bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radial distribution function analysis study on alkali and heat‐treated ramie fiber
Authors: Sao K. P. , Samantaray B. K. , Bhattacherjee S. 
Published: April 2003

AbstractThe radial distribution function (RDF) analysis of wide‐angle X‐ray diffraction by ramie fibers in untreated condition and after treatment with alkali of mercerizing strength or heat have been carried out. Interatomic distances, coordination numbers, mean square displacements, and coupling constants for different atom pairs have been calculated. The results have been interpreted in terms of a difference in both the conformation and packing of molecular chains in raw and alkali‐treated ramie. In general, the coupling constant values have been found to be more in alkali‐treated ramie, indicating relatively weak bond strength. Heat‐treated ramie shows a marginal decrease in coupling constant values. © 1994 John Wiley & Sons, Inc.
Toughened polystyrene composites by the concentrated emulsion pathway
Authors: Ruckenstein Eli , Li Hangquan 
Published: April 2003

AbstractRubber–styrene solutions of various compositions and containing a suitable initiator have been polymerized starting from concentrated emulsions in which the above solutions constitute the dispersed phase and solutions of sodium dodecylsulfate in water the continuous phase. Latexes of rubber‐modified polystyrene composites have been thus obtained. Solutions of rubber–styrene have been also polymerized by bulk polymerization for comparison purposes. The molecular weights have been determined from intrinsic viscosity measurements, and the mechanical properties of the composites have been studied via tensile testings. Because of the lower mobility of the high‐molecular radicals in the concentrated emulsions, higher molecular weights have been obtained by the concentrated emulsion polymerization than by the bulk polymerization method. The tensile properties and toughness of the composites have been determined. While the two polymerization methods provide high, comparable toughness, the concentrated emulsion method generates latexes that can be easily processed in any desirable shape. © 1994 John Wiley & Sons, Inc.
Synthesis and thermal dissociation of phenol‐ and naphthol‐blocked diisocyanates
Authors: Kothandaraman H. , Nasar A. Sultan , Lakshmi R. Kamal 
Published: April 2003

AbstractPhenol‐, 2‐naphthol‐, and 1‐nitroso‐2‐naphthol‐blocked toluene diisocyanate (TDI) and isophorone diisocyanate (IPDI) adducts and their polymers with PPG‐1000 were prepared and characterized by nitrogen estimation, IR, and 1H‐NMR spectroscopy. The absence of an IR absorption band at 2270 cm−1 confirmed the completion of the reaction between the isocyanate and the blocking agents, whereas the presence of a band at 1075–1150 cm−1 confirmed the formation of poly(ether urethanes). The deblocking temperatures were determined by the use of DSC and by the carbon dioxide evolution methods. The thermal stabilities of the 2‐naphthol‐blocked diisocyanates were less than the phenol‐blocked diisocyanates. Dissociation temperature was also reduced by the nitroso group in the blocking agent. Mass spectral data confirmed the product analysis. The solubility of the adducts were determined in the different polyols. Adducts based on IPDI showed better solubility than did those based on TDI. © 1994 John Wiley & Sons, Inc.
Poly(ϵ‐caprolactam)–poly(butadiene‐co‐acrylonitrile) block copolymers. I. Synthesis, characterization, mechanical properties, and morphology
Authors: Yn Meng‐Song , Ma Chen‐Chi M. 
Published: April 2003

AbstractPoly(ϵ‐caprolactam)–poly(butadiene‐co‐acrylonitrile) block copolymers have been synthesized that were suitable for the pultrusion process. The effects of amine‐terminated butadiene acrylonitrile copolymer (ATBN) content on copolymerization rate, conversion, crystallization behaviors, and mechanical properteis and morphology of NY 6–ATBN copolymers were investigated. The conversion was over 90% and the copolymerization was completed within 3 min (up to 20 wt % ATBN) at 145–165°C. The higher the [MgBr—CPL] (ϵ‐caprolactam magnesium bromide) initiator concentration, the lower the molecular weight [or intrinsic viscosity (IV)] of the copolymers and the less the copolymerization time. Relationships among mechanical properties, morphology, and structure of copolymers have been studied. The notched Izod impact strength of the NY 6–ATBN copolymers (< 10.5 wt % ATBN) increased more than 10‐fold, while the flexural modulus only reduced 10%. Transmission electron micrographs showed that ATBN rubber particle size changed slightly with ATBN content, but interparticle distance (T) decreased with increasing ATBN content. As T decreased, the ductility of the copolymers increased. When ATBN content reached 10.5–13 wt % (T = 0.32–0.45 μm), the copolymers showed a very high ductile behavior. © 1994 John Wiley & Sons, Inc.
Squeeze film rheology of polymer melts: Determination of the characteristic flow curve
Authors: Pham Hoang T. , Meinecke Eberhard A. 
Published: April 2003

AbstractThe advantage of the constant‐speed squeeze film flow is that the shear rate is not constant but changes with gap height and position. This allows the rheological characterization of a material to be carried out in a shorter amount of experimentation time. A method for determining the characteristic flow curve is proposed. The characteristic flow curves obtained from squeeze film flow is compared with the curves obtained from capillary rheometry are presented. © 1994 John Wiley & Sons, Inc.
The direct fluorination of a porous functionalized polymer
Authors: Hewes John D. , Curran Sean , Leone Edgar A. 
Published: April 2003

AbstractMacroporous sulfonated polystyrene ion exchange resin was reacted with elemental fluorine in a liquid‐phase suspension reactor at low temperature. This method gave retention of the bulk structure of the resin bead and resulted in a space‐selective distribution of fluorine across the resin bead cross‐section, as determined using 19F secondary ion mass spectroscopy (LMI‐SIMS). The polymer modification was additionally characterized using x‐ray photoelectron spectroscopy, photoacoustic IR spectrophotometry, 19F, and 13C MAS NMR spectrometry, and mercury porosimetry. © 1994 John Wiley & Sons, Inc.
Effects of water‐soluble polymers and aqueous‐phase viscosity on the interfacial tension behavior of reacting oil–alkaline systems
Authors: Touhami Y. , Neale G. H. , Hornof V. 
Published: April 2003

AbstractThis study presents the results of an experimental study of the effects of water‐soluble polymer additives on the dynamic interfacial tension behavior of reacting oil–aqueous systems as measured by the spinning drop tensiometer. Polymer additives can exert both a direct physico‐chemical effect and an indirect viscosity effect on the measured interfacial tension. This work, which complements an earlier study dealing with the effects of oil‐soluble polymer additives, reveals that the nominal effects of aqueous‐phase viscosity are opposite to those of oil‐phase viscosity. In particular, an increase in aqueous‐phase viscosity produces an increase in the rate of increase of the apparent interfacial tension after attainment of the minimum value. These differences are explained in terms of the dependence of diffusion rates and interfacial adsorption on aqueous‐phase viscosity. The conclusion of principal practical interest is that although aqueous‐phase viscosity exerts only a small effect on the dynamic interfacial tension at small times (i.e., prior to attainment of the minimum value) it exerts a very significant effect thereafter. © 1994 John Wiley & Sons, Inc.
Torsional braid analysis of the aromatic amine cure of epoxy resins
Authors: Zukas Walter X. 
Published: April 2003

AbstractThe cure behavior of diglycidyl ether of bisphenol A (DGEBA) type of epoxy resins with three aromatic diamines, 4,4′‐diaminodiphenyl methane (DDM), 4,4′‐diaminodiphenyl sulfone (44DDS), and 3,3′‐diaminodiphenyl sulfone (33DDS) was studied by torsional braid analysis. For each curing agent the stoichiometry of the resin mixtures was varied from a two to one excess of amino hydrogens per epoxy group to a two to one excess of epoxy groups per amino hydrogen. Isothermal cures of the resin mixtures were carried out from 70 to 210°C (range depending on epoxy—amine mixture), followed by a temperature scan to determine the glass transition temperature (Tg). The times to the isothermal liquid‐to‐rubber transition were shortest for the DDM mixtures and longest for the 44DDS mixtures. The liquid‐to‐rubber transition times were also shortest for the amine excess mixtures when stoichiometry was varied. A relatively rapid reaction to the liquid‐to‐rubber transition was observed for the epoxy excess mixtures, followed by an exceedingly slow reaction process at cure temperatures well above the Tg. This slow process was only observed for epoxy excess mixtures and eventually led to significant increases in Tg. Using time—temperature shifts of the glass transition temperature vs. logarithm of time, activation energies approximately 50% higher were derived for this process compared to those derived from the liquid‐to‐rubber transition. The rate of this reaction was virtually independent of curing agent and was attributed to etherification taking place in the epoxy excess mixtures. © 1994 John Wiley & Sons, Inc.
Glass transition temperature (Tg) versus fractional conversion for a linear thermosetting polyamic acid ester–polyimide system
Authors: Venditti R. A. , Gillham J. K. , Chin E. , Houlihan F. M. 
Published: April 2003

AbstractThe relationship of the glass transition temperature, Tg, to fractional conversion, x, for the conversion of the cyclohexylmethyl ester of the benzophenone tetracarboxylic dianhydride–oxydianiline polyamic acid to polyimide has been investigated using dynamic mechanical analysis (torsion pendulum, TBA). The glass transition temperature and conversion measurements were obtained on a single solvent‐free polyamic acid ester specimen during cooling after heating to successively higher cure temperatures. Conversion was determined from the intensity of a sub‐Tg mechanical relaxation peak that has been assigned to a relaxation of the cyclohexyl group. The resulting Tg versus x relationship is nonlinear. The Tg versus x relationship is adequately modeled using an expression derived by Couchman. © 1994 John Wiley & Sons, Inc.
Molecular and macroscopic NLO properties of organic polymers
Authors: Man H. T. , Shu C. F. , Althoff O. , McCulloch I. A. , Polis D. , Yoon H. N. 
Published: April 2003

AbstractTwo classes of aryltrienes in which the conjugation was incorporated in six‐membered rings have been developed. The microscopic nonlinear susceptibility, μβ, the product of the dipole moment and the second‐order nonlinear susceptibility, of these chromophores were measured using electric field‐induced second harmonic generation (EFISH). The chromophores were then copolymerized as side‐chain pendant groups in a methacrylate backbone copolymer with methyl methacrylate and their macroscopic electrooptic coefficients, r, were experimentally determined using a reflection technique after electric field poling of the polymers. When compared with 4,4′‐N,N‐dimethylaminonitrostibene (DANS), these molecules demonstrated electrooptic activities up to three times of DANS, when measured at 1.3 μm. By using a simple two‐level free‐gas model, the two sets of measurements corresponded closely at low poling fields. At high fields, the simple model breaks down as more detailed poling parameters are required to accurately describe the nonlinear poling effects. The results of the analysis of the high‐field poling data will be published separately. © 1994 John Wiley & Sons, Inc.
Concentration of biological liquids by dialysis with modified acrylonitrile copolymer membranes
Authors: Godjevargova Ts. , Dimov A. 
Published: April 2003

AbstractAcrylonitrile copolymer membranes were subjected to partial hydrolysis in order to improve their dialysis characteristics. The partial hydrolysis time and temperature, as well as the concentration of the hydrolyzing agent, were the variable parameters. The changes in the chemical and physical characteristics of the membrane were proved by infrared spectroscopy, elemental analysis, differential scanning calorimetry, and Mercury intrusion porometry. After each degree of modification, the permeability of the membrane with respect to a solution of vitamin B12 was determined under static conditions and at temperature of 298 K. The improvement in the permeability at a definite degree of hydrolysis is explained by the conversion of nitrile groups to amide and carboxyl groups, as well as increase of the volume of the pores with average radius. The efficiency of the modified PAN membranes for concentration of biological liquids (diluted serum) was studied. © 1994 John Wiley & Sons, Inc.
Vulcanization of liquid carboxyl‐terminated rubber filled with leather buffing dust
Authors: Klásek A. , Vaněk P. 
Published: April 2003

AbstractVulcanization of the system of liquid carboxyl‐terminated rubber–triepoxide–diisocyanate–chromium catalyst–leather buffing dust has been investigated. Using the method of statistical planning of experiments, regression equations were obtained, describing the effects of the components weight ratio on the vulcanization parameters and on the physical properties of the vulcanized rubber. © 1994 John Wiley & Sons, Inc.
Spectroscopic analysis of Fraké treated with periodic acid. I. Electron spectroscopy for chemical analysis (ESCA)
Authors: Noah Joseph N. , Prud'Homme Robert E. 
Published: April 2003

AbstractFraké, a tropical wood species from Cameroon, was reacted with 1% periodic acid solution at room temperature for 24 h. Untreated and treated woods were analyzed by ESCA. As expected, O1s and C2s were the predominant species in the spectra. While the O1s peak is featureless, the C1s peak can be decomposed into several components. These contributions were calculated, and it was observed that untreated and treated woods exhibit carbon atoms in classes C1 (carbon atoms bonded by a CC or a CH bond), C2 (carbon atoms bonded by a CO bond), and C3 (carbon atoms bonded by a CO or by a OCO bond). Class C4, which refers to carbon atoms bonded by OCO bonds, is completely absent. The periodic acid treatment produces a reduction in C1, an increase in C2, with C3 remaining relatively small. Accordingly, the expected oxidation of hydroxyl groups to carbonyl groups is not observed. It can be postulated that wood–periodic acid intermediates, which are believed to be cyclic periodic esters, do not decompose to form carbonyl groups but rather remain as stable complexes. © 1994 John Wiley & Sons, Inc.
Thermally reversible polymeric sorbents for acid gases: CO2, SO2, and NOx
Authors: Diaf Abderrahmane , Garcia Jose L. , Beckman Eric J. 
Published: April 2003

AbstractWeakly acidic gases such as CO2, SO2, NO2, and NO discharged directly into the atmosphere have been suggested to contribute to the formation of acid rain and to global climate changes. In an effort to develop an effective process by which to remove these pollutants from gas streams, we synthesized polymeric sorbents that bind acid gases. In an earlier work, we reported that polymers carrying pendant amine groups are capable of absorbing carbon dioxide to form thermally reversible amine/CO2 addition products. In this study, we investigated the effects of amine structure on acid gas sorption and the thermal reversibility of the sorption–desorption reactions of various acid gases including CO2, SO2, NO, and NO2 with both linear and cross‐linked polymers using thermogravimetric analysis. © 1994 John Wiley & Sons, Inc.
Nonstationary peeling apparatus
Authors: Obori Hiroyoshi , Takenaga Mitsuru , Abdulla Aniwar , Nakamura Akira 
Published: April 2003

AbstractA piece of apparatus for measuring the peel adhesion behavior of pressure‐sensitive adhesive tapes was developed. The apparatus allows peel rates to be varied as any functions of time or peel distance. In a cycle run of the accelerating and decelerating peel processes, nonstationary peeling was investigated over a wide range of peel rates using relatively short‐length samples. The resultant behavior in nonstationary peeling indicated that in the interfacial failure regime, a good agreement with the normal stationary peeling can be obtained. This nonstationary peeling apparatus is expected to be useful for evaluation of peel adhesion. © 1994 John Wiley & Sons, Inc.
Separation of water–alcohol mixtures by pervaporation through asymmetric nylon 4 membrane
Authors: Lai Juin‐Yih , Chu Yuh‐Hsiu , Huang Shih‐Liang , Yin Yih‐Lang 
Published: April 2003

AbstractThe dehydration of aqueous alcohol solutions through asymmetric nylon 4 membranes were investigated using pervaporation processes. The formation of asymmetric pervaporation membranes are discussed in terms of the content of the nonsolvent in the casting solution, polymer concentration, and compositions of the coagulation medium. The effects of the feed composition, feed temperature, and molar volume of the alcohols on the pervaporation performances of the asymmetric membranes are discussed. A separation factor of 4.72 and a permeation rate of 0.78 kg/m2 h for the asymmetric membrane were obtained. Compared to the conventional homogeneous nylon 4 membrane, the asymmetric membrane can effectively overcome the pervaporation performances of the nylon 4 membrane for separation of water–alcohol mixtures. © 1994 John Wiley & Sons, Inc.
Effect of an oxidative environment on the creep compliance of poly(ether urethane urea)
Authors: Wu Y. K. , Sletten K. R. , Topolkaraev V. , Lodoen G. A. , Anderson J. M. , Baer E. , Hiltner A. 
Published: April 2003

AbstractSecondary creep of unstabilized poly(ether urethane urea) (PEUU) in an oxidative environment appears as a linear time‐dependent component superimposed on the logarithmic, viscoelastic response. The surfaces of unstabilized PEUU crept in H2O2/CoCl2 have been characterized by scanning electron microscopy and ATR–FTIR. By examining PEUU crept for various periods of time, it is found that surface damage proceeds at gradually increasing size scales, culminating in large voids. It is hypothesized that the initial chain scission creates a flaw that grows in size under the influence of the applied load into a “nano‐pit,” which grows further by coalescence into a pit and, finally, a void. The initial stages of voiding occur during an induction period when there is no measurable effect on the creep response. It is possible to estimate the average compliance of the damaged PEUU by assuming a composite model with an undamaged center layer sandwiched between damaged surface layers. When the contribution of the surface layers to the creep compliance is estimated from the creep curves, the average compliance of the damaged layer is found to be about 1.6 times higher than that of the undamaged PEUU. Independent calculations of the damaged layer compliance from the void fraction indicate that the damaged layer behaves as a flexible foam in the early stages, then as a more rigid foam at longer creep times. © 1994 John Wiley & Sons, Inc.
Stereocomplex formation between enantiomeric poly(lactic acid)s. X. Binary blends from poly(D‐lactide‐CO‐glycolide) and poly(L‐lactide‐CO‐glycolide)
Authors: Tsuji Hideto , Ikada Yoshito 
Published: April 2003

AbstractBinary blend films from lactide‐rich poly(D‐lactide‐co‐glycolide) (PDLG) and poly(L‐lactide‐co‐glycolide) (PLLG) were obtained by casting methylene chloride solutions of the two mixed copolymers with different D‐ and L‐lactide contents (XDI and XLI), and their crystallization was studied by differential scanning calorimetry (DSC). Four combinations were selected from the binary (A‐B) blends: mixing of the same polymer [XDI(A) = XDI(B) or XLI(A) = XLI(B)], blending under XDI(B) = XLI(A), blending of a D‐lactide homopolymer [XDI(B) = 1] with other PDLGs, and blending of a D‐lactide homopolymer [XDI(B) = 1] with other PLLGs. Racemic crystallites were exclusively formed between PDLG and PLLG when they had high lactide unit contents. The melting point and enthalpy of fusion of the racemic crystallites decreased with a decrease in XDI of PDLG or XLI of PLLG, suggesting that glycolide units in the polymer disturbed the growth of the racemic crystallites. A similar behavior was also observed for the homocrystallization in nonblended copolymer films. Homocrystallites composed entirely either of D‐lactide unit or L‐lactide unit sequences were formed when one component was crystallizable and the other component had the same sign of optical rotation or very different lactide content. An interesting finding was that even nonhomocrystallizable lactide‐poor PDLG and PLLG could form racemic crystallites when both were blended. © 1994 John Wiley & Sons, Inc.
Studies on interpenetrating polymer networks based on nitrile rubber‐poly(vinyl chloride) blends and poly(alkyl methacrylates)
Authors: Mathew Annakutty , Chakraborty B. C. , Deb P. C. 
Published: April 2003

AbstractSeveral interpenetrating polymer networks (IPNs) based on nitrile rubber‐poly(vinyl chloride) blends and various alkyl methacrylates have been synthesized. The rubber blends were swollen in methacrylate monomers containing required amounts of initiator and crosslinker for specific time periods and then polymerized at higher temperature. The composition of the IPNs could be varied by changing the swelling time. The IPNs were characterized for their glass‐transition temperature, dynamic mechanical properties, and tensile properties. The effect of structure and composition on the vibration damping characteristics of these IPNs are discussed. © 1994 John Wiley & Sons, Inc.
Macromolecular entanglement. IV. Modulus of swelling acrylic fibers as a means of studying macromolecular entanglements
Authors: Qian B. , Zhu J. , He J. , Hu P. , Wu C. 
Published: April 2003

AbstractIn a swelling state at a temperature of incipient dissolution, an acrylic fiber is highly elastic just like a rubber. A system of entangled macromolecular chains is considered analogous to a cross‐linked rubber network and from the theory of rubber elasticity, the measured extension modulus of an acrylic fiber at the terminal swelling state may be used to calculate the number of entanglements. By means of a capillary rheometer, a series of model acrylic fibers with varied degrees of entanglements were prepared. The entanglements present in these model fibers were then measured by the other two thermal methods (SDSC and SSS/SS methods) already established in our laboratory. The die swell ratios were also measured microscopically at the exit of the capillary rheometer. The experimental results of entanglements measured by the various methods were well correlated, at least qualitatively. © 1994 John Wiley & Sons, Inc.
Acetylacetonates of nickel(II) and copper(II) as accelerators for the epoxy resin system
Authors: Reddy P. V. , Gowda N. M. Nanje 
Published: April 2003

AbstractThe acetylacetonates of nickel(II) and copper(II) serve as accelerators for the anhydridecurable epoxy resin system. An appreciable lowering in the cure gel time and a substantial increase in the rate of curing is observed with enhanced concentrations of the metal chelates. Cure kinetic studies and cure schedules have been followed using a differential scanning calorimeter. The thermal and electrical insulation characteristics of the cured epoxy system are little affected by the variation of temperature, voltage, and aging under UV radiation. © 1994 John Wiley & Sons, Inc.