bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ideal crosslinked‐polymers and their characterization in free‐radical monovinyl‐divinyl copolymerizations
Authors: Matsumoto Akira , Okamoto Atsushi , Okuno Seiji , Aota Hiroyuki 
Published: April 2003

AbstractThe critical conditions in which the classical Flory‐Stockmayer gelation theory (F‐S theory) is applicable to monovinyl‐divinyl copolymerizations were pursued in detail. The resulting prepolymers or precursors of ideal crosslinked‐polymers were characterized as standard polymers for the discussion of network formation in free‐radical monovinyl‐divinyl copolymerizations. Methyl methacrylate was copolymerized with a small amount of ethylene dimethacrylate, butylene dimethacrylate or nonapropyleneglycol dimethacrylate in the presence of lauryl mercaptan, a chain transfer agent to reduce the occurrence of a thermodynamic excluded volume effect and intramolecular crosslinking as the primary and secondary factors, respectively, for the greatly delayed gelation in the free‐radical monovinyl‐divinyl copolymerizations and, moreover, to keep the primary chain length constant by inhibiting a gel effect. The ratio of the actual gel point to the theoretical one reached 1.1, supporting the validity of F‐S theory. The resulting prepolymers were subjected to SEC‐MALLS analysis to determine the molecular weights, the molecular‐weight distributions and the radii of gyration; the correlations of molecular weight vs. elution volume and radius of gyration vs. molecular weight were useful for the characterization of the precursors of ideal network‐polymers.
A polymer network of unsaturated polyester and bismaleimide resins: Yielding and fracture behaviour
Authors: Abbate Mario , Martuscelli Ezio , Musto Pellegrino , Ragosta Giuseppe 
Published: April 2003

AbstractThe yielding and the fracture behaviour of an intercrosslinked polymer network obtained by the simultaneous curing of an unsaturated polyester (UP) and a thermosetting bismaleimide resin (BMI) was investigated in a wide range of temperatures and testing rates. The yield stress σy and the Young's modulus E increase by increasing the testing rate and decreasing temperature. Moreover, under the same testing conditions, σy and E increased as the BMI content in the blend was enhanced. On the other hand, it was found that the fracture parameter Kc was not affected by the presence of BMI. The yielding process was analyzed using the theories both of Argon and Bowden and the molecular parameters derived there were related to the molecular structure of the network developed upon curing.
Polycondensation of novolacs containing dominately ortho‐ortho‐methylene linkages
Authors: László‐Hedvig Z. , Szesztay M. , Tüdős F. 
Published: April 2003

AbstractIn an early stage of the polycondensation of phenol/formaldehyde (Ph/F) systems catalyzed by bivalent metal acetates (Me2+(ac)2), 2‐hydroxy‐benzylalcohol (2‐OH‐BA) formation was selective in the weak acidic medium and only in the presence of the catalyst. The concentration change in 2‐OH‐BA and its hemiformal (HF) was followed by GPC as a function of the pH value of the system and the catalyst concentration and was found to be independent of the type of metal used in the catalyst but dependent on the pH value of the medium and on the catalyst concentration. An extremely high catalyst concentration does not cause further increase in the overall rate of 2‐OH‐BA formation. It was proved by 1H NMR that at higher conversion and in the presence of Me2+(ac)2 catalyst, the o‐o′‐ArCH2Ar isomers are dominating over o, p′ and p,p′ ones. Novolacs with overwhelming o‐diphenylmethane structures are thermally stable up to 400°C and can be crosslinked without hexamethylenetetramine (HEXA).
Miscibility of linear low density polyethylene (LLDPE)‐graft‐poly(methyl methacrylate) with poly(vinylidene fluoride) (PVF2) and its application as compatibilizer LLDPE/PVF2 blends
Authors: Li Lin , Tang Tao , Huang Baotong 
Published: April 2003

AbstractDifferential scanning calorimetry (DSC), Fourier‐transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X‐ray photoelectron spectroscopy (XPS) were used to study the miscibility of blends of a graft copolymer of poly(methyl methacrylate) on linear low density polyethylene (LLDPE‐g‐PMMA, G‐3) with poly(vinylidene fluoride)Systematic name: poly(1,1‐difluoroethylene).
(PVF2) and the compatibilization of blends of LLDPE/PVF2. The specific interaction between PMMA side chains and PVF2 in G‐3/PVF2 binary blends is weaker than that between the homopolymers PMMA and PVF2. There are two states of PVF2 in the melt of a G‐3/PVF2 (60/40, w/w) blend, one as pure PVF2 and the other interacting with PMMA side chains. The miscibility between PMMA side chains and PVF2 affects the crystallization of PVF2. LLDPE‐g‐PMMA was demonstrated to be a good compatibilizer in LLDPE/PVF2 blends, improving the interfacial adhesion and dispersion in the latter. Diffusion of PMMA side chains into PVF2 in the interfacial region reduces the crystallization rate and lowers the melting point (Tm) and the crystallization temperature (Tc) of PVF2 in the blends.
Matrix‐assisted laser desorption/ionization mass spectrometry of synthetic polymers. 3. Analysis of condensation polymers
Authors: Pasch Harald , Rode Karsten , Ghahary Reza , Braun Dietrich 
Published: April 2003

AbstractMatrix‐assisted laser desorption/ionization mass spectrometry is shown to be a suitable method for the analysis of condensation polymers. Although these products are rather low in molar mass, they exhibit a complex chemical structure. Phenolic novolacs and resols can be analysed with respect to the degree of polymerization and the type and number of functional groups. Modified phenolic resins, such as epoxidized novolacs, can be identified and the degree of epoxidation can be determined. It is shown for polycarbonates and polyesters that depending on the reactant ratio linear oligomers with different endgroups and cyclic oligomers are formed.
Molecular characterization of branched thermoplastic polyurethane in dilute solutions on N‐methyl‐2‐pyrrolidinone
Authors: Lederer Klaus , Macko Tibor , Imrich‐Schwarz Gabriele , Aust Nicolai , Kolmanics Thomas , Schwarz Thomas 
Published: April 2003

AbstractSeven homologous samples of a thermoplastic polyurethane (TPU) were characterized in dilute solutions of N‐methyl‐2‐pyrrolidinone (NMP) by size exclusion chromatography (SEC) on normal‐phase silica gel, low‐shear viscometry and membrane osmometry. The Staudinger‐Mark‐Houwink (SMH) constants of this homologous series were obtained by a new procedure of calculation on the basis of universal calibration of SEC with narrow polystyrene standards. The calculated SMH constants for these TPU samples in NMP at 298 K (K = 3.94 mL g−1, a = 0.29) prove the branched structure of this TPU samples and were further confirmed by osmometry.
Dielektrische Untersuchung der Härtung eines Epoxidharzes mit anhydridmodifizierten phenolischen Härtern
Authors: Böschel Dorit , Schramm Frank , Fedtke Manfred 
Published: April 2003

AbstractDie Härtung verschiedener Epoxidharzsysteme wurde mit Hilfe der dielektrischen Analyse verfolgt. Da sie sehr empfindlich ist, erwies sie sich zur Beobachtung der Nachhärtungsperiode besser geeignet als die Differentialkalorimetrie. Am Beispiel der Vernetzung von Diandiglycidylether mit anhydridmodifizierten Phenolnovolaken wird gezeigt, daß mittels dielektrischer Analyse die Bestimmung von Glasumwandlungstemperaturen möglich ist; dagegen ist diese Methode für die Ermittlung von Gelierzeiten nicht geeignet.
Linear polythioesters, XXVI. Products of interfacial polycondenation of bis(4‐mercaptomethylphenyl)methane with some aliphatic and isomeric phthaloyl dichlorides
Authors: Podkościelny Wawrzyniec , Podgórski Mieczysław 
Published: April 2003

AbstractNew polythioesters were synthesized by interfacial polycondensation of bis(4‐mercaptomethylphenyl)methane with selected aliphatic and isomeric phthaloyl dichlorides. To determine optimum polycondensation conditions, the influence of the following factors on reduced viscosity and yield were studied: type of organic phase, concentration of hydrogen chloride acceptor (NaOH), concentration of reagents, aqueous/organic phase ratio, rate of acid chloride addition, reaction time and reaction temperature.A thorough examination was carried out only for the polycondensation of dithiol with adipoyl and isophthaloyl dichlorides chosen as model systems. The structures of polythioesters were confirmed by elemental analysis, X‐ray analysis and infrared spectroscopy. Some physicochemical, mechanical and electrical properties were determined. The molecular weights were not measured, because of the low solubility of the obtained polythioesters.
Blocked isocyanate. Reaction and thermal behaviour of the toluene 2,4‐diisocyanate dimer
Authors: Querat E. , Tighzert L. , Pascault J. P. , Dušek K. 
Published: April 2003

AbstractDue to the difference in reactivity between free isocyanates and uretdione rings, diisocyanate dimers can be used as blocked isocyanates. They offer the potential advantage that no volatile by‐products are formed. The toluene 2,4‐diisocyanate dimer contains one uretdione ring, formed by dimerization of two isocyanate groups, and two free isocyanate groups. The latter react rapidly with the hydroxy groups of a polycaprolactone diol at temperatures above 80°C. The pure dimer thermally dissociates above 150°C; dissociation is reversible. In the presence of OH groups, the regenerated isocyanate groups can then react to form urethanes. Our experiments have also revealed the formation of allophanate groups as reaction products of an uretdione ring with a hydroxy group. The influence of initial molar ratio of reactants and of temperature on the mechanisms have been discussed. Allophanates are not stable at high temperature in presence of remaining hydroxy groups, their dissociation leads to urethanes. Application of branching theory has shown that the system can gel due to allophanate formation in a wide range of initial molar ratios of NCO to OH groups.
The effect of alumina particulate morphology on the properties of reinforced poly(propylene) and poly(ethylene‐co‐vinyl acetate) composites
Authors: Prachar Michael Jiri , Hay James , Ponton Clive 
Published: April 2003

AbstractThe effect of alumina particulates on a thermoplastic matrix is investigated, in particular the effect altering the alumina particle size and morphology has on the mechanical properties. Different grades of alumina are used and two thermoplastic matrices; namely poly(propylene) and poly(ethylene‐co‐vinyl acetate). Investigations showed that optimum properties were achieved with the alumina of smallest particle size and lowest aspect ratio. Preliminary work has also been performed on the use of silane coupling agents and they have proved effective in increasing the tensile properties of the composites.
Optimal design of free‐radical batch polymerizations with one charge of monomers and initiator
Authors: Hollbeck Christoph , Bandermann Friedhelm , Günther Claus 
Published: April 2003

AbstractBased on an earlier paper of Chen and Lee, a procedure is developed to determine optimal reaction times for predetermined monomer conversions and number‐average degrees of polymerization in an azeotropic free‐radical batch copolymerization with one charge of monomers and initiator. The procedure allows for the calculation of the admissible range of monomer concentrations, the determination of an appropriate initiator and its most suited concentration to arrive at the goal in reaction times as short as possible. The validity of the model was tested in the free‐radical copolymerization of acrylonitrile and butadiene in chlorobenzene at 343 K, using 1,1′‐azocyclohexanenitrile (ACN) and 2,2′‐azoisobutyronitrile (AIBN) as initiators. The agreement of theoretical and experimental data was satisfying. It is pointed out that the gel effect can be incorporated into the model, and that the procedure can also be used in the design of free‐radical homopolymerizations.
ÉTude préliminaire des propriétés microlithographiques d'une résine renfermant un polyimide et un bis‐azide sensible aux UV lointains
Authors: Sailhan Valérie , Kasseh Abdeslam , Mertz Christian , Montginoul Claude , Giral Louis , Schué François 
Published: April 2003

AbstractL'étude préliminaire des propriétés microlithographiques des résines obtenues en mélangeant un polyimide et un bis‐azide a permis de montrer que de telles résines pourraient probablement être utilisées en tant que résines microlithographiques sensibles aux UV lointains. En effet ces résines donnent des couchages homogènes qui ont des épaisseurs convenables. De plus, elles sont très sensibles aux irradiations: elles subissent alors des modifications de structure lorsqu'on les irradie par des radiations de longueur d'onde égale à 254 nm. Les parties ainsi insolées sont insolubles dans les solvants constitués par des mélanges d'eau et de dioxane ou d'eau et de 1‐N‐méthylpyrrolidone alors que ces mêmes solvants solubilisent parties non insolées.
The role of molar volume of the organic solvents in the swelling system EPDM vulcanizate/solvent
Authors: Hrnjak‐Murgić Z. , Jelenĉić J. , Bravar M. 
Published: April 2003

AbstractEight samples of poly(ethylene‐co‐propylene‐co‐diene) (EPDM, containing 55 wt.‐% ethylene) were vulcanized with 0.5–8.0 phr dicumyl peroxide. The influence of molar volumes V1 of cyclohexane, hexane, heptane, iso‐octane, tetrachloromethane, carbon disulfide, xylene, benzene, toluene, tetrahydrofuran, trichloromethane and chlorobenzene on the swelling intensity of the EPDM vulcanizates was studied, and it was found that regardless of the solubility parameters, polarity, dielectric constants, acidity or basicity of solvents, a linear relationship exists between V1 and number of moles of solvent in the gels, n1. With increase of V1, n1 decreases.
Zur substituentenverteilung in kationischen xylanderivaten
Authors: Ebringerová Anna , Hromádková Zdena 
Published: April 2003

AbstractTrimethylammonium‐2‐hydroxypropylxylans with degrees of substitution (DS) ranging from 0.25 to 0.98 were hydrolysed to monomer units, and the 13C NMR spectra of the hydrolysates as well as products separated therefrom were taken and assigned. Monosubstitution of the xylose units was found mainly to occur in the studied DS range. At lower DS, substitution of OH‐2 groups is preferred, whereas at higher DS the regioselectivity is lost.
Urethane‐acrylate compositions cured by UV radiation as intermediate protective covers of optical fibers
Authors: Podkoscielny Wawrzyniec , Tarasiuk Bogdan , Rayss Jan , Podkoscielny Wiesław Marian 
Published: April 2003

AbstractThe present paper deals with studies concerned with an optimization of the synthesis of urethane‐acrylic UV‐cured resins intended for application as protective coatings for optical fibers. Oligoetherdi‐ and triols, toluylene diisocyanate and isophorone diisocyanate, as well as hydroxyethyl methacrylate and hydroxypropyl methacrylate were used for synthesis. Active diluents butyl acrylate, 2‐ethylhexyl acrylate, 1,4‐butanediol diacrylate or their mixtures, and 2,2‐dimethoxy‐2‐phenylacetophenone as a photoinitiator were added to the urethane‐acrylic dimers comprising polymerization‐active double bonds. The compositions were characterized by the determination of density, viscosity, refractive index, gel content, glass transition temperature, Shore hardness, Young's modulus, breaking stress, relative elongation at break, thermal resistance and water vapour diffusion coefficient before and after curing.The utility of these compositions for protective intermediate coatings of optical fibers was checked and confirmed under manufacturing conditions.
Electric resistivity of hydroscopic copoly(ester‐ether)s containing zwitterionic units and their utilization for antistatic modification of polyester fiber
Authors: Sano Yoshiyuki , Lee Chan Woo , Kimura Yoshiharu , Saegusa Takeo 
Published: April 2003

AbstractBlock copoly(ester‐ether)s containing different ionic units, i.e., sulfobetaine (S‐betaine), carbobetaine (C‐betaine), and ammonium tosylate, were prepared and evaluated as antistatic modifiers of PET fiber. The ionic units were readily derived from N,N‐bis(2‐hydroxyethyl)methylamine and co‐condensed randomly with the polyester and poly(oxyethylene) (PEO) units. For the copolymers containing S‐betaine units, a thick filament was melt‐spun to evaluate their apparent electric resistivity. Depending on the unit compositions (25–75 wt.‐% of PEO and 1–2 mol‐% of S‐betaine), resistivities ranging from 108 to 1010 Ω cm‐1 were obtained. Then, the three copolymer‐type modifiers were blended with poly(ethylene terephthalate) (PET) by the ordinary blend‐spinning technique. The blend PET fibers obtained showed not only good mechanical properties, but also improved antistatic properties. Particularly, the fiber blended with the copolymer containing S‐betaine units had the shortest half‐life time of leakage of static charge, although the surface area resistivity, being in the order of 1013 Ω cm‐2, was similar to that of the fibers blended with the copolymers containing C‐betaine and ammonium tosylate units. These blend PET fibers were found to retain good antistatic properties even after dyeing and repeated washings, because both the hydrophilic and ionic groups are immobilized with the polyester chains.
Untersuchungen zum reaktionsverhalten beim vorliegen von depolymerisationsreaktionen. Untersuchung von copolymerisationen des α‐methylstyrols
Authors: Fleischhauer Jürgen , Schmidt‐Naake Gudrun , Scheller Dieter 
Published: April 2003

AbstractFür die radikalischen Copolymerisationen von α‐Methylstyrol (MS) mit Methacrylnitril (MAN) sowie MS mit Acrylnitril (AN) wurden Untersuchungen zur Prüfung der in der Literatur postulierten kinetischen Modelle des „sequenzlängenunabhängigen”︁ bzw. „sequenzlängenabhängigen”︁ Terminalmodells mit Depolymerisationsschritten durchgeführt. Sie basieren auf Analysen der Sequenzverteilungen aus 13C‐NMR‐Spektren. Resultate von 13C‐NMR‐Untersuchungen an MS/MAN‐Polymeren variabler Zusammensetzung werden vorgestellt. Reaktionsparameter und Gleichgewichtskonstanten wurden direkt aus den Informationen der 13C‐NMR‐Spektren für das Terminalmodell mit Depolymerisationsschritten in Abhängigkeit von der Reaktionstemperatur der Polymeren bestimmt. Hieraus konnten die Polymerisationsenthalpie ΔH = 26,5 ± 0,5 kJ mol−1, die Polymerisationsentropie ΔS = 95 ± 5 J mol−1 K−1 sowie die Ceilingtemperatur Tceiling = 65 ± 1°C für MS bestimmt werden. Es wurde nachgewiesen, daß im Rahmen der Terminalnäherung auch mit Berücksichtigung von Depolymerisationseinflüssen keine adäquate Beschreibung des Copolymerisationsverhaltens im Falle der untersuchten Systeme möglich ist. Vielmehr konnten als Ergebnis der Untersuchungen sowohl in Copolymeren von MS mit AN als auch mit MAN signifikante Penultimate‐Effekte nachgewiesen werden. Aufbauend auf diesen Ergebnissen wird die Anwendung eines auf einer Penultimate‐Näherung basierenden Modells, welches auch das Gleichgewicht in den Wachstumsreaktionen von MS berücksichtigt, zur theoretischen Vorhersage des Copolymerisationsverhaltens vorgeschlagen.
Instrumented impact testing of phenolphthalein polyether ketone
Authors: Han Yanchun , Li Binyao , Yang Yuming 
Published: April 2003

AbstractThe Charpy impact fracture behaviour of unnotched specimens of phenolphthalein polyether ketone (PEK‐C) was studied over a temperature range from room temperature to 220°C by using an instrumented impact tester. The load‐time and energy‐time curves of PEK‐C at different temperatures were recorded. From these curves, some important parameters, such as the maximum impact load, the maximum stress, the total impact energy, the crack initiation energy, the crack propagation energy etc., were obtained and their temperature dependences of PEK‐C were investigated. The point of 100 percent maximum load on the load‐time trace was shown to be the yield point. Two parameters, the ductile ratio (D.R.) and the ductility index (D.I.) were applied to characterize the ductility of PEK‐C and their relationships to the relaxation processes were discussed.
On the copolymerization of styrene with some UV stabilizers based on triazinylaminobenzotriazole
Authors: Konstantinova T. 
Published: April 2003

AbstractThe copolymerization of styrene with three polymerizable UV stabilizers based on triazinylaminobenzotriazole was investigated. The relationship between the polymerization rate and the character of the UV stabilizer was established. The general conclusion was that the presence of the UV stabilizer retarded the polymerization of styrene, without significant effect on the molecular weight and the thermostability of the copolymers thus obtained.
Cardanol‐phenol‐formaldehyde resins. Thermal analysis and characterization
Authors: Huong Nguyen Le , Nieu Nguyen Huu , Tan Ton That Minh , Griesser Ullrich J. 
Published: April 2003

AbstractPhenolic resins (resols) based on phenol and cardanol, a natural alkyl phenol from cashew nut shell liquid (Anacardium occidentale L.), were synthesized, and their thermal and chemical resistances as well as their mechanical properties were determined. The results show that the addition of certain amounts of cardanol (less than 15 wt.‐%) to phenol distinctly improves the chemical resistance and some mechanical properties such as tensile, flexural and Izod impact strengths of the resins. At the same time, the high thermal stability of pure phenol‐formaldehyde resins still remains in the temperature range of high relevance.
Effects of surface crystallinity on dynamic mechanical properties of compression‐molded polypropene sheets
Authors: Kawamoto Naoshi , Mori Hideharu , Yui Nobuhiko , Nitta Koh‐hei , Terano Minoru 
Published: April 2003

AbstractDynamic mechanical properties are measured for a series of compression‐molded polypropene sheets having the same bulk crystallinity but different surface crystallinity. The temperature of the α‐dispersion was shifted to lower temperatures with lowering the surface crystallinities of the sheets. A shoulder peak, which is ascribed to the surface layer, appeared between the α‐ and β‐dispersion for the sheets. In addition, the application of the Takayanagi model to the experimental results suggests the difference in the continuity of the amorphous phase between the surface layer and the bulk.
Electrically conductive polyaniline/poly(butadiene‐co‐styrene‐co‐2‐vinylpyridine) latex composites
Authors: Xie Hong‐Quan , Liu Hao , Liu Zhi‐Hong , Guo Jun‐Shi 
Published: April 2003

AbstractA series of conducting polyaniline/poly(butadiene‐co‐styrene‐co‐2‐vinylpyridine) (PBSP) latex composites was prepared by polymerization of aniline in the presence of PBSP latex. The mass loading of polyaniline in the composite latex can be controlled by varying the PBSP latex/aniline charging ratio and oxidant/aniline molar ratio. The composites were characterized by elemental analysis, transmission electron microscopy and thermogravimetric analysis. The effects of the concentration of the reactants on the conductivity at room temperature and the mechanical properties of the composite films formed from the latices were studied.
Synthesis of benzoin terminated poly(tetrahydrofuran)s
Authors: Önen AyşLen , Yagci Yusuf , Schnabel Wolfram 
Published: April 2003

AbstractLiving poly(tetrahydrofuran) (PTHF) was terminated with the sodium salt of benzoin to yield polymers with photoactive end groups. The PTHF macroinitiators obtained were characterized and used as an initiator in the free radical polymerization of methyl methacrylate.