bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diffusion of electrolytes across inhomogeneous permselective membranes
Authors: Narębska Anna , Wódzki Romuald 
Published: April 2003

AbstractPermeability of sulphuric acid through cation‐exchange membranes of different inhomogeneity has been investigated. It has been found that the diffusion coefficient of the acid within the membrane Di is related to that in the aqueous solution D0,i by the equation:

where V is the membrane volume fraction inaccessible for diffusion. This volume was calculated as the sum of the polymer volume fraction Vp and the volume fraction of the internal solution VG with the local concentration of the ionogenic groups equal or higher than the concentration of the external electrolyte. Introducing the volume V into the equations by Meares, Prager and Yasuda it is possible to find a high correlation between Di and f(V), which is related to the membrane structure and their inhomogeneity.The best results have been obtained with the equation of Prager; the calculated diffusion coefficients D0,i for different membranes are then close to the coefficient of H2SO4 in a free aqueous solution.
Viscosity temperature relationship for dilute solutions of poly[2,2′‐(alkylene‐arylene)‐5,5′‐bibenzimidazolyl]
Authors: Varma I. K. , Gupta Veena 
Published: April 2003

AbstractVarious copolymers having benzimidazole rings along with alkylene and arylene groups in the backbone were prepared from 3,3′‐diaminobenzidine tetrahydrochloride dihydrate and dicarboxylic acids in polyphosphoric acid. The viscosities of these polymers in concentrated sulphuric acid (98%) have been determined at 30, 40 and 50°C. There is no systematic variation in the value of K′ (Huggins constant) with temperature. Values of Q and A in the expression η = A exp(Q/RT) were obtained for these polymer samples in H2SO4. On the basis of the ‘A’ values, it has been concluded that most of these polymers were stiff chains with the exception of those containing cis‐vinylene groups in the backbone.
Antioxidants and stabilizers, LXXIII photooxidation of 2,6‐di‐tert‐butyl‐4‐hydroperoxy‐4‐methyl‐2,5‐cyclohexadiene‐1‐one
Authors: Taimr L. , Pivcová H. , Pospíšil J. 
Published: April 2003

AbstractThe photooxidation of 2,6‐di‐tert‐butyl‐4‐hydroperoxy‐4‐methyl‐2,5‐cyclohexadiene‐1‐one (I) in heptane with oxygen at wave‐lengths larger than 355 nm proceeds through a low stable 4‐acetyl‐2,5‐di‐tert‐butyl‐2‐hydroperoxy‐3‐cyclopentene‐1‐one (II). The mechanism of the reaction is close to that of the di‐π‐methane rearrangement. The structure of II was determined from transformations under various conditions (Scheme 1).
Untersuchung des einflusses einiger retarder auf die pyrolysegeschwindigkeit von polyäthylenterephthalat mit hilfe der differential‐thermischen und thermogravimetrischen analyse
Authors: Minčeva Wesselina , Wojnova Simeona , Dimitrov Dimtscho 
Published: April 2003

AbstractMittels DTA und TGA wurde die Abhängigkeit der Zersetzungsgeschwindigkeit von Polyäthylenterephthalatproben mit verschiedenen Retardern untersucht. Der Einfluß der Zusätze auf die thermische Stabilität der Polymeren wurde bestimmt. Weiterhin wurde der Einfluß der flammhemmenden Zusätze auf die in fester Phase ablaufenden Pyrolyseprozesse ermittelt.
Coordination polymers of 3,3′‐benzidine dicarboxylic acid
Authors: Patel M. N. , Patel J. B. 
Published: April 2003

AbstractPolymeric metal complexes of 3,3′‐benzidine dicarboxylic acid with bivalent metal ions such as copper, nickel, cobalt, zinc and manganese have been synthesized and their properties, composition, IR‐absorption spectra and magnetic susceptibilities were investigated. The coloured, powderly solids were obtained by refluxing the metal acetate and the ligand in the appropriate ratio for about half an hour and dried at 110°C. The compounds are stable and insoluble in common solvents.The analytical data indicate the general formula, [ML]n for Cu(II), Mn(II) and [M4L5]n for Ni(II), Co(II) and Zn(II). The mode of coordination of the ligand with metal ions has been elucidated by comparing IR spectra of the ligand and the complexes. A polymeric structure is proposed for the complexes.
Gelchromatographische untersuchungen von ungehärteten kondensaten aus melamin und formaldehyd
Authors: Braun Dietrich , Pandjojo Wirjopartono 
Published: April 2003

AbstractMit Merckogel PVA OR 6000 als Gelmaterial und DMF als Elutionsmittel gelingt die gelchromatographische Trennung der ungehärteten Reaktionsprodukte aus Melamin und Formaldehyd ohne vorherige Derivatisierung. Die Trennung erlaubt Aussagen über den Einfluß der Reaktionsbedingungen auf die Geschwindigkeit der Umsetzung von Melamin mit Formaldehyd. Dabei konnte u. a. festgestellt werden, daß die Reaktion mit steigendem Formaldehyd‐Melamin‐Molverhältnis schneller verläuft.
Metallalkylfreie katalysatoren zur polymerisation von cycloolefinen
Authors: Küpper Friedrich‐Wilhelm 
Published: April 2003

AbstractGemische aus Wolframhexachlorid und cis,trans‐1,5‐Cyclodecadien, cis,trans,trans‐1,5,9‐Cyclododecatrien, cis,cis‐1,6‐Cyclodecadien, endo‐Dicyclopentadien oder cis,cis‐1,2‐Divinylcyclohexan initiieren die metathetische Polymerisation von cis,cis‐1,5‐Cyclooctadien und z. T. von anderen Cycloolefinen. Die höchste Aktivität erreichen die neuartigen Katalysatoren bei den einzelnen Monomeren bei unterschiedlichen Cokatalysator‐Wolframhexachlorid‐Verhältnissen. Eine Deutung der Wirkungsweise wird anhand der experimentellen Ergebnisse versucht.
Gelpermeationschromatographie von Polyamiden
Authors: Pastuska Gerhard , Just Ulrich 
Published: April 2003

AbstractEs wird ein Verfahren zur Gelpermeationschromatographie von Polyamiden beschrieben. Benzylalkohol wird als Lösemittel verwendet. Die Trennungen werden bei 100°C an Kieselgelsäulen vorgenommen. Das Verfahren eignet sich sowohl für hochmolekulare Guß‐Polyamide als auch für PA12.
Synthèse et propriétés de polyépoxydes modifiés à l'aide d'oligomères à terminaisons réactives
Authors: Mallouhi I. , Pillot C. , Pascault J. P. 
Published: April 2003

AbstractNous avons préparé différents polyépoxydes durcis avec un anhydride d'acide et modifiés par des oligomères téléliques. La compatibilité du mélange initial dépend de la structure chimique des 2 types d'oligomères époxyde et modificateur, elle est facillitée par la présence de groupes nitriles, mais par contre il est très difficile de préparer des mélanges homogènes à partir de polyoxyde de propylène. L'influence du pourcentage de modificateur sur les propriétés mécaniques dynamiques des polyépoxydes montre que nous n'avons dans tous les cas qu'une seule transition β qui peut s'étentre sur un grand domaine de températures. Les photos de microscopie électroniqe ne nous permettent pas de différencier très nettement les phases souples et rigides. Ceci peut s'expliquer par une miscibilité partielle de ces phases souples et rigides. Les résultats confirment l'hypothèes de précipitation avant le point de gel d'un oligomère du type (époxyde‐modificateur‐époxyde); la masse moléculaire de cet oligomère dépend de la réactivité du prépolymère époxyde. Nous observons également des comportements différents selon la nature des fonctions réactives – COOH ou – OH du modificateur.
Sorption of Pd(II) from aqueous solutions of chlorocomplexes by the copolymer of glycidylmethacrylate and ethylenedimethacrylate modified with ethylenediamine. The structure of complexes
Authors: Radová Z. , Kálalová E. , Kálal J. , Kukushkin Yu. N. , Simanova S. A. , Konovalov L. V. , Pak V. N. 
Published: April 2003

AbstractThe sorption of chlorocomplexes of palladium (II) from aqueous HCl and KCI solutions by the macroporous copolymer of glycidylmethacrylate and ethylenedimethacrylate modified with ethylenediamine was investigated. The reaction between chlorocomplexes of palladium (II) with functional groups of the copolymer which occurs during sorption from HCI solutions gives rise to a complex of the [diAmH2] [PdCl4] type, that occurring during sorption from KCl solutions yield a complex of the [Pd(diAm)Cl2] type, diAm being the functional group of the copolymer. The highest amount, 1.93 mmol Pd/g dry sorbent is sorbed from a solution of Pd(II) in 0.01 N KCl. Complexes of Pd(II) arising by a reaction with the functional groups of the copolymer were investigated using model complexes of Pd(II) with N‐(2‐aminoethyl)‐2‐amino‐1‐ethanol especially synthesized for this purpose. The results concerning the mode of binding of palladium (II) on the sorbents were used to study the possibilities of elution. Combined elution with a solution of HCl and NH3 released 99.2% of sorbed metal. The copolymer makes possible separation of palladium from other transition metals in industrial waste waters.
On the radius of gyration of macromolecules in semi‐dilute solutions
Authors: Aharoni Shaul M. , Walsh Eugene K. 
Published: April 2003

AbstractFrom the shape of the curves of scattered light intensity plotted against sin2θ/2 where θ is the scattering angle, one may estimate the concentration interval where one surpasses the upper bounds of the dilute solution and enters into the semi‐dilute solution region. This transition interval, approximating C*, is at a concentration where the large‐angle part of the curve flattens out and does not yet show a concavity in the small angle part of the curve. This concavity appears in the semi‐dilute region at C>C* and is shown to be strongly dependent on molecular aggregation at these concentrations. The aggregation effects were demonstrated by means of filtration through various pore sizes, and by mixing visible iodized polystyrene (PS) with invisible PS in bromoform.It is further shown that the apparent radius of gyration (RG) obtained from dissymmetry measurements change as a function of concentration, passing through a minimum at a concentration C = C*. It is proposed that C* may be experimentally determined from either the flatness of the scattered light intensity curves, or from the minimum in the curves of apparent RG as obtained from dissymmetry measurements.
Reactive polymers. XXVI. Sorption properties of the glycidylmethacrylate‐ethylenedimethacrylate copolymer modified with ammonia
Authors: Jehličková Alena , Švec František , Kálal Jaroslav 
Published: April 2003

AbstractSorption properties of the glycidylmethacrylate‐ethylenedimethacrylate copolymer with the OH and NH2 groups were characterized by using the static and dynamical procedure. Hg(II) was found to be sorbed selectively from the acetate buffer. Using sorption and desorption isoplanes determined in the measurements, conditions of the sorption of Hg(II) and its separation from an excess of some metal ions (Cu(II), Pb(II), Cd(II), Co(II), Zn(II), Ca(II), Mg(II)) were determined.
Studies of some basic aspects in easy‐care cotton finishing, II. Influence of urea pad on free formaldehyde and strength of crosslinked cotton
Authors: Hebeish A. , Nassar F. A. , Ibrahim N. A. , Islam A. M. 
Published: April 2003

AbstractThe conventional pad‐dry‐cure technique used in easy care cotton finishing with N‐methylol compounds was modified by introducing an extra urea pad. That is, the modified technique involves padding the cotton fabric with an aqueous solution of the finishing agent followed by padding with an aqueous urea solution; drying and curing. Advantages of the modified technique lie in smaller amount of free formaldehyde in the finished fabric as well as higher retaining strength. The magnitude of the reduction in the amount of free formaldehyde and that of the improvement in the retained strength depend upon urea concentration in the extra padding bath as well as upon nature and concentration of the catalyst used.
Untersuchung der Gelierung von Suspensions‐PVC
Authors: Pazonyi Tamás , Pukánszky Béla , Kalló Aranka , Komáromi Sarolta 
Published: April 2003

AbstractDie Untersuchung der Weichmacheraufnahme von Suspensions‐PVC Pulvern verschiedener Morphologie ergab, daß deren Weichmacheraufnahmemechanismus gleich, ihre Kinetik jedoch unterschiedlich ist, was in der Korngrößenverteilung der Trockenmischung bedeutende Unterschiede verursacht.Bei der Untersuchung der thermomechanischen Bearbeitung der Trockenmischung wurde festgestellt, daß in gewissen Temperaturbereichen die Schmelzviskosität eine lineare Funktion des Volumenverhältnisses des PVC‐Weichmachers ist. Die Abnahme der Schmelzviskositäten mit der Temperatur der aus Pulvern verschiedenen K‐Wertes hergestellten Mischungen erreicht um 190°C einen Grenzwert, der molekulargewichtsabhängig und annähernd dem Quadrat des K‐Wertes proportional ist.Während der thermomechanischen Bearbeitung verändern sich die Produkteigenschaften bedeutend, wobei die Transparenz und die auf den Reißquerschnitt bezogene Reißfestigkeit (relative Reißfestigkeit) am charakteristischsten ist. Berücksichtigt man die Größe der relativen Reißfestigkeit, stellt man fest, daß der Weichmacher eine erhöhte Orientierung der PVC‐Matrix auch bei Raumtemperatur ermöglicht. Ferner wurde festgestellt, daß‐die relative Reißfestigkeit eine lineare Funktion des Volumenbruches von PVC ist.Experimentell wurde nachgewisen, daß die Vorgänge bzw. Begriffe Weichmachung und Gelierung zu trennen sind. Es scheint, daß der erstere im segmentalen, der letztere im molekularen bzw. supramolekularen Bereich vor sich geht.
Cycloaliphatische Glycidylester als Harze von erhöhter Kriechstrom‐ und Lichtbogenfestigkeit
Authors: Matynia Tadeusz 
Published: April 2003

AbstractEs werden Untersuchungen zur Beurteilung von Epoxidharzkomopositionen des Typs cycloaliphatischer Glycidylester beschrieben, die aus Diels‐Alder‐Addukten von im Kolophonium enthaltenen Harzsären sowie Terpenkohlenwasserstoffen als Bestandteile des Terpentins und Maleinsäureanhydrid hergestellt und mit cycloaliphatischen Anhydriden gehärtet wurden. Diese wurden zu den Kompositionen, die aus den handelsüblichen cycloaliphatischen Harzen durch Oxidierung ungesättigter Bindungen erhalten wurden, untersucht.
Gelchromatographische Untersuchung niedermolekularer Harnstoff‐Formaldehyd‐Reaktionsprodukte
Authors: Braun Dietrich , Bayersdorf Friedrich 
Published: April 2003

AbstractMethylolgruppenhaltige Harnstoff‐Formaldehyd‐Reaktionsprodukte können mit N‐Trimethylsilylimidazol selektiv veräthert werden. Die quantitative Umsetzung erfolgt unter sehr schonenden Reaktionsbedingungen und führt zu gut in organischen Lösungsmitteln Iöslichen Derivaten. Intramolekulare und intermolekulare Wasserstoffbrückenbindungen werden aufgehoben und hydrodynamische Volumenunterschiede verstärkt, wodurch die Trennleistung verbessert wird.Die Derivatisierung ermöglicht die präparative Trennung der monomeren Methylolverbindungen des Harnstoffs und erleichtert deren Charakterisierung mittels NMR‐und Massenspektroskopie. Die Fraktionierung silylierter Methylolverbindungen aus Monomeren und Dimeren erfolgt entsprechend dem Methylolierungsgrad; als Gemische können sie ohne gelchromatographische Vortrennung nach dem Kondensationsgrad hingegen nicht in Einzelverbindungen aufgetrennt werden.
Radiation induced graft copolymerization of methyl methacrylate on natural and modified wool III. Thermal behaviour
Authors: Varma D. S. , Sadhir R. K. 
Published: April 2003

AbstractThe thermal behaviour of natural wool and chemically modified wool fibres (oxidized, reduced, methylated and crosslinked) and their graft‐copolymers with methyl methacrylate were investigated by dynamic thermogravimetry in air and differential thermal analysis in nitrogen atmosphere. The relative thermal stability depended on the chemical modification and oxidized wool was found to be thermally more stable than natural wool. Grafting reduced the overall thermal stability of the fibres.
On the anisotropy of thermal expansion in drawn and annealed poly(butylene terephthalate)
Authors: Fakirov S. , Wendorff J. H. 
Published: April 2003

AbstractOn the basis of studies on the dependence of the anisotropy of the thermal expansion of drawn and crystallized poly(butylene terephthalate) (PBT) on the annealing temperature Ta it is demonstrated that the material can be considered as consisting of three different components, crystalline lamellae, a lateral and longitudinal amorphous component. It was concluded that the concentration of the longitudinal component increases with increasing Ta whereas the concentration of the lateral component decreases with increasing Ta. The properties of the amorphous components were found to depend strongly on the annealing temperature, possibly due to the relaxation of taut tie molecules. Similar results were obtained for amorphous regions in the undrawn material.
Studies of some basic aspects in easy‐care cotton finishing, IV. Effect of acid scavengers on free formaldehyde in and strength of crosslinked cotton
Authors: Hebeish A. , Nassar F. A. , Ibrahim N. A. , Islam A. M. 
Published: April 2003

AbstractWhen cotton fabric was padded with a solution containing dimethylol dihydroxy ethylene urea (DMDHEU) (200 g/l) at pH 2.5, batched for one hour, given a wash through padding with water, dried and cured, the crosslinked cotton showed a crease recovery of 287° and 307° in the dry and wet state respectively and a retained strength of ca. 68%. Incorporation of sodium hydroxide in the washing pad accentuates the retaining strength. The latter attained a value of ca. 90% without seriously affecting the dry and wet crease recovery. However, the amount of free formaldehyde in the crosslinked cotton was quite substantial. Increasing the concentration of NaOH up to 2 g/l in the washing pad caused a significant decrease in crease recovery of and a considerable increase in the amount of free formaldehyde in the crosslinked cotton fabric. Replacement of sodium hydroxide by sodium carbonate at a concentration of up to 2 g/l reduced the amount of free formaldehyde without adversely affecting the crease recovery. Utilization of urea in the washing pad at a concentration of up to 16 g/l provided advantages in terms of lesser amount of free formaldehyde (388 ppm), higher retaining strength (ca. 80%)and excellent crease recovery (above 280°). On the other hand, addition of sodium sulphite at a concentration of up to 8 g/l in the washing pad was accompanied by a significant decrease in crease recovery, and a significant increase in the amount of free formaldehyde. Nevertheless the role of sodium sulphite as acid and formaldehyde scavanger could be ameliorated through lowering the pH of DMDHEU padding bath or addition of sodium chloride or sodium dihydrogen phosphate to this bath.
Untersuchung der thermischen eigenschaften von polythiourethan‐elastomeren auf der basis von oligobutadien
Authors: Lipatov Yuri S. , Müller Steffi , Privalko Valery P. , Singer Hans 
Published: April 2003

AbstractDie Arbeit untersucht die thermischen Eigenschaften von Polythiourethanen (PUR) auf der Basis von Oligobutadiendithiol, Decandithiol‐1,10 und 4,4′‐Diphenylmethan‐diisocyanat mit Hilfe eines Differential‐Mikrocalorimeters. Thermisch nicht vorbehandelte Proben zeigen eine „Domänenstruktur”︁, verursacht durch die Zusammenlagerung der polaren „Hartsegmente”︁ einerseits und der unpolaren „Weichsegmente”︁ andererseits. Die harten Blöcke beeinflussen den Glasübergang der weichen (um 200 K) nur wenig. Mit großer Wahrscheinlichkeit treten niedermolekulare kristalline Anteile auf. Erwärmung führt zur Homogenisierung der PUR. Es zeigt sich eine deutliche Abhängigkeit der Glastemperatur von der Zusammensetzung der Proben. Unter der Annahme, daß an dem beobachteten Glasübergang neben dem Oligobutadien neue Segmente teilnehmen, ist die Gleichung von Fox anwendbar. Erwärmung führt weiterhin zu chemischen Änderungen der Polymeren durch Prozesse des thermooxydativen Abbaus, der Cyclisierung und der Vernetzung.
Studies on syntheses and permeabilities of special polymer membranes. XX. Permeabilities of alcohols and hydrocarbons through acrylonitrile‐butadiene‐styrene terpolymer membranes
Authors: Uragami Tadashi , Yono Tadanori , Sugihara Mizuho 
Published: April 2003

AbstractThe permeabilities of n‐alcohols and n‐hydrocarbons through acrylonitrile‐butadiene‐styrene terpolymer membranes were investigated. The permeation rates of linear alcohols and hydrocarbons were found to decrease with an increase in number of carbon atoms in the alcohol and hydrocarbon molecules. These permeation rates, the contents of the permeating species in the membranes, and the burst strengths of the membranes were influenced by the molecular sizes, solubility parameters, viscosities, modified Small's numbers, and surface tensions of the permeating molecules. It was found that the interactions between the membrane and the hydrophobic groups were far smaller than those with the polar groups, however, the former interactions were not negligible.
Segmented copolyethers with urethane and urea or semicarbazide links for blood circulation systems II. Infrared‐spectroscopic investigations
Authors: Hummel D. O. , Ellinghorst G. , Khatchatryan A. , Stenzenberger H.‐D. 
Published: April 2003

AbstractThe infrared spectra of urethane‐, urea‐, and semicarbazide‐linked aliphatic polyethers (poly(oxyethylene), poly(oxytetramethylene) and poly(oxypropylene)) have been measured at 300 K and 153 K. The assignment of the different structural units to certain groups of absorption bands (“characteristic band combinations”) was made by the evaluation of the spectra of reference compounds and of literature data. The low‐temperature effects (band splitting, shift of band maxima) facilitate the identification of structural units in these polymers. The observed effects do not signify crystallinity but beginning regularity of the poly(oxyethylene) and poly(oxytetramethylene) sequences.
Compatibility of poly(vinyl chloride)/polyurethane blends
Authors: Pigłowski Jacek , Łaskawski Włodzimierz 
Published: April 2003

AbstractThe compatibility and mechanical properties of poly(vinyl chloride) (PVC) and thermoplastic polyurethane (PU) are described in this paper. The compatibility has been estimated using a variety of methods including the measurements of viscosity of polymer solutions, comparison of solubility parameters of PVC and PU, sorption and dynamic mechanical testing. The solubility parameters were taken for calculation of heats of mixing. From a study of the sorption of organic solvent vapour by the investigated polymers and their mixtures, the Gibbs free energies of mixing for polymer‐solvent systems were calculated and next the free energy of mixing of two polymers. Blends of PVC with PU are shown to the incompatible. With increasing PU content in the blends impact strength was increased but tensile strength at the breaking point was decreased.
The alkaline hydrolysis of methacrylates
Authors: Hynková Vlasta , Hrabák František 
Published: April 2003

AbstractThe hydrolysis of a number of methacrylates in a 2,5% water‐alcoholic solution of sodium hydroxide at 25°C was investigated. The hydrolysis of the ester group in 2‐(N‐methylanilino)ethyl(III), 3‐ and 4‐dimethylaminobenzyl‐(IV, V)‐2‐carboxyphenyl (VI) and 2,2,2‐trichloroethyl (VII) methacrylate proceeded at approximately the same rate as in methyl methacrylate (I) and dimethylaminoethyl methacrylate (II); within 25 min, some 80% of the original esters were hydrolyzed. In alkaline solutions of 1,2,2,2‐tetrachloroethyl (VIII), 2‐(1,2,2,2‐tetrachloroethoxy)ethyl (IX) and 1‐(4‐chlorophenyl)‐2,2,2‐trichloroethyl(X) methacrylates, the rate of hydrolysis of the ester group is decreasing in the order VIII>IX>X. The hydrolysis of the ester group was characterized by the rate constants of second order.