bluuebunny/crossref_metadata_2025_split huggingface dataset:
Blockiness of olefin copolymers and possible microphase separation in the melt
Authors: Wardhaugh Leigh T. , Williams Michael C. 
Published: December 2004

AbstractSolid‐catalyzed copolymerization reactions of ethylene and α‐olefins can produce complex mixtures generally regarded as “polyethylenes” (including linear low‐density polyethylene). The selective nature of those catalysts can lead to block‐like character in segments of polymer molecules, and these segments are sufficiently dissimilar (from a thermodynamic viewpoint) to allow for the possibility of microphase separation in the melt. Such a molecular‐level phase separation would substantially alter the melt rheology, the crystallization process, and hence the mechanical and optical properties of the resulting product. It would, in principle, be identical to those occurring in conventional well‐defined block copolymers, allowing the thermodynamic models developed for those systems to be extended to block‐like polyolefins.
The development of laminar morphology during extrusion of polymer blends
Authors: Kamal M. R. , Garmabi H. , Hozhabr S. , Arghyris L. 
Published: December 2004

AbstractStudies of the microstructure and permeability of extruded ribbons of polypropylene (PP)/ethylene vinyl alcohol copolymer (EVOH) and polyethylene (PE)/polyamide‐6 (PA‐6) blends have shown that it is possible to control the flow‐induced morphology to generate discontinuous overlapping platelets of EVOH or PA‐6 dispersed phase in a PP or HDPE matrix phase. The effects of the following factors on morphology development and blend properties were considered: blending sequence, melt temperature, composition, compatibilizer level, die design, screw type, and cooling conditions. The impact properties and interfacial adhesion of laminar blends of PP and EVOH were improved without diminishing the barrier properties. The oxygen and toluene permeability of extruded samples with EVOH content of 25 vol% resembled values obtained with multilayer systems. Processing conditions had a major influence on the morphology of blends of high density polyethylene and polyamide‐6 (HDPE/PA‐6), and, under special processing conditions, laminar morphology was obtained in this system. The toluene permeability of extruded ribbons of HDPE/PA‐6 blends was in the range obtained with multilayer systems.
Ultrasonic behavior of polymer blends
Authors: Gendron R. , Tatibouët J. , Guèvremont J. , Dumoulin M. M. , Piché L. 
Published: December 2004

AbstractDuring the last few years, improvements in control strategies became a necessity, with controls being targeted on material properties. The ever‐increasing demand for polymer blends spells the need for in‐line instrumentation capable of monitoring blend properties such as morphology. Since ultrasonics have proved to be sensitive to properties of multiphase materials, their performance for discriminating blend morphology was explored here. In‐line and off‐line (static, with no flow) ultrasonic measurements were made on different blends of polystyrene (PS), polyethylene (PE), and polypropylene (PP) for various viscosity ratios, and over the entire range of composition. Blends were compounded on a ZSK‐30 Werner & Pfleiderer intermeshing co‐rotating twin‐screw extruder. In‐line ultrasonic measurements were performed on both single‐screw and twin‐screw extruders. Ultrasonic properties (velocity and attenuation) were found to vary approximately linearly with composition. Mixing rules were evaluated for the description of ultrasonic behavior. For the attenuation measurements, the positive deviations from these rules were found significant. The additional attenuation was attributed to scattering generated by the presence of the minor phase inclusions.
Development of polymer blend morphology during compounding in a twin‐screw extruder. Part IV: A new computational model with coalescence
Authors: Huneault M. A. , Shi Z. H. , Utracki L. A. 
Published: December 2004

AbstractIn Part II of this series of publications, the first generation model of morphology evolution during polymer blending in a twin‐screw extruder was presented. The model was based on a simplified flow analysis, and an assumption that dispersion occurs via drop fibrillation followed by disintegration. In the present Part IV, several modifications of the model are discussed. (i) The flow analysis was refined by computing the pressure profiles. (ii) The flow paths and strain history of the dispersed droplets within the screw elements are computed directly, which makes it possible to determine the drop susceptibility to deformation and break. (iii) Besides the fibrillation mechanism, a drop‐splitting mechanism for low supercritical capillary numbers is incorporated. (iv) The choice of breakup mechanism is based on micro‐rheological criteria. (v) The coalescence effects are taken into account. (vi) The theoretical model is self‐consistent, without adjustable parameters. The validity of theoretical assumptions was evaluated by comparing the model predictions with the experimental droplet diameters at different positions in the twin‐screw extruder.
The conducting behavior and stability of conducting polymer composites
Authors: Chen X. B. , Issi J‐P. , Devaux J. , Billaud D. 
Published: December 2004

AbstractResults of measurements of the electrical conductivity of low density polyethylene/polypyrrole and polystyrene/polypyrrole composites are reported. It is observed that the electrical conductivity of the composite vs. concentration follows the power law predicted by the percolation theory. The manufacturing process influences the homogeneity of the composite at microscopic scale and thus the percolation threshold. Annealing studies show that the stability of the electrical conductivity of the composite is related to the thermal expansion of the polymers and the relaxation of the polymer chains. The decrease of the electrical conductivity of the composite is attributed to the interruption of the percolation path.
Diffusion of low molecular weight substances into a laminar film. I: Rigorous solution of the diffusion equation in a composite film of multiple layers
Authors: Fukuda Mitsuhiro , Kawai Hiromichi 
Published: December 2004

AbstractA rigorous solution of the diffusion of penetrant into a laminar film comprised of multilayers of m components is presented by an orthogonal‐expansion method. As the simplest practical cases of m − 2 and m − 3, with stepwise distribution of both diffusion coefficients and solubility coefficients at the boundary between respective layers, the diffusion properties in the transient state are analyzed in detail. That is, changes in the penetrant concentration distribution within the laminar film and the total amount of penetrant sorbed within the film both with time after exposing the film to an atmosphere of fixed penetrant concentration are calculated for A–B as well as A–B–A type layer arrangements. The calculation is performed while keeping (L2/L1) at a constant value of 2.0 but varying the diffusion coefficient ratio of (D1/D2) from 102 to 10−2, and/or varying the solubility coefficient ratio of (S1/S2) from 1 to 10, where L1 and (L2 − L1) are the thickness D1 and D2 are the diffusion coefficients of penetrant, and S1 and S2 are the solubility coefficients in the A‐component and B‐component, respectively. The sorption curves deviate considerably from those of Fickian curves of homogeneous film with (D1/D2) − 1 in their respective ways. The results obtained here can be applied to the diffusion in a single component polymer film having a surface layer with different diffusion properties from that of the inner side of the film caused by differing distributions in molecular orientation or degrees of crystallinity.
An experimental and computational evaluation of ethylene/styrene copolymerization with a homogeneous single‐site titanium(IV)‐constrained geometry catalyst
Authors: Martínez S. , Exposito M. T. , Ramos J. , Cruz V. , Martínez M. C. , López M. , Muñoz‐Escalona A. , Martínez‐Salazar J. 
Published: December 2004

AbstractStyrene was copolymerized with ethylene using the geometry constrained Me2Si(Me4Cp)(N‐tert‐butyl)TiCl2 Dow catalyst activated with methylaluminoxane. Increasing the styrene/ethylene ratio in the reactor feed had the effects of reducing both the activity of the catalyst and the molecular weight of the copolymers produced. However, the higher the styrene/ethylene ratio used, the greater the amount of styrene that became incorporated in the copolymer. We discuss these experimental findings within the framework of a computational analysis of ethylene/styrene copolymerization performed through hybrid density functional theory (B3LYP). In general, there was good agreement between the experimental and theoretical results. Our findings point to the suitability of combining experimental and theoretical data for clarifying the copolymerization mechanisms that take place in α‐olefin‐organometallic systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 711–725, 2005
A new method for Characterization of the Surface Energy of Hydrophobic Particles
Authors: Fuerstenau Douglas W. , Williams Mark C. 
Published: December 2004

AbstractA film flotation technique has been developed for assessing the hydrophobicity/hydrophilicity of an assembly of particles which have a distribution of surface energies. With this method, particles are partitioned by placing them on the surface of a series of aqueous solutions of different surface tensions and determining the fraction imbibed into the liquid. From the results, a cumulative distribution of particles versus their critical wetting surface tension (surface energy) can be made. The mean critical wetting surface tension can be used as an index for making correlations with surface‐based processes.
Laser Diffraction Spectrometry: Fraunhofer Diffraction Versus Mie Scattering
Authors: de Boer Gerben B. J. , de Weerd Cornelis , Thoenes Dirk , Goossens Hendrik W. J. 
Published: December 2004

AbstractLaser diffraction spectrometry (LDS) is often claimed to operate on the principle of Fraunhofer diffraction. This is only true, however, if particles are large compared to the wavelength of light or if the ratio of the refractive indices of the disperse and continuous phases, m, is clearly different from unity. In this study it has been established that LDS, as applied to particle and droplet sizing in suspensions and emulsions, is based on Miescattering. Scattering patterns of single particles may be calculated if the refractive indices of both phases are known. Thus, a theoretical basis has been provided for the application of LDS to size‐measurement in suspensions and emulsions, and for extension of this method to the lower size ranges and those cases in which the refractive indices of the disperse and continuous phases are similar. Extension of the work presented in this paper will enable the calculation of scattering matrices so that calibration of the apparatus with standard materials may be avoided.
The Probable Number of Particles in Contact when Spread on a Microscope Slide
Authors: Hawkins Arthur E. 
Published: December 2004

AbstractIt is shown that the number of particles which may be placed upon a slide is surprisingly limited if each particle is to be isolated. This is particularly relevant if automatic image analysis of size or shape is to be achieved without tedious editing. Using a simple mathematical treatment it is possible to calculate, for any particular size of particle, the number of particles on a slide which should not be exceeded.
Laser Doppler Anemometry – a non‐intrusive optical measuring technique for fluid velocity
Authors: Ruck Bodo 
Published: December 2004

AbstractThe present paper gives an introduction to laser Doppler anemometry. The fundamental principles of this measuring technique, as well as the basic features of its instrumental realizations, are explained. The application of laser Doppler anemometry to fluid investigations often requires an adaptation of the LDA‐system to the measuring problem. Basic formulas for the lay‐out and adaptation are given.
Polygonal Harmonics of Silhouettes: Shape analysis
Authors: Clark Nigel N. , Diamond Harvey , Gelles Gregory , Bocoum Brigitte , Meloy Thomas P. 
Published: December 2004

AbstractOne well documented method for finding the fractal dimension of a silhouette involves approximating the silhouette with polygons which have all but one side equal and the vertices of which fall upon the silhouette edge. These are constructed using a divider stepping method or a computer algorithm which mimics this process. If one does not complete the polygon with an unequal side, as is usually done, but continues the analysis by stepping around the silhouette several times, the dividers start to „walk in their own footsteps”︁ and describe an equilateral polygon in the silhouette. These phenomena, termed polygonal harmonics, are examined and discussed in detail. A rule is developed for harmonic stability and specific cases of the circle, triangle and smooth curves are examined to gain insight into the convergence process.
In‐situ Determination of the Molecular Composition of Aerosol Particles in a Monodisperse Model Aerosol
Authors: Schweiger Gustav 
Published: December 2004

AbstractThe in‐situ determination of the molecular composition of aerosol particles, composed of DES and DBP and suspended in an air flow, is described. The laser‐Raman scattering technique was applied to determine the composition of a monodisperse, model aerosol, 10 m̈m in diameter, which flows through the scattering volume.
How to Reduce Errors in Test Sieving
Authors: Müller Helmut , Kubier Bernd , Rudolph Lutz 
Published: December 2004

AbstractStudies of and experiences with the reduction of errors in test sieving are presented. The preparation of the test material and, above all, the errors in sample splitting are included in the considerations. Errors due to the manufacture of test sieves are discussed, for example the influence of the aperture width distribution. The method applied at the Forschungsinstitut für Aufbereitung (FIA) for the inspection and calibration of test sieves is described in detail. The use of test materials for the calibration of sieves is recommended.
Persistence of Polygonal Harmonics as Shape Descriptors
Authors: Hurter Patricia , Clark Nigel N. 
Published: December 2004

AbstractCharacterization of the overall (lage scale) shape of rugged particles poses a problem which is not readily solved by existing shape analysis techniques. Recent research on the divider stepping method used in factal analysis has led to the examination of polygonal harmonics which can be constructed in both smooth and rugged particle silhouettes. The persistence of these harmonics is defined as the ratio of the longest step length to shortest step length which can be used to create that harmonic. It is proposed that the persistences of the first three harmonics provide useful descriptors for particle shape. Variation of these persistences within several geometric figures is explored, protocols for the analysis are adopted and some preliminary work on rugged silhouettes is discussed. Characterization by this technique holds great promise in the development of a general approach to particle shape description.
Particle Size Analysis of Carbon Black
Authors: Blackford David B. , Simons Gary R. 
Published: December 2004

AbstractA new technique is described for measuring the size distribution of submicrometer sized powders, such as carbon black. Powder is first dispersed as an aerosol and the particle size is subsequently measured with a differential mobility classifier and an aerosol concentration detector.The technique has been used to provide a size distribution for seven American Society for Testing and Materials (ASTM)/D1765 designated grades of carbon black (N110, N234, N299, N330, N650, N683, N762). In addition, four grades (N234, N330, N683, N762) are designated by ASTM D24 committee on carbon black as Standard Reference Blacks in the SRB‐3 series (C3, B3, D3, A3, respectively).The effectiveness of the dispersion technique is discussed and size distribution data is presented on the seven ASTM grades of carbon black. For the sake of comparison, the same carbon blacks have been sized with a completely different measurement technique. This technique measures the diffusion coefficient of a dilute particle suspension from which a mean hydrodynamic particle diameter is determined. Size distribution data using this technique is also presented.
Optimal Scaling of the Inverse Fraunhofer Diffraction Particle Sizing Problem: The linear system produced by quadrature
Authors: Dan Hirleman E. 
Published: December 2004

AbstractSolution of the linear system of equations obtained by discretization and numerical quadrature of the Fredholm integral equation describing Fraunhofer diffraction by a distribution of particles is considered. The condition of the resulting system of equations depends on the discretization strategy. However, the specific set of equations is shown to depend on the discretization scheme used for the scattering angle domain (the number, positions and apertures of the detectors) and for the size domain (the number and extent of the discrete size classes). The term scaling is used here to describe particular formulations or configurations of the scattering angles and size classes, and a method for optimally scaling the systems is presented. Optimality is determined using several measures of the condition (stability) of the resulting system of linear equations. The results provide design rules for specifying an optimal photodetector configuration of a Fraunhofer diffraction particle sizing instrument.
Modeling of Multiple Scattering Effects in Fraunhofer Diffraction Particle Size Analysis
Authors: Dan Hirleman E. 
Published: December 2004

AbstractA model for the direct problem of calculating the forward scattering signature of a multiple scattering medium is presented. The new formulation is optimized for integration into schemes for reconstructing the particle size distribution from laser diffraction (forward scattering) signatures obtained from optically thick media. The analysis is valid for media where the particle sizes and interparticle spacings are large (relative to the wavelength and the particle size, respectively) such that Fraunhofer diffraction theory adequately describes the properties of the forward scattered light from individual scattering events. The simulated performance of laser diffraction particle sizing instruments was then studied using predictions of the scattered light signatures which would be measured by laser diffraction instrument under multiple scattering conditions. The results were compared with experimental data and theoretical calculations based on other models.
Interaction between a Sphere and a Gaussian Beam: Computations on a micro‐computer
Authors: Corbin Frédéric , Gréhan Gérard , Gouesbet Gérard , Maheu Bruno 
Published: December 2004

AbstractThis paper presents some characteristics of the light scattered by one spherical particle illuminated by a Gaussian beam. The basic theory is a generalization of the Lorenz‐Mie Theory. The fact that the computations can be easily carried out on a micro‐computer is pointed out.
Phase‐Doppler‐Anemometry and the Log‐Hyperbolic Distribution applied to Liquid Sprays
Authors: Bhatia Jagdish C. , Domnick Joachim , Durst Franz , Tropea Cameron 
Published: December 2004

AbstractThe paper provides a description of the local drop‐size distributions in a liquid spray issuing from a 60° oil‐burner nozzle obtained experimentally using a phase‐doppler anemometer. The details of the optical system and the signal processing electronics of the phase‐Doppler anemometer are included.Details have also been given concerning the use of the log‐hyperbolic distribution and in particular of a procedure for determining the four defining parameters from a given experimental distribution, in this case that of drop size. Analytical formulae to compute moments of the distribution and the mean diameters are also given.All size distributions are shown to be well described by the log‐hyperbolic distribution involving four parameters. The variation of these parameters along the axis of the jet clearly reveals a developing region of the spray followed by a fully developed state, for which physical reasons are given. The parameters can also be used to predict the local drop‐size distribution at any intermediate location on the spray axis.
Measurement of Particle Rotational Velocity Using a Laser Anemometer
Authors: Kale Sunil R. , Ramezan Massood , Anderson Rodney J. 
Published: December 2004

AbstractAn electrodynamic balance and a frequency shifted Laser Doppler Anemometer (LDA) were used to obtain rotational velocity data from nonspherical particles undergoing pure rotation. A charged oil shale particle (150μm × 150 μm × 60 to 80 μm thick) was suspended in an electric field and rotated at a constant velocity by subjecting it to a vertical air jet. The measuring volume of the LDA was located on the particle, and Doppler bursts were observed from both stationary and rotating particles. This observation suggests that micron‐sized surface irregularities can act as individual scattering sources for LDA measurements. Signal analysis was performed with a counter type processor and a PDP‐11 computer. The particle motion was recorded on video tapes from which the true rotational velocity and maximum radius of rotation were obtained. Within the experimental uncertainties, the maximum rotation‐induced surface velocity measured with the LDA agreed well with that obtained from video tapes.
Particle Dispersion in a Swirling Confined Jet Flow
Authors: Sommerfeld Martin , Krebs Werner 
Published: December 2004

AbstractThe characteristics of swirling single‐ and two‐phase flows discharging into a sudden pipe expansion were studied in detail by the use of laser‐Doppler anemometry. The results are compared with those for the comparable non‐swirling case. The central recirculation zone established for a swirl number of 0.56 was found to have an annular shape, which was a result of the subcritical nature of the flow and the area contraction at the end of the test section.The behaviour of the particles in both swirling and non‐swirling flow was studied by flow visualization, particle concentration and velocity measurements. Initially, the spreading of the particle jet is about the same for both cases owing to the particle inertia. In the middle of the recirculation bubble the particles start to spread more rapidly under the acting of centrifugal forces established in a swirling flow. This finally results in a high concentration of particles near the wall of the test section and a particle‐free region in the core of the vortex. The numerical simulations of the non‐swirling flow showed good agreement for both the gas and particle phases in comparison with the experimental results.