bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymere Dispergiermittel I. Molmasse und Dispergierwirkung der Melamin‐ und Naphthalin‐Sulfonsäure‐Formaldehyd‐Polykondensate
Authors: Pieh Stefan 
Published: April 2003

AbstractDer Einfluß des mittleren Molekulargewichts (Viskositätsmittel) von Naphthalinsulfonsäure‐ und Melaminsulfonsäure‐Formaldehyd‐Polykondensaten auf ihre Eigenschaften als Dispergiermittel wurde an wässrigen Portlandzement‐ und Anhydritsuspensionen untersucht. Die rotationsviskosimetrische Erfassung der Dispergierwirkung führte zur Definition eines allgemein anwendbaren Dispergierindex. Es zeigte sich, daß die untersuchten Polykondensate nur in einem verhältnismäßig schmalen Molekulargewichtsbereich, und zwar von Grenzviskositätszahl [η] = 0,02 dl/g bis [η] = 0,10 dl/g eine gute Dispergier‐ und Plastifizierwirkung zeigen und oberhalb dieses MV‐Bereichs zur Erhöhung der Viskosität, also Versteifung der Zement‐ und Anhydritsuspensionen führen. Basierend auf Adsorptionsuntersuchungen zur Bestimmung der adsorbierten Polymermenge und der DLVO‐Theorie wird versucht, in der mit steigender Molekülgröße auftretenden Überlappung der Polymerhüllen eine Erklärung für diesen Zusammehang zu finden.
Glasübergänge in Poly(vinylchlorid)/Poly(methacrylat)‐Systemen
Authors: Pigłowski Jacek 
Published: April 2003

AbstractPoly(methylmethacrylat) (PMMA), Poly‐n‐(butylmethacrylat) (PnBMA) sowie Poly(methylmethacrylat‐ran‐n‐butylmethacrylat) sind mischbar mit Poly(vinylchlorid) (PVC). Die Dreikomponentenmischungen liegen jedoch in zweiphasigen Systemen vor. Jede dieser Phasen besteht aus PVC und entsprechenden Methacrylatpolymeren. Die Abhängigkeit der Glastemperatur von der Mischungszusammensetzung für PVC/PnBMA läßt sich durch Einführen eines zusätzlichen Terms in der Gordon‐Taylor‐Gleichung beschreiben.
Polymerization of n‐butyl vinylether initiated by polymeric peroxycarbamates and active polystyrenes
Authors: Yagci Yusuf , Acar Metin , Hizal Gurkan , Yildirim Huseyin , Baysal Bahattin 
Published: April 2003

AbstractThe free radical promoted cationic polymerization of n‐butyl vinylether (BVE) was achieved by thermal decomposition of polymeric peroxycarbamates (PPC) or active polystyrene (APS), having fragments of PPC in the presence of diphenyliodonium hexafluorophosphate (Ph2I+ PF) or silver tetrafluoroborate (AgBF4). Polymerizations were accompanied by phase separation. Formation of block copolymers, mainly in the solid phase, was evidenced by NMR spectroscopy. Polymer samples obtained by this procedure contained only a very small fraction of block copolymer structure due to the phase separation and very effective chain transfer reactions predominating the cationic polymerization of BVE.
Studies on the thermal degradation of aromatic polyamides by pyrolysis‐field ionization mass spectrometry and pyrolysis‐gas chromatography
Authors: Schulten H.‐R. , Plage B. , Ohtani H. , Tsuge S. 
Published: April 2003

AbstractThe thermal degradation of aromatic polyamides such as poly&(1,4‐phenyleneterephthalamide) (Kevlar) and poly&(1, 3‐phenylene‐isophthalamide) (Nomex) was studied by pyrolysis‐field ionization mass spectrometry (Py‐FIMS) and pyrolysis‐gas chromatography (Py‐GC). In Py‐FIMS, the thermal degradation products were recorded which were formed in the ion source of a double focusing mass spectrometer. Usually a temperature range from 50 to 750°C and a heating rate of 1.2°C/s were employed. Various common and characteristic products for the two samples, respectively the corresponding para‐ or meta‐isomers, were observed up to m/z 500 with significant differences in intensity. The main products observed were produced by both radical homolytic and hydrolytic decompositions.On the other hand, in flash Py‐GC the instantaneous thermal degradation products at 720°C were gas‐chromatographically separated by a fused‐silica capillary column and detected both by a flame ionization detector and a mass spectrometer with electron ionization (EI). Although many of the degradation products were identical with those observed by Py‐FIMS, the former almost entirely consisted of the fragments formed through radical homolytic degradation. In general, the differences between the samples with Py‐GC were much less than those observed in Py‐FIMS.
Effect of some free and chelated iron ions on the aqueous polymerization of methyl methacrylate
Authors: Abd El‐Ghaffar M. A. , Abd El‐Hakim A. A. , Badran A. S. , Moustafa A. B. 
Published: April 2003

AbstractThe aqueous polymerization of methyl methacrylate was carried out in absence and in presence of some inorganic iron salts and complexes using sodium bisulphite as a producer of initiator radicals. Polymerization in absence of iron salts or complexes resulted in the highest average molecular weights formation and the least reaction rates, while using salts in which the iron is ionizable lowered both the apparent energy of activation (Ea) of the system and the obtained average molecular weights and increased the initial rates. On the contrary, when the iron is chelated, as in case of potassium ferrocyanide and potassium ferricyanide, a retardation or complete inhibition of the polymerization reaction took place, respectively.
Thermal stability of some acetylenic poly‐ and copolymers obtained by electrochemical polymerization
Authors: Simionescu C. I. , Bulacovschi V. , Grovu‐Ivǎnoiu Maria 
Published: April 2003

AbstractThe thermal stability of some polymers with conjugated double bonds has been studied under dynamical conditions of heating. It was found that nature of the substituents plays an important role in the thermal behaviour of the polymers.
Effect of the anhydride structure and the epoxy fortifier on the reactivity in curing of epoxy resins
Authors: Patel Ravji D. , Patel Ranjan G. , Patel Vithal S. 
Published: April 2003

AbstractThe curing reactions of the epoxy resin triglycidyl‐p‐aminophenol with acid anhydrides using tertiary amine as catalyst were studied kinetically by differential scanning calorimetry. The dynamic scans in the temperature range 30–300°C were analyzed to estimate the activation energy and the order of the reaction for the curing process using some empirical relations. The curing process was found to follow a simple Arrhenius type kinetics having activation energies in the range 75 – 142 kJ/mol and the order of the reaction is about 1. The effect of the variation in acid anhydride structure and of the incorporation of the epoxy fortifier on the cure characteristics is investigated.
A modification of diglycidylether of Bisphenol A with diimide‐diacids
Authors: Serra Angels , Cádiz Virginia , Mantecón Ana 
Published: April 2003

AbstractA conventional epoxy resin derived from Bisphenol A has been modified with aromatic diacids containing a preformed imide ring in order to achieve an improvement in their thermal properties. These new resins were characterized by IR and 13C‐NMR spectroscopy, and it was possible to verify two types of oxirane ring openings by diimide‐diacid.
Interactions of polymer backbones and complexation of polychelatogens with methylthiourea ligands in aqueous solution
Authors: Geckeler K. E. , Shkinev V. M. , Spivakov B. Y. 
Published: April 2003

AbstractThe interactions of the polymeric backbone and complex formation with a series of metals were investigated for poly(ethyleneimine), poly(vinylpyrrolidinone), and poly‐(acrylamide) as basis polymers with methylthiourea as ligand. Retention studies by application of membrane filtration of aqueous solutions were used for the evaluation of interaction between the metal ions and macromolecules as function of pH. It was shown for the Na, Co, Ni, Cu, Zn, Cd, Hg, Fe ions that the interaction depends both on the type of polymer backbone and the pH.Whereas for poly(ethyleneimine)‐based copolymers the retention data were influenced only slightly by pH, the two other copolymers investigated showed a strong pH dependency for the individual metals. A dominating effect of the functional ligand comonomer in terms of the interaction over the basis monomer was observed for the majority of metal ions investigated.
Preparation and properties of selectively p‐chlorinated polystyrene
Authors: Kiji Jitsuo , Konishi Hisatoshi , Okano Tamon , Takada Hiroyuki 
Published: April 2003

AbstractPolystyrene has been chlorinated in the liquid phase by SbCl3 catalyst combined with 10‐trifluoroacetylphenothiazine to afford a polymer, which is represented by the formula . The aromatic substitution reaction (x > 1) occurs predominantly at the p‐position, the ratio of p‐ to o‐chlorination being 10‐12. The intrinsic viscosity of the toluene solution at 30°C decreases with content of chlorine, x. The refractive index, nD, increases with x. The nD value of a 25.05% chlorine‐containing polymer (x ≃ 1) is 1.6041.
Studies on chemical resistance of polyesters
Authors: Bansal Raj K. , Malik G. S. , Singh Parkash , Dabholkar D. A. 
Published: April 2003

AbstractChlorendic anhydride based polyester (I,) tetrachlorophthalic anhydride based polyester (II), dibromoneopentyl glycol based polyester (III,) general purpose polyester (IV,) blend of dibromoneopentyl glycol based polyester with general purpose polyester (V,) chlorendic anhydride and dibromoneopentyl glycol based polyester (VI), and a blend of chlorendic anhydride based polyester and dibromoneopentyl glycol based polyester (VII) were prepared and their chemical resistance and moisture absorption studied in various reagents, acid, alkali, and water, at 25 and 65°C. It is found that the polyester (III) is the least affected in the presence of the acids. In 20% NaOH, there was a decrease in weight for all polyesters at both the temperatures compared to the control except the polyester (VII). Increase in weight of all the polyesters was observed during the absorption of moisture both at 25 and 65°C. The increase was higher at higher temperature. Polyester (III) thus shows the least absorption of moisture.
Synthesis and characterization of some polyurethanes
Authors: Patel Prashant , Patel Mayur , Suthar Bhikhu P. 
Published: April 2003

AbstractPolymers containing urethane units were synthesized by solution polymerization of bisphenols A, C, and F with diisocyanates viz. toluene‐2,4‐diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and diphenylmethane diisocyanate, respectively. Thus obtained polymers were pale yellow amorphous powders. These polymers were characterized by infrared spectral studies and nitrogen content. The number‐average molecular weights (M̄n) were estimated from conductometric titration and limiting viscosity number [η] in dimethyl formamide. From thermogravimetric analyses, the thermal behaviour was studied. Kinetic parameters for their degradation were computed.
Synthesis of asymmetric diglycidyl ester compounds. Reaction with aromatic diamines
Authors: Mantecón Ana , Cádiz Virginia , Serra Angels , Martínez Pedro Alberto 
Published: April 2003

AbstractNew diglycidyl esters coming from the corresponding diacids and epichlorohydrin were synthetized using a quaternary ammonium salt as a catalyst. The new asymmetric compounds were characterized by spectroscopic methods and employed as starting monomers in a crosslinking process. The course of the reactions was followed by IR spectroscopy. Some intermediate species were identified in the onset of the reactions by recording 13C‐NMR spectra until the products became insoluble in the usual deuterated solvents. The thermal behaviour of these cured epoxy resins was also studied.
Modification of cyclohexanone‐formaldehyde‐resin
Authors: Akar Ahmet , Öztürk Turan 
Published: April 2003

AbstractThe reactions of cyclohexanone‐formaldehyde‐resin via its hydroxy and carbonyl functional groups with a number of different reagents such as acetic anhydride, benzoyl chloride, hydroxylamine, semicarbazide, and phenyl hydrazine were studied. Melting points, IR spectrums, and solubilities in various solvents of the products were determined.
PAN‐Grafted guaran. II. Short‐chain grafting
Authors: Naidoo Sugantheran , Joffe Ray , Neuse Eberhard W. 
Published: April 2003

AbstractThe room‐temperature grafting of polyacrylonitrile (PAN) onto guaran (guar gum) in 2.5 × 10−3 M aqueous sols or aqueous‐methanolic suspensions, initiated by (NH4)4 Ce(NO3)6 in 1M HNO3, leads to PAN‐branched polysaccharides with graft contents of 11 – 53%. Main chain degradation by treatment with boiling aqueous HCl results in detachment of the PAN side chains, for which number‐average molecular masses of ca. 15000 – 48000 are determined viscometrically with the aid of the known Mark‐Houwink relationship (K = 3.92 × 10−4, a = 0.75). Grafting frequencies are in the range of 0.004 – 0.012, equivalent to an average of 80 – 250 non‐grafted repeat units for every singly grafted unit in the guaran main chain. The graft copolymers are of interest as precursors of carboxyl‐functionalized, water‐soluble polysaccharides to serve as polymeric micronutrient and drug carriers of future studies.
Synthesis and applications of reactive carbohydrates. III. Preparation and methylolation of polyacrylamide‐carboxymethyl cellulose graft copolymers
Authors: El‐Sisi Fatma , Hafiz Sayed Abdel‐Samea Abdel , Hebeish Ali 
Published: April 2003

AbstractCarboxymethyl cellulose (CMC) was treated with HCl at 80°C for different time periods (15 – 60 min). The hydrolyzed CMC samples as well as the original sample were graft copolymerized with acrylamide using K2S2O8 as initiator. It was disclosed that the increasing duration of acid hydrolysis is accompanied by a progressive increment in the copper number of CMC, meanwhile its carboxyl content decreases. Acid hydrolysis enhances significantly the susceptibility of the CMC toward grafting. The latter reduces the copper number of the hydrolyzed CMC samples most probably via conversion of the aldehydic to carboxylic groups under the action of K2S2O8 during grafting. Grafting also reduces the carboxyl content of the original CMC sample while increasing those of the hydrolyzed CMC samples. Methylolation of the polyacrylamide‐CMC graft copolymers results in reactive finishes. When the latter were applied to cotton fabric according to the conventional pad‐dry‐cure method followed by a thorough washing, the fabric retained ca. 86% of the finish derived from the copolymer of CMC and 92% of finishes derived from the copolymers of hydrolyzed CMC.
Free radical grafting of some hydrophilic monomers onto unsaturated segmented polyurethanes — a kinetic study
Authors: Egboh Sunday H. O. 
Published: April 2003

AbstractGrafting of unsaturated segmented polyurethanes with some hydrophilic monomers such as N‐vinyl pyrrolidone, 2‐hydroxyethylmethacrylate and acrylamide in N,N‐dimethylformamide have been studied using 2,2′‐azobisisobutyronitrile (AIBN) as initiator. Graft copolymers were isolated from homopolymers by selected solvent extraction using a Soxhlet apparatus. A kinetic study of graft copolymerization reactions showed that the reactions follow the conventional kinetic behaviour of free radical polymerization. The dependencies of the grafting rate on initiator and N‐vinyl pyrrolidone concentrations were of 0.5 and 1.00 order, respectively. However, for the 2‐hydroxyethylmethacrylate, the dependencies of the grafting rate on initiator and monomer concentrations were found to be of 0.5 and 2.00 order, respectively. The overall activation energy for the graft copolymerization of the 2‐hydroxyethylmethacrylate and N‐vinyl pyrrolidone were 21.81 kJ/mol and 16.28 kJ/mol, respectively.
Styrene‐N‐Vinylcarbazol copolymers with enhanced thermal stability
Authors: Schopov Ivan , Bratschkov Christo 
Published: April 2003

AbstractStyrene copolymers with low (up to 5 wt.‐%) N‐vinylcarbazol content were prepared. The copolymers showed enhanced thermal stability in comparison with the pure polystyrene. This is explained by a charge transfer complex formation between the carbazol rings as donor and the radicals, formed during the degradation, as acceptors.
Dielectric behaviour of shellac‐incorporated natural rubber gum stocks
Authors: Goswami D. N. , Singh Radha , Khanna B. B. 
Published: April 2003

AbstractThe dielectric properties of shellac‐incorporated natural rubber gum stocks were studied in the frequency range 100 Hz to 100 kHz and at different periods of curing. Incorporation of shellac in the gum stock resulted in decrease of the dielectric loss values of natural rubber.
Mechanochemically initiated copolymerizations, 10. Kinetic data on the copolymerization of the acrylonitrile/vinyl acetate/α‐methyl styrene ternary system by vibratory milling
Authors: Oprea Cleopatra Vasiliu , Popa Marcel , Dumitriu Severian 
Published: April 2003

AbstractThe kinetics of mechanochemical copolymerization of the ternary system based on acrylonitrile, vinyl acetate, and α‐methyl styrene, by vibratory milling activation was studied. A general relation for expressing the reaction rate is proposed as follows:

Kinetics has been followed by measuring the amount of unreacted monomer by gas chromatography. Partial reaction orders – related to each comonomer, had almost unitary values, being determined from the conversion‐time curves for 7 ternary systems with different comonomer ratios. The values of the reaction rate constant – taken for three temperatures – permitted the computation of the activation energy (18.82 kJ mol‐1), such a low value showing that the contribution of the thermal energy in this type of synthesis is unsignificant.
Neue synthetische träger zur fixierung von enzymen
Authors: Burg Karlheinz , Mauz Otto , Noetzel Siegfried , Sauber Klaus 
Published: April 2003

AbstractEs wird die Synthese von perlförmigen makroporösen Tägern für Enzyme durch Suspensionspolymerisation von Vinylacetat und N,N'‐Divinylethylenharnstoff in Wasser, durch partielle Verseifung der Acetat‐ zu Hydroxygruppen und durch anschließende Umsetzung mit Epichlorhydrin beschrieben. Reaktive Gruppen der Träger sind Epoxide. Die Hydrophilie der Träger ist durch Vinylalkohol‐ und Harnstoffgruppen gegeben.Die physikalischen Eigenschaften der Träger im nicht gequollenen Zustand wurden mit Hilfe der Elektronenmikroskopie, der Quecksilber‐Porosimetrie und von BET‐Messungen untersucht.Eine Reihe von Enzymen (Trypsin, Chymotrypsin, Urease und Penicillinacylase) wurde auf verschiedenen Trägern (Anzahl der Epoxidgruppen, Teilchengröße der Träger) fixiert. In Abhängigkeit vom Epoxidgruppengehalt, vom Enzymangebot und vom pH‐Wert der Substratlösung weisen die Enzyme deutliche Unterschiede bezüglich spezifischer Aktivität und Bindungsausbeute auf.Im Falle der trägergebundenen Penicillinacylase war eine 65‐fache Wiederverwendung ohne Aktivitätsverlust möglich. Die Trägermaterialien überstehen eine Dampfsterilisation ohne Eigenschaftsveränderung.
Kohlenstoffasern auf der basis von mit wasserstoff‐peroxid voroxidierten PAN (S.A.F)‐fasern
Authors: Popovska Nadeshda 
Published: April 2003

AbstractUntersucht wurde die Voroxidation einer speziellen hochfesten PAN(S.A.F)‐Faser (93% Acrylnitril, 6% Methylacrylat, 1% Itaconsäure) mit Wasserstoffperoxid in alkalischen Lösungen (2 – 10 Gew.‐% NaOH) als erste Stufe der Herstellung von Kohlenstoffasern. Die kombinierten Ergebnisse aus IR‐ und DTA‐Untersuchungen zeigen, daß die Voroxidation in schwachalkalischen Lösungen (2 – 5 Gew.‐% NaOH) die Geschwindigkeit der Cyclisierungs‐ und Oxidationsprozesse bei anschließender Stabilisierungsstufe erhöht. Eine hohe Konzentration an Reaktionszentren und ein hoher Gelanteil (oberhalb 90%) einer in 8 bzw. 10 proz. NaOH voroxidierten PAN‐Faser verzögern die anschließenden Stabilisierungsreaktionen. Die Cyclisierung der nicht voroxidierten und der voroxidierten PAN‐Fasern verläuft nach einem ionischen Mechanismus. Die Kohlenstoffasern aus mit Wasserstoffperoxid in schwach alkalischen Lösungen voroxidierten PAN(S.A.F)‐Fasern weisen erhöhte Zugfestigketis‐und E‐Modul‐Werte auf bei Glühtemperaturen bis 1350°C. Weitere Steigerung der Glühtemperatur verschlechtert die mechanischen Eigenschaften der gewonnenen Kohlenstoffasern. Eine deutliche Korrelation zwischen E‐Modul und magnetischer Suszeptibilität bzw. Anisotropieverhältnis wurde festgestellt.
Stability of plastics ‐ characteristic property or environmental problem?
Authors: Hubeny Helmut 
Published: April 2003

AbstractPlastics in general exhibit a high stability. For decades, technical and scientific research has endeavoured to improve polymers in such areas as ageing, light fastness, climatic stability, resistance to rotting, chemical stability, and resistance to stress crazing and cracking,Today, many of the demands put forth in the interest of disposal, reusability of products, as well as the questionable nature of certain additives and their concentration found in waste, seem to countermand this development. This paper discusses the problems and contradictions of some successful long‐range applications (tubings, sheets, building materials), of some short‐range uses (packaging), as well as of certain select materials systems.A state‐of‐the‐art solution to the problem is being offered in view of the dual function of plastics as work‐materials and as transducers of energy as, for instance, in closed circuitry.
Accelerated and natural ageing of PVC foils
Authors: Genova Fenka , Gancheva Tamara , Marinova Atanasija 
Published: April 2003

AbstractThe photooxidation stability of PVC foils with various thicknesses (0,4; 0,2; 0,3 and 0,14 mm) intended for agricultural use is investigated during accelerated and natural ageing.The surface state variations are investigated by surface crazing, total colour variation and chemical composition of the surface layer (IR‐spectra of MIR‐IR‐spectroscopy).The foil volume variations are investigated by means of differential IR‐spectra, light transmission decrease and the specific elongation. An analogy in the PVC foils properties of 0,4 mm thickness both for accelerated and natural ageing is observed. It is established that during the 12 months induction period of time foils change negligibly their properties. The original properties of foils with thickness of 0,14 mm weathering for 15 months have changed less. For a period of 12 months the changes are considerable: the specific elongation decreased more than 50%, the plasticizers' concentration decreased by 8% and the light transmission — by 40% compared to the original values. The msuface roughness increased up to 5—7μm and the total colour rariation Δ E*ab achieved 25–40 relative units.During the artificial ageing in Xenotest‐1200 it is found out that the foil thickness induces the photooxidation processes.
On the weathering of modified PVC based compounds during the polymerization process
Authors: Gancheva Tamara , Genova Penka , Marinova Atanasija 
Published: April 2003

AbstractThe variations of molecular spectra, colours and characteristic viscosity of modified and unmodified PVC compounds during the polymerization process in various periods of time of natural ageing have been investigated.The PVC types modified during synthesis by 0,25 % vol. plasticizers or plasticizers' mixture are characterized by 10 – 12°C lower glass transition temperature, higher thermal stability, long‐term behaviour and better physical and mechanical properties. The Charpy‐impact resistance is increased by 50 to 85%. The rate of the relative UV‐sorption variation during outdoor exposure was lower for compounds based on the modified PVC types.The polyene parts amount of chain length n = 13, evaluated by means of Raman spectra, was increased during the first and second month, both on non‐irradiated and irradiated surface. The total colour variation ΔEab of the new PVC grades in a 10‐month poriod of weathering was of 10‐30% less compared to the unmodified PVC grades.By means of IR‐spectroacopy the variations of the hydroxyl‐ and carbonyl groups were .valuated and the diffemncee in the oxidation kinetica were establiehed.