bluuebunny/crossref_metadata_2025_split huggingface dataset:
Syntheses and reactions of photopolymers, II. Interfacial polycondensation, microencapsulation, photodegradation, release measurements
Authors: Nuyken Oskar , Dauth Jochen , Stebani Jürgen 
Published: April 2003

AbstractPhotosensitive microcapsules, which are thermally quite stable, are formed via interfacial polycondensation in which one of the shell‐forming reactants contains an azo function.An azo monomer, containing α,ω‐carboxylic diacid dichloride was reacted with a trifunctional aliphatic amine on the oil‐water interface resulting in a shell‐forming crosslinked polyamide. The size of the resulting photosensitive microcapsules was determined. It could be shown that these microcapsules can be opened by means of UV‐light.
The dependence of enzyme leakage on crosslink density in poly(N‐vinyl‐2‐pyrrolidone) hydrogels with immobilized urease
Authors: Güven Olgun , Şen Murat 
Published: April 2003

AbstractUrease enzyme was immobilized in hydrogels prepared from vinyl pyrrolidone/water/crosslinking agent ternary mixtures by γ‐irradiation of the solutions at room temperature. Two types of crosslinking agents used, namely ethylene glycol dimethacrylate and trimethylol propane triacrylate, yielded hydrogels with different swelling and crosslink density properties. The activity of immobilized urease was measured at the optimum conditions of temperature and pH over a period of time. It has been determined that for hydrogels with average molecular weights between crosslinks, Mc, above 2000, urease leakage is a serious problem. When Mc is around and below this value, immobilized systems showed a long time activity.
Die reaktive Verarbeitung von Polyethylen und Ethylen‐Vinylacetat‐Copolymerem. Verfolgung des Reaktionsverlaufs und Nachweis der Eigenschaftsänderungen
Authors: Vogel Jürgen , Heinze Carina 
Published: April 2003

AbstractDer Reaktionsverlauf der peroxidischen Vernetzung (1 Gew.‐% Dicumylperoxid (DCP)) von Polyethylen niederer Dichte (LDPE) mit Ethylen‐Vinylacetat‐Copolymerem (EVA) im Kleinstkneter wurde anhand der Anderung des temperaturkorrigierten Drehmomentes verfolgt. über die Variation der Temperatur und Drehzahl wurde der Einfluß der Verarbeitungsbedingungen auf die Vernetzungskinetik untersucht. Sowohl Temperatur‐ als auch Drehzahlerhöhung bewirkten eine Beschleunigung der radikalischen Reaktion. Die Vernetzung der einzelnen Komponenten und des LDPE/EVA Compounds führte zu einer signifikanten Abnahme des Kristallinitătsgrades, was sich makroskopisch in einem Abfall des E‐Moduls im dynamischen Biegeschwingversuch bemerkbar machte. Für den Reaktionsverlauf und die sich ausbildende Morphologie sowie für die mechanischen Eigenschaften des Compounds ist die Schmelzemorphologie vor dem radikalischen Angriff von entscheidender Bedeutung.
Untersuchungen zur thioladdition an polybutadiene
Authors: Klemm Elisabeth , Gorski Ute 
Published: April 2003

AbstractDie radikalische Addition von Octylmercaptan (RSH) an Polybutadiene unterschiedlicher zahlenmittlerer Molmasse und Konfiguration der Doppelbindungen erfolgt stereoselektiv an die 1,2‐vinyl‐ und 1,4‐cis‐konfigurierte Doppelbindung, während die 1,4‐trans‐konfigurierte Doppelbindung unverandert bleibt. Die Reaktivitätsabstufung 1,2‐ > cis‐ > trans‐Doppelbindung wird in Modellversuchen an den isorneren Pentenen gleichfalls bestatigt. Die Addition ist durch einen Olefin/RSH‐Charge‐Transfer‐Komplex als Pre‐Initiierungsschritt begünstigt.
Sulfobetaine polyurethane ionomers, 2. Dielectric relaxation in polyether‐based polymer and related compounds with Co2+
Authors: Diaconu I. , Buruiană T. , Buruiană E. C. , Coman P. 
Published: April 2003

AbstractDielectric relaxation processes in sulfobetaine polyurethane ionomers based on polyether, were studied comparatively to nonionic polyurethane and related compounds with Co2+ (complexed and H2S‐treated forms) by using thermally stimulated depolarization currents (TSDC).Four relaxation processes denoted as γ, βs, β′ and βh in polyurethane ionomers over the 110–370 K range were observed. Molecular origin of these processes was suggested. The effects of the hard segments content, complexation and H2S treatment on the relaxation processes were explained in terms of the structural modifications of the hard and soft microphases.
Metal ion complexation of poly(acrylamide)‐supported amines crosslinked with N,N′‐methylene‐bis‐acrylamide
Authors: Mathew Beena , Rajasekharan Pillai V. N. 
Published: April 2003

AbstractThe complexation of amino functions supported on poly(acrylamides) with 2–20 mol‐% of N‐(acrylamidomethyl)acrylamide (NNMBA) crosslinks towards Co(II), Ni(II), Cu(II), Zn(II), and Hg(II) ions was investigated. The metal ion uptake was found to be dependent on the extent of the NNMBA crosslinking. The observed trend in complexation is Hg(II) ≫ Cu(II) > Zn(II) > Ni(II) > Co(II). The kinetics of complexation was found to be of first order. The derived metal complexes were characterised by IR and EPR. The complexed resins can be recycled several times without capacity loss. The metal‐desorbed resins showed specificity to the metal ion which was initially present. The extent of swelling of the complexed resins is lower than that of the uncomplexed resins and it varies with the extent of crosslinking.
Conduction mechanism of polycarbonate doped with different transition metals
Authors: Amin M. , Mounir M. , El‐Shekeil Ali , Darwish K. A. , Abu Elez M. 
Published: April 2003

AbstractThe electrical conduction of polycarbonate (PC) doped with different transition metals was studied in the temperature range of 293–493 K. The conductivity of PC doped with FeCl3 is 7 orders higher in comparison with the other samples. The effective potential barrier (Φ) for pure PC was calculated (0.2 eV). Also, the dielectric constant at different temperatures was studied.
Volume change by solvent and temperature of poly(vinyl alcohol) crosslinked by electron irradiation
Authors: Yoshii Fumio , Sudradjat Adjat , Darwis Darmawan , Razzak Mirzan T. , Makuuchi Keizo 
Published: April 2003

AbstractResponsive poly(vinyl alcohol) PVA hydrogels obtained by electron irradiation after heating of a water‐swollen film show higher elasticity and tougher properties even after boiling in water, although some swelling did occur. The volume of the hydrogel after boiling was very sensitive to solvent (acetone) and temperature. The crosslinked hydrogels show higher tensile strength after rapid contraction by immersion in acetone. The crosslinked PVA was boiled and cooled to induce contraction and swelling cycles. The swelling ratio of hydrogel decreased remarkably at temperatures higher than 40°C.
Change of mechanical properties of crosslinked polyethylene during its thermo‐oxidative aging
Authors: Langlois V. , Audouin L. , Courtois P. , Verdu J. 
Published: April 2003

AbstractThe thermal aging of extruded samples of electron beam‐crosslinked linear polyethylene has been studied in the 110–170°C temperature range. Short and long term changes of mechanical (tensile) properties were observed, and the corresponding mechanisms are discussed on the basis of complementary sol‐gel and gravimetric measurements on whole samples, and density, FTIR and tensile testing on microtome sections.Two mechanisms are involved in short term changes: a post‐crosslinking and a change of the crystalline morphology (for samples exposed above the melting point). The latter effect is especially important in the case under study where the polymer was crosslinked in the solid state and leads to a noticeable decrease (∼5 MPa) of the yield stress.The long term changes take place after the end of the induction period of oxidation. They can be interpreted in terms of ductile‐brittle transition induced by structural changes occurring on the macromolecular level (chain scission) as well as macroscopically (core‐shell structure resulting of the diffusion control of oxidation kinetics). It appears that noticeable changes of ultimate elongation occur just before the end of the induction period as detected by IR or DSC method.
Poly(3‐octylthiophene) as semiconductor for schottky barrier: Effects of doping and storage time
Authors: Chen Show‐An , Fang Yih 
Published: April 2003

AbstractSchottky diodes of aluminium/poly(3‐octylthiophene)(P30T)/indium‐tin oxide with large active area are prepared by using the proposed new casting technique. Their rectifying behavior and junction characteristics are dependent on whether the P30T is doped and on the storage time, but independent of the thickness of the P30T layer. The present technique can also be applied in a fabrication of electronic devices with other soluble conjugated polymers.
Thermal properties of copoly(1,4‐arylene‐1,2,4‐oxadiazole)s having n‐alkyloxymethyl side branches
Authors: Park Sang‐Bong , Jung Jin Chul 
Published: April 2003

AbstractTwo series of copoly(1,4‐arylene‐1,2,4‐oxadiazole)s (co‐PAOs) having n‐butyloxymethyl and n‐octyloxymethyl side branch were prepared by solution cyclodehydration of the corresponding precursor copoly(1,4‐arylene terephthaloyl amide oxime)s (co‐PAAs) obtained by solution polycondensation of mixtures of 2,5‐bis(n‐alkyloxymethyl)‐1,4‐benzenediamide oximes (DIS‐TADO) and terephthaldiamide oxime (TADO) with terephthaloyl chloride. Thermal properties of the copolymers were investigated and discussed in connection with the length and the content of side branches. All the copolymers are crystalline.
Polyurethane ureas with various urea structures. Solution behaviour and morphology
Authors: Joel Detlef , Pohl Gerhard , Hiller Wolf‐Gerald 
Published: April 2003

AbstractBoth the effect of the diamine chain extender on solution properties and the effect of added LiCl destroying the urea hydrogen bonds of the PUU's (polyurethane ureas) in DMF have been investigated. PUU solutions with an even number of CH2 units in the chain extender have higher viscosities than the corresponding solutions with an odd number of CH2 units. While the viscosity of solutions with odd‐numbered methylene groups is independent of time, the even‐numbered ones show a drastic increase in dependence on time and gelation may even occur. Due to diminished associates, time‐independent solution systems of low viscosity have also been obtained by adding a small amount of LiCl to solutions with even‐numbered methylene groups.In films cast from the solutions the effect of LiCl has been proved in the solid state.
Syntheses of cellulose exchangers carrying chelating anchor groups for selective separation of uranyl ions
Authors: Fischer H.‐J. , Lieser K. H. 
Published: April 2003

AbstractSyntheses of cellulose exchangers carrying tailor‐made chelating anchor groups are described. One type of anchor groups offers three coplanar carboxy groups for the complexation of UO2+2, a second type coplanar amidoxime‐hydroxamic acid groups and a third type amidrazone‐hydrazide groups. The distance of the groups is varied by use of different terminal dibromo‐n‐alkanes. The anchor groups of type 1 are obtained from malonic acid diethyl ester and dibromalkanes, type 2 and 3 from cyanacetic acid ethylester and dibromoalkanes. The products containing malonic acid diethylester and alkane groups or cyanoacetic acid ethylester and alkane groups, respectively, in the mole ratio 3 : 2 are coupled with hydrazinedesoxycellulose. The carboxy groups are set free by hydrolysis of the ethyl esters in case of type 1, whereas the anchor groups of types 2 and 3 are obtained by reaction with hydroxylamine and with hydrazine, respectively.The procedures of the syntheses are presented in detail. The products are characterized by the degree of substitution and the content of the individual groups. The anchor groups are inverstigated by means of their 1H‐NMR spectra. The exchange properties are discussed.
Effect of impregnation on the degree of polymerization of cellulose during bleaching of sodapulped sugar cane bagasse
Authors: Marx‐Figini Marianne , Maximino Mirta 
Published: April 2003

AbstractSamples of sugar cane bagasse pulps, digested at different times without and with previous impregnation, have been bleached and the bleached materials submitted to a detailed study of their degree of polymerization (DP) and the corresponding distributions. The respective results turn out that like in the case of the effect of impregnation on the digestion process, impregnation affects also the bleaching reaction of the digested samples, causing a further remarkable decrease of the degree of polymerization of the cellulose molecules and a deviation of its distribution from the character of a most probable one. The impregnated bleached materials show in addition to the decrease of their DP a certain, albeit slight, diminution in their tensile strength.
Porous ion exchange membranes as potential antifoulants
Authors: Bryjak Marek , Trochimczuk Witold 
Published: April 2003

AbstractThe effect of surface hydrophilization on antifouling properties of ultrafiltration membranes was investigated. The enhanced film model as well as experimental data showed the vital role of surface charge on amount of deposited bovine serum albumin. Two types of materials were studied: high flux polysulfone (capillary, asymmetrical) and low flux polyethylene (flat, symmetrical) membranes. The antifouling effect, revealed mostly by polyethylene membranes, pointed on solute convection as an important factor. When membrane and solute borne this same sign of charge the antifouling effect was governed by the net charge of membrane.
Chemical surface treatment of poly(tetrafluoroethylene) powder
Authors: Huang Chi‐Yuan , Chiang Wen‐Yen 
Published: April 2003

AbstractPoly(tetrafluoroethylene) powder has been treated with sodium‐naphthalene complex in tetrahydrofuran (THF) to improve its surface properties. The cryocondition (−40°C) was taken to keep the active species alive so that the PTFE powder surface could be etched homogeneously and a large area of PTFE could be etched. The Na‐treated PTFE powder was examined by IR, ESCA (electron spectroscopy for chemical analysis), X‐ray diffractometry, thermal analysis and SEM (scanning electron microscopy). IR spectra showed that the surface structure of Na‐treated PTFE powder possessed a lot of CFCF− double bond structures. ESCA surface analyses also revealed the formation of CFCF− double bonds. During the process of sodiumnaphthalene complex etching, most of NaF salt formed was adsorbed on the surface of treated PTFE (CPTFE, NaF adsorbed) and a small amount of NaF salt was found doped into treated PTFE. As a result, part of the surface of treated PTFE was found doped into treated PTFE. As a result, part of the surface of treated PTFE was similar to a free alkali‐fluoride‐doped polyfluoroacetylene. It was shown by SEM that the etched PTFE had a web‐like surface.
A novel Si‐containing copolymer for a resist highly etching‐resistant to oxygen plasma
Authors: Chiang Wen‐Yen , Lu Jin‐Yuh 
Published: April 2003

AbstractA new copolymer, poly(maleimide‐alt‐trimethylvinylsilane) (PMVS), with a high silicon content was synthesized by free‐radical copolymerization, in order to obtain a positive photoresist containing diazonaphthoquinone sulfonate as a dissolution inhibitor. PMVS shows a high etching selectivity of 1 : 16 compared to a commercially available, hard‐baked photoresist (HPR‐204). In addition, the rigid cyclic maleimide group is responsible for high temperature stability.
Characteristics of permeation and separation of aqueous alcoholic solutions with chitosan derivative membranes
Authors: Uragami Tadashi , Kinoshita Hiroyuki , Okuno Hiroshi 
Published: April 2003

AbstractPermeation and separation characteristics for the feed vapours from aqueous alcoholic solutions through chitosan derivative membranes such as chitosan acetate (GA‐ChitoA), chitosan (GA‐Chito), and carboxymethyl chitosan acetate (GA‐CM‐ChitoA) membrane crosslinked with glutaraldehyde were investigated by evapomeation. The GA‐Chito and GA‐CM‐ChitoA membranes prepared from casting solutions containing an optimum amount of glutaraldehyde showed a high permeation rate and high water permselectivity for an azeotropic composition in an aqueous ethanol solution. The permselectivity for water through the GA‐CM‐ChitoA membrane in evapomeation was in the order of aqueous solutions of methanol < ethanol < 1‐propanol. The effect of the chemical and physical structure of these hydrophilic membranes on the permeation and separation characteristics is discussed.
Coemulsion and electrodeposition properties of mixtures of a poly(oxypropylene)‐modified cationic epoxy resin and nonionic crosslinker system
Authors: Chen Yahn‐Haur , Yang Chin‐Ping 
Published: April 2003

AbstractThe emulsification and electrodeposition properties of mixtures of a poly(oxypropylene) (POP)‐modified cationic epoxy resin (III) and nonionic pentaerythritol/toluene diisocyanate/2‐ethylhexanol (PETOL‐TDI‐2EH, V) were investigated and the compositions of their electrodeposited films were obtained by Fourier Transform Infrared (FTIR) quantitative analysis to study the effects of soft segments (oxypropylene groups) contained in resins III on the coemulsion and electrophoretic behavior.The results indicate that the deposition yield and throwing power of an emulsion of individual III are deeply affected by its average molecular weight (AMW). Resin III with higher AMW has higher deposition yield but lower throwing power. Moreover, the deposition yield of V/III coemulsion also increases with increasing the AMW of III. On the other hand, the throwing power of V/III coemulsion is not related to the AMW of III but affected by the amount of soft segments in III. Increasing “Soft segment” Content in III increases the throwing power of coemulsion. Furthermore, at the conditions providing stable coemulsion, the composition of electrodeposited film is almost equal to the resin composition of coemulsion.
Chemical modification of poly(epichlorohydrin) with unsaturated potassium carboxylates
Authors: Reina J. A. , Cádiz V. , Mantecón A. , Serra A. 
Published: April 2003

AbstractPoly(epichlorohydrin) was modified by nucleophilic substitution with some aliphatic potassium carboxylates containing terminal double bonds (10‐undecenoate, 4‐pentenoate and 3‐butenoate). In order to monitor the degree of substitution achieved, different reaction conditions were tested. The polyethers obtained were characterized by spectroscopic techniques, elemental analysis, thermal methods, viscosity determinations and osmometric measurements. A slight crosslinking and the reported main chain cleavage were both detected. Finally, it must be pointed out that, during the substitution reaction with the vinylacetate, isomerization to crotonic ester took place.
Viscosity characteristics of some para‐nonylphenol formaldehyde novolac epoxy resins
Authors: Caşcaval Constantin N. , Mustaţǎ Fǎnicǎ , Roşu Dan 
Published: April 2003

AbstractPara‐nonylphenol formaldehyde novolac epoxy resins with molecular weights between 640 and 3150 were studied regarding the viscosity behaviour. The estimation of both the intrinsic viscosity and the molecular weight of the epoxidized resins resulted in a straight relationship between these experimental parameters: [η] = k1 + k2M̄n, where k1 = 137 dl/g and k2 = 99.2·10−3 dl/g.Study of the flow behaviour of the molten epoxide resins allowed the measurement of the apparent shear viscosity, the shear stress, the shift factor, the melt flow index, the consistency index, and the flow activation energy. The flow data, which were analysed both as a function of temperature and of the shear rate, led to the conclusion that para‐nonylphenol formaldehyde novolac epoxy resins show a non‐Newtonian rheological behaviour of pseudoplastic type.
Antioxidants and stabilizers, 118. Influence of the carbon black chezacarb EC on thermooxidation of cyclohexene doped with hydroperoxide decomposers and metal deactivators
Authors: Rotschová Jitka , Pospíšil Jan 
Published: April 2003

AbstractA model system consisting of cyclohexene and various amounts of carbon black was oxidized with O2 at 60°C in the presence of hydroperoxide decomposers, bifunctional antioxidants and metal deactivators. No metal deactivating contribution to the antioxidant effect was observed with phosphites. Efficient chain‐breaking activity was achieved with 4,4′‐thiobis(2‐tert‐butyl‐5‐methylphenol). However, metal deactivators were able both to prolong the induction period and retard the oxidation rate after the induction period. An efficient long‐term stabilization with Chezacarb EC cannot be achieved without chelate‐forming stabilizers.
Photo‐ and thermoinitiated curing of epoxy resins by sulfonium salts
Authors: Stapp Bernhard , Schön Lothar , Bayer Heiner , Hoffmann Michael 
Published: April 2003

AbstractA number of benzylthiolanium salts have been synthesized, analysed and evaluated by differential scanning calorimetry and viscosity measurements with respect to their potential use as thermal curing agents for epoxy resins. Over a wide range of Hammett constants a correlation exists between initial reactivity, shelf life and the electronic substituent effects of the benzyl group. A combination with arylsulfonium salts leads in singular cases to dual cure systems with attractive properties of thermal and UV induced curing. The sensitization of benzylthiolanium salts also leads to dual cure systems. This opens up new possibilities for UV curable epoxy resins in electronic applications requiring additional curing in shaded areas.
Grafting of different vinyl monomers onto sodium salt of partially carboxymethylated amylose
Authors: Patel Bipin K. , Patel Chandrakant P. , Trivedi Harikrishna C. 
Published: April 2003

AbstractIn order to study the reactivity of different vinyl monomers, the grafting of different vinyl monomers such as acrylonitrile (AN), methylacrylate (MA), ethylacrylate (EA), methyl methacrylate (MMA), butylacrylate (BA) and vinyl acetate (VAc) onto the sodium salt of partially carboxymethylated amylose (DS = 0.313) has been carried out using ceric ammonium nitrate as an initiator. The following reactivity order of monomers has been found: AN > MA > EA > MMA > BA > VAc.
Preparation and characterization of carboxylic cation exchange resins from the reaction of poly(vinyl alcohol) with melamine‐formaldehyde and some hydroxy acids
Authors: Ibrahim N. A. , Abo‐Shosha M. H. 
Published: April 2003

AbstractThe synthesis of cation exchange resins via the reaction of poly(vinyl alcohol) as a carrier, citric acid as a catalyst and reactive additive to produce resin structures with grafted carboxy groups, along with a melamine‐formaldehyde precondensate, responsible for crosslinking‐reinforcing and insolubilizing the resin structure as well as for fixing and binding the acidic functional groups onto the resin structure, has been investigated using varied molar ratios of reactants and varied time as well as temperature. Reaction conditions were selected to prepare a cation exchange resin based on citric acid. Two other cation exchange resins based on tartaric acid and glycolic acid, were also prepared under the same selected reaction conditions. These three resins were characterized by potentiometric titration, water solubility and swellability, as well as durability to use.