bluuebunny/crossref_metadata_2025_split huggingface dataset:
TRANSPARENTE POLYMERE MEHRPHASENSYSTEME
Authors: Biangardi Harald J. , Sturm Harald , Kostersitz Georg 
Published: April 2003

AbstractUsually two phase polymer blends are not transparent because of differences in the refractive indices of their components and the resulting light scattering. By means of model calculations on the basis of the Mie‐theory, the conditions for transparency in two‐phase polymer blends are investigated. The models used are homogeneous spheres or spheres with a core‐shell morphology imbedded in the polymer matrix. The light scattering of these particles is calculated as a function of diameter, refractive index, wavelength and particlecomposition. Results are presented that show the limits of diameter and difference in the refractive indices between matrix and particle for homogeneous particles to obtain transparency. In the case of large differences in the refractive indices or of large diameters the use of spheres with a core‐shell morphology is favourable. Depending on the refractive indices of the respective phases, there exists an optimal composition of these spheres to obtain transparent polymer‐blends. Another way to transparency is the minimization of light scattering by interparticle interferences, which can be achieved by special types of block‐copolymers.
POYCARBONAT UND LICHT
Authors: Käumpf Günther , Freitag Dieter , Witt Werner 
Published: April 2003

AbstractPolycarbonate (PC) based on 4,4'‐dihydroxydiphenyl‐2,2‐propane has adchieved an outstanding market relevance due to its extraordinary physical and technical properties, especially due to the combination of excellent impact strength and high heat distortion temperature (HDT) combined with good optical and electrical properties.This very attractive balance of properties has led to a broad and still expanding use of PC in different optical application areas. Therefore it has reached a significant importance as a material for glasing (compact sheet and twin wall sheet) and also for optical lenses. For lenses the high refraction index of PC (n = 1,58) and its low density have shown as additional advantages. Recently PC was introduced as a base material for polymeric optical fibers (POF) in the market: Despite its inherently high optical loss (about 800 dB/km at λ = 820 nm) PC has proved as an attractive material because of its high refractive index (cheap cladding, narrow bending radii) and its good HDT (use at relatively high temperatures, e.g. near the engine of automobiles), so far the maximum fiber length will not exceed 30 m.During the last decade PC with extremely high flow and purity became the material of choice for music consumer industry (compact disk: CD) and for optical data storage technology. So far all the CDs were produced worldwide from PC (1988: 450 Mio CD, 1989 about 650 Mio CD). These special PC grades are used for WORM disks (write once read multiple) and EOD disks (erasable optical disks) with diameter up to 13 cm. These disks are still in the phase of market introduction. For disk diameters greater than 13 cm up to 30 cm experimental products with very low birefringence combined with increased stiffness are currently under development (e.g. blends of modified PC with modified SAN).The continuous improvement of the commercial PC grades and the new development of structurely modified PC and special blends based on PC will lead to a further increasing consumption of PC and to further expanding applications of PC especially in the optical market area.
Graft copolymers of starch and poly(ethyl acrylate) dilution effects
Authors: Okieimen Felix E. , Egharevba Felix , Jideonwo Arthur 
Published: April 2003

AbstractGraft copolymerization of ethyl acrylate onto starch initiated by ceric ion in an aqueous medium was studied at 29°C. It was found that the grafting frequencies and molecular weights of grafted poly(ethyl acrylate) changed from 2 graft polymer molecules per 104 anhydroglucose units (AGU) and 3.03 · 105 to 34 and 6.80 · 105, respectively, when the starch content was varied from 1.0 wt.‐% to 0.2 wt.‐%. The influence of dilution of ceric ion on the extent and rate of graft polymerization of ethyl acrylate onto starch was also examined.
Graft copolymerization of 4‐vinylpyridine onto cotton. The ceric ion concentration effect
Authors: Leza M. L. , Casinos I. , Guzmán G. M. 
Published: April 2003

AbstractFor the study of the effect of ceric ammonium nitrate (CAN) initial concentration on the graft copolymerization of 4‐vinylpyridine (4‐VP) onto cotton three series of experiments were carried out. In the first one the CAN concentration was varied from 0.5 to 100 mmol/l and so, parallely, the total nitrate ion concentration. In the other two series the CAN initial concentration was varied, but keeping the total nitrate ion concentration constant at 1.09 and 1.59 M, respectively, by sodium nitrate addition. Increasing the ceric salt concentration the graft yield and total conversion reached a maximum. When the nitrate ion concentration was kept constant the maximum graft yield value was achieved at CAN concentrations lower than when it was varied. However, for all the three series of experiments the maximum graft yield value was nearly the same. The ceric ion consumption increased with increasing initiator concentration. The higher the total nitrate ion concentration, the higher was the ceric ion consumption.
Pervaporation separation of aqueous mixtures using crosslinked poly(vinyl alcohol), I. Characterization of the reaction between PVA and amic acid
Authors: Yeom C. K. , Huang R. Y. M. 
Published: April 2003

AbstractFor the purposes of new membrane material development for pervaporation separation based on crosslinked polyvinyl alcohol (PVA), IR spectroscopy and DSC were used to characterize the crosslinking reaction and the imidization of the (PVA)‐amic acid system. The IR spectra and the thermal analysis were performed on specimens that had been reacted for several different times at 150°C. The crosslinking reaction between the hydroxy groups of PVA and the carboxylic groups of amic acid was faster than the imidization of the amic acid. The best reaction times were about 30 min for the crosslinking reaction and 90 min for the imidization. The effects of the reaction time and the amic acid content on the thermal and mechanical properties have also been investigated.
Effect of frequency and temperature on dielectric properties of polystyrene at microwave frequencies
Authors: Chaki Tapan K. , Khastgir Dipak K. 
Published: April 2003

AbstractAmbient dielectric measurements as functions of frequency in X‐band microwave region have been made on solid samples of polystyrene. Effects of temperature (−120 to +160°C) at three different frequencies have also been studied. The measurement technique applied based on short‐circuited waveguide method of Roberts and von Hippel modified by Dakin and Works for low loss and medium loss samples. Two different types of relaxations are identified originating from main chain motion, wagging, and rotational motions of pendent phenyl group. Intrinsic activation energy for polystyrene molecule, dipole moment per repeat unit, and the average apparent energy of a polystyrene molecule associated with its induced transient dipoles have also been calculated and the data so obtained are explained and compared with standard literature.
Polyurethane‐crosslinked epoxy resins. II. Compatibility and morphology
Authors: Han J. L. , Tseng S. M. , Mai J. H. , Hsieh K. H. 
Published: April 2003

AbstractThe polyurethane(PU)‐crosslinked diglycidyl ether of bisphenol A (DGEBA) was prepared from the reaction of the pendent secondary hydroxy group in DGEBA with the isocyanate‐terminated group present in the PU prepolymer. Though the PU acted as a crosslinking agent for the DGEBA, the morphology and dynamic mechanical behaviour of these PU‐crosslinked DGEBA could be different among themselves depending on the type and molecular weight of polyols employed in the PU. There was no significant shift in the loss modulus (E″) peaks of the DGEBA crosslinked with the polyester‐type and polyether‐type polyurethanes, but the intensity of the E″ peaks increased as the polyester‐type PU employed. The morphology of this polyester‐type PU‐crosslinked DGEBA exhibited a homogeneous one‐phase system, while the DGEBA crosslinked with the polyether‐type PU showed a two‐phase morphology with the PU particles dispersed in DGEBA matrix.
Study of polymer‐polymer complex formation involving phenolic copolymer, non‐ionic polymers, and polyelectrolytes
Authors: Chatterjee S. K. , Ghosh S. , Chatterjee N. 
Published: April 2003

AbstractMulticomponent interpolymer complexes have been prepared by interacting a phenolic copolymer of known composition with several non‐ionic homopolymers, e.g., PVP, PEO, PVA and polyelectrolytes, such as PAA and PEI. The formation of these complexes has been studied by several techniques, such as viscometry, potentiometry, conductometry, and IR spectra. A scheme has been presented to explain the mode of interaction of the various component polymers.
ABA block copolymers without tapering by isokinetic living anionic polymerization in a series of stirred tank reactors
Authors: Hesterwerth D. , Bandermann F. 
Published: April 2003

AbstractEquations for the molecular weight distribution and the average molecular weights of a living anionic polymerization with very rapid or slow initiation are presented for a series of stirred tank reactors. It is shown that polydispersity of the polymer in the last vessel of a cascade takes for nearly complete conversion of monomer then a minimum, when the reaction is performed isokinetically with concern to monomer conversion, i.e. when monomer conversion in each vessel of a cascade of n tanks is 1/n. Now, polydispersity of the polymer in the mth vessel of the cascade (1 ≤ m ≤ n) is Dm = 1 + 1/m. Values of all systems variables needed for isokinetic control of the polymerization may be precalculated from kinetic models. For vessels of equal size and with equal residence times reaction temperature is suggested as control variable increasing stepwise from vessel to vessel. The proposed procedure was checked for the systems styrene/n‐butyllithium/toluene, styrene/s‐butyllithium/benzene, and isoprene/s‐butyllithium/n‐heptane. A satisfying agreement between calculated and measured values of the objectives monomers conversion, number average molecular weight, and polydispersity was found. It is proposed to use the described procedure for the preparation of ABA block copolymers with negligible tapering between the blocks by living anionic polymerization in a series of stirred tank reactors.
Sequences in copolymers studied by high‐mass oligomers in pyrolysis‐field ionization mass spectrometry
Authors: Plage B. , Schulten H.‐R. 
Published: April 2003

AbstractPoly(acrylonitrile), butadiene‐acrylonitrile copolymer, and styrene‐acrylonitrile copolymers with acrylonitrile contents between 8 and 50 mol‐% have been investigated by pyrolysis‐field ionization mass spectrometry. Molecular ions of thermally‐formed oligomers containing up to 16 monomeric subunits were recorded in the mass range 50 to 1200 g/mol. With the butadiene‐acrylonitrile copolymer, the relative abundances of signals due to oligomers with the same total number of monomeric subunits is close to the random distribution of these subunits in the polymers. In contrast, with the styrene‐acrylonitrile copolymers the acrylonitrile contents indicated by relative abundances are too high with all samples. On the other hand, the mass spectra confirm that styrene‐acrylonitrile sequences are more abundant than expected from random distribution of the monomeric subunits, whereas the relative abundances due to oligomers containing styrene‐styrene or acrylonitrile‐acrylonitrile sequences are significantly lower than expected for random systems. These results can be explained by the enhanced stability of styrene‐acrylonitrile diads.
Dibenzoyl peroxide as an initiator of radical polymerizations: Reactions of the benzoyloxy radical with monomers
Authors: Bevington John C. 
Published: April 2003

AbstractExperimental methods for comparing the reactivities of unsaturated substances towards the benzoyloxy radical are considered. Results for various monomers are discussed. It is shown that some substances show high reactivity towards the radical although they do not ordinarily give homopolymers or act as comonomers; they include β‐methylstyrene, stilbene and related substances, and 1.4‐diphenylbuta‐1, 3‐diene.
GEORDNETE EPOXIDNETZWERKE AUS 4‐GLYCIDYLPHENYL‐4‐GLYCIDYL‐BENZOAT und 3‐ BZW. 4‐AMINOPHENYL‐4‐AMINOBENZOAT
Authors: Kirchmeyer Stephan , Karbach Alexander , Müller Hanns‐Peter , Meier Helmut‐Martin , Dhein Rolf 
Published: April 2003

AbstractThe introduction of mesogenic groups in main‐ and sidechains of epoxy thermosets results in an ordered multiphase network with cellular structure, if gelation occurs below the maximal cure temperature Tmax. Tmax is individual for a given combination of monomers. The multiphase network consists of relatively soft anisotropic cell nuclei and hard isotropic cell walls. If gelation occurs above Tmax single phase networks are obtained. The size of the cell nuclei strongly depends on the used monomers and varies up to two orders of magnitude. The multiphase structure was found to have no impact on the tensile elastic modulus.
Dimensions‐ und Dichteänderung von Polymidformteilen durch Wasseraufnahme
Authors: El Sayed A. , Eckert A. 
Published: April 2003

AbstractAdditive in Polyamiden wie Nukleierungsmittel oder Verstärkungsmittel beeinflussen das Kristallisations‐ und Erstarrungsverhalten. Während der Herstellung von Probekörpern bilden sich morphologische Strukturen, die die Verarbeitungsschwindung, den linearen Ausdehnungskoeffizienten und die Dimensionsänderung während der Wasseraufnahme beeinflussen. Anhand der Volumenänderungen wird der Zusammenhang zwischen der Wasseraufnahme und der Dimensionsänderung in allen drei Raumrichtungen verständlich dargestellt.
Synthesis of macromonomers of poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Wicker Michael , Heitz Walter 
Published: April 2003

AbstractPoly(2,6‐dimethyl‐1,4‐phenylene oxide) with exactly one functional endgroup was synthesized by oxidative polymerization, halogen substitution polymerization, and by phase transfer catalysis. Reaction with 4‐vinylbenzoyl chloride resulted in a quantitative conversion to a macromonomer as shown by GPC and endgroup analysis. The macromonomer is a glassy material with a Tg from 150 to 190°C depending on the molecular weight.
Tensile strength of thermoplastic blends and composites
Authors: Andradi L. N. , Löwenhaupt B. , Haufe A. , Hellmann G. P. 
Published: April 2003

AbstractFailure of purely thermoplastic blends has so far, in contrast to that of thermoplastic‐elastomeric blends, not been studied extensively. In this investigation, the tensile strength of the brittle thermoplastics polymethylmethacrylate and polystyrene, of their random copolymers, their blends, and also of blends of polymethylmethacrylate with the copolymers was measured. The polymers behave all mechanically similarly, but the blends assume all degrees of miscibility and coarseness of phase morphology. For comparison with the blends, also macroscopic composites were tested.
Chain length effect of alkenyl succinic anhydride on thermal and mechanical properties of the cured epoxy resins
Authors: Jung Jin Chul , Lee Sung‐Koo , Lee Kwang‐Sup , Choi Kil‐Yeong 
Published: April 2003

AbstractAs epoxy curing agents three alkenyl succinic anhydrides (ASA) with varying side chain length (2‐octenyl, 2‐dodecenyl and 2‐hexadecenyl succinic anhydride) were prepared by the ene synthesis and thermal and mechanical properties of a bisphenol A epoxy resin cured with the ASA's were measured. With increase in the side chain length of the ASA the Tg, the tensile strength and the impact strength decreased. All the cured samples exhibited excellent transparency and flexibility.
UNTERSUCHUNGEN ZUR ALKALIBEHANDLUNG VON CELLULOSEFASERN. TEIL 1. INFRAROTSPEKTROSKOPISCHE UND RÖNTGENOGRAPHISCHE BEURTEILUNG DER ÄNDERUNG DES ORDNUNGSZUSTANDES
Authors: Richter Ute , Krause Thomas , Schempp Walter 
Published: April 2003

AbstractDie als Folge einer Behandlung mit Natronlauge im Konzentrationsbereich von 0–50% NaOH eintretenden Veränderungen des Ordnungszustandes verschiedener Cellulosefasern (Holzzellstoffe und Baumwollinters) wurden infrarotspektroskopisch und röntgenographisch verfolgt. Die Bestimmung eines IR‐Index als Relation der Peakflächen im Wellenzahlenbereich von 1370 und 670 cm−1 gestatteten eine mit geringem Aufwand durchzuführende Bestimmung insbesondere der im Gebiet der Natronlaugenkonzentrationen von 7.5–15%iger Lauge signifikant abfallenden Kristallinität. Weitaus aufwendigere röntgenographische Messungen des Kristallinitätsindex bestätigen die infrarotspektroskopisch erhaltenenen Befunde. Es ergibt sich die Möglichkeit, anhand gewisser Unterschiede im Verlauf der IR‐Indexkurven Schlüsse in bezug auf die Aktivierungsfähigkeit einzelner Faserproben zu ziehen.
ZUM EINFLUSS DES MOLEKULARGEWICHTS AUF DIE MAKROSKOPISCHE GRENZFLÄCHE BINDENAHT
Authors: Mennig G. 
Published: April 2003

AbstractKnit lines or weld lines are observed in plastics processing, e.g. injection moulding and extrusion, when separated streams of melt are rejoined. The result is quite often a visible mark of reduced mechanical strength. The investigation deals with the influence of molecular weight on knit line strength. Injection moulded test specimens from different polymethyl methacrylates show that the relative knit line strength decreases with increasing molecular weight. However, for constant viscosity, i.e. same mobility of macromolecules, the knit line strength remains constant. The observations coincide nicely with the general understanding with the mechanism of interdiffusion.
ZERSTÖRUNGSFREIE PRÜFUNG VON POLYMEREN MITTELS PHOTOTHERMISCHER MEßMETHODEN 1. DIE PHOTOTHERMISCHE INFRAROTRADIOMETRIE
Authors: Eickmeier Achim , Bahners Thomas , Schollmeyer Eckhard 
Published: April 2003

AbstractEs wird eine Einführung in die als photothermische Meßmethoden bezeichneten Absorptionsspektroskopien gegeben und Experimente zur Prüfung und Vermessung von polymeren Werkstoffen mit der photothermischen Infrarot‐Radiometrie beschrieben. Der Vergleich zwischen einem HeNe‐Laser und einem UV‐Excimerlaser als Primäranregung zeigt, daß es nur durch den Einsatz der UV‐Lichtquelle möglich ist, transparente Polymerproben photothermisch zu untersuchen. So konnten unter Verwendung eines KrF‐Excimerlasers empfindliche Dickenmessungen an PETP‐Folien durchgeführt werden.
A structure rheological study with poly (oxyethylene)
Authors: Schurz J. , Pfragner J. , Abd‐Elrahim F. M. , Moustafa A. B. 
Published: April 2003

AbstractFour samples of poly(oxyethylene) dissolved in water have been studied rheologically. Flow curves have been obtained for different molecular mass and concentration. From no the mass of network strand, the apparent chain element and the penetration hindrance have been obtained. The polymer turns out to form in water entanglement network solutions with somewhat hindered penetration.
Macroporous membranes. 3. Properties of macroporous membranes synthesized from glycidyl methacrylate, ethylene dimethacrylate and alkyl‐ or hydroxyalkyl methacrylate
Authors: Hradil J. , Jelinkova M. , Ilavsky M. , Svec F. 
Published: April 2003

AbstractA series of macroporous membrances composed either of glycidyl methacrylate and ethylene dimethacrylate with an addition of other monomer chosen from a group comprising 2‐hydroxyethyl methacrylate, butyl methacrylate, octyl methacrylate or dodecyl methacrylate, or of a copolymer of 2‐hydroxyethyl methacrylate and ethylene dimethacrylate were synthesized and their properties were determined. The addition of a third monomer changes the porous properties only when the concentration of the monomer in the polymerization feed is rather high. The presence of bulkier alkyl side chains in a polymer matrix raises hydrophobicity and reduces the water regain while the strength of the membrane increases.
RINGÖFFNENDE METATHETISCHE POLYMERISATION (ROMP) VON 5‐CYANO‐2‐NORBORNEN
Authors: Thorn‐Csányi Emma , Harder Christian 
Published: April 2003

AbstractDie ringöffnende metathetische Polymerisation (ROMP) von 5‐Cyano‐2‐norbornen wurde unter Einsatz von Wolframhexachlorid, Wolframoxidterachlorid, Bis(dichloralkoxo)wolframtetrachlorid und Bis(dichloralkoxo)wolframoxiddichlorid als Übergangsmetallkomponente untersucht. Als Cokatalysatoren dienten Methylaluminoxan, Diethylaluminiumethoxid, Tetraisobutyldialuminoxan und Tetrabutylzinn. Als Lösungsmittel wurden Toluol, Chlorbenzol und Dichlormethan verwendet. Die Konzentration der Wolframkomponente lag im Bereich 5 × 10−4 − 5 × 10−3 mol/l. Unter den geprüften Katalysatoren erwies sich Wolframhexachlorid in Verbindung mit Diethylalumiumethoxid als der geeignetste. Mit diesem System verlief die Polymerisation auch bei großen Monomer/Wolfram‐Verhältnissen (10200 :1) hochselektiv und führte zu großen Umsätzen (≥82%).
Strength retention of self‐reinforced, absorbable polyglycolide rods in hydrolytic environment
Authors: Törmälä Pertti , Mikkola Heta‐Maija , Vasenius Jarkko , Vainionpää Seppo , Rokkanen Pentti 
Published: April 2003

AbstractAbsorbable polyglycolide suture fibers were sintered with the compression molding techniques to cylindrical rods at temperatures between 205°C and 232°C for 3–5 min with final pressures of 50–80 N/mm2. The cylindrical rods had nominal diameters between 1.5–4.5 mm and a length of 50 mm. The initial bending moduli and the initial bending strengths of the rods were between 9–15 GPa and 220–430 MPa, respectively. The shear strengths of the rods were between 165–255 MPa.The hydrolytic loss of mechanical strength of the above self‐reinforced, absorabable polyglycolide rods were studied in phosphate buffer at 37°C and 77°C.It was found that the rate of strength loss decreases with the increasing diameter of the rods. On the other hand, the rate of strength loss increases when the temperature of the buffer solution is raised. The strength, retention time at 37°C was between 7–10 weeks showing that the loss of mechanical strength of self‐reinforced polyglycolide rods occurs more rapidly in vivo than in vitro.
Kinetics of radical polymerization, LIII. The absolute rate constants in the radical polymerization of ethyl acrylate
Authors: Tüdős F. , Nagy A. , Földes‐Berezsnich T. 
Published: April 2003

AbstractThe dependence of dilution on the chain propagation and termination rate constants was investigated in the polymerization of ethyl acrylate in benzene solution at 50°C, with the rotating sector method. The errors of the above rate constants were determined and, by our method applied to decrease these errors, the errors of the propagation rate constant was reduced to its half value. By the application of our earlier results in polymerization kinetics, we found that in this system the chain propagation step is exclusively responsible for the solvent effects observed. Our experimental results can be quantitatively described in terms of the hot redical theory.
Dielectric and optical properties of liquid crystalline side chain polymers. A MNDO‐analysis
Authors: Birenheide Richard , Budesheim Klaus W. , Wendorff Joachim H. 
Published: April 2003

AbstractSemiempirical quantum mechanical MNDO‐calculations were performed on side chain liquid crystalline polymers to predict their electronic properties and thus their anisotropic dielectric and optical properties. These predictions are compared with the corresponding experimental results. The conclusion is that the predictions are sufficiently accurate, which suggests to use such methods for screening potentially interesting polymer liquid crystals prior to synthesizing them.