bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organophosphorus antioxidants action mechanisms and new trends
Authors: Schwetlick Klaus , Habicher Wolf D. 
Published: April 2003

AbstractPhosphite and phosphonite esters can act as antioxidants by three basic mechanisms depending on their structure, the nature of the substrate to be stabilized and the reaction conditions. All phosph(on)ites are hydroperoxide‐decomposing secondary antioxidants. Their efficiency in hydroperoxide reduction decreases in the order phosphonites > alkylphosphites > arylphosphites > hindered arylphosphites. Five‐membered cyclic phosphites are capable of decomposing hydroperoxides catalytically due to the formation of acidic hydrogen phosphates by hydrolysis and peroxidolysis in the course of reaction. Hindered aryl phosphites can act as chain‐breaking primary antioxidants being substituted by alkoxyl radicals and releasing hindered aryloxyl radicals which terminate the radical chain oxidation. At ambient temperatures, the chain‐breaking antioxidant activity of aryl phosphites is lower than that of hindered phenols, because the rate of their reaction with peroxyl radicals and their stoichiometric inhibition factors are lower than those of phenols. In oxidizing media at medium temperatures, however, hydrolysis of aryl phosph(on)ites takes place giving hydrogen phosph(on)ites and phenols which are effective chain‐breaking antioxidants.2,2,6,6‐Tetramethyl‐ and 1,2,2,6,6‐Pentamethylpiperidinyl phosphites and phosphonites (HALS‐phosph(on)ites) surpass many common phosphites, phenols and HALS compounds as stabilizers in the thermo‐ and photo‐oxidation of polymers. Their superior efficiency is probably due to an intramolecular synergistic action of the HALS and the phosph(on)ite moieties of their molecules.
Polymers from renewable resources, VI. Synthesis and characterization of thermosetting resins derived from cashewnut shell liquid/formaldehyde/substituted aromatic compounds
Authors: Sahoo S. K. , Swain S. K. , Mohapatra D. K. , Nayak P. L. , Lenka S. 
Published: April 2003

AbstractA large number of resins have been synthesized by reacting cardanol, a constituent of cashewnut shell liquid, with formaldehyde and substituted aromatic compounds in the presence of acidic and basic catalysts. The resins have been characterized by IR spectra. They were shown to be selective ion exchangers for certain metal ions. A batch equilibrium method was used for studying the selectivity of the metal ions. The thermal behaviour of the resins has been studied and a plausible degradation mechanism has been suggested.
The role and utilization of tetrachlorosilane/ethanol reagent in the crosslinking of poly(p‐vinylacetophenone)
Authors: Abdelaal Magdy Y. , Elmorsy Saad S. 
Published: April 2003

AbstractPolystyrene has been modified through its acetylation into poly(styrene‐co‐vinylacetophenone) in a good yield. The obtained copolymer was then treated with tetrachlorosilane/ethanol reagent leading to the formation of triphenylbenzene units, either as crosslinking nodes or as pendent groups, and silyloxy derivatives of the acetyl groups attached to the styrene units as well as some unreacted acetyl groups. The percentages of the composition of all products were determined as well as silicon content.
Diffusion von wasserdampf durch feinschichtharze
Authors: Seycek Otakar , Scherz Norbert 
Published: April 2003

AbstractAls Modell für die Gelcoat‐ oder Topcoatschicht eines glasfaserverstärkten Laminates wurden dünne, planparallele Platten definierter Dicke aus zwei Gelcoatharztypen (Isophthalsäure‐Neopentylglykol‐ (UP) und Phenacrylat‐Harz (PHA) auf Basis von Bisphenol A) gegossen, und es wurde der Einfluß der Unterhärtung sowie der Harzverdünnung mit Styrol auf die Wasserdampfdurchlässigkeit dieser Platten untersucht. Die Harzverdünnung führt in beiden Fällen zu einem evidenten Anstieg der Permeationskoeffizienten P. Die Unterhärtung (Aushärtungsgrade um 97%) und anschließende Extraktion des nicht auspolymerisierten Styrols läßt beim UP die Permeabilität von Wasserdampf ebenfalls ansteigen, beim PHA wurde dagegen ein leichtes Sinken des Permeationskoeffizienten verzeichnet. Die Ergebnisse werden im Zusammenhang mit den Unterschieden in der Kinetik der Aushärtungsreaktion beider Harztypen diskutiert.
Mechanical behaviour of PS/PVC blends compatibilized with block‐graft copolymers based on poly(styrene‐block‐butadiene)
Authors: Braun D. , Fischer M. 
Published: April 2003

AbstractBlends composed of polystyrene (PS) and polyvinylchloride (PVC) are incompatible due to unfavourable interactions. Consequently, their mechanical properties such as impact strength and elongation at break are only very poor. The key to successfully influence the properties of such heterogeneous blends lies in the control of the interface. High interface tensions and an insufficient phase adhesion often lead to coarse phase morphologies which are thermodynamically and kinetically unstable. However, with radically synthesized, tailor made block‐graft copolymers P(S‐b‐(B‐g‐CHMA, MMA)) based on a styrene/butadiene two‐block copolymer P(S‐b‐B) which are grafted with poly(cyclohexylmethacrylate) (PCHMA) or poly(methylmethacrylate) (PMMA), the phase morphology can be markedly refined and the blends surprisingly show ductile behaviour. Thus, the impact strength of so modified PS/PVC 1 : 1 blends is about ten times higher than in the unmodified case and is thereby similar to impact modified PS.Electron microscopy (SEM, TEM) reveals that the modified PS/PVC blends owe their improved mechanical properties to the interface selectivity of the block‐graft copolymers and therefore to a superior phase adhesion.
Synthesis and characterization of poly(amideimide)s containing aliphatic diamine moieties
Authors: Yi Mi Hie , Jin Moon Young , Choi Kil‐Yeong 
Published: April 2003

AbstractNew poly(amideimide)s (PAI) containing aliphatic diamines as comonomers were synthesized by polycondensation of trimellitic anhydride chloride with mixed diamines. Preliminary results of copolymerization with various alicyclic diamines suggested that isophoronediamine (IPDA) is more preferable as a comonomer for PAI. The copolyamide imides with IPDA showed that IPDA is more rigid than mbisaminophenoxydiphenylsulfoneSystematic name: 4,4′‐Sulfonylbis(1,3‐phenylenoxy)dianiline.
(m‐BAPS) and 4,4′‐diaminodiphenyl ether (ODA), but less than m‐phenylenediamine (m‐PDA). And they showed good mechanical properties with 105 ∼ 118 MPa of tensile strength and Tg's were ranged 232 ∼ 301 °C depending on molecular weight and comonomers. The solubility was improved due to the aliphatic character of IPDA in the copolymers. Rheological properties were also improved compared with conventional PAI. The melt viscosity of the copolymers ranged 1.6 · 103 ∼ 2.1 · 103 Pa · s, thus, the reported PAIs may be considered to be new candidates for melt processable high‐performance polymer materials.
Rationelle stärkeacetat‐synthesen
Authors: Reinisch Gerhard , Radics Ute , Roatsch Birgit 
Published: April 2003

AbstractMit Kaliumcarbonat als Aktivator werden aus Hochamylosestärke (HAS) mit überschüssigem Acetanhydrid bei Reaktionszeiten von 1 – 2 h in hohen Ausbeuten Produkte mit hohen Durchschnittssubstitutionsgraden (DS) erhalten.In N‐Methyl‐2‐pyrrolidon können HAS mit stöchiometrischen Mengen Acetanhydrid und mit nichtflüchtigen starken organischen Basen wie 4‐Dimethylaminopyridin oder 1,4‐Diazabicyclo[2.2.2]octan als Katalysatoren in Reaktionszeiten von weniger als 1 h und in hohen Ausbeuten zu Acetaten mit DS < 2 umgesetzt werden.
Triazine‐based polymers, 3. Synthesis and characterization of polyamines
Authors: Braun D. , Ghahary R. , Ziser T. 
Published: April 2003

AbstractA series of 16 triazine‐based polymines was synthesized by interfacial polycondensation, using various dichlorotriazine derivatives and diamines as monomers. The effect of the reaction parameters temperature, reaction time, concentration of monomers, type of organic solvent and type of base on the reduced specific viscosity and yield of polyamines was investigated. Solubilities, glass transition temperatures and thermogravimetric data were determined. Dynamic‐mechanical thermal analyses of two polyamines are reported.
Steam‐exploded wheat straw fibers as reinforcing material for polypropylene‐based composites. Characterization and properties
Authors: Avella Maurizio , Bozzi Claudio , dell'Erba Ramiro , Focher Bonaventura , Marzetti Annamaria , Martuscelli Ezio 
Published: April 2003

AbstractComposites of wheat straw fibers with polypropylene (iPP) and maleic anhydride modified polypropylene (iPPMA) were prepared.Before being mixed with polypropylene matrices, the wheat straw fibers were subjected to a steam explosion process that induces morphological and structural changes in lignocellulosic materials. Such changes are able to enhance the interactions with the thermoplastic matrix.Compared with iPP, the modified matrix (iPPMA) has shown higher mechanical performances (tensile and impact behavior) and a remarkable decrease of water absorption, that is one of the main drawbacks of natural fiber composites.Finally, the presence of covalent bonds between maleic anhydride and steam‐exploded (STEX) fibers, by means of an esterification reaction, produced during the melt‐mixing process, can explain the resulting good interfacial adhesion found in iPPMA‐based composities.
Determination of branching in polybutadienes, poly(1,3‐butadiene‐co‐1‐octene) and poly(1,3‐butadiene‐co‐1‐dodecene)
Authors: Mähner C. , Kaulbach R. , Lechner M. D. , Nordmeier E. H. , Gehrke K. 
Published: April 2003

AbstractThis paper deals with the determination of long‐chain branching in polybutadienes, poly(1,3‐butadiene‐co‐1‐octene), and poly(1,3‐butadiene‐co‐1‐dodecene). These polymers were synthesized by polymerization using a neodym and aluminium‐based catalyst system. Short‐chain branches were introduced by incorporating olefins into the polybutadienes, leading to an improvement of their mechanical properties. The polymers were examined by static and dynamic light scattering, viscosimetry, and gel permeation chromatography. These measurements yield the g‐, h‐, and gη‐factors. The olefin incorporation was performed to increase the degree of branching. But this could not be shown clearly. It is also possible that the degree of branching increases because the polymer molar mass or the width of polymer molar mass distribution (MMD) increases. Thus, branching due to the olefin incorporation may be simulated. To analyse the influence of olefines on the degree of branching more exactly, one would need polymers having identical molar mass and MMD. Moreover, it is possible, depending on whether octene and dodecene chains are long enough, that they can be detected by means of long‐chain branching (LCB) analysis. A decrease of the Lewis acid concentration in the catalyst system changes the MMD and the degree of branching. If the system contains two active centres the MMD is bimodal, whereas if there is only one active centre the MMD is unimodal. In addition, a reduction in Lewis acid concentration leads to an excess of Al(i‐But)3in the catalyst system. Since Al(i‐But)3is a carrier for branching reactions the degree of branching increases.
Radiation‐induced graft polymerization of vinyl monomers onto polyamide‐6
Authors: Kaur Inderjeet , Misra B. N. , Barsola Raghuvir 
Published: April 2003

AbstractRadiation‐induced graft copolymerization of 4‐vinyl pyridine (VP) and a binary mixture of VP and acrylonitrile (AN) onto polyamide‐6 (PA6) fiber has been studied. Optimum reaction conditions leading to maximum percentage of grafting have been evaluated. The graft copolymers have been characterized by IR spectroscopy, thermogravimetric analysis and also by studying the dyeing behaviour of the grafted and ungrafted fiber. It has been observed that, although the thermal properties of fibers had changed upon grafting, the dyeing behaviour, with respect to the total dye uptake, did show only little improvement.
Synthesis and properties of chelate polymers of Cu(II), Ni(II), Co(II), Mn(II) and Zn(II) with a schiff's base of 5,5′‐methylene‐bis(3,3′‐dinitrosalicylaldehyde) with 1,6‐hexanediamine
Authors: Patel M. N. , Sutaria D. H. , Patel S. D. 
Published: April 2003

AbstractThe synthesis, characterization and coordination aspects of the title polymer ligands are reported. The polymeric chelates were prepared by polycondensations of transition metal ions (M) with a poly(Schiff's base) (L). The analytical data propose a (ML)n formula for the chelates. All the polychelates are stable and insoluble in common organic solvents. The geometry around the central metal ion in each chelate is proposed on the basis of measurements of magnetic susceptibilities and UV reflectance spectra. The ligand field splitting parameters 10 Dq, the interelectronic repulsion parameter B, the nephelauxetric parameter β and ligand field splitting energies (L.F.S.E.) have been calculated for Ni(II) and Co(II) chelates. All chelates are resistant to moderately concentrated acids and dilute alkalies at ambient temperature. They exhibit thermal stabilities to varying degrees. IR spectra show that the ligand usually coordinates via the carbonyl oxygen (C=O) and the phenolic OH with replacement of hydrogen by metal ions.
Air plasma treatment of polyacrylonitrile porous membrane
Authors: Bryjak Marek , Gancarz Irena , Krajciewicz Adam , Pigłowski Jacek 
Published: April 2003

AbstractThe effect of plasma treatment of porous polyacrylonitrile membranes is discussed. It is shown that air plasma increases the surface polarity at low‐energy treatment and gradually diminishes it when the energy is increased. When the plasma is set at energies of 12, 30 or 60 W, etching of polymers dominates. Pore diameters of the membranes increase and their distribution functions become broader. When plasma of higher energies (120 or 180 W) is used, the effect of changes of the pore distribution disappears. Membranes modified with plasma of 60, 120 or 180 W do not differ in their porous structure. A simple method of an evaluation of pore diameter distribution function is presented.
Verwendung von schwefelhaltigen salzen für die homogene sulfatierung von polysacchariden im system dimethylformamid/N2O4
Authors: Torgaschov Wadim I. , Gert Evgenij W. , Bildjukewitsch Alexander W. , Kaputskii Fjodor N. 
Published: April 2003

AbstractSulfatations of cellulose and of other types of polysaccharides by the salts of acids H2SnO2n+1 and H2SnO3n+1 in DMF/N2O4 medium have been carried out. Uniformly substituted biologically active sulfates of polysaccharides have been obtained.
Hybrid carbon‐glass fiber vinyl ester resin composites
Authors: Tan Ton That Minh , Nieu Nguyen Huu 
Published: April 2003

AbstractHybrid carbon‐glass fiber composites of novolak epoxy‐based vinyl ester resins have been investigated. The chemical resistance, the thermo‐oxidative stability and the mechanical properties such as tensile strength and tensile modulus, as well as flexural strength and flexural modulus, interlaminar shear strength (ILSS) and impact strength have also been estimated. The combination of glass and carbon fibers in the hybrid turns out to be an excellent mix. These composites have good tensile and flexural properties as well as the good chemical resistance of the carbon fibers and the high impact strength of the glass fibers and also the thermo‐oxidative stability of highly aromatic vinyl ester resins based on novolak epoxy.
Crosslinked polymers from resin acids
Authors: Bicu Ioan , Mustata Fanica 
Published: April 2003

AbstractNew polymers were synthesized by addition of epichlorohydrin to the polyamides or poly(amideimide)s derived from the polycondensation of poly(alkylenepolyamide)s with some Diels‐Alder adducts of resin acids. The adducts were prepared by the reaction between resin acids (extracted from rosin) and acrylic acid or maleic anhydride. The obtained polymers, which were investigated by usual physical and chemical methods, are three‐dimensional, thermosetting and fairly thermostable.
Multiblock copolymers consisting of polyester and polyaliphatic blocks
Authors: Fray Mirosława El , Słonecki Jerzy 
Published: April 2003

AbstractMultiblock‐(AB)n‐copolymers, consisting of hard segments of poly(butylene terephthalate) (PBT) and soft segments of dimerized fatty acid were synthesized and analysed with DSC and DMTA. The polymers were characterized by their limiting viscosity number and melt flow index. The glass transition temperature (Tg) and melting temperature (Tm) increase with decreasing weight fraction of the dimerized fatty acid and with the increase of the crystalline phase content. It was found that the elasticity (ϵ) depends on the content of dimerized fatty acid in the amorphous phase. Tensile properties were described as a function of the degree of polycondensation Pk (molecular weight).
Amphiphilic enzyme membranes, I. Preparation of amphiphilic membranes using poly(HEMA) and poly(HEMA‐co‐st)
Authors: Liu Jui‐Hsiang , Chung Yi‐Chang , Liu Hung‐Tsai 
Published: April 2003

AbstractCopolymers of 2‐hydroxyethyl methacrylate (HEMA) and styrene (St) with various HEMA contents were synthesized in this investigation. Amphiphilic membranes were fabricated by using one layer of hydrophilic poly(HEMA) and one layer of hydrophobic poly(HEMA‐co‐St) in the presence of a photosensitizer. The oxygen permeability and the water penetration of the amphiphilic membranes with various HEMA contents were estimated. The dependence of the mole fraction of HEMA on hydrophilicity and binding forces on the surface of the amphiphilic membranes were investigated. Characteristics of the amphiphilic membranes on the enzyme immobilization were compared with those of traditional two‐layer systems. The response time, stability and pH dependences of the amphiphilic enzyme membrane were also evaluated.
Aromatic‐aliphatic polysulfides. Products of the polycondensation of 4,4′‐bis(mercaptomethyl)biphenyl with some dihalogen hydrocarbons
Authors: Podkoscielny Wawrzyniec , Tarasiuk Bogdan 
Published: April 2003

AbstractPolysulfides were synthesized by high‐temperature solution polycondensation of 4,4′‐bis(mercaptomethyl)biphenyl with selected aliphatic and aromatic‐aliphatic dihalogen hydrocarbons. To determine the optimum polycondensation conditions, the influence of the following factors on reduced viscosity and yield were studied: type of organic solvent, type of hydrogen halide (HX) acceptor, concentration of reagents, reaction temperature and reaction time.A through examination was carried out only for the polycondensation of dithiol with bis(4‐chloromethylphenyl)methane and 1,6‐dibromohexane chosen as model system. The structures of polysulfides were confirmed by elemental analysis, X‐ray analysis and infrared spectroscopy. The temperature of initial decomposition, the percentage of its mass loss, and the temperature of the fastest decomposition process were determined from the curves of differential and thermogravimetric analysis. Some physicochemical, mechanical and electrical properties were determined.
Modell zur beschreibung der viskoelastischen eigenschaften von synthetischen fasern
Authors: Schulz Jakob , Stalevitsch Arkadij , Eickmeier Achim , Bossmann Adelgund , Schollmeyer Eckhard 
Published: April 2003

AbstractZur Beurteilung des viskoelastischen Verhaltens von Synthesefasern sind zeitaufwendige Relaxationsuntersuchungen erforderlich. Um zu schnelleren Aussagen zu gelangen, werden mathematische Modelle benötigt. Charakteristisch für Synthesefasern ist, daß bereits bei sehr kleinen Dehnungen < 1% kein lineares viskoelastisches Verhalten angenommen werden kann. Es wird ein auf der Grundlage der Boltzmann‐Theorie erweitertes Modell vorgestellt, welches das nichtlineare viskoelastische Verhalten von Synthesefasern beschreibt. Unter Anwendung des hier vorgestellten Modells wird das Relaxationsverhalten der Synthesefasern Nomex® und PEEK beschrieben und ein Konzept zur Messung und Auswertung des Ergebnisses vorgestellt.
New aspects of the synthesis of polymercaptals
Authors: Sensfuß Steffi 
Published: April 2003

AbstractThe proton‐catalyzed polycondensation of aromatic aldehydes with aliphatic and aromatic α,ω‐dithiols leads to polymercaptals. The reaction may be carried out in bulk or solution. The bulk polycondensation was catalyzed by hexafluorophosphorous acid (HPF6), formed photochemically by irradiation of the samples containing diaryliodonium salt. The polymers were obtained in high yields but with low molecular weights of Mn 2300–5700 determined by vapour pressure osmometry (VPO). High‐molecular‐weight products of Mn 9100–24000 (VPO) were obtained by solution polycondensation in dichloromethane catalyzed by p‐toluenesulfonic acid. The polymers have been characterized by NMR, VPO, GPC and TGA. Cyclic side products have been isolated and identified. Polyrotaxane structures were found under special conditions.
Thermal behaviour of graft copolymers of sodium alginate
Authors: Shah Samir B. , Patel Chandrakant P. , Trivedi Harikrishna C. 
Published: April 2003

AbstractThe thermal stability of sodium alginate (SA) and its graft copolymers of acrylonitrile (AN), methyl acrylate (MA), ethyl acrylate (EA) and methyl methacrylate (MMA) has been examined in air atmosphere by means of thermogravimetric analysis. The following order of decreasing stability was found from characteristic decomposition temperatures: SA‐g‐PAN > SA‐g‐PMA > SA‐g‐PEA > SA‐g‐PMMA. The overall thermal stability of the different SA graft copolymers was evaluated by comparing their activation energies of thermal degradation; it agreed with the same order of thermal stability.
Plastic zone in front of mode I crack in phenolphthalein polyether ketone
Authors: Han Yanchun , Yang Yuming , Li Binyao , Feng Zhiliu 
Published: April 2003

AbstractThe plastic zone size and crack opening displacement of phenolphthalein polyether ketone (PEK‐C) at various conditions were investigated. Both of them increase with increasing temperature (decreasing strain rate), i.e. yield stress steadily falls. Thus, the mechanism increasing the yield stress leads to increased constraint in the crack tip and a corresponding reduction in the crack opening displacement and the plastic deformation zone. The effect of the plastic deformation on the fracture toughness is also discussed.
Preparation of hydrophilic membranes by grafting acrylic acid onto pre‐irradiated teflon‐FEP films
Authors: Aouadj S. , Chapiro A. 
Published: April 2003

AbstractGrafting of acrylic acid onto pre‐irradiated poly(tetrafluoroethylene‐hexafluoropropylene) (Teflon‐FEP) films was investigated, and the reaction parameters dose, dose rate, monomer concentration and grafting temperature were examined.The results show that the degree of grafting depends on the dose (5‐60 kGy), the weight of grafted specimen increased up to 37%. The degree of grafting was found to be independent of the dose rate.The overall activation energies were calculated to be 28.8 and 81.6 kJ mol‐1 for treatments at above and below 50°C, respectively.The swelling of grafted films was measured in water, aqueous potassium hydroxide and methanol. The degree of swelling was found to increase with the length of grafted chains.