bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adsorption of dyes on chitin. I. Equilibrium studies
Authors: McKay G. , Blair H. S. , Gardner J. R. 
Published: April 2003

AbstractEquilibrium isotherms have been studied for the adsorption of four dyestuffs, namely, Acid Blue 25, Acid Blue 158, Mordant Yellow 5, and Direct Red 84, onto chitin. Langmuir and Freundlich constants have been determined and the effects of chitin particle size and solution temperature have been investigated. Theoretical isotherms have been compared with experimental data and good agreement was obtained using a composite isotherm of the general form: Ye = iCe/(1 + jCem), where i,j, and m are constants.
Simulation of three‐stage nylon 6 reactors with intermediate mass transfer at finite rates
Authors: Gupta Santosh K. , Kumar Anil , Agrawal K. K. 
Published: April 2003

AbstractA three‐stage isothermal nylon 6 reactor with a kinetic scheme incorporating ring opening, polycondensation, polyaddition, cyclic dimer formation, and reaction with monofunctional acids has been modeled. In the first and third stages, removal of the condensation by‐product, water, is prevented. The second stage of this sequence, however, involves finite rates of diffusion of water to cocurrently flowing inert gas bubbles. the number‐average chain length of the polymer obtained in this reactor differs substantially from that obtained assuming instantaneous water removal and is a function of the various design variables. It is observed that several choices of these design variables can be made to obtain the same product, thus emphasizing the need for more comprehensive optimization studies than hitherto carried out.
Preparation of functional polymer‐microspheres by suspension copolymerization of ethylene glycol dimethacrylate with hydrophilic monomers
Authors: Ohtsuka Yasuji , Kawaguchi Haruma , Yamamoto Takuya 
Published: April 2003

AbstractA study was made of suspension copolymerization of ethylene glycol dimethacrylate (EDMA) with some hydrophilic monomers (M2) to prepare gel particles having a large number and various kind of functional groups on their surface. Delayed charge of M2 to partially prepolymerized EDMA suspension resulted in the formation of favorable particles. The polymerization leveled off despite an appreciable amount of remaining M2 in the aqueous phase, and the amount of copolymerized M2 and the fraction of on‐surface M2 units depended significantly on the kind of M2 as well as the mode of M2 charge. These dependences were explained in terms of the partition coefficient of M2 between EDMA and water and the monomer reactivity ratio.
Studies on effect of irradiation on semipermeable membranes
Authors: Ramachandhran V. , Misra B. M. 
Published: April 2003

AbstractThe effect of γ irradiation on reverse osmosis (RO) semipermeable membranes has been studied in order to evaluate their performance under the radiation environment arising in the processing of various streams in nuclear industry by reverse osmosis process. Both cellulosic and noncellulosic membranes in dry as well as wet conditions were used. A Co60 source was used for γ doses from kilorads to megarads. The transport properties, namely, salt retention and water flux of membranes determined before and after irradiation, suggested deterioration in the membrane properties due to irradiation. The tensile strength and viscosity of membrane polymer also suggested membrane degradation. Differential scanning calorimetry was taken to look into any structural changes in the membrane polymer as a result of irradiation. IR spectra and X‐ray of membrane polymer was also undertaken to understand the changes on the molecular level.
Chemical factors affecting soiling and soil release from cotton‐containing durable press fabric. VI. Effect of introduction of carboxymethyl groups in the cotton component of polyester/cotton blend
Authors: Hebeish A. , El‐Rafie M. H. , El‐Aref A. T. , Khalil M. I. , Abdel‐Thalouth I. , El‐Kashouti M. , Kamel M. M. 
Published: April 2003

AbstractPartial carboxymethylation of the cotton component of polyester/cotton blend prior to durable press finishing with dimethyloldihydroxyethylene urea in presence of MgCl2·6H2O was carried out under different conditions to control the carboxyl content as well as alteration of the blend components accompanying the chemical modification. The susceptibility of these modified blend samples before and after crosslinking to aqueous and nonaqueous oily soiling and their ability to release the soil was examined. The general indications are that introduction of carboxymethyl groups in the molecular structure of the cotton component of the blend imparts soil release characteristics of the blend provided that (a) the condition of partial carboxymethylation is not accompanied by profound changes in neither the microstructure of the cotton component nor in the polyester content of the blend and (b) the carboxymethyl content should not be so high. It is proposed that the anionic nature of the modified cotton component of the blend during washing helps in repelling the negatively charged soil particles from the blend surface. In addition, a reduction in the interfacial tension at the soil–water interface assists in rolling up the soil and subsequent removal. This can be turned to the opposite if the electrostatic repulsion is masked through creation of soft swollen environment by significantly increasing the carboxymethyl content, decreasing the polyester content, and/or increasing the swellability of cotton component of the blend.
Preparation of silicon carbide–silicon nitride fibers by the controlled pyrolysis of polycarbosilazane precursors
Authors: Penn B. G. , Ledbetter F. E. , Clemons J. M. , Daniels J. G. 
Published: April 2003

AbstractExperiments to produce polycarbosilazane resin and high‐strength silicon carbide–silicon nitride (SixNyCz) fibers as well as resin/fiber characteristics are reported. Polycarbosilazane resin was drawn into fibers from the melt and subsequently treated and pyrolyzed into SixNyCz fibers. These materials are characterized by high tensile modulus (29 × 106 psi for 0.4‐mil diameter) and high electrical resistivity (6.9 × 108 Ω·cm for 0.6‐mil diameter).
Estimation of heat evolution during viscoelastic crack propagation by liquid crystal film technique
Authors: Kobayashi Akira , Munemura Masayuki , Ohtani Nobuo , Suemasu Hiroshi 
Published: April 2003

AbstractHeat generated during dynamic crack propagation in viscoelastic solids was investigated by visible liquid crystal film technique to observe the thermal boundary front emanating from a running crack tip. The crack propagation velocity was also measured by the velocity gauge method. The heat so estimated is correlated with the crack propagation velocity.
Effect of large dosage irradiation in air on polyethylene
Authors: Fujimura Takashi , Hayakawa Naohiro , Kuriyama Isamu 
Published: April 2003

AbstractThe large dosage irradiation effect on polyethylene in air was examined by the method of double irradition. Polyethylene was first irradiated with γ‐rays to a dosage of a few hundred Mrad in air at 298°K. The formed radicals were destroyed, and the polymer, changed chemically and morphologically, was irradiated again in vacuo at 77°K with a dose of 12.7 Mrad. The thermal decay of radicals produced in polyethylene by the second irrdiation was investigated. The results were compared with the sample not exposed to the first irradiation. The results were also compared with previous data of polyethylene irradiated in vacuo to a great extent and then treated in the same manner as that in the present experiment. The results show that scission of the polymer chain by oxidation makes the radical decay faster. Simultaneously, crosslinks formed in polyethylene irradiated in air to a great extent slow down the radical decay. Almost the same number of double bonds was formed in polyethylene irradiated in air as in polyethylene irradiated in vacuo. These double bonds react with alkyl radicals to form allyl radicals.
Adsorption of dyestuffs onto chitin. External mass transfer processes
Authors: McKay G. , Blair H. S. , Gardner J. 
Published: April 2003

AbstractThe effect of several variables on the adsorption rate of four dyestuffs onto chitin was studied. A model is proposed enabling the film mass transfer coefficients to be determined. The coefficients were independent of initial dye concentration, chitin mass, chitin particle size, and temperature; a slight dependence with agitation was obtained. The film mass transfer coefficients at 400 rpm were 2.8×10−3, 2.9×10−3, 3.9×10−3, and 0.9×10−3 cm/s for Acid Blue 25, Acid Blue 158, Mordant Yellow 5, and Direct Red 85, respectively.
Rheograms of cellulosic polymers from the melt flow index
Authors: Shenoy A. V. , Saini D. R. , Nadkarni V. M. 
Published: April 2003

AbstractData on the variation of melt viscosity over a wide range of shear rates and temperatures are necessary in the processing of cellulosic polymers. An effective method has been proposed to estimate the viscosity vs. shear rate flow curves of a cellulosic resin at temperatures relevant to the processing conditions, from its melt flow index and glass transition temperature. The method involves the use of a master curve obtained by coalescing the rheograms of various grades in terms of a modified viscosity, η˙MFI, and a modified shear rate, γ˙/MFI. Master curves have been reported for cellulose esters and ethers.
Highly reactive wood pulps for cellulose acetate production
Authors: Sears K. D. , Hinck J. F. , Sewell C. G. 
Published: April 2003

AbstractWood pulps highly reactive in both high‐ and low‐catalyst cellulose acetate processes can be prepared by mercerization and then treatment with alkylene oxides; only trace levels of substitution are required. The fiber inactivating effects of mercerization after drying are overcome, and several acetate properties are improved by this process. The reactivity characteristics cannot be duplicated by similar modifications of nonmercerized fibers; in low catalyst processes such pulps actually show reduced reactivity.
Solution behavior of ionomers. III. Sulfo‐EPDM‐modified hydrocarbon solutions
Authors: Lundberg Robert D. 
Published: April 2003

AbstractThe solution viscosity of polymer thickened hydrocarbons normally decreases markedly as temperature is increased. It has been observed that metal sulfonate ionomers, such as sulfonated ethylene propylene terpolymer, or sulfo‐EPDM, when dissolved in a mixed solvent behave much differently. Specifically, sulfonated ionomers, dissolved in xylene or paraffinic oils with low levels of a polar cosolvent, can provide solutions whose viscosities are either relatively constant or can actually increase with increasing temperature. This isoviscosity effect can be manifested over broad temperature ranges and is mechanistically different from the behavior of conventional polymer solutions. This unusual behavior is explained on the basis of a simple equilibrium involving solvated ion pairs and is shown to be a specific example of a general phenomenon.
Boiling water aging of a miscible blend of polycarbonate and a copolyester
Authors: Joseph E. A. , Paul D. R. , Barlow J. W. 
Published: April 2003

AbstractExtruded films and injection molded bars of a copolyester based on 1,4‐cyclohexanedimethanol condensed with a mixture of isophthalic and terephthalic acids, of a bisphenol‐A based polycarbonate, PC, and of the miscible blends of these compounds were exposed to boiling water for up to 15 days. The ductility and strengths of film specimens rich in PC were found to degrade as a result of PC hydrolysis. These properties of specimens rich in copolyester were found to decline as a result of crystallization of the copolyester. Best overall performance was obtained for 50/50 blends of PC and copolyester. All amorphous materials showed a transition from ductile to brittle behavior at the same weight average molecular weight as previously observed for pure PC. This feature plus the observation that PC hydrolyzes in the blend at the same rate as it does in the pure state allows most of the superior performance of the 50/50 blends to be explained in terms of blend molecular weight.
Interaction of heavy metals with chitin and chitosan. III. Chromium
Authors: Maruca R. , Suder Billie Jo , Wightman J. P. 
Published: April 2003

AbstractThe interaction of the natural marine polymer chitin and its deacetylated derivative chitosan with chromium has been investigated. The uptake of chromium from aqueous solution was determined from changes in concentration as measured by atomic absorption spectroscopy. The uptake of Cr(III) on chitosan was significantly greater than that on chitin. The smaller the size fraction of the chitin/chitosan, the greater the uptake of Cr(III). The Cr(III) uptake increased with increasing solution pH. Minimal desorption of chromium was observed on washing previously chromium‐equilibrated chitosan with distilled water. The uptake of Cr(III) by chitosan was enhanced in the presence of phosphate, whereas the converse was not observed. Minimal uptake of Cr(VI) as dichromate by chitin and chitosan was measured. Cr‐containing nodules were noted in the SEM/EDAX analysis for Cr(III)‐equilibrated chitosan. Cr‐containing clusters were detected for Cr(III)‐ plus phosphate‐equilibrated chitosan. XPS results supported the conclusions drawn from the isotherm studies.
Mechanochemical process in cotton cellulose fiber
Authors: Hon David N.‐S. , Srinivasan K. S. V. 
Published: April 2003

AbstractMechanical processing of cotton cellulose by means of a fiber cutter resulted in the disaggregation and defiberation of fiber bundles, shortening of fiber length, and loss of degree of polymerization. It is evident that the mechanical energy supplied by shear forces is sufficient to cause homolytic scission of cellulose main chains. Mechanoradicals formed in the interim were verified by ESR studies. The crystallinity of cellulose was not influenced by mechanical treatments, but accessibility of the polymer was substantially increased due to the creation of new surfaces. The mechanically treated fiber inclined to proceeded oxidative chain reaction during aging. Regardless of their treatment conditions, cellulose fiber reached its limiting lower molecular weight after 100 days of aging.
Permeation of methyl chloride and benzene through FEP Teflon
Authors: Duncan T. , Koros W. J. , Felder R. M. 
Published: April 2003

AbstractPermeabilities and diffusivities of methyl chloride and benzene vapors at low activities in FEP Teflon membranes were measured in a continuous‐flow permeation cell, at temperatures ranging from 47°C to 150°C. In all cases investigated, the permeabilities and diffusivities were independent of the penetrant partial pressure, and the permeation process was well described by a Henry's law sorption–Fickian diffusion model. The activation energies for permeation and diffusion and the sorption enthalpy were respectively 34.8 kJ/mol, 50.1 kJ/mol, and −15.3 kJ/mol for methyl chloride and 49.5 kJ/mol, 69.1 kJ/mol, and −19.6 kJ/mol for benzene. The diffusional activation energies for these two substances and other low molecular weight hydrocarbons correlate reasonably well with the Lennard–Jones collision diameters of the penetrant molecules. The solubilities correlate approximately with the penetrant boiling points, but the highly polar nature of methyl chloride and the aromaticity of benzene lead to deviations between the solubilities of these substances and those of nonpolar aliphatics with the same tendency to condense from the vapor phase.
Glass transition temperature predictions in some epoxy polymers
Authors: Lee Gilbert , Hartmann Bruce 
Published: April 2003

AbstractThe glass transition temperature as an additive property was studied on a series of epoxy/amine crosslinked polymers. Various methods from the literature of analyzing the glass transition temperature in terms of components are presented and then judged to determine which of these methods gives the best agreement between calculated and measured glass transition temperature. It was found that predictions agree on the average with the measurements to within the accuracy of the measurements, approximately 3%.
An approach in modeling the tubular polymer reactor
Authors: Nigam K. M. , Nigam K. D. P. 
Published: April 2003

AbstractAn analytical solution for diffusion with a homogeneous first‐order reaction in the bulk and a heterogeneous reaction at the reactor wall in a non‐Newtonian laminar flow tubular reactor is presented by using the Galerkin technique. The effect of reaction rate constants on dispersion is studied under isothermal conditions. It is found that, for the same mean velocity of the flow, the effective dispersion coefficient decreases with increase in the chemical reaction rate constants.
Role of micellar equilibria on modelling of batch emulsion polymerization reactors
Authors: Morbidelli Massimo , Storti Giuseppe , Carrà Sergio 
Published: April 2003

AbstractA comprehensive model of emulsion polymerization batch reactors is presented. The nucleation mechanism via micelles is examined in detail through the introduction of a micellar equilibria model. This allows to predict the influence on the process of the emulsifier amount and type and of the solution ionic strength. A comparison with experimental data of styrene and butadiene polymerization is performed.
Coordination copolymerization of butadiene and isoprene with rare earth chloride–alcohol–aluminum trialkyl catalytic systems
Authors: Zhiquan Shen , Xiangyu Song , Shuxiu Xiao , Jipo Yang , Xianglan Kan 
Published: April 2003

AbstractButadiene and isoprene were copolymerized with LnCl3–ROH–AIR3 catalytic system. The products obtained were confirmed to be copolymers by their glass transition temperatures and characteristic pyrolytic chromatograms, etc. The equation for copolymerization rate may be expressed as Rp = Kp(M)2(cat). The rate constants of copolymerization, activation energy, and monomer reactivity ratios for catalytic systems containing various rare earth elements in III‐B family and different solvents were determined. It was found that the reactivity ratio of butadiene was greater than that of isoprene and r1r2 near 1, and the composition and microstructure of copolymers were not much affected by variation of polymerization conditions. Both monomer repeat units in the copolymers had cis‐1,4 contents above 95%, which is a distinguishing feature of coordination polymerization with the lanthanide catalyst system.
Studies on syntheses and permeabilities of special polymer membranes. XLVII. Active transport and selective transport of metal ions through membranes from poly(isobutylene‐alternative co‐maleic anhydride) and poly(vinyl alcohol)
Authors: Uragami Tadashi , Watanabe Shizuharu , Nakamura Reiichi , Yoshida Fumihiko , Sugihara Mizuho 
Published: April 2003

AbstractWhen a cation exchange membrane having carboxyl groups, made of poly(isobutylene‐alternative co‐maleic anhydride) and poly(vinyl alcohol), was set in a diaphragm type cell, in which one side of the solution was adjusted to be acidic and the other side alkaline, metal ions were actively transported from the alkaline side to the acidic side across the membrane against the concentration gradient of metal ions between both sides. The driving force of the transport of metal ions was the difference in H+ ion concentration between both sides. It was presumed that the active transport was carried out chemically and physically. In the selective transport of metal ions, the selectivity was dependent on both the hydrated ionic radius for the metal ions and the affinity between the carrier fixed to the membrane, the carboxyl group, and the metal ions.
The adsorption of dyes in chitin. III. Intraparticle diffusion processes
Authors: McKay G. , Blair H. S. , Gardner J. 
Published: April 2003

AbstractIntraparticle diffusion processes for the adsorption of dyestuffs onto chitin have been studied. The amount of dye adsorbed per gram of chitin has been plotted against the square root of time. The slope of this plot is linear and has been defined as a rate parameter k. This rate parameter has been determined for a number of process variables, including initial dye concentration, agitation, chitin particle size, chitin mass, temperature, and solution pH. However, sometimes two and even three linear regions are apparent on the root time plots indicating a possible branched pore mechanism. The controlling mechanisms are due to macropores and micropores in the chitin particle creating rapidly and slowly diffusing regions.
Improved processing of thermotropic liquid crystalline polyesters
Authors: Demartino Ronald N. 
Published: April 2003

AbstractA series of thermotropic liquid crystalline polyesters based onp‐hydroxybenzoic acid, terephthalic acid, 2,6‐dihydroxynaphthalene and containing small amounts of either Bisphenol A, 2,7‐dihydroxynaphthalene, or polyethylene terephthalate (PET) as comonomers were prepared. The latter three materials were investigated as a means of lowering the spinning temperature of the base polymer without sacrificing properties. Samples containing 1–2.5% Bisphenol A or 2.5–5% 2,7‐dihydroxynaphthalene retained most of the properties (modulus fell slightly), but spinning temperature reduction was minimal. Polymers containing 2.5–5% PET retained full properties at spinning temperatures 60–80°C below the control.
Dynamic mechanical properties of elastomers for use in circulatory assist devices
Authors: Murayama T. , McMillin C. R. 
Published: April 2003

AbstractThe dynamic mechanical properties of several polyurethane and polyolefinic elastomers for use in circulatory assist devices have been studied. This work was a part of a project on the characterization of elastomers suitable for cardiovascular application. In this paper, changes in the dynamic modulus and internal friction of these elastomers (Avcothane‐51®, Biomer®, butyl rubber, Pellethane®, and Hexsyn®) are described as a function of long‐term static and dynamic exposure to whole human blood. The dynamic moduli of control of Pellethane and Hexsyn are higher than that of Avcothane, NBS butyl rubber, and Biomer at human body temperature (at 37°C). The dynamic moduli of Biomer specimen fatigued in whole human blood at 37°C are least affected in temperature range of 25°C to 140°C as compared with the control. The loss tangents are decreased slightly. It indicates small structural changes after fatigue in whole human blood. These five materials should be considered for use in most or some cardiovascular applications because their mechanical properties do not change appreciably. Biomer performs well under a variety of experimental conditions, long‐term exposure to blood, uniaxial and biaxial fatigue test, and dynamic mechanical properties of specimen fatigued in whole human blood.
Sequential nature of the exothermic reactions leading to the formation of flexible polyurethane foams
Authors: Van Gheluwe P. , Leroux J. 
Published: April 2003

AbstractThe exotherms of the reactions leading to the formation of polyurethane foams were measured. The inflection points of the exotherm curves were made evident by continuous differentiation with respect to time. The position and magnitude of the inflection points demonstrated the sequential nature of the reactions. The effects of the functionality of the polyol, the concentrations of the tin and amine catalysts, and the silicone surfactant are discussed.