The above results are discussed considering the PBTFP membrane structure in evapomeation and pervaporation.
Homogeneity of styrene‐maleic anhydride‐methyl methacrylate terpolymers in batch polymerization processes
Authors: Szirmai László 
Published: April 2003

AbstractThe formation of styrene‐maleic anhydride‐methyl methacrylate terpolymers was studied in batch polymerization process. The process of polymerization was investigated in quasi‐steady‐state time periods by the Markov statistics. The results of the calculations for high conversions were compared with the experimental results. Based on the advantage of the method, PVC blends were produced which (with 40% of blend component) increased the Vicat‐A and Vicat‐B heat‐resistance of PVC by 40–43°C and 18–21°C, respectively.
Structural investigations on low‐molecular‐weight polyisobutenes
Authors: Günther Wolfgang , Maenz Karsten , Stadermann Dietmar 
Published: April 2003

AbstractStructural investigations of low‐molecular‐weight polyisobutenes synthesized by selective polymerization and of commercial polyisobutenes were made by 1H‐ and 13C‐NMR spectroscopy. It is possible to attribute the signals to “normal” and to some unusual olefinic structures. A comparison was made to literature data.
A novel process for the chlorination of polymers in solution
Authors: Friese K. , Hößelbarth B. , Reinhardt J. , Newe R. 
Published: April 2003

AbstractA new uniform process for the solution chlorination of PVC, PE, and natural rubber has been developed with initiation by γ‐irradiation or radical initiators (azocompounds). The solvent used is dichloromethane instead of the industrially used tetrachloroethane or tetrachloromethane. The reaction is carried out in an autoclave with stirrer at temperatures between 70 and 100°C and pressures from 4 to 7 bar. As a result of the simultaneous chlorination of the solvent, trichloromethane is formed and only less than 1 wt.‐% tetrachloromethane. Characterization of the chlorinated polymers by DSC and NMR measurements showed no differences to conventionally chlorinated products.
Kinetik der polykondensation von natriumsulfidhydrat und 1,4‐dichlorbenzol zu poly(thio‐1,4‐phenylen)
Authors: Dauben Michael , Platkowski Kristina , Reichert Karl‐Heinz 
Published: April 2003

AbstractDie Kinetik der Polykondensation von Natriumsulfidhydrat und 1,4‐Dichlorbenzol in 1‐Methyl‐2‐pyrrolidon zu PolyphenylensulfidSystematischer Name: Poly(thio‐1,4‐phenylen).
im Temperaturbereich von 220 bis 280°C wurde mit Differential Scanning Calorimetry untersucht. Es wurde festgestellt, daß die Polykondensation autokatalytisch verläuft, wobei die Kinetik mit Modellansätzen einfacher Form über nahezu den gesamten Umsatzbereich gut beschrieben werden kann. In allen Fällen haben sich Gesamtreaktionsordnungen von etwa eins als optimal für die Anpassung der Geschwindigkeits‐Umsatz‐Verläufe erwiesen. Dieses wird mit der Tatsache erklärt, daß Natriumsulfid im untersuchten Temperaturbereich nur in geringen Mengen in komplexierter Form in 1‐Methyl‐2‐pyrrolidon löslich ist und dessen Konzentration näherungsweise als zeitlich konstant angesehen werden kann. Der autokatalytische Effekt wird erklärt mit der Zunahme der Geschwindigkeitskonstanten im Anfangsbereich der Polykondensation, wobei als Ursache hierfür eine wachsende Reaktivität der Oligomeren mit der Kettenlänge angenommen wird. Mittels stochastischer Methoden können Zahlen‐ und Massenmittelwert des Polykondensationsgrades der während des Reaktionsprozesses entstehenden Produkte modelliert werden. Dabei wird von einem einfachen Modell mit zwei verschiedenen Geschwindigkeitskonstanten im Kondensationsgeschehen ausgegangen. Für eine befriedigende Beschreibung der Molmassen muß die Konzentration von Natriumsulfid in der reaktiven Phase über nahezu den gesamten Umsatzbereich als konstant angesehen werden, wobei sie etwa 2–5% des Wertes der Dichlorbenzol‐Konzentration zu Reaktionsbeginn beträgt.
Synthesis and characterization of poly(vinyl alcohol)‐β‐cyclodextrin copolymer
Authors: Sreenivasan K. 
Published: April 2003

AbstractA poly(vinyl alcohol)‐β‐cyclodextrin (PVA‐BCD) copolymer was prepared by successive reaction of BCD with toluylene diisocyanate and PVA. Copolymer formation was evidenced by infrared spectroscopy, differential scanning calorimetry and gel permeation chromatography. Scanning electron micrographs show morphological differences between PVA and the copolymer. The copolymer, being almost insoluble in common solvents with an equilibrium swelling in water of 50%, is a potential membrane material.
Study on electrorheological properties of semiconducting polyaniline‐based suspensions
Authors: Xie Hong‐Quan , Guan Jian‐Guo 
Published: April 2003

AbstractElectrorheological (ER) fluids composed of a dispersing medium with a low dielectric constant and polyaniline particles, deprotonated with ammonia or sodium hydroxide at different concentrations for 24 h were studied. The effects of dielectric constant, conductivity and volume fraction of the polyaniline particles, the kind of dispersing medium, addition of surfactant, as well as the electric field strength and temperature on the ER properties of the ER fluids were investigated. The results showed that a moisture‐insensitive, highly ER‐active fluid can be obtained from chlorinated paraffin oil and polyaniline particles deprotonated with ammonia water at certain pH values and exhibited a static yield stress > 10 kPa and current density < 40 μA cm−2 at 2.8 kV mm−1 DC electric field.
Pultruded fiber‐reinforced polyurethane‐toughened phenolic resin, I. Reactivity and morphology
Authors: Wu Hew‐Der , Ma Chen‐Chi M. , Lee Ming‐Shiu , Wu Yin‐Don 
Published: April 2003

AbstractA phenolic resin/polyurethane copolymer was synthesized by reaction of a phenolic resin, a blocked‐polyurethane and p‐toluene sulfonic acid. The copolymer provides a good balance between the processability (including pot life, reactivity) and toughness. The reactions that proceeded during the synthesis of the copolymer was investigated by IR spectroscopy. It was found that blocked polyurethane reacted with the hydroxy group of the phenolic resin. Glass fiber‐reinforced composites showed excellent bonding between fiber and matrix as revealed by SEM photographs. An overlap peak was found from the DMA diagram; it indicated that an interaction existed between phenolic resin and polyurethane and that improved the toughness of the phenolic resin.
Wasserabsorptionseigenschaften natürlicher polyionenkomplexe
Authors: Ichikawa Tomoko , Nakajima Toshinari 
Published: April 2003

AbstractDie Wasserabsorptionseigenschaften natürlicher Makromoleküle, die als kationische Aminogruppen das Polysaccharid Chitosan oder das Polypeptid Polylysin und als anionische Carboxygruppen das Polysaccharid Carboxymethylcellulose oder das Polypeptid Polyglutaminsäure (PGA) enthalten, wurden untersucht. Bei Kombinationen von Polysacchariden oder Polyaminosäuren untereinander zeigten Gemische mit einem Ionenverhältnis von 1 : 1 die geringste durch Wasser hervorgerufene Quellung. Demgegenüber fand sich im Falle von Chitosan/PGA‐Gemischen bei Zusammensetzungen mit PGA‐Überschuß ein Minimalwert, während die Polyaminosäuren eine strukturell verhältnismäßig freie räumliche Anordnung einnahmen.Durch Vergleiche der durch DSC‐Analyse bestimmten Enthalpien wurde bestätigt, daß die Komplexe mit Pyranose‐Ringstrukturen enthaltenden Filmkomponenten größere Mengen Wasser in Form von nicht ausfrierbarem Wasser halten können. Ferner ergab ein Vergleich der mechanischen Festkörpereigenschaften, daß sich bei Zusammensetzungen der Komplexe mit großen Mengen an Polysacchariden eine Tendenz zu einem erhöhten Elastizitätsmodul zeigt.
Surface modification of synthetic fibers by excimer laser irradiation
Authors: Watanabe Hirosuke , Takata Tadahiko 
Published: April 2003

AbstractIt was attempted to improve the fiber/rubber adhesion by surface modification of fibers by excimer laser irradiation. The fibers were first treated with a glycidyl ether acrylate compound which is sensitive to UV rays, then cured with a KrF laser and treated with an ordinary RFL (resorcinol formalin rubber latex), and then cured in heat. For poly(ethylene terephthalate) (PET) and poly(p‐phenylene‐3,4′‐oxydiphenylene terephthalamide) (PPODPTA) fibers, the adhesion performances were improved, whereas for poly(p‐phenylene terephthalamide) (PPTA) fibers they were not. In PET fibers, the surface layer was converted into the amorphous state, and therefore the affinities for the treating agents were enhanced. As for the aramid fibers, the copolymer components of the PPODPTA fibers contain crystalline domains, independently, which are oriented sufficiently, leaving almost no amorphous state in which molecules remain relaxed, and are difficult to be fibrillated. On the other hand, the PPTA fibers comprise a skin layer and a core layer composed of fibrils stacked into blocks. Between the blocks, amorphous phases containing a relatively large number of molecular chain ends are present, facilitating the fibrillation. Probably, the molecules in the non‐crystalline state of both of the fibers were relaxed differently, causing different susceptibilities to ablation. This might result in different affinities to the acrylate compound, or different adhesion performances, respectively.
The influence of ageing and polymerization conditions on the polymerization of butadiene using a neodymium catalyst system
Authors: Oehme Annekatrin , Gebauer Ulrich , Gehrke Klaus , Lechner M. Dieter 
Published: April 2003

AbstractThe homopolymerization of butadiene in the presence of a rare earth‐containing catalyst system was examined at 60°C. The catalyst system consists of neodymium octanoate, diethylaluminium sesquichloride and triisobutyl aluminium in n‐heptane. This catalyst shows high activity also at low polymerization temperature and yields polymers with a cis‐1,4 content of nearly 99%. The catalyst ageing and the polymerization conditions were varied and the behaviour of molar mass distribution, conversion and microstructure of polymers is illustrated. Attention is focussed on molar mass distribution of cis‐1,4‐polybutadiene samples which can be unimodal or bimodal in dependence on the preparation conditions.