bluuebunny/crossref_metadata_2025_split huggingface dataset:
Species distribution during the cure of dicyanate ester
Authors: Owusu A. Osei , Martin G. C. 
Published: May 2005

AbstractThe network formation process for bisphenol A‐based cyanate ester resin was examined using size exclusion chromatography (SEC) and differential scanning calorimetry (DSC). A kinetic scheme based on the SEC data was used to predict the species distribution in the reaction medium in the pregel region. After gelation, the molecular species undergo retroversion as the high molecular species are predominantly attached to the growing network structure.
The use of sodium salts as nucleation agents for polyethylene terephthalate with minimal molecular weight reduction
Authors: Gilmer J. W. , Neu R. P. , Liu Y. J. , Jen Alex K.‐Y. 
Published: May 2005

AbstractThe sodium salts of carboxylic acids and other weak acids are routinely used as nucleation agents for injection moldable poly(ethylene terephthalate) (PET) resins. One of the primary drawbacks accompanying their use is the degradation of the PET resulting from the attack of the ester by the sodium carboxylate. Several sodium carboxylates have been found based on pyrrole carboxylic acid that are effective as nucleants but which do not cause a reduction in the molecular weight of PET. In addition, tetraphenyl borate salts, although only marginally effective as nucleants, were observed to be efficient additives to PET for counteracting molecular weight loss caused by chemical nucleants.
Magnesium chloride supported high‐mileage catalysts for olefin polymerization. IV. FTIR and quantitative analysis of modifiers in the catalysts
Authors: Chien James C. W. , Wu Jiun‐Chen , Kuo Chi‐I. 
Published: May 2005

AbstractFourier transform infrared (FTIR) spectra were obtained for a typical MgCl2‐supported, high‐mileage catalyst for propylene polymerization. When ball‐milling MgCl2 with ethyl benzoate (EB), the latter is incorporated into the support (I) by Lewis acid‐base complexation involving both oxygen atoms of the ester. Reaction of (I) with p‐cresol (PC) resulted in a material (II) that contains all the characteristic IR bands of PC. The reaction of (II) that contains all the characteristic IR bands of PC. The reaction of (II) with AlEt3 (TEA) resulted in (III) whose spectrum supports the reaction observed by product analysis and NMR spectroscopy. There was no evidence of any reaction between TEA and EB. Further reaction of (III) with an excess of TiCl4 caused substantial removal of the p‐cresol moiety as shown by the diminution of its characteristic bands. Finally, activation with 3TEA‐1MT (methyl‐p‐toluate) complexes gave spectra that revealed the presence of MT in the activated catalyst without any visage of p‐cresol moiety. The nondestructive FTIR method, however, is not quantitative. Quantitative analysis of the organic components in the support materials (I), (II), and (III) and the catalysts was accomplished by hydrolysis of the inorganic components, extraction with ether, and analysis by gas chromatography. The results are in good agreement with composition deducted from elemental analysis and substantiate the FTIR conclusions.
Determination of composition distribution of acrylonitrile‐styrene copolymers by thin‐layer chromatography
Authors: Ogawa Toshio , Ishitobi Wataru 
Published: May 2005

AbstractDetermination of chemical composition distribution of acrylonitrile‐styrene copolymers was carried out by thin‐layer chromatography (TLC). A mixture of benzene and methyl ethyl ketone gave the most suitable calibration curve of Rf values versus acrylonitrile (AN) contents, where a concentration gradient technique was applied for development. Average AN contents obtained by TLC are coincident with those found by elemental analysis. The copolymers extracted from ABS resins are sufficiently arranged in the order of breadth of composition distribution by using the data from TLC. The agreement between the composition distribution curve and that from the theory of copolymerization is good.
Cation binding properties of crown ether‐modified polyethylenimines
Authors: Anzai Jun‐Ichi , Sakata Yoko , Suzuki Yasuhiro , Ueno Akihiko , Osa Tetsuo 
Published: May 2005

AbstractCrown ether‐modified polyethylenimines (PEI‐CR) were prepared to elucidate their cation binding efficiency and selectivity by liquid‐liquid and solid‐liquid extraction methods. With alkali metal cations it was found that polyethylenimines containing benzo‐15‐crown‐5 moieties (Ia and Ib) extracted all cations examined more efficiently than their monomeric analogs, especially in the cases of K+ and Rb+ cations. The solid‐liquid extraction revealed clearly that the polymers complexed with K+ and Rb+ cations according to a 1:2 cation‐to‐crown stoichiometry. The high selectivities of the polymers for K+ and Rb+ were interpreted in terms of the favourable conformation of the polymer chain for the formation of intramolecular 1:2 complexes. On the contrary, these polymers bound alkali earth cations less effectively with low selectivities.
Charge mosaic membrane with a microstructure of poly(styrene‐b‐4‐vinylpyridine)
Authors: Ishizu Koji , Inagaki Katsumi , Fukutomi Takashi 
Published: May 2005

AbstractWell defined AB and BAB type poly[styrene(ST)‐b‐4‐vinylpyridine(4VP)]s were prepared by anionic living polymerization in tetrahydrofuran (THF) at −78°C. Casting AB and BAB type poly(ST‐b‐4VP)s with a composition of about 50 mol% PST from 1,1,2‐trichloroethane (TCE) produced specimens with lamellar microdomain structures. Quaternization of P4VP and sulfonation of PST domains (lamellar and spherical structures), accompanied by each domain fixing, were carried out under various reaction conditions. The piezodialysis of the prepared charge mosaic membrane with its lamellar microdomain structure was measured from a sodium chloride (NaCl) aqueous solution. The results are discussed in some detail.
Dilute solution properties of branched polymers
Authors: Kim Jong Ryul , Ree Taikyue 
Published: May 2005

AbstractFor calculating the ratio of the intrinsic viscosities of branched and linear polymers of the same molecular weight, [η]B/[η]L, a new theory taking into account the excluded volume effect is presented. By using the modified Flory equation, the excluded volume effect of branched polymers is predicted with the aid of the first‐order perturbation theory. The linear expansion factor αs is converted to the hydrodynamic expansion factor αη by using the Kurata‐Yamakawa theory. Our calculated results, i.e., [η]B/[η]L and 〈s2〉B/〈s2〉L, agree well with experiment for various type branched polymers, i.e., randomly branched and comb‐shaped polymers of poly(vinyl acetate).
Synthesis and characterization of crosslinked polydiacetylene and its two‐component interpenetrating polymer networks
Authors: Ika Prasad V. S. , Frisch Harry L. , Frisch Kurt C. 
Published: May 2005

AbstractThe synthesis of crosslinked polydiacetylenes and its two‐component interpenetrating polymer networks (IPNs) was carried out utilizing its polar and flexible substituent groups. Polydiacetylenes were crosslinked by the formation of allophanate linkages utilizing urethane groups in the substituent groups of the polydiacetylenes. Elemental analysis, DSC, TMA, solvent resistance, and IR spectra are presented as evidence for the formation of crosslinked polydiacetylenes. IPNs of polydiacetylenes and an epoxy resin (diglycidyl ether of bisphenol A) were synthesized by using simultaneous and sequential methods of synthesis. A study of phase morphology of the simultaneous and sequential IPNs was carried out using electron microscopy, TMA, and DSC.
Model reactions for crosslinking polydiacetylene materials
Authors: Ika Prasad V. S. , Frisch Harry L. , Frisch Kurt C. 
Published: May 2005

AbstractA series of reactions are presented which allowed us to crosslink polydiacetylenes containing carbamate groups in the side chain without attacking the triple bond. These reactions involved syntheses of carbamates and allophanates from butyl alcohol and phenyl isocyanate with metal and tertiary amine catalysts using a model compound, 2,4,7,9‐tetramethyl‐5‐decyn‐4,7‐diol. Elemental analysis, IR and UV spectroscopy, and high performance liquid chromatography (HPLC) were used as analytical tools. Metal catalysts were found to favor the formation of allophanates in higher yields and purity as compared to tertiary amine catalysts.
Polymer catalysts. X. Vanadium complexes of bipyridine‐based polyureas for epoxidation of alkenes
Authors: Zhang Keda , Kumar G. Sudesh , Neckers D. C. 
Published: May 2005

AbstractIn this article we report on the epoxidation of olefins with hydroperoxides in the presence of a polymer‐anchored vanadium catalyst. Incorporation of vanadium (V) into polar, bipyridine‐based polyureas and the evaluation of the activity and selectivity of the catalyst were investigated.
Polymerization of surface‐active monomers. I. Micellization and polymerization of higher alkyl salts of dimethylaminoethyl methacrylate
Authors: Nagai Katsutoshi , Ohishi Yoshiyuki , Inaba Hiroshi , Kudo Shuichi 
Published: May 2005

AbstractMicellization of cationic salts of dimethylaminoethyl methacrylate (DMAEMA) quaternized with n‐alkyl bromides such as octyl, lauryl, myristyl, and stearyl bromide and their polymerizations were investigated. The critical micelle concentration (cmc) in water at 25°C was determined by electrical conductivity and dye(azobenzene) solubilization methods and the relation log(cmc) = 1.46–0.31N was obtained, where cmc is in mmol L−1 and N corresponds to carbon number of alkyl bromides used for the monomer preparations. All of these monomeric salts exhibited a high radical polymerizability in water and benzene. The polymerizations in water appeared to proceed with a higher rate with increasing a chain length of the alkyl moiety of the monomers and those in benzene gave the polymers with a remarkably high viscosity. The rate of polymerization of lauryl bromide salt in anisotropic solutions (in water and benzene) was exceedingly fast as compared with that in isotropic solution(in acetonitrile). All of the polymers obtained here were insoluble in water. Solubility characteristics of these monomers and polymers in other solvents were also presented. The reduced viscosity, in dimethylformamide and methanol, of poly(lauryl bromide salt) prepared in water increased with dilution but that for the polymer obtained in benzene exhibited an inverse concentration dependence. Some discussions were made on the peculiarities of the polymerizations of these monomers and the resulting polymers.
Extended Phase‐Doppler System for Characterization of Multiphase Flows
Authors: Naqwi Amir , Durst Franz , Liu Xiaozhi 
Published: May 2005

AbstractAn extended phase‐Doppler anemometry (PDA) system is described, which allows the user to measure the refractive index of spherical particles, in addition to their velocity, diameter and concentration. The extended PDA system incorporates two additional detectors on the receiving side. Each particle generates four Doppler signals. Phase shifts between two pairs of signals are recorded. The ratio between two measured values of phase shifts is a function of the particle refractive index. The phase ratio is shown to be fairly independent of particle velocity or diameter.Calculations based on Mie scattering theory demonstrated the feasibility of the concept. Measurements with monosize droplets of glycerine‐water mixture, covering the refractive index range 1.33–1.44, were used to verify the theoretical predictions. The instrument was also tested with spray flows.It is also shown how the phase‐Doppler technique may be used to distinguish between reflecting and refracting particles. This means that the extended phase‐Doppler system may be employed to recognize particle material, and also to measure locally particle velocities, sizes and concentrations, in a multiphase flow with several transparent dispersed phases and one dispersed phase consisting of reflecting particles.
Shape Characterization of Crystals and Crystal Agglomerates
Authors: Riebel Ulrich , Kofler Volker , Löffler Friedrich 
Published: May 2005

AbstractCrystals and crystal agglomerates exhibit a number of specific shape features which evolve in close relation to the conditions of growth and agglomeration. Hence the quantitative evaluation of these shape features by adequately defined shape parameters can serve to obtain a deeper insight into the mechanisms and kinetics of crystal agglomerate formation and to quantify more precisely the quality of crystallization products.
Hierarchical Properties of Particle Shape for the recognition of powdered materials
Authors: Bonifazi Giuseppe , Massacci Paolo , Patrizi Giacomo 
Published: May 2005

AbstractParticle shape recognition procedures can be used to determine constituent materials. The problem of recognizing the association between the shape and mineralogical composition of a particle, resulting from comminution of a raw ore, is of great interest.An algorithm is presented and computational results are given for the classification of particles of iso‐proportional constituents. In this way, the washability function of a set of particulate raw ores can be estimated by taking into account only the contour of the particles. This classification procedure is useful when there are difficulties in the estimation of some relevant properties such as specific gravity or magnetic susceptibility.The procedure has been successfully applied to the recognition of the mineralogical composition of particles resulting from the comminution of a chromite ore and to the classification of particles in iso‐composition classes.
Particle Size Distribution of Inorganic Colloidal Dispersions: A comparison of different techniques
Authors: Delgado Angel , Matijevié Egon 
Published: May 2005

AbstractThe particle size distributions of a latex and of four different inorganic colloidal systems, consisting of spherical particles suspended in aqueous solutions, have been evaluated by three techniques: electron microscopy (EM, scanning and/or transmission), classical light scattering (CLS, polarization ratio method), and photon correlation spectroscopy (PCS, commercial instrument). Both light scattering techniques appear to be exceedingly sensitive to even a relatively small level of aggregation. Thus, the effect of treating the dispersions by ultrasonic energy was tested in order to establish the best experimental conditions. While a shorter sonication results in a minimum or constant value for the average particle diameter (or the polydispersity of the suspension), longer times may promote reaggregation of particles. Good correlation of the results by different light scattering techniques was found as long as the conversion to number averages of the PCS data involved the proper corrections for polydispersity. The agreement with the EM depended on the chemical nature of the dispersed particles; i.e., drying and exposure to the electron beam greatly affected the histograms in some cases.
Particle Sizing by Photon Correlation Spectroscopy Part I: Monodisperse latices: Influence of scattering angle and concentration of dispersed material
Authors: De Jaeger Nicolas , Demeyere Hugo , Finsy Robert , Sneyers Rik , Vanderdeelen Jan , van der Meeren Paul , van Laethem Marc 
Published: May 2005

AbstractThe possibilities and limitations of Photon Correlation Spectroscopy as a practical tool for particle sizing are revisited. In a first step, well characterized monodisperse polystyrene latices with particle sizes ranging from about 30 nm to about 2 μm were examined in five different industrial and academic laboratories. Particular attention was paid to the effect of particle concentration and scattering angle. It turned out that for a particle diameter less than 0.5 μm reliable particle sizes can be obtained. In the range of 0.5 to 1 μm this was only possible within a very narrow range of concentration of dispersed material. For the largest size investigated (about 2 μm) the PCS measurements were less reliable which was reflected in a considerable variation of the results.
A technique for measuring contact angles at particles
Authors: Bröckel Ulrich , Löffler Friedrich 
Published: May 2005

AbstractThe behavior of particles at the phase transition between a gas or liquid and another liquid phase may be characterized by the so‐called wetting (or contact) angle. In contrast to plane surfaces, which allow such measurements to be conducted relatively easily, the determination of the wetting angle between a liquid and the surfaces of fine particles demands extensive preparative measures. The method adopted by Heertjes and Kossen [12] for example, involves compressing a tablet from the powder in question, from which the wetting angle may then be derived. The compression process naturally modifies the superficial structure of the particles, and hence their wetting characteristics. This paper describes a preparation technique with which the wetting angle between a liquid and fine particles can be derived without modifying the surface texture. This involves coating and adhering a monolayer of the powder on a carrier plate and measuring the composite wetting angle of the particles and the adhesive film. The specification of the adhesive's wetting angle and areal porosity of the carrier medium allows the wetting angle of the given powder subsequently to be evaluated.
Asbestos Fiber Concentrations Resulting from the Installation, maintenance and removal of vinyl‐asbestos floor tile
Authors: Lundgren Dale A. , Vanderpool Robert W. , Liu Benjamin Y. H. 
Published: May 2005

AbstractThis paper presents the results of a systematic study to measure the exposure to asbestos fiber concentrations associated with occupational use of asbestos‐containing floor tile. Specifically, air measurements were made during floor tile installation, maintenance and removal. The procedures for these tests are outlined and the results of the air sampling and analysis are discussed.
Light Scattering Applied to LDA and PDA Measurements. Part 1: Theory and numerical treatments
Authors: Naqwi Amir A. , Durst Franz 
Published: May 2005

AbstractMathematical tools are provided for computation of the scattered field produced by a spherical particle moving through the region of interference of two crossing laser beams. This formulation is readily applicable to laser Doppler and phase Doppler anemometers (PDAs). In particular, the geometry of PDAs is treated in the most general terms. The cases of very large and very small particles are considered in detail. In the first part the theory underlying the computer code STREU, which was produced during the present work, is discussed and relevant mathematical formulations are presented. Also, graphical tools are provided for the convenience of the designers.In Part 2 the utility of the computer code is demonstrated with the help of examples in the area of phase Doppler anemometry. It is shown that the phase Doppler technique may be used for sizing of submicron particles in addition to large particles. Measurement of particle refractive index, in addition to the diameter, is also made possible.
Measurement of Polydisperse Colloidal Suspensions with quasielastic light scattering
Authors: Madani Hassan , Kaler Eric W. 
Published: May 2005

AbstractThe measurement of polydisperse populations of colloidal particles with quasielastic light scattering (QLS) is a common and dangerous practice. Here intensity autocorrelation functions with different linewidth distributions are simulated. The simulated data are treated with the histogram and exponential sampling methods and the results are contrasted with the results of the Laplace inversion routine of Provencher. All methods work well in calculating the size distribution from noise‐free correlation functions. In analyzing noisy data the methods may produce results that bear no relation to the true size distribution. The histogram method fails to determine size distributions from noisy simulated and real correlation functions. The exponential sampling method gives a qualitative measure of the size distribution when the required resolution does not exceed the limitations set by noise theory. Provencher's routine extracts smooth unimodal distributions very accurately even from noisy correlation functions, but determination of bimodal distributions may be unreliable. The importance of taking data at many scattering angles is emphasized and experimentally determined size distributions of samples of polystyrene latex spheres measured at multiple scattering angles are presented.
Regularized Inversion of the Laplace Transform: Accuracy of analytical and discrete inversion
Authors: Ross Douglas A. , Dhadwal Harbans S. 
Published: May 2005

AbstractDynamic light scattering is a technique used for the optical determination of a colloidal particle size distribution. A simple procedure, based on a trapezoidal model for the linewidth distribution function, is given for obtaining a constrained regularized inversions of correlation data obtained in dynamic light scattering experiments, and estimating the accuracy of such inversions. Based on the eigenfunction decomposition of the Laplace integral equation, error bars, which are directly related to the accuracy of the correlation data, may be placed on both analytical and discrete inversions. By using a regularization procedure, and a nonnegativity constraint, problems with statistical noise in data may be handled effectively.
Control and Use of a Miniaturized Droplet Generator
Authors: Blümcke Erich , Eickhoff Heinrich , Hassa Christoph 
Published: May 2005

AbstractA miniaturized droplet generator with some new features, working on the principle of laminar liquid jet instability and break‐up was designed. The instrument has been used to study the dispersion of monosized droplets in a turbulent swirling flow, exhibiting the main features of combustion chamber flows of modern gas turbines.The operating range of the generator was evaluated by phase‐Dopper anemometry (PDA). It was demonstrated that the device also works in some metastable operating modes, producing coherent droplet streams with very small standard deviations for drop size and drop velocity. Special attention was directed to the reliability of the device and to the control of drop size. The PDA measurements showed that, in contrast to the evaluated optimum excitation frequency, the drop size cannot be determined from the orifice diameter.
Etude de la rupture des poudres pour armes
Authors: Benhaim P. , Paulin J. L. , Zeller B. 
Published: May 2005

AbstractPendant la phase d'allumage des charges propulsives pour munitions destinées aux armes à tube, des grains de poudre sont accélérés et compactés brutalement contre le culot du projectile. Des ruptures de grains en résultent qui peuvent induire des pics de pression dangereux.Les critères de rupture ont été étudiés expérimentalement par projection de grains de poudre contre une plaque d'acier. Les paramètres étudiés sont:

la température,
la géométrie des grains,
la composition.
Il a été observé:

une probabilité non négligeable de rupture des grains à la température ordinaire pour des vitesses d'impact aussi basses que 30 m/s,
une augmentation de la fragilité aux basses températures,
un mode de rupture dépendant de la température, de la vitesse d'impact et de la composition de la poudre, et induisant des effets différents qui ont été mis en évidence par tirs en bombe manométrique sous haute pression.