bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bisacryloylpiperazine as vinylating agent for enzyme immobilization by graft‐copolymerization onto polysaccharides
Authors: D'Angiuro L. , Vecchio G. , Mazzola G. , Cantafi R. , Cremonesi P. 
Published: April 2003

AbstractA method of enzyme immobilization by graft‐copolymerization onto polysaccharides is reported. Bisacryloylpiperazine has been used as a vinylating reagent and the reaction product with several enzymes (HRP, GOD, Am, ChT, Cel) was copolymerized onto different matrices (cellulose, Sepharose, Sephadex, starch). Immobilization parameters which influence the copolymer activity have been studied for the insolubilization of horseradish peroxidase onto cellulose. These parameters are pH, time, and temperature of bisacryloylpiperazine enzyme activation reaction.Under the best immobilization conditions copolymer activity linearly depends on enzyme concentration. Enzyme coupling efficiency depends on the type of enzyme and it ranges from 7 to 20%.The most important characteristics of these immobilized enzyme systems were tested and compared with those of similar systems obtained by glycidylmethacrylate enzyme activation (stability in continuous washing, kinetic characteristics, and storage, thermal, and operational stability). Immobilized enzyme graft copolymers have kinetic behaviour very close to that of the free enzymes. Diffusion is not seriously limited because immobilization reaction does not alter the enzymatic activity. By means of bisacryloylpiperazine it was possible to immobilize chymotrypsin with better results than those previously obtained, particularly coupling efficiency and long term continuous working.
Effect of mineral filler sepiolite on sulphur‐free thiuram vulcanization of natural rubber
Authors: Hernández L. Gonzáles , Rueda L. Ibarra , Díaz A. Rodríguez 
Published: April 2003

AbstractThe effect of sepiolite on the sulphurless vulcanization of NR by tetramethylthiuram disulphide, with and without activator (triethanolamine) was studied. The influence on: a) kinetic vulcanization parameters, b) crosslinking density, c) crosslinking types, d) efficiency factor E and e) zinc sulphide formation was considered. The vulcanization rate increases with increasing sepiolite level but crosslinking density is reduced. Based on these results a vulcanization mechanism is proposed and discussed.
Polymerization of spiro‐orthoesters. III. Syntheses of monomers
Authors: Trathnigg Bernd , Hippmann Gerhard , Junek Hans 
Published: April 2003

AbstractConvenient syntheses are given for several 1,4,6‐trioxa‐spiro‐(4,4)‐nonanes, which possess the remarkable ability to polymerize under expansion in volume or at least with very low shrinkage.
Polymerization of spiro‐orthoesters. IV. Density measurements
Authors: Trathnigg Bernd , Hippmann Gerhard 
Published: April 2003

AbstractThe apparent partial specific volumes of some substituted 1,4,6‐trioxa‐spiro‐(4.4)‐nonanes and their polymers in THF at 25.00°C were determined with high accuracy using a density measuring device according to the mechanical oscillator method. The measurements confirm, that some monomers of this series expand on polymerization.
Resacetophenoneoxime‐formaldehyde resins, IV. Chelation ion‐exchange properties
Authors: Parmar J. S. , Patel M. R. , Patel M. M. 
Published: April 2003

AbstractResacetophenoneoxime‐formaldehyde resins showed to be selective chelating ion exchange resins for certain metal ions. A batch equilibrium method was used in the study of the selectivity of metal ion uptake. The method involved the measurement of distribution of a given metal ion between an aqueous solution and the resin. The study was carried out over a wide pH range and in media of various ionic strengths.
Polymerization of lactams, 44. Molecular characterization of the copolymers of 6‐caprolactam and 12‐dodecanelactam
Authors: Alijev Rizo , Tuzar Zdeněk , Kondelíková Jaroslava , Verlová Hana , Králíček Jaroslav , Buděšínský Miloš 
Published: April 2003

AbstractEquilibrium copolymers of 6‐caprolactam and 12‐dodecanelactam differing in chemical composition have been prepared, fractionated and characterized by light scattering, viscometry and 13C‐NMR. It has been found that the copolymers have a statistical distribution of comonomer units and are practically homogeneous in chemical composition. Intrinsic viscosities for the copolymer fractions in m‐cresol, regardless of their chemical composition, fit fairly well the same Mark‐Houwink relationship whose constants K = 7.55.10−4 and a = 0.71 have the values between those for polycaprolactam and polydodecanelactam.
Polymerization of lactams, 45.The 13C‐NMR analysis of copolymers of 6‐caprolactam with 12‐dodecanelactam
Authors: Alijev Rizo , Buděšínský Miloš , Kondelíková Jaroslava , Králíček Jaroslav 
Published: April 2003

AbstractThe copolymers of 6‐caprolactam with 12‐dodecanelactam were prepared by the hydrolytic, cationic and spontaneous mechanisms. The composition of copolymers was determined by means of 13C‐NMR spectra and information about the relative reactivity of individual monomers, the type of copolymer and the mean length of homogeneous blocks was obtained from intensities of carbonyl signals. It has been proved that a random copolymer is formed at the equimolar initial ratio of monomers irrespective of the polymerization mechanisms used. Investigation of the time course of hydrolytic copolymerization proved the higher reactivity of 6‐caprolactam in comparison with 12‐dodecanelactam.
Zusammenhänge zwischen Glasübergang, thermodynamischen und mechanischen Größen als Möglichkeit zur Voraussage über Materialeigenschaften aus der chemischen Struktur
Authors: Batzer Hans , Kreibich Ursula T. 
Published: April 2003

AbstractIn Fortsetzung einer früheren Arbeit über die Vorausberechnung der Glasübergangstemperatur Tg von linearen und vernetzten Polymeren aus der Kohäsionsenergie Ecoh normiert auf die Anzahl selbständig schwingungsfähiger Strukturelemente \documentclass{article}\pagestyle{empty}\begin{document}$\sum\limits_{\rm i} {{\rm a}_{\rm i} } $\end{document} im wiederkehrenden Segment wurden Zusammenhänge zwischen Tg und der normierten Molwärme Cp sowie dem normierten Segmentgewicht MGSeg gefunden. Es ergibt sich eine lineare Abhängigkeit der Größen Cp, Ecoh und MGSeg untereinander, wobei die Normierung entfällt. Damit kann insbesondere die sonst schwer zugängliche Kohäsionsenergie aus der gemessenen Molwärme bzw. den leicht bestimmbaren Tg‐Werten ermittelt werden.Die Anwendung der Relationen führt zur Verknüpfung thermodynamischer Größen mit mechanischen Eigenschaften wie z.B. der spezifischen Kohäsionsenergie bezogen auf die Dichte mit dem Schubmodul bzw. der Biegefestigkeit im Yield‐Punkt bei 298 K bei vernetzten Epoxidharzen.
Methoden zur Herstellung und Charakterisierung von Kunststoffen mit verbesserter Blutverträglichkeit
Authors: Fischer Johannes Paul , Fuhge Peter , Burg Karlheinz , Heimburger Norbert 
Published: April 2003

AbstractAus 10 verschiedenen Kunststoffen (CPE, EPDM, ETFE, EVA, LDPE, PP, PTFE, PUR, PVC und Silicone) wurden Schläche von unterschiedlichem Innendurchmesser (ID) hergestellt:

Schläuche von 4–5 mm ID für in vitro‐ und ex vivo‐ Blutverträglichkeits‐Tests mit Human‐Blut,
Schläuche von 0,3–0,4 mm ID für ex vivo‐ Blutverträglichkeits‐Messungen über die Blutungszeit nach Einführen des Kapillarschlauches in die Ohrrandvene von Kaninchen.
Die Schläuche wurden zum Teil oberflächlich durch Pfropfung mit N‐Vinyl‐N‐methyl‐acetamid (VIMA) modifiziert.Für die Original‐ und die gepfropften Schläuche wurden Korrelationen gefunden zwischen den physikochemischen Charakterisierungskriterien (Pfropfungsgrad, FT‐ATR‐IR, SEM) und den Ergebnissen der in vitro‐ und ex vivo‐Blutverträglichkeits‐Tests.Für die in vitro‐Blutverträglichkeits‐Tests wurden Schläuche von 4–5 mm ID mit Human‐Citratblut inkubiert und Veränderungen der Gerinnungsparameter bestimmt. Beim Human‐ex vivo‐Test wurden Schläuche von 4 mm ID an der menschlichen Armvene von Blut durchflossen und anschließend die Innenoberfläche der blutdurchflossenen Schläuche untersucht. Diese Ergebnisse korrelieren mit den Ergebnissen der Human‐in vitro‐Tests.Ein Vergleich mit den am Markt angebotenen Schläuchen für medizinisch‐technische Anwendungen (PVC und Silicon) zeigt, daß PTFE/VIMA, LDPE/VIMA, PUR und EVA‐Kunststoffe eine gegenüber diesen Marktprodukten verbesserte Blutverträglichkeit besitzen, während die ungepfropften Ausgangs‐Kunststoffe PTFE und LDPE schlechter sind.
Neue Initiatoren zur Polymerisationsauslösung
Authors: Braun Dietrich , Jakobi Rolf 
Published: April 2003

AbstractAzoester des Typs PhR1R2CN=NCR2R1Ph (R1 = Alkyl, R2 = Carbonsäurerest) werden zur Polymerisation eingesetzt. Als Testmonomere dienen Styrol und Methylmethacrylat, wobei sowohl zu geringen als auch zu hohen Umsätzen polymerisiert wird. Die Eigenschaften dieser Initiatoren werden im Zusammenhang mit ihren Zerfallstemperaturen, Strukturmerkmalen und den erzielten Molekulargewichten der Polymeren charakterisiert. Einige der Azoester sind in ihrem Verhalten dem Azoisobutyronitril sehr ähnlich.
Reactivity of crosslinked polymers, 1. Aminoplasts as blowing and initiating agents
Authors: Simionescu C. I. , Benedek I. 
Published: April 2003

AbstractCertain crosslinked aminoplasts used as fillers and pigments in other industrial areas were investigated in the thermomechanical processing (injection and extrusion moulding) of the common thermoplasts as blowing agents. The use of the macromolecular blowing agent in the temperature range of 175 – 210°C with concentrations of 0.5 – 2.0 wt. % led to polymers having a white colour, uniform porosity and reduced density (0.75 – 0.9 g/cm3 for polystyrene foam). Examination by extrusion moulding of the blowing effect showed that the aminoplast had only a slight sensitivity toward the working parameters (temperature, pressure). This was explained by the thermogravimetric data, which demonstrated that the blowing effect was due to the volatilization of a small (about 10%) fraction of the resin, on the basis of its residual reactivity.In order to avoid the main disadvantages of the macromolecular blowing agent (e.g. the low blowing yield and its hard regulation), organic acid additives (e.g. maleic anhydride, malic, adipic acid, etc.) were investigated as kicker. From these compounds the use of maleic anhydride which did not exhibit blowing properties led to an improvement of 100 – 150% of the blowing degree and facilitated its regulation. In order to establish an optimal use of the aminoplast‐maleic anhydride blowing system, the dependence of the blowing effect on the processing parameters and on the composition of the blowing agent were investigated. DTA showed an increased weight loss in the blowing system up to 200°C, attributed in part to sublimation of the anhydride and to its decomposition on the other part. This decomposition was accompanied by a non explosive decarboxylation‐polymerization process connected to the aminoplast. Consequently, in the aminoplast‐maleic anhydride system the aminoplast acted as starter.The endotherm decarboxylation‐polymerization of maleic anhydride (E = 21.7 ± 2.9 · 103 J/mol for decarboxylation) besides the carbon dioxide blowing gas led to a dark coloured polymer, identified by IR, solubility and softening temperature as poly(maleic anhydride). Other organic acids (malic, maleamic, citric acid, etc.) undergoing transformations into maleic acid derivatives led also to polyanhydride‐like polymers by thermochemical processing together with aminoplasts. No copolymers were formed.The differences in activity of the aged and fresh reaction mixture, the reduced decomposition temperature (155 – 165 °C) of the aminoplast‐anhydride system, the progress the weight loss registered by DTA, that of the measured gas volume and of the blowing degree showing a maximum at a concentration of 40 – 60% anhydride, suggested that maleic anhydride did not decompose as such, but as hydrated or aminated compound. Crystalline intermediates identified by DTA, IR spectroscopy and solubility as maleic and maleamic acid were isolated from the reaction mixture, but they were responsible for the blowing effect only in part.
Dynamic mechanical relaxations in polyimide and polyamideimide
Authors: Pereña José M. 
Published: April 2003

AbstractDynamic mechanical measurements of polyimide (PI) and polyamideimide (PAI) films are carried out using a dynamic viscoelastometer in the temperature range from −150 to 250°C. Two relaxations were observed in each polymer at 3.5 Hz. One of them occurs at −107°C (PI) and −80°C (PAI) and is attributed to the water bound to the carbonyl group. The location of the maxima and their activation energies are related to the water content. The other relaxation, due to coupled oscillations of p‐phenylene rings, takes place at 80°C (PI) and 46°C (PAI). Their different activation energies are explained in connection with the structure of each polymer.
Functionalized resins, 1. Gel and macroporous chloromethylated styrenic resins prepared in the presence of toluene as a pore forming agent
Authors: Negre M. , Bartholin M. , Guyot A. 
Published: April 2003

AbstractDepending on the amount of porogenic (toluene) or crosslinking (divinyl benzene) agent, the suspension copolymerization of styrene‐divinyl benzene (DVB) — vinyl benzylchloride (VBC) leads to gel type or macroporous resins. Partial replacement of styrene by VBC does not change much the morphology of the resins. A rather sharp boundary is observed between the two kinds of resins, macroporous resins can be visualized as small nodules of highly crosslinked material linked by loose chains strained in the dry state (narrow distribution of very small pores) and relaxed in the swollen state, thus accounting for the very high swelling ratio observed either in the solvent or in nonsolvent.
Segmented copolyetherurethane‐ureas and semicarbazides for blood circulation systems, III. Mass spectrometric investigations 1, pyro‐field ion mass spectrometry
Authors: Düssel H.‐J. , Wenzel N. , Hummel D. O. 
Published: April 2003

AbstractThe pyro‐field ion mass spectra of urea or semicarbazide linked copolyetherurethanes have been measured with a maximum pyrolysis temperature of 873 K. The polyethers with hydroxy endgroups [poly(oxyethylene), poly(oxytetramethylene), poly(oxypropylene)] and the diisocyanates [4,4′‐diisocyanatodicyclohexylmethane, 4,4′‐diisocyanatodiphenylmethane, 2,4‐diisocyanatotoluene] used for the synthesis can be identified from the spectra without difficulty. Among the diamines [ethylenediamine, hexamethylenediamine, 4,4′‐diaminodiphenylmethane, 1,3‐bis(aminomethyl)benzene] and isophthalic acid dihydrazide used for the coupling of the prepolymers bearing isocyanate endgroups, the aromatic diamines can easily be identified. Aliphatic diamines and isophthalic acid dihydrazide as structural units cannot be identified with the same reliability. Possible pyrolysis fragments suitable for the rapid and unambiguous identification of the building units of the polymer chains (“key fragments”) are given.
Synthesis and thermal stability of methylanisole‐1,2‐dichloro ethane resins
Authors: Patel R. M. , Patel J. C. , Patel K. C. , Patel R. D. 
Published: April 2003

AbstractResin samples have been prepared by the Friedel‐Crafts polymerization of methylanisole with 1,2‐dichloro ethane. The samples were characterized by IR‐spectra and number average molecular weights Mn by vapour pressure osmometry (VPO). The thermal characterization has been carried out by differential thermal analysis (DTA), thermogravimetry (TG) and differential scanning calorimetry (DSC). Kinetic parameters for the decomposition are determined from TG‐ and DTA‐studies. Thermal stability is found to be dependent upon the position of the methyl group on the aromatic nucleus.
Études Diélectriques de Copolymères α‐Acétoxystyrène/Styrène Parasubstitués
Authors: Seytre Gérard , Monthéard Jean Pierre , Camps Marcel , Kawaye Saadallah 
Published: April 2003

AbstractCette étude a pour objectif général l'examen de divers copolymères à propriétés diélectriques améliorées. Elle concerne plus particulièrement la modification de comportement électrique apportée par l'introduction de groupements fortement polarisables sur des copolymères α‐acétoxystyrène/styrène, les groupes polaires étant portés par le styrène. La synthèse et la caractérisation physicochimique de ces poly‐mères réalisées précédemment permettent une corrélation structure‐propriétés. L'examen des caractéristiques électriques (constante diélectrique, tangente d'angle de perte) a été effectué dans un large domaine de températures et de fréquences et a conduit à sélectionner des matériaux filmogènes susceptibles de convenir pour la réalisation de condensateurs.
Einfluß der Änderung des Ordnungsgrades des Ethylens mit der Druckerhöhung auf den Verlauf der radikalischen Polymerisation
Authors: Stoiljković Dragoslav , Jovanović Slobodan 
Published: April 2003

AbstractNach Kargin und Kabanov1 sind für die Polymerisationen von Monomeren, die sich im Zustand höherer Ordnung befinden, folgende Merkmale charakteristisch: Induktionsperiode, Selbstbeschleunigung, vernachlässigbare Aktivierungsenergie und die Abwesenheit der Abbruchreaktion.In dieser Arbeit wird gezeigt, daß bei der radikalischen Polymerisation von Ethylen unter verschiedenen Drücken und Temperaturen alle erwähnten Merkmale nachzuweisen sind, und sich, unserem Modell2 entsprechend, Ethylen bei Druckerhöhung in einem Zustand höherer Ordnung befindet. Durch diese Arbeit hoffen wir, unser Modell2 über das Verhalten von Ethylen bei Druckerhöhung zu unterstützen und zur besseren Kenntnis dieser komplizierten Reaktion beizutragen.
Solid state extrusion of thermoplastic elastomers, 2. Structure and properties of solid state extruded block copolyesters
Authors: Bandara Upali , Dröscher Michael 
Published: April 2003

AbstractBlock copoly(ether ester)s based on poly(butylene terephthalate) containing different amounts of poly(oxytetramethylene) were oriented by solid state extrusion. The degree of die swell decreases with increasing crystallinity of the extrudates. The morphological properties of the extrudates depend on the extrusion conditions. The long period is only determined by the undercooling. The dependence of the mechanical and dynamical‐mechanical properties of the extrudates on the extrusion condition was investigated. The chemical composition influences the mechanical behaviour strongly. It was concluded that this is due to the different concentration of the taut tie molecules.
Coordination polymers, 4. Electrical properties of some bisphenolic chelate polymers
Authors: Spiratos Mihaela , Rusu Gheorghe Ioan , Airinei Anton , Ciobanu Aglaia 
Published: April 2003

AbstractThe electrical properties of Ni(II) and Cu(II) chelate polymers of bis(2,4‐dihydroxybenzaldehyde), bis(2,4‐dihydroxyacetophenone), bis(2,4‐dihydroxybenzophenone), bis(2,4‐dihydroxybenzaldehyde)ethylenediimine, bis(2,4‐dihydroxyacetophenone)‐ethylenediimine, bis(2,4‐dihydroxybenzophenone)ethylenediimine and bis(2,4‐dihydroxyacetophenoneimine) and aromatic acid chlorides have been studied. The chelate polymers with the most rigid structure were found to have the highest conductivities.
Processable heat‐resistant polymers. VIII. Synthesis and characterization of polyamideimide from N‐(4‐carboxy phenyl) trimellitimide and sulfanilamide
Authors: Maiti Sukumar , Ray Atanu , Maiti Manoranjan 
Published: April 2003

AbstractA novel polyamideimide was synthesized by reacting sulfanilamide and N‐(4‐carboxy phenyl) trimellitimide or its diacid chloride derivative. The solution, thermal, electrical and a few other properties of the polymer were studied. The polymer was found to be soluble in the highly polar solvents. The polymer solution was relatively stable. Thermogravimetric data revealed that the polymer underwent 12% weight loss at 375 °C in air. The dielectric constant of the polymer at 30 °C was found to be 5.45 at 1 kHz. X‐ray diffraction data revealed that the polymer is crystalline in nature.
Migration in a strongly interacting model system “plastic sheet/contact medium”: Transfer of low molecular components out of high‐impact polystyrene into tricaprylin
Authors: Klahn Jürgen , Figge Karl 
Published: April 2003

AbstractMoulded sheets made of high‐impact polystyrene (HI‐PS), containing three different commercial additives of which one at a time was 3H‐labelled were kept in contact with 14C‐labelled tricaprylin at 40 °C. The penetration of the tricaprylin into the HIPS sheets and the simultaneous migration of the additives into the tricaprylin were analyzed by means of radio‐tracer techniques, applied to thin cut sections of the plastic sheets.It turned out that irrespective of the special additive under investigation, the migration process is nearly totally determined by the swelling of the HI‐PS. The reason for this is to be found in the extraordinary strong interaction between HI‐PS and tricaprylin which is by no means representative of a contact system “plastic/edible fat” in general. By application of a simplified version of the mathematical model developed recently in our institute, a concise description of the migration process in the contact system “HI‐PS/tricaprylin” is given.
Substituted and branched polychalcones, 3. Thermal properties of the polymers
Authors: Malm Bo‐Johan 
Published: April 2003

AbstractThe thermal properties of polychalcones prepared from vanillin (2a), p‐hydroxybenzaldehyde (2b) and benzaldehyde (2c) by Friedel‐Crafts acetylation were investigated by thermogravimetry in air and nitrogen and by differential scanning calorimetry. The polymers were thermally stable up to 550–650 K. Various current methods developed for the kinetic parameters from the TG data are compared and discussed. The polychalcones were found to degrade by first‐order reactions with respect to their pyrolysis maxima. The decomposition occurred in three degrees. The activation energies and the Arrhenius pre‐exponents were determined. The IR spectra of the pyrolysis residues indicated that oxidation was the main way of the degradation of the polychalcones.
Zur Analyse von Polyamiden. Bestimmung der Molekülmassen und ihre Verteilung
Authors: Pastuska Gerhard , Just Ulrich , August Hans 
Published: April 2003

AbstractEs werden Verfahren zur Bestimmung der Molekülmassen und ihrer Verteilung in Polyamiden beschrieben. Neben der Gelchromatographie ist die Kleinwinkel‐Laser‐lichtstreuung als Nachweisverfahren geeignet. Bei Kombination eines Gelpermeationschromatographen mit einem Kleinwinkel‐Laserlichtstreudetektor sind direkte Bestimmungen der Molekülmassenverteilung möglich.
Photolytische 1,2‐Cycloaddition von Maleimiden an trans‐Polypentenamer
Authors: Heinzl Johann , Heusinger Helmut 
Published: April 2003

AbstractZiel der Arbeit war, die aus der Literatur bekannte photolytische 1,2‐Cycloaddition von Maleinsäurederivaten an monomere Olefine auf ein Polymeres mit isolierten Doppelbindungen zu übertragen. Dazu wurden Lösungen von trans‐Polypentenamer und Maleinsäureimid, verschiedenen N‐Alkylmaleimiden und N‐Phenylmaleimid einer UV‐Bestrahlung unterworfen.Bis auf N‐Phenylmaleimid, das auch bei langen Bestrahlungszeiten nur in sehr geringem Umfang reagierte, konnten alle Maleimide quantitativ umgesetzt werden. Hauptreaktionen der Maleimide waren die 1,2‐Cycloadditionen an das Polymere und Dimerenbildung (d. h. 1,2‐Cycloaddition zweier Maleimidmoleküle). Während der Addition fand an 30% der Polymerdoppelbindungen cis‐Isomerisierung statt. Bei Verwendung von N,N'‐Dodekamethylenbismaleimid ließ sich über die 1,2‐Cycloaddition eine Vernetzung des Polymeren erreichen. Eine wesentliche Beteiligung anderer Reaktionswege wie Copolymerisation und substituierende Addition (En‐Reaktion) am Reaktionsverlauf sind auszuschließen.