bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoabbau von copolymeren aus styrol, methylmethacrylat und acrylnitril mit 2‐naphthylmethacrylat
Authors: Boudevska H. , Bratschkov Ch. , Todorova O. , Bezdadea E. , Braun D. 
Published: April 2003

AbstractCopolymere aus Styrol, Methylmethacrylat und Acrylnitril mit steigenden Gehalten an 2‐Naphthylmethacrylat (2‐NMA) wurden photooxidativ abgebaut, um den Einfluß dieses Comonomeren als inneres Modifizierungsmittel beim Photoabbau dieser Polymeren untersuchen zu können. Es wurde festgestellt, daß 2‐Naphthylmethacrylat bei Gehalten bis zu 15 Gew.‐% in Copolymeren mit Styrol zu einer Stabilisierung führt. Auch im Falle der Copolymeren mit Acrylnitril bestätigte sich diese stabilisierende Wirkung des 2‐Naphthylmethacrylats. Bei den Copolymeren mit Methylmethacrylat kann der Einfluß des 2‐Naphthylmethacrylates wegen der Depolymerisierungstendenz der MMA‐Grundbausteine nicht eindeutig interpretiert werden, obwohl sich bei dem Photoabbau eines Copolymeren mit ca. 16 Gew.‐% 2‐NMA die Uneinheitlichkeit verringerte.
Composites von novolak‐lignit zur herstellung von aktivkohle
Authors: Simitzis Johannis 
Published: April 2003

AbstractNovolak‐Harze, mit unterschiedlichen Anteilen an Lignit vermischt, wurden gehärtet und dann bis 1000°C verkohlt. Die während der Verkohlung entwichenen Gase CH4 und CO wurden gemessen, ebenso der Gewichtsverlust und das Schrumpfen der Proben. Es zeigte sich, daß zum thermischen Abbau der Proben mindestens 800°C notwendig sind. Die Porengrößenverteilung der Verkohlungsrückstände wurde bestimmt. Es wurde gefunden, daß das Verhältnis der Novolak‐Lignit Mischungen so gewählt werden kann, daß schließlich die kohlehaltigen Materialien denen gleichen, die nur aus Lignit Ausgangsmaterial (hauptsächlich Makroporen enthaltend) oder nur aus Novolak (hauptsächlich Übergangsporen enthaltend) hergestellt sind. Es zeigte sich auch, daß die hergestellten kohlehaltigen Materialien die Fähigkeit haben, Methylenblau aus seinen wäßrigen Lösungen zu adsorbieren.
Epoxy resins modified by carbon dioxide
Authors: Rokicki Gabriel , Lewandowski Marcin 
Published: April 2003

AbstractThe modification of epoxy resins by means of carbon dioxide is presented. The resulting resins contained different amounts of cyclic carbonates (1,3‐dioxolane‐2‐one rings) instead of a part of epoxy groups. The effect of the cyclic carbonate content on viscosity, gel time, peak exotherms, and crosslinking extent of the above mentioned resins was investigated.Mechanical and thermomechanical properties of the modified resins cured with triethylenetetramine have been determined. It was found that heat‐distortion temperature, impact resistance, hardness, compressive strength, and lap shear strength of the resins containing cyclic carbonates were higher than those of unmodified ones.
N,N'‐Diglycidylimides and their polymers
Authors: Mantecóan Ana , Cádiz Virginia , Serra Angels , Martínez Pedro‐Alberto 
Published: April 2003

AbstractAt first new epoxy derivatives, namely glycidylimide compounds, have been prepared using benzyltrimethylammonium chloride as catalyst and epichlorohydrin in excess. Their chemical and physical properties were studied. Spectral data confirmed these new structures.Afterwards new epoxy resins have been synthesized by the reaction of diimides and their glycidyl derivatives in N,N‐dimethylformamide. The physical characteristics of the obtained polymers and also their solubilities are reported.Their IR, 1H‐ and 13C‐NMR spectra allowed to confirm the polymer structure. Thermal analysis of these compounds showed their good thermal properties.
Synthesis and properties of compounds related to stilbazole
Authors: Nethsinghe Lakshman P. , Plesch Peter H. , Hodge David J. 
Published: April 2003

AbstractWe report attempts to create conjugated polymers consisting of alternating phenylene and heterocyclic rings separated by double bonds by means of condensations between terephthalaldehyde and dimethyl nitrogen bases. Because the products precipitated during their formation even at 180°C in N‐methyl‐2‐pyrrolidinone (NMP), only oligomers of up to ca. 30 rings (DP = 15) could be obtained; most of the adequately soluble products had DP between 4 and 8, and from these oligomers films on glass or quartz could be made. When the films were exposed to I2, NO2, or SbF5, most of them, initially very good insulators, showed an increase in electrical conductivity of up to 6 powers of 10; but the rapid reversal of this change when the reagent evaporated and the lack of any clear changes in the UV‐vis spectrum of the films showed that most likely true “doping” had not occurred.Extensive syntheses with a variety of quaternised bases also failed to yield oligomers oxidisable by electron‐acceptors.For reference purposes, especially for their spectra, a large number of pure “model” compounds of the distyrylpyridine and distyrylpyrazine type, and quaternised analogues of the former, were synthesised, many of them new compounds. These were also used as calibrants for a GPC column operating with NMP solutions.Several improvements were made in the synthetic techniques.
Influence des copolymères greffés sur les propriétés mécaniques des alliages de polyéthylène avec polystyrène
Authors: Boutevin Bernard , Piétrasanta Yves , Sarraf Tarek 
Published: April 2003

AbstractNous avons étudié l'utilisation des copolymères greffés polyéthylène‐graft‐poly‐styrène (P(E‐g‐S)) dont les mélanges de polyéthylène basse densité et polystyrène. Les copolymères P(E‐g‐S) sont préparés par la polymérisation du styrène en présence de polyéthylène hydroperoxydé. L'addition de 2,5% en poids de P(E‐g‐S) au mélange polyéthylène‐polystyène augmente considérablement leur contrainte à la rupture εR mais beaucoup moins leur allongement à la rupture εR. Une comparaison entre les copolymères greffés et séquencés utilisés comme des émulsifiants des mélanges polyéthylène‐polystyrène montre que le P(E‐g‐S) est intermédiaire entre les copolymères greffés et séquencés cités en ce qui concerne leur influence sur les propriétés mécaniques des mélanges. Les photographies de la surface de fractures des mélanges montrent la diminution de la taille de phase après addition du P(E‐g‐S) aux mélanges.
Photo‐oxydation d'elastomèeres EPDM et EPM en présence de systèmes photosensibles, 1. rôle des dérivés de phénylacétophénone
Authors: Bousquet Jean‐Alain , Fouassier Jean‐Pierre 
Published: April 2003

AbstractLa photo‐oxydation d'élastomères de type poly[éthylène‐co‐propène‐co‐(1,4‐hexadiène)] (EPDM) et de type poly(éthylène‐co‐propène) (EPM) photosensibilisés avec différents dérivés alcoxylés de phényl acétophénone: 2,3 diméthoxy (DMPA), 2‐méthoxy (MPA), 2‐éthoxy (EPA), à l'état de mélange a été étudiée dans le but de préciser la nature des mécanismes primaires de transfert d'énergie et d'amorçage radicalaire ainsi que le mode de développement des principales réactions d'oxydation dans un milieu hétérogène où les valeurs des rendements quantiques sont difficilement accessibles. Par analogie avec des systèmes modèles précédemment étudiés, l'importance du rôle joué par les fonctions hydroperoxydes et les photoproduits issus de la dégradation du photo‐amorceur, a été mise en valeur. La photoréticulation des échantillons irradiés apparaît faire partie intégrante du processus général de photooxydation dans lequel deux phases réactionnelles consécutives ont été distinguées.
Structure and properties of acrylonitrile‐functional silane copolymers
Authors: Rao V. Lakshmana , Eshwar M. C. , Babu G. N. 
Published: April 2003

AbstractX‐ray diffraction, thermomechanical and thermogravimetric studies on polyacrylonitrile (PAN), poly(acrylonitrile‐co‐vinyl‐tris(methoxyethoxy)silane) (poly(AN‐co‐VTMES)), poly(acrylonitrile‐co‐vinyltriethoxysilane) (poly(AN‐co‐VTES)), and poly(acrylonitrile‐co‐methylmethacryloyloxypropyltrimethoxysilane) (poly(AN‐co‐MPTMS)) have been made for investigating their structure. The thermomechanical analysis results revealed that the glass transition temperature (Tg) for the copolymers are lower than for PAN. The lowering of Tg in poly(AN‐co‐MPTMS) is more significant than those of poly(AN‐co‐VTES) and poly(AN‐co‐VTMES). The incorporation of silane comonomers in the copolymer resulted in the reduction of crystallinity but the crystalline lattice was not disturbed, what is suggested to be due to the location of the silane containing segments in the amorphous region. Thermal stability of the copolymers was also studied.
Immobilization of trypsin on poly(alginic acid‐g‐glycidyl methacrylate‐co‐methyl methacrylate)
Authors: Reddy C. Raghuram , George Anne , Reddy C. Rami 
Published: April 2003

AbstractA method of enzyme immobilization by graft copolymerization onto alginic acid is reported. Glycidylmethacrylate along with methyl methacrylate was used as a vinylating reagent. The enzyme trypsin has been chosen for our studies. The effects of various parameters such as pH optima, temperature optima, pH stability, thermal stability, storage stability, and re‐usability were studied.
Antioxidants and stabilizers, 103. Typical impurities of antiozonants, N‐alkyl‐N′‐phenyl‐1,4‐phenylenediamines, and their antioxidant behaviour
Authors: Taimr Luděk , Pospíšil Jan 
Published: April 2003

AbstractIn various samples of the industrially used antiozonant N‐isopropyl‐N′‐phenyl‐1,4‐phenylenediamine (IPPD, Ib), a typical, intensively coloured impurity was detected, and its structure was determined (IIb). The same compound IIb was prepared independently by an acid catalyzed reaction of 4‐aminodiphenylamine (IV) with N‐isopropyl‐N′‐phenyl‐1,4‐benzoquinonediimine (IIIb). IIb is formed by the same route also in technical IPPD, both in the production process and during storage. In the autoxidation of squalene (rubber model) IIb behaves as an effective antioxidant. The simultaneous presence of IPPD does not produce any antagonistic effect. IIa, which is an analogous impurity of technical N‐(1,3‐dimethylbutyl)‐N′‐phenyl‐1,4‐phenylene‐diamine (HPPD, Ia), behaves as an antioxidant similar to IIb. Thus, with respect to the antioxidant effect, the presence of impurities IIa or IIb in technical HPPD or IPPD does not matter.
Solvent/nonsolvent solubility and polarity parameters in fractional separation of oligomers. 1. Epoxy resins
Authors: Spychaj Tadeusz 
Published: April 2003

AbstractEpoxy resins from epichlorohydrin and bisphenol A have been fractionated in various binary solvent/nonsolvent systems. Low molecular weight (M ⋍ 400) and higher molecular weight (M ⋍ 1000) resins were fractionated using solvent/nonsolvent pairs in a wide range of polarities. Two solvent‐derived parameters: total solubility parameter δT and polarity index P′ have been applied to correlated experimental data. An empirical solubility diagram in coordinates P′ = f(δT) prepared on the basis of phase separation experiments, makes it possible to predict whether other solvent/nonsolvent pairs will work as efficient systems for epoxy resin fractionation. Two areas of solvent/nonsolvent parameters have been found for efficient epoxy resin fractionation: the first δT ⋍ 15.4–19.0 MPa1/2; P′ ⋍ 0.4−2.8 and the second of δT ∼ 19.5, P′ ∼ 6.0. In addition, the fractional precipitation of epoxy resins permits an evaluation of δT and P′ range of the resin for specific fractionation mixtures.
Studies on β‐picolinium‐p‐chlorophenacylide initiated copolymerization of methyl methacrylate with styrene
Authors: Nigam S. K. , Shukla A. K. , Saini S. , Kumar P. , Srivastava A. K. 
Published: April 2003

AbstractThe alternating copolymerization of methyl methacrylate (MMA) with styrene (S) using β‐picolinium‐p‐chlorophenacylide (β‐PCPY) as radical initiator at 55, 60, and 65°C for 3 h has been kinetically investigated. The copolymerization rate (Rp) is proportional to the square root of [β‐PCPY] and indicates bimolecular termination. The average degree of polymerization decreases as [β‐PCPY] increases. The values of kp2/kt and energy of activation have been evaluated as 1.43 · 10‐3 l mol‐1 s‐1 and 87 kJ mol‐1, respectively. The NMR spectroscopy has been used to determine the structure, composition, and stereochemistry of copolymers.
Influence of carbon black filler on the autohesion of polybutadiene rubber
Authors: Oppermann Wilhelm , Chakraborty Kalyan Kumar 
Published: April 2003

AbstractA study of the autohesion of polybutadiene rubber filled with different amounts of carbon black has been made. When the elastomer is uncrosslinked, the autohesive strength initially rises linearly with square root of contact time and finally shows a time independent course. The initial autohesion at time zero increases almost linearly with increasing carbon black content, while the ultimate strength is markedly influenced only when the filler content exceeds 30%. The time necessary to achieve ultimate strength decreases significantly when small amounts of filler are added.Experiments with slightly crosslinked polybutadiene did not show a characteristic time dependence. The autohesive strength increases strongly up to 30% carbon black content and seems to decrease again on further addition of filler.
Functionalization of atactic polypropylene using allyl and azide compounds
Authors: Borsig Eberhard , Braun Dietrich 
Published: April 2003

AbstractAtactic polypropylene was functionalized by reaction with dicumyl peroxide (8 wt.−%) and allyl compounds (8 wt.−%) such as eugenol methylether, allylphenylether, allylurea, N‐allylthiourea, diethyl allylmalonate, N‐allylaniline at 170°C. Using tert‐butyl azidoformate carbamate groups (1.8 wt.−%) were attached to atactic polypropylene. The mechanism of both types of reactions is discussed.
Characterization of low molecular compounds in dashboard foils by extraction, preparative high performance liquid chromatography, and IR‐spectroscopy
Authors: Standt Ulrich‐Dieter 
Published: April 2003

AbstractA procedure to obtain information concerning the low molecular weight compounds of dashboard foils is described. Solvent extracts of the foils were fractionated by preparative reversed or normal phase HPLC, respectively. The fractions were characterized by their infrared spectra. The benefits and the shortcomings of the two methods are discussed.
Studies on graft copolymerization of methyl methacrylate onto chemically modified tussa silk fibers. Peroxydisulfate‐thiourea redox system
Authors: Mohanty A. K. , Singh B. C. , Misra M. 
Published: April 2003

AbstractThe graft copolymerization of methyl methacrylate (MMA) onto chemically modified tussa silk fibers in aqueous media using potassium peroxodisulfate‐thiourea redox initiator system was studied at 60°C. The effects of time of reaction, concentrations of oxidant, thiourea (TU), monomer (M), amount of silk fibers on graft yield have been studied. The effects of reaction medium, acid concentration, and some inorganic salts and organic solvents on grafting have also been investigated. A significant increase in percent of grafting was observed with increasing monomer concentration to 65.86 · 10−2mol · 1−1; a further increase of monomer concentration is associated with the decrease of graft yield. The graft yield increases with an increase of thiourea concentration up to 10 · 10−1mol · 1−1, beyond which it decreases very significantly. A measurable increase of the graft yield was also observed with an increase of the oxidant concentration up to 0.08 mol · 1−1beyond which the graft yield decreased. The graft yield was medium dependent. The reaction mechanism of the grafting process has been proposed and a rate expression has been derived on the basis of experimental findings. IR spectra of the grafted fiber and original fiber have been taken and their characteristic bands have been identified. The thermal behaviour of the original and grafted silk fibers has been studied by TGA and DTG analysis. Grafting has improved thermal stability as well as the light fastness of silk dyed with Rhodamine B.
The effect of γ‐irradiation on optical and electrical properties of polycarbonate
Authors: Amin Mohamed , Darwish Khairia Ahmed , Mounir Mohamed 
Published: April 2003

AbstractPoly‐(bisphenol A carbonate) (PC) samples were exposed to different doses of γ‐rays from a 60Co source (from 0.05 to 0.3 M rad) at room temperature. Conductivity and dielectric constant as well as optical measurements were carried out. It was noticed that almost no work has been reported on the electrical conductivity of polycarbonate at high temperatures. γ‐irradiation of polycarbonate is believed to create free radicals which increases the state of disorder and perturb the orientation of dipoles inside the polymer. At about 95°C, the electrical conductivities of irradiated samples were found to increase by nearly one order of magnitude with respect to the unirradiated one. The dielectric constant, ϵ, of fresh polycarbonate was nearly temperature independent over a range of ∼ 70°C, then it increased with temperature, but for γ‐irradiated samples (from 0.05 to 0.3 M rad) the dielectric constant increased continuously with temperature and also with respect to the fresh sample what confirms the effect of γ‐irradiation in perturbing the orientation of the dipoles in the polymer. It was found that the UV absorption spectrum has a broad band at 0.280 μm and the absorption intensity was strongly dependent on the dose of γ‐irradiation.
Nitric oxide initiated polymerization of acrylonitrile
Authors: Mishra Mahendra Kumar 
Published: April 2003

AbstractNitric oxide initiated polymerization of acrylonitrile in dimethylsulfoxide was carried out. The dependence of monomer and initiator concentrations and temperature on polymer yield and initial rate of polymerization (Rin) was studied. The over‐all activation energy of polymerization was found to be about 19.96 kcal · mol−1 (83.43 kJ · mol−1). The polymerization of acrylonitrile appears to occur via free radical mechanism. A kinetic scheme and rate expression have been proposed.
Macromolecular structure of coals, 7. Mass spectrometry of pyridine extracts and depolymerized coal
Authors: Lucht Lucy M. , Hill Mary E. , Peppas Nikolaos A. 
Published: April 2003

AbstractElectron impact mass spectrometry and mass ion kinetic energy spectrometry were used to analyze: (i) the structure of uncrosslinked, predominantly aliphatic chains obtained by pyridine extraction of bituminous coals; and (ii) the identity of compounds found in depolymerized coal samples produced by the technique of Hooker et al. (1986).
Degradation of polypropylene: Effect of stabilizers
Authors: Choudhary V. , Varshney S. , Varma I. K. 
Published: April 2003

AbstractThe relative effectiveness of five commercially available stabilizers on the photooxidation and thermal ageing of polypropylene (PP) was investigated by following changes in mechanical properties. Samples of PP containing different percentages of Cyasorb UV‐531 were prepared (designated as PC0.5‐31, PC1‐31, PC1.5‐31, and PC2‐31, respectively). The effect of photooxidation on thermal behaviour was investigated by differential scanning calorimetry and thermogravimetric analysis. 2‐Hydroxy‐4‐n‐octyloxy benzophenone (2% w/w) was most effective in stabilizing PP towards discolouration and brittleness. After 32 h irradiation, 81% retention in yield strength was observed in case of PC1‐31 against 18% in case of PP.
Study of polymerization of methacrylamide initiated by persulphate with different activators
Authors: Behari K. , Raja G. D. , Lal M. 
Published: April 2003

AbstractThe aqueous polymerization of methacrylamide was studied by using persulphate/malic acid and persulphate/ethanolamine redox pairs under nitrogen atmosphere. The order with respect to persulphate was found to be one half with both the redox systems. Malic acid and ethanolamine show half order and zero order, respectively. Methacrylamide has first order dependence on the rate of polymerization initiated by K2S2O8‐malic acid system and one and half order dependence on the rate of polymerization initiated by K2S2O8‐ethanolamine redox pair. Viscometric average molecular weight was determined for the samples obtained under different kinetic conditions.
Untersuchungen zum mechanismus der thiol‐en‐photoadditionspolymerisation
Authors: Klemm Elisabeth , Holfter Uta , Sensfuß Steffi , Flammersheim Hans‐Jürgen 
Published: April 2003

AbstractDSC‐ und ESR‐Messungen zur photosensibilisierten Polymerisation von 1,8‐Dithio‐3,6‐dioxaoctan/Phthalsäurebisallylester zeigen, daß die Reaktion in jedem Reaktionsschritt photoaktiviert erfolgt und daß C‐Radikale intermediär auftreten. Modelluntersuchungen am System 1‐Octanthiol/Phenylallylether ergaben, daß bevorzugt Photoaddition eintritt und daß Radikalrekombinationen von untergeordneter Bedeutung sind. Diese Befunde werden durch 1H‐, 13C‐NMR‐ und Massenspektren belegt.
Conductivity variations of iodine‐ and tungsten chloride‐doped polyacetylene under applied voltages
Authors: Chen Show‐An , Huang Ching‐Feng 
Published: April 2003

AbstractFor iodine‐ and tungsten chloride (WCl6)‐doped polyacetylene (PA), conductivity shows decreasing with time on standing in inert atmosphere. The doping levels investigated for the former are 0.006 to 0.088 mol per mol, and for the latter 0.006 to 0.053. As a voltage is applied, the conductivity shows an accelerated decreasing with time. As the voltage increases further, the acceleration becomes more pronounced; and the doped PA can even break into two pieces as a critical voltage is reached. This critical voltage (11.0 V to 26.5 V for the iodine cases and 13 V to > 40 V for the WCl6 cases) is found to increase with decreasing doping level. This break‐down is attributed to the occurrence of nonuniform doping in the doped PA.
The use of micro‐HPLC with gradient elution for the characterization of phenol‐formaldehyde resins
Authors: Preussler Vít , Šlais Karel , Hanuš Jiří 
Published: April 2003

AbstractPhenol‐formaldehyde resins of the Novolak and Resol type were chromatographed on a reverse‐phase micro‐column packed with octadecylsilane on silica gel. A good separation of most components was achieved by the use of gradient elution with methanol‐water; the contents of methanol in the mobile phase increased continually from 10 to 90%. The gradient was generated in a simple tubular mixer with an internal volume of 1.5 ml. Samples were applied to the column in a non‐eluting solvent, using a six‐port injection value with a 10 μl sample loop. The method, which shows a good reproducibility, is suitable for the characterization of phenol‐formaldehyde resins.
Morphology of ultrahigh molecular weight polyethylene surface slid against steel
Authors: Kōmoto Tadashi , Hironaka Seiichiro 
Published: April 2003

AbstractA morphological study was made to examine the friction and wear mechanisms of ultrahigh molecular weight polyethylene in air and water by means of transmission electron microscopy of a carbon replica film of a very thin layer of the polymer surface slid against a steel ball. Electron diffractions revealed that a molecular orientation with a typical fiber pattern was formed in the friction in air, while thin ribbon‐like crystals with particular crystal orientations were formed in water in a way that the sliding took place on the crystallographic a—c plane, giving rise to a low friction coefficient of the polymer.