bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polybenzimidazole and polysulfone blends
Authors: Chung Tai‐Shung , Glick Morton , Powers Edward J. 
Published: December 2004

AbstractPolybenzimidazole (PBI) and polysulfone (PS) do not form miscible blends; however, the tensile modulus and strength of their blend fibers are comparable to, or better than, that of PBI fibers, depending on process conditions. Fibers spun from an 80/20 PBI/PS solution blend have PBI‐like LOI (limiting oxygen indices) and flame shrinkage behavior. Sulfonation and stabilization of this fiber improve its thermal properties. The process window for these blend fibers has been determined. There was no aging phenomenon on as‐spun PBI/PS blend fibers, while as‐spun fibers made from PBI/polyarylate (PA) and PBI/high modulus aramides (HMA) exhibited remarkable aging effects on fiber properties. This difference probably arises from the fact that (1) the former is not a miscible blend, while the latter are; and (2) the former does not have hydrolysis groups, such as ester and amide groups, as that in the PA and HMA systems.
Modeling of the Dynamics of Water and R‐11 blown polyurethane foam formation
Authors: Baser S. A. , Khakhar D. V. 
Published: December 2004

AbstractPolyurethane foam formation involves both polymerization and expansion processes. The dynamics of the water and R‐11 blown foams depend on the rates of chemical and physical blowing processes, along with the rate of viscosity increase of the reacting mixture. Experiments were carried out to study the dynamics of free rising, water and R‐11 blown rigid polyurethane foams. The density and temperature change during the foam formation were monitored. A theoretical model was developed to predict the density and temperature variation with time. In the model, the physical blowing agent (R‐11) evaporation process is assumed to be heat generation–controlled and the carbon dioxide generation process to be controlled by the rate of the water‐isocyanate reaction. The kinetic parameters of the reactions of isocyanate with polyol and water were obtained separately and were asssumed to be independent of each other. The water‐isocyanate reaction appears to follow first‐order kinetics with respect to concentration of water. The theoretical predictions of the model show good agreement with the experimental data for density variation with time. The model predictions for temperature rise also match experimental data, except at the later stages of foaming when it is found to be slower than the experimental measurements. However, this deviation does not affect the dynamics of density change since it occurs after the completion of the expansion process.
A finite element model for complex profile calibration
Authors: Sheehy P. , Tanguy P. A. , Blouin D. 
Published: December 2004

AbstractA new finite element model named Corrected Slice Method (CSM) has been developed to cope with three‐dimensional vacuum cooling calibrator problems. Such problems appear whenever the cooling channel lay‐out comprises transverse channels in the calibrator. The CSM is an extension of the 2D approach (8), which takes into account the axial heat fluxes within the calibrator. The proposed model was validated by comparing the numerical results obtained on a test problem with a rigorous finite element approach. Moreover, a real complex profile‐calibrator system was simulated in order to illustrate the full performance of the porposed method.
Measurement of crosslinking degree for electron beam irradiated block copolymers
Authors: Kanbara Hisashige , Huang Samuel J. , Johnson Julian F. 
Published: December 2004

AbstractThe molecular weight between crosslinking junctions (Mc) of styrene‐butadiene‐styrene (SBS) and that of styrene‐isoprene‐styrene (SIS) irradiated by electron beams (5 Mrad to 100 Mrad) was measured by dynamic modulus, glass transition temperature, static modulus, and swelling. The change in dynamic modulus at low temperature was smaller than that at high temperature in both SBS and SIS. The shift of Tg to higher temperature was observed in both SBS, and SIS systems except for 100 Mrad of SIS. Both dynamic and static moduli increased with irradiation doses, however, the change of static modulus was smaller than that of dynamic one. Those mechanical measurements were compared with the swelling measurements and discussed.
Time‐resolved small‐angle light scattering for the study of phase separation kinetics in bisphenol‐a polycarbonate/poly(methy methacrylate) blends
Authors: Perreault François , Prud'Homme Robert E. 
Published: December 2004

AbstractAn automated, solid‐state small‐angle light scattering apparatus has been constructed for the investigation of polymers; the main features of this system are a bidimensional CCD (charge coupled device) detector with 12‐bit resolution and custom‐made, user‐friendly software for the acquisition and treatment of the scattering data. The miscibility and phase separation kinetics of several bisphenol‐A polycarbonate/poly(methyl methacrylate) blends have been investigated using this apparatus. It was found that the rate of phase separation can be altered significantly by replacing part of the polydisperse poly(methyl methacrylate) (PMMA) in the blends by monodisperse PMMA.
Rheo‐Optical behavior of binary polymer blends: The effect of simple shear flow on phase behavior
Authors: Chen Z. J. , Wu R.‐J. , Shaw M. T. , Weiss R. A. , Fernandez M. L. , Higgins J. S. 
Published: December 2004

AbstractThe phase behavior of polymer blends under simple shear flow has been studied using a custom‐designed rheo‐optical system consisting of a two‐dimensional small‐angle light scattering (SALS) device incorporated into a conventional rheometer. Two‐dimensional SALS images were gathered for model polymer blend systems with different quiescent phase behavior: polystyrene/polyisobutylene (PS/PIB) that exhibits upper critical solution temperature phase behavior and polystyrene/poly(vinyl methyl ether) (PS/PVME) that shows lower critical solution temperature phase behavior. For the PS/PIB blend, shear‐induced phase mixing occurred at a critical shear rate. Below that critical shear rate, the dispersed phase was highly elongated parallel to the flow direction. For PS/PVME blends, a streak scattering pattern was observed even though the sample became optically clear after shearing. We observed, apparently for the first time, the development of a bright‐streak pattern from a transient dark‐streak pattern for a polymer blend system under shear. Rheo‐microscopy studies revealed an intriguing wave pattern that developed coincident with the observation of a streak pattern by SALS. The relationship between the two phenomena has not yet been established.
Milligrams to kilograms: An evaluation of mixers for reactive polymer blending
Authors: Sundararaj Uttandaraman , Macosko Christopher W. , Nakayama Akinari , Inoue Takashi 
Published: December 2004

AbstractThe dispersions of both reactive and nonreactive polymer‐polymer blend systems achieved in three different mixers are compared. The dispersions are prepared using an industrial scale twin‐screw extruder, a laboratory internal mixer, and a miniature cup and rotor mixer. The morphology development in the three mixers is remarkably similar: The dispersed phase is stretched into sheets and ribbons; these sheets and ribbons then break into cylinders, which subsequently break into droplets via Rayleigh‐type instabilities. Drop size distributions can be accurately predicted if we know the size of cylinders formed in the high shear fields of the mixer. There is a significant effect of quenching time on blend morphology—i.e, to properly evaluate mixing, blends must be quenched extremely quickly (well within a minute). Otherwise, we need to consider the morphology development during the quenching time, which may not be relevant to the mixing. There is a uniform shear stress in the miniature mixer, unlike the other mixers, which have varying stress levels. It is shown that a high stress level followed by a lower stress level is required in polymer blending to achieve efficient mixing. In the high stress level, the dispersed phase is stretched into extended shapes, which undergo instabilities and break up upon entering the low stress level. In the miniature mixer, the dispersed phase sees only one stress level, and thus very extended shapes persist at the end of mixing. The final dispersions in the twinscrew extruder and internal mixer at matched maximum shear rates are almost identical. For similar shear rates in the miniature mixer, the final dispersion of reactive blends is comparable to the other mixers. However, the miniature mixer does a poor job in dispersing high viscosity uncompatibilized blends, and the mixing conditions must be altered to obtain efficient mixing.
Morphologies of mechanically mixed amorphous blends before and after annealing
Authors: Andradi L. N. , Hellmann G. P. 
Published: December 2004

AbstractThe morphologies of amorphous polymer blends produced by extrusion were investigated by transmission electron microscopy. Polymers with similar viscosities, i.e. poly(methyl methacrylate) (PMMA), polystyrene (PS), and random copolymers P(SxMMA1 − x) were mixed pairwise, in different compositions. Finely dispersed phase structures were produced in the blends, with domains in the submicron range. The structure patterns were considerably perturbed by the stress fields in the extruder. Domain‐matrix and co‐continuous morphologies were obtained, in a distribution controlled mainly by the viscosity ratio. Annealing after extrusion led to structure coarsening, whereby the patterns were changed until a steady state was established. Sometimes, matrix inversion was observed.
Electrosteric stability of styrene/acrylic acid copolymer latices under emulsion polymerization reaction conditions
Authors: Reynhout Xaviera E. E. , Beckers Mark , Meuldijk Jan , Drinkenburg Bart A. H. 
Published: December 2004

AbstractAcrylic acid (AA) is used in many emulsion polymerization formulations to improve the colloidal stability during and after the production of latex products. Theoretically, the improved stability originates from electrostatic repulsion complemented with steric repulsion. The objective of this work was to study the contribution of AA to the colloidal stability of polystyrene and styrene/AA copolymer latices under simulated reaction conditions. The strength of electrostatic and steric repulsion forces as a function of the electrolyte concentration, pH, and temperature was investigated via coagulation experiments with monomer‐swollen latices in stirred tank reactors. Transmission electron microscopy pictures and dynamic light scattering measurements provided an understanding of the conditions and mechanisms leading to coagulation. The experiments demonstrated that the presence of surface‐bound carboxylic groups only improved the colloidal stability if the carboxylic groups were charged, that is, at a high pH. At a low pH, the copolymer latices were even less stable than the homopolymer latex, and this indicated that the addition of AA did not improve the colloidal stability of a growing polystyrene latex. With respect to emulsion polymerization process operations, insufficient mixing and a highly concentrated electrolyte feed were found to be sources of fouling and enhanced macroscopic coagulation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 726–732, 2005
Feature‐specific Measurement of Surface Roughness in SEM Images
Authors: Russ John C. , Russ J. Christian 
Published: December 2004

AbstractCharacterization of the roughness of surfaces of individual features present in SEM images is obtained from the slope and intercept of a plot of the brightness difference between pixels as a function of their separation distance, in directions parallel and perpendicular to the scan lines within the outlines of the feature. The descriptive names contrast and texture are given to the intercept and slope of this plot, respectively. These parameters can be used to classify features, just as measures of size, shape, etc. are used for selection, distribution plots and statistical comparison. Evidence is also shown for a correlation between the texture and the fractal dimension of the feature profile, and consequently with the surface fractal dimension of the feature.
Alternative Model‐Independent Inversion Programme for Malvern Particle Sizer
Authors: Bayvel Leopold P. , Knight Jonathan , Robertson Gerald 
Published: December 2004

AbstractThe Malvern Particle Sizer, developed in 1977, is used extensively for measuring the size distribution of solid particles and drops. It has several modes of operation based on a priori assumption of a particle size distribution function and a so‐called “model independent” programme in which no prior assumptions are made about the nature of the size distribution. Unfortunately neither the developers nor the manufacturers of the instrument have revealed the algorithm which is used to obtain the particle size distribution from the light scattering data. A number of people who have attempted to verify the performance of the instrument using the model‐independent programme have encountered discrepancies which cannot be explained without knowing the details of the Malvern inversion algorithm.The results obtained in this paper show that the light scattering data recorded, using the hardware of the Malvern instrument, can be successfully processed using Shifrin's inversion technique in order to the obtain particle size distribution. The use of Shifrin's inversion algorithm, which is described fully in the open literature, has a number of advantages over Malvern's proprietary software in the context of particle sizing research. It provides the research worker with a simple and mathematically elegant alternative method of processing the light scattering data which is particularly suitable for investigating the limits of applicability of the Fraunhofer diffraction particle‐sizing technique.
Comparison of Methods for the Measurement of Linear Grade Distributions in Liberation Analysis
Authors: Lin Chen L. , Miller Jan D. , Herbst John A. , Rajamani Kuppuswamy 
Published: December 2004

AbstractAn evaluation was made to assess whether linear grade distribution measurements determined from polished sections of randomly oriented particles can be used to estimate the extent of liberation for multiphase particles of specified size. Two techniques, optical image analysis and microprobe analysis, were used to establish the linear grade distributions for samples of different composition from a copper porphyry flotation circuit and these two were found to be equivalent. An estimate of the variance in the experimental data was made by measuring the average chalcopyrite content in these samples and comparing the results to chemical assays. The statistical significance of the linear grade distribution data obtained by optical image analysis was assessed and, for a given accuracy, the number of particles required to obtain an unbiased representation of the sample was determined.
Thermodynamic Characterisation of Microcrystalline and Microfine Cellulose Powders
Authors: Stanley‐Wood Nayland 
Published: December 2004

AbstractCellulose produced by different processes. (Spray dried and comminuted) have been characterised by low temperature (77K) nitrogen adsorption to determine the specific surface areas, micro‐ and meso‐porosities together with the thermodynamic properties of the Polanyi surface potential and heat (enthalpy) of adsorption.These physico‐chemical and thermodynamic parameters are then correlated with the physico‐mechanical properties of compactability to indicate the bonding strenghts of microcrystalline and microfine celluloses.
Fraunhofer Diffraction by Random Irregular Particles
Authors: Jones Alan R. 
Published: December 2004

AbstractA statistical model is developed for Fraunhofer diffraction by random irregular particles. This is described in terms of a distribution function for radii and a correlation function in the surface. Results are presented for a variety of particle types, and the consequences to particle sizing discussed. Comparison with a “best” sphere suggests a radius based on the average 〈Rn〉 where n > 3.
Mie Scattering near the Critical Angle
Authors: Fiedler‐Ferrari Nelson , Nussenzveig Herch Moysés 
Published: December 2004

AbstractComplex angular momentum theory is applied to the problem of high‐frequency critical light scattering by a spherical cavity near the critical angle. The main contributions to the scattering arise from a critical domain close to critical incidence. The results are in good agreement with the exact Mie solution.
Particle Sizing by Laser Light Diffraction: Improvements in Optics and Algorithms
Authors: Kouzelis Dimitris , Candel Sebastien M. , Esposito Emile , Zikikout Souad 
Published: December 2004

AbstractA major problem encountered in particle sizing by laser light diffraction concerns the inversion of the diffraction pattern measured in a given experiment.Conventional methods for solving the linear system obtained can not be used in this problem, because the matrix is ill‐conditioned and also because the diffraction pattern is usually determined with a low resolution annular diode detector. These problems may be solved with up to date optical detectors (linear CCD‐arrays comprising 1024 photodiodes) and refined inversion techniques (conjugate gradient method and the analytical formulation due to Shifrin).These two aspects are described in this paper. Two inversion methods are compared and experimental results are discussed.
Realization of a Concept for the Complete Evaluation of Double Pulse Holograms of Particulate Phases in Flows
Authors: Schäfer Michael , Umhauer Heinz 
Published: December 2004

AbstractDouble pulse holography is, for experimental investigations, an extremely valuable means of measuring transport processes in disperse phases. This method allows the single or two dimensional frequency distributions of particle size, velocity, momentum and energy to be determined for each recorded sub‐collective, with the additional possibility of checking the existence of their correlation. Being an imaging method, the distributions of the particles in space can be displayed along with the instantaneous values of the concentration and particle flux density.A complete and very exact evaluation of the holographic images, coupled with the certainty of image pairing, is one of the prerequisites of a successful application. The best evaluation in this sense is, at present, produced by a semi‐automatic, interactive system in which the assessment of certain crucial factors is left to an operator.Although the effort incurred by such a total evaluation is by no means insignificant, it is justified by the profusion of information to be obtained.The present report explains the whole concept including a programme system with which the primary data is further processed and with which a variety of results may be called up and displayed.
Determination of Particle Size Distribution in Fluids using photon correlation spectroscopy
Authors: Krahn Werner , Luckas Michael , Lucas Klaus 
Published: December 2004

AbstractPhoton correlation spectroscopy (PCS) has been applied to various systems of particles suspended in a fluid. Computer simulations were used to analyse CONTIN, a program for the numerical inversion of the experimental data. Measurements were performed on a spectrometer equipped with a digital correlator. Various suspensions of polysterene latex spheres differing both in size and size distribution were prepared in double distilled water. Further some samples provided by an external institution without prior specification were analysed. Diffusivity measurements on submicron DES (di‐2‐ethylhexyl sebacate) particles in nitrogen were also performed. The results obtained demonstrate the strengths and the limitations of PCS as a method of determining particle size distributions in particle fluid systems.
A Theoretical Interpretation of Meloy's Law of Morphological Coefficients
Authors: Vlad Marcel Ovidiu 
Published: December 2004

AbstractThis note deals with the Fourier representation of particle shape. A frequency distribution pn, n = 1,2, …, expressing the contribution of the different harmonics to the dispersion of the position vector is defined. The Meloy law of morphological coefficients may be derived by optimizing the value of the informational entropy which is attached to pn.
Aerosol Generation Method for Measuring Particles Suspended in Water – Detection of Particulate Impurities in Ultrapure Water and Sizing of Fine Powders –
Authors: Niida Tohru , Kousaka Yasuo , Oda Shinji 
Published: December 2004

AbstractThe method described is based on the fact that the measurement of particles in the gaseous phase is generally easier than that in the liquid phase for fine particles smaller than 1 μm in diameter. The system consists of a liquid nebulizing unit, evaporator, condenser, mixing diluter and two different aerosol sizing instruments. It has been found that this method can continuously detect particulate impurities in ultrapure water in situ and can measure the size distribution of fine powders in the submicron particle size range down to about 0.05 μm.
Determination of Particle Size Distribution Parameters using a Laser‐Scattered Light Spectrometer
Authors: Blum Klaus , Fissan Heinz 
Published: December 2004

AbstractA method based on the measurement of scattered light intensity distributions is demonstrated to be able to determine directly the particle size of monodisperse supermicron‐size particles. In all other cases of a particle cloud, information about the size distribution can be acquired from comparison of measured and calculated intensities as a function of scattering angle. This indirect method is only applicable if the assumptions made in the theory used for comparison are fulfilled. Therefore, the method is limited to spherical particles with known refractive index. The type of size distribution also has to be known. In the cases considered a log‐normal size distribution was assumed. The uncertainty of the result increases with increase in the number of parameters that have to be determined. The method seems to be limited to unimodal distributions described with two parameters.
Sizing of Submicron Aerosol Particles by the Whisker Particle Collector Method
Authors: Schäfer Hans J. , Pfeifer Hans J. 
Published: December 2004

AbstractSamples of an alumina powder aerosol were collected on whisker particle collectors and analysed following an improved evaluation scheme which allows the empirical size distribution to be corrected for the effect of a non‐uniform collection efficiency. The measurement results are given in terms of log‐normal distribution functions. Some ambiguity was encountered in interpreting particle aggregates that were found on the whisker collectors. By including the results of laser light‐scattering experiments in the size analysis, this ambiguity was removed. Advantages and disadvantages of the whisker collector concept compared with light‐scattering methods are discussed.