bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoabbau von PVC‐Folien. IV. Einfluß des Sauerstoffs
Authors: Braun Dietrich , Bezdadea Eugen 
Published: April 2003

AbstractEs wurden Masse‐PVC‐Folien verschiedener Dicke sowohl unter Stickstoff und Sauerstoff als auch unter mehreren Gemischen dieser beiden Gase mit einer Quecksilberhochdruckdampflampe bestrahlt. Verschiedene Aspekte des eingetretenen Photoabbaus wurden untersucht, darunter die HCI‐Abspaltung, die Zunahme der Carbonylkonzentration in den bestrahlten Folien mit der Sauerstoffkonzentration im Trägergas und die Abhängigkeit der Strukturänderungen des Polymeren von der Temperatur der Probe.Es wurde gefunden, daß zwischen den beobachteten chemischen Veränderungen der bestrahlten Folien und der Sauerstoffkonzentration im angewendeten Gasgemisch eine direkte Beziehung besteht.
Investigation of the effect of gamma rays on the properties of polyamide fibres, I. The changes of some mechanical and chemical properties
Authors: Szymański W. , Lerke G. , Rymian B. 
Published: April 2003

AbstractMeasurements of mechanical resistance and of some chemical changes were performed for a γ‐irradiated PA 6 polyamide fibre in the form of surgical threads. A relatively high radiation durability was established for irradiation doses of the order of 104 Gy. The sterilizing dose was assumed to be 3 ·104 Gy. It was argued that in this dose range a deterioration of the mechanical properties of about 5% should be expected.
Konversion von epoxidharzen im kritischen zustand
Authors: Liška Vladimír , Adámková Gabriela 
Published: April 2003

AbstractKritische Größen der mit üblichen Härtemitteln vom Polyamin‐ und Anhydridtyp auszuhärtenden Epoxidharze wurden chemorheologisch bestimmt. Die im kritischen Zustand chemisch bestimmte Konversion von Epoxidgruppen wurde mit dem Charakter des Härtemittels und mit der Reaktivität von Epoxidharz/Härter‐Mischung korreliert.
The analysis of 13C NMR spectra of mixtures containing isotactic and atactic polystyrene
Authors: Standt Ulrich‐D. , Klein Joachim 
Published: April 2003

AbstractA method to calculate the portion of isotactic polystyrene from the 13C‐NMR spectra of mixtures containing atactic and isotactic polystyrene is proposed and applied to an extract from an isotactic raw polymer. The result is in acceptable agreement with DSC measurements.
Autohäsion von Elastomeren
Authors: Bothe Lothar , Rehage Günther 
Published: April 2003

AbstractBringt man zwei Proben des gleichen Elastomeren in Kontakt, so tritt eine Haftung auf, die man Autohäsion nennt.Die Haftfestigkeitszunahme mit der Kontaktzeit wird durch eine grenzflächenüberschreitende Diffusion von beweglichen Makromolekülkettenenden hervorgerufen. Bei der Autohäsion von unvernetzten Elastomeren läuft dieser Vorgang so lange ab, bis die Volumenfestigkeit des Elastomeren in der Kontaktzone erreicht wird.In dieser Arbeit wurde die Autohäsion von Polybutadien, Acrylnitril‐Butadien‐Copolymeren, Ethylen‐Propylen‐Copolymeren und Polychlorbutadien untersucht. Im einzelnen wurden die Einflüsse des Molekülbaus, polarer Seitengruppen, der Kristallinität, der Kontaktzeit, der Zerreißgeschwindigkeit sowie der Einfluß von Lösungsmitteln auf die Haftungseigenschaften der Elastomeren behandelt.
A new method of characterizing molecular networks with the van der waals equation of state
Authors: Eisele U. , Heise B. , Kilian H.‐G. , Pietralla M. 
Published: April 2003

AbstractThe utility of the van der Waals equation of state for real networks is demonstrated by its application to various rubbers. A new method of characterization of networks as well as a discussion of its consequences are presented.
The heterogeneous structure of polyurethane networks
Authors: Lipatova T. E. , Shilov V. V. , Minenko N. N. 
Published: April 2003

AbstractUsing small‐angle X‐ray scattering the microheterogeneous structure of amorphous polyurethane networks was investigated. It was found to be determined by the corresponding structural characteristics of the initial oligomeric diols. The structure of the oligomers is preserved more or less depending on their chain length in polymeric networks (poly(oxypropyleneglycol) with molecular weights of 2000 and 500 g/mol, resp.). In the latter case a great influence on the structure is exerted by rigid fragments around crosslinks which are characterized by great concentrations of H‐bonds. This is leading to a decrease in the heterogeneity. The heterogeneous structure of the polyurethane networks becomes more distinct with an increase in the oligomer chain length and degree of conversion. The observed effects are explained by the change in the degree of aggregation of parts of the network structure.
Structural changes of acrylic solutions during non‐Newtonian flow
Authors: Stoyanov A. I. 
Published: April 2003

AbstractBy means of the Eyring‐Frenkel equation \documentclass{article}\pagestyle{empty}\begin{document}$\eta = {\rm A}_{0} e^{\Delta {\rm G}_{{\rm VISC}} /{\rm RT}}$\end{document} and the assumption that A0 = 10−3 poise the influence of shear rate, molecular weight and concentration on some structural changes of acrylic solutions during non‐Newtonian flow was investigated. It was established that the shear rate and the concentration influenced the activation heat and the activation entropy of viscous flow. The structural changes of acrylic solutions depending on molecular weight possessed an entropy character.
Photochemical grafting of acrylated azo dyes onto polymeric surfaces, IV. Grafting of 4‐(N‐ethyl‐N‐2‐acryloxyethyl)amino‐4′‐nitro‐azobenzene onto cellulose
Authors: Bellobono Ignazio Renato , Calgari Seba , Leonardi Maria Cristina , Selli Elena , Paglia Ernestina Dubini 
Published: April 2003

AbstractPhotochemically induced grafting and graft‐polymerization of 4‐(N‐ethyl‐N‐2‐acryloxyethyl)amino‐4′‐nitro‐azobenzene I, brought into contact in the solid state with cellulose by evaporation of solvent from monomer solutions, has been investigated kinetically at 30°C. Two constant rate periods were observed. The first one was interpreted on the basis of a self‐sensitized grafting mechanism of monomeric or oligomeric species of I, photochemically initiated by hydrogen abstraction from the cellulose surface. The second one was explained as a self‐sensitized photochemically induced graft‐polymerization of I on the first grafted layer. Some particular features, such as concurrent photodegradation of the first grafted layer at low surface coverage, are discussed in the light of the proposed mechanism.
Bifunctional initiators, II. Synthesis and characterization of 5,5′‐azo‐bis‐(5‐cyanocaproyl)‐benzoyl diperoxide
Authors: Shaikh Abdul Sattar , Comǎniţǎ Eugenia , Dumitriu Severian , Simionescu Cristofor 
Published: April 2003

Abstract5,5′‐Azo‐bis‐(5‐cyanocaproyl)‐benzoyl diperoxide was synthesized starting from 5,5′‐azo‐bis‐(5‐cyanohexanoic) acid, obtained in its turn from 5‐keto‐hexanoic acid, hydrazine sulphate and sodium cyanide.5,5′‐Azo‐bis‐(5‐cyanohexanoic) acid was then converted into acid chloride and condensed with perbenzoic acid. The structures of intermediates and of the product were elucidated by means of elemental analysis and IR and NMR spectral measurements.In order to settle the bifunctional character of the synthesized initiator the thermolysis rate constants for azo and peroxy groups, energies of activation and half‐life times were settled. By comparing the kinetic data with those obtained in 4,4′‐azo‐bis‐(4‐cyanovaleryl)‐benzoyl diperoxide thermolysis the decomposition rate was found to increase and the bifunctional character to enhance with increasing length of the radical connecting the azo and peroxy groups.
Effect of mercerization‐stretching on vinyl graft polymerization of cotton
Authors: Hebeish A. , El‐Rafie M. H. , Khalil M. I. 
Published: April 2003

AbstractScoured ply cotton yarn was slack mercerized and slack mercerized followed by restretching the yarn in the mercerizing solution to 90, 94, 96, 100, and 103% of the original length. The six substrates so obtained together with scoured cotton were grafted independently with methyl methacrylate and acrylonitrile using ceric ammonium nitrate as initiator. The extent and rate of grafting found with slack mercerized cotton were significantly higher than those of scoured cotton irrespective of monomer used.The same holds, but lo lesser degree, good for slack mercerized cotton followed by restretching to 90% of original length. Different situation was encountered with slack mercerized cotton followed by restretching to 94 and 103%; these substrates showed lower extent and rate of grafting than scoured cotton. Moreover, the extent and rate of grafting decreased by increasing the magnitude of stretching. Similar trend was observed when all the said substrates were subjected to oxidation with ceric ions. It is believed that there must be differences in microstructural features between scoured cotton, slack mercerized cotton and slack mercerized‐restretched cottons that account for this.
Studies on syntheses and permeabilities of special polymer membranes, 32. New preparation method of cellulose membranes
Authors: Uragami Tadashi , Sugitani Yasuhiro , Sugihara Mizuho 
Published: April 2003

AbstractThe preparation of cellulose membranes from mixtures of cellulose, nonprotonic polar organic solvents, paraformaldehyde, and basic catalyst was studied. When dimethyl sulfoxide was used as casting solvent, the resulting membrane was the densest. An increase of an additional amount of triethyl amine used as basic catalyst gave denser membranes.
Studies on polymers prepared from thiophenol: An electroanalytical approach. I. Studies on poly(phenylene sulphides)
Authors: Viswanathan P. S. , Vasudevan P. 
Published: April 2003

AbstractIn this paper we report some of the physico‐chemical changes occurring in poly(phenylene sulphide) prepared by the homopolycondensation of thiophenol. The various electrical properties measured on these polymers were used to identify the temperatures at which these transitions occur.
Polymerization of lactams, XLI. Molecular characterization of linear and branched polycaprylolactam
Authors: Prokopová Irena , Tuzar Zdeněk , Kondelíková Jaroslava , Schmiedová Daniela , Králíček Jaroslav 
Published: April 2003

AbstractSamples of linear polycaprylolactam have been prepared and fractionated, and the [η]‐Mw relationship has been established in m‐cresol. Statistically branched samples have been obtained by copolymerizing 8‐caprylolactam with bislactams. The degree of branching as well as the branching ability of different bislactams are discussed and compared with the corresponding data for branched polycaprolactams.
Grafting onto wool, XVII. Graft copolymerization of methyl acrylate and ethyl acrylate by use of VO(acac)2 as initiator. Comparison of monomer reactivities
Authors: Misra B. N. , Sood D. S. , Sharma R. K. 
Published: April 2003

AbstractGraft copolymerization of acceptor monomers methyl acrylate and ethyl acrylate onto Himachali wool fiber has been studied in aqueous medium by using vanadium oxyacetyl acetonate as initiator at 40, 50, 60, and 70°C. Graft copolymerization was carried out for various reaction periods and nitric acid was found to catalyse the reaction. Percentage of grafting and percent efficiency have been determined as functions of concentration of nitric acid, concentration of initiator, concentration of monomer, time, and temperature. Under optimum conditions, methyl acrylate and ethyl acrylate afforded maximum grafting to the extent of 28.4 and 18.5%, respectively. Relative reactivities of methyl acrylate and ethyl acrylate towards grafting have been compared with those of methyl methacrylate, acrylic acid and vinyl acetate reported earlier from this laboratory. Different vinyl monomers showed the following reactivity order: MMA > MA > EA > AAc > VAc. Several grafting experiments were carried out in the presence of various additives which included tert‐butylhydroperoxide (TBHP), dimethylsulfoxide, pyridine, and dimethylformamide. Only TBHP was found to enhance grafting to a considerable extent, other additives decrease percent grafting of both methyl acrylate and ethyl acrylate.
A contribution to the investigation of PVC‐plasticizer interactions
Authors: Drexler Jiří , Šimoník Josef 
Published: April 2003

AbstractTemperature dependent characteristics of blends of suspension poly(vinyl chloride) with low and high molecular weight plasticizers in the region of processing temperatures have been investigated. The interaction process has been studied under dynamic conditions using the differential thermal analysis (DTA) method under non‐iso‐thermal conditions. As a result of the DTA curves evaluation as well as of the discussion of results it has been shown that the energy transformation occurring during the PVC‐plasticizer system processing is manifested by changes of thermal behavior. The values of heat released, corresponding to the maximum heat transfer rate have been identified as primary data which can be used in correlations describing the quality of plasticizers present in the system. The correlational relations covering the region of processing temperatures provide a “homogeneity” criterion of the system, corresponding to the plasticizing capability of the plasticizer involved.
Study of the reaction between urea and formaldehyde by dsc and 13C NMR spectroscopy
Authors: Šebenik A. , Osredkar U. , Žigon M. , Vizovišek I. 
Published: April 2003

AbstractThe reactions of urea with formaldehyde were studied by means of 13C NMR spectroscopy and differential scanning calorimetry (DSC) in acid and neutral medium, the temperature range being between 290 and 390 K. At higher pH the peak of the DSC curve splits into two peaks one of which belongs to the addition of formaldehyde to urea and the second to the subsequent condensation of the latter. For both reactions, the activation energy, heat of polymerization, reaction order and temperature maximum have been determined. The usefulness of DSC to study the kinetics of more complex polycondensation reactions was established.
Structure and properties of poly(ethylene terephthalate) crystallized by annealing in the highly oriented state. 3. Dynamic‐ and static‐mechanical properties
Authors: Fakirov Stoyko , Stahl Dieter 
Published: April 2003

AbstractCommercial undrawn and cold drawn (5 × ) poly(ethylene terephthalate) (PETP) fibers and bristles have been annealed with fixed ends for 6 h in vacuum at different temperatures between 60 and 260°C. With these samples static‐ and dynamicmechanical measurements have been carried out.It has been found that the α‐and β‐processes as well as the moduli depend on the annealing temperature (Ta) in different way, for undrawn and drawn material. The temperature position of the β‐peak evaluated from tg δ and loss modulus as well as the step height of α‐ and β‐processes are unsensitive to the Ta for the undrawn material in contrast to the drawn one for which maxima are observed. The appearance of these maxima is explained by the dominating role at the corresponding crystallization temperature of one of the two concurrent processes ‐ crystallization and disorientation, reflected in the change of the effective density of amorphous regions.The dynamic and static measured moduli as well as the stress at break for drawn PETP decrease with the increase of annealing temperature as generally observed. The predominating significance of orientation and the state of amorphous phase in comparison with crystallinity is demonstrated.An extremely high deformation ability at room temperature (up to 200%) of previously drawn and annealed at 255 or 260°C bristles is observed. This originates from the solid state postcondensation and premelting phenomena taking place during annealing in vacuum.
Methoden zur Verfolgung der Herstellung von Melamin‐Formaldehyd‐Harzen
Authors: Braun Dietrich , Günther Peter , Pandjojo Wirjopartono 
Published: April 2003

AbstractBei der Kondensation von Melamin (M) mit Formaldehyd (F) wurde zur schnellen Reaktionskontrolle die Bestimmung der Wasser‐ und Acetonverträglichkeit herangezogen. Die Einflüsse von pH‐Wert und MF‐Molverhältnis auf diese Messungen wurden untersucht. Sowohl mit den mit Wasser ausgefällten als auch mit den in Lösung verbliebenen Harzfraktionen wurden gelchromatographische Untersuchungen durchgeführt.Die Bestimmungen von Wasser‐ und Acetonverträglichkeit sind wegen der starken Abhängigkeit der Meßergebnisse von den Reaktionsbedingungen nur bedingt zur Beschreibung von Harzzusammensetzungen geeignet.
Enzymatic hydrolysis of cotton wastes. Effect of γ‐ray pretreatments
Authors: Focher Bonaventura , Marzetti Annamaria , Santoro Cataldo , Sarto Virginio , D'Angiuro Luigi 
Published: April 2003

AbstractTextile cotton wastes were irradiated with γ‐rays at different doses and solubilized with 10% NaOH solutions. The regenerated products underwent enzymatic hydrolysis and their degradation pattern was compared with that of the cotton celluloses untreated or treated only with γ‐rays. The different samples were characterized by measurements of X‐ray diffraction, degree of polymerization, moisture regain and water retention. The structural and morphological modifications induced by the pretreatments were correlated with the variations of kinetic parameters, particularly the Vmax/Km ratio, defined as specificity constant. Only the combination of irradiation with dissolution pretreatments gave a considerable increase of hydrolysis reaction effectiveness.
Untersuchungen der Molgewichtsverteilung von Harnstoff‐Formaldehyd‐Leimharzen
Authors: Dunky Manfred , Lederer Klaus 
Published: April 2003

AbstractHandelsübliche, als wäßrige Dispersionen angelieferte UF‐Leime wurden gefriergetrocknet und das Leimharz in DMSO gelöst mit GPC (Gele auf Basis von Vinylacetat‐Divinyladipat, Säulenlänge 2‐10 m), Dampfdruckosmometrie und Lichtstreuung untersucht. Dabei wurde festgestellt, daß höherkondensierte UF‐Harze Anteile mit sehr hohem Molekulargewicht (M > 100 000 g/mol) enthalten. Es wurde nachgewiesen, daß sich diese Anteile in der dispersen Phase des Leimes anreichern und in DMF weitgehend unlöslich sind. Die Leistungsfähigkeit der entwickelten Methodik zur GPC von UF‐Leimharzen wird schließlich anhand von Untersuchungen der Alterung in wäßriger Dispersion (20°C) und in DMSO (60°C) demonstriert.
Copolyimides new polybenzoxazinone‐imides
Authors: Neamţu Gabriela , Brumǎ Maria 
Published: April 2003

AbstractNew polybenzoxazinone‐imides have been synthesized by cyclopolycondensation reaction of 4,4′‐diaminodiphenylmethane‐3,3′‐dicarboxylic acid with diacid chlorides containing preformed imide rings. The low temperature solution polycondensation technique, used in these experiments, afforded poly(amic acids) of high molecular weight in the first step, which subsequently underwent thermal cyclodehydration at 200–300°C to give polybenzoxazinone‐imides in the second step. The obtained polymers have been characterized by IR absorption, elemental and thermogravimetric analyses. From 10% polymer solution flexible and transparent films have been cast with good mechanical and insulating properties.
High‐temperature polymers polybenzothiazole‐amide‐imides
Authors: Neamţu Gabriela , Mandric G. , Zugrǎvescu I. 
Published: April 2003

AbstractA series of new polymers containing benzothiazole, imide and amide units in macromolecular chains were prepared. The polymers were synthesized by low temperature polycondensation of aromatic diamines containing benzothiazole rings with diacid chlorides containing preformed imide rings. The obtained polymers are soluble in aprotic dipolar solvents and they have high molecular weights (ηinh = 0.4−1.2 dl/g), high thermal stability up to 400°C and good chemical resistance. From 10% polymer solutions flexible and transparent films have been cast with good physicomechanical properties.
Preparation of silica by acid dissolution of sepiolite and study of its reinforcing effect in elastomers
Authors: Hernández L. González , Rueda L. Ibarra , Diaz A. Rodriguez , Antón C. Chamorro 
Published: April 2003

AbstractThe preparation of amorphous silica by acid treatment of a natural magnesium silicate and its use as reinforcing filler for NR and SBR compounds are studied. Limited to the treatment with nitric acid, the rate constants at different temperatures and acid concentrations and the activation energy are calculated, as a function of percentage of extracted magnesium.The resulting material is basically an amorphous silica (92.5% SiO2), as shown by X‐ray analysis, that keeps the fibrous morphology of the original mineral. According to a preliminary technological study the resulting silica is a suitable reinforcing filler for general purpose rubbers; a comparison between the experimental results and those obtained with a commercial fine particle precipitated silica was made. Using a SBR compound the effect of silane coupling agents on the new silica was studied.
Polymerization of glycidyl methacrylate, methacrylic acid, acrylamide and their mixtures with cotton fabric using fe2+‐thioureadioxide‐H2O2 redox system
Authors: Waly A. , Abou‐Zeid N. Y. , El‐Alfy E. A. , Hebeish A. 
Published: April 2003

AbstractPolymerization of glycidyl methacrylate (GMA), methacrylic acid (MAA), acrylamide (Aam) and their binary mixtures with cotton cellulose fabrics using Fe2+‐thioureadioxide‐H2O2 redox system was investigated under a variety of conditions. While temperatures of 50, 80, 65, and 95°C constituted the optimal polymerization temperature for GMA, MAA, Aam and GMA/MAA (8:2), respectively, maximum polymerization of GMA/MAA (2:8), Aam/MAA (8:2) and Aam/MAA (2:8) occurred at 75°C. The polymerization reaction proceeded initially very fast then levelled off irrespective of the monomer or monomer mixtures used. However, the magnitude of the polymer add‐on at levelling off of polymerization followed the order GMA > GMA/MAA (2:8) ≥ GMA/MAA (8:2) > Aam/MAA (2:8) ≥ MAA ≥ Aam/MAA (8:2) > Aam. The polymer add‐on enhanced by increasing the H2O2 concentration up to a certain limit and then decreased. The same situation was encountered with respect to thioureadioxide concentration. The involvement of the epoxy ring of GMA with MAA during polymerization of their mixture with cellulose occurred only at a higher ratio of GMA in the mixture. Also a significant contribution of Aam in the polymer add‐on obtained with a Aam/MAA mixture could only be achieved at a higher ratio of Aam in this mixture.
Catalytic effect of nickel metal and some of its compounds on the aqueous polymerization of methyl methacrylate
Authors: Moustafa A. B. , Rabie A. M. , Badran A. S. 
Published: April 2003

AbstractPolymerization of methyl methacrylate (MMA) in water was carried out in presence of nickel metal powder, some of its oxides and salts at temperatures of 40, 50, and 60°C using sodium bisulfite as an initiator. It has been found that nickel metal powder retards the polymerization reaction, and increases the apparent activation energy from 6.4 kcal/mol to 13.3 kcal/mol, while nickel salts and nickel oxides were found to catalyze the polymerization process. Nickel nitrate was found to have the highest catalytic effect and resulted in the formation of the least average molecular weights. Nickel sulfate resulted in obtaining the least salt catalytic effect and the highest average molecular weight.