bluuebunny/crossref_metadata_2025_split huggingface dataset:
The recirculating screw mixer: A new small‐volume mixer for the polymer laboratory
Authors: Scott Chris E. , Macosko Christopher W. 
Published: December 2004

AbstractThe recirculating screw mixer (RSM), a new small‐volume intensive mixer for the polymer laboratory, is designed, built, modeled, and tested. This type of batch mixer is intended for the mixing of 1 to 30 cm3 of viscous material at high shear rates. A material element in the mixer experiences alternating screw pump and tubular flows with reorientation between these flows. A mixer with a 10 cm3 sample capacity is built for testing and evaluation. Flow visualization experiments are used to investigate the quality of the distributive mixing achieved. The flows in the mixer are modeled for the cases of a Newtonian fluid and a power law fluid. The Newtonian model accurately predicts the recirculation time for particles suspended in Newtonian silicone oils. The power law model accurately predicts the screw torque obtained with a polystyrene and polyethylene. A method for the measurement of fluid rheology from the operating conditions of the RSM is proposed and tested. The mixing achieved by the RSM is compared to that obtained by a batch mixer with roller blades. Both mixers are used to prepare blends of ethylene‐propylene rubber in polystyrene. The morphologies of the resultant blends are compared and differences in the mixing action are discussed. The mixers are also used to prepare composites of fumed silica in polyethylene. The quality of mixing obtained in the RSM compares quite favorably with that obtained in the batch mixer with roller blades for polystyrene/ethylene‐propylene rubber reactive blends and polyethylene/silica composites.
Refinement of the converging flow method of measuring extensional viscosity in polymers
Authors: Bersted B. H. 
Published: December 2004

AbstractA critical evaluation of assumptions made in the converging flow analysis of Cogswell is made, and a refined analysis is given by relaxing two of these assumptions. This reexamination of the Cogswell method was motivated by some recent encouraging comparative studies by Laun and Schuch of conventional extensional results and converging flow data. Of the two assumptions relaxed in the analysis, the relaxation of the assumption of a constant extensional viscosity above the orifice, into which the converging flow takes place, is shown to be primarily responsible for the substantially improved agreement with conventional extensional viscosity measurements. Because the variation of the extensional viscosity above the orifice is not known, solution of the equations is not given in closed form, and their solution is solved by an iterative procedure. The good agreement of the results of the modified converging flow analysis given here with conventional extensional measurements over a large range of rates demonstrates that converging flow methods can provide an accurate and relatively routine method of measuring extensional viscosity in molten polymers.
Morphology and mechanical properties of virgin and recycled polyethylene/polyvinyl chloride blends
Authors: Ajji A. 
Published: December 2004

AbstractIn this study, blends of virgin and recycled polyethylene (PE) and poly(vinyl chloride) (PVC), with a methylmethacrylate‐ethylacrylate copolymer as a processing aid, were prepared in the molten state. Different additives such as ethylenevinylacetate copolymers, ethylene‐methacrylic acid ionomer, and two peroxides (dibenzoyl and dicumyl), in the presence of a coupling agent, were used to compatibilize the blend or possibly induce graft structures. The blends' morphologies, tensile properties, and impact properties were studied. For blends with low copolymer concentration (below 3 wt%) the mechanical test data indicated a good performance. In the case of blends with ethylene methacrylic acid ionomer, improvements in the mechanical properties were obtained also at higher additive concentrations. Of the two peroxides, better results were obtained using the dibenzoyl one. The morphological studies indicated that the blends that showed good mechanical properties were better dispersed and had improved interphase adhesion.
Application of statistical experimental strategies to the process optimization of waterborne polyurethane
Authors: Yang Chien‐Hsin , Lin Shih‐Min , Wen Ten‐Chin 
Published: December 2004

AbstractA modified acetone process for the preparation of aqueous polyurethane (PU) dispersion is investigated. PU dispersions were prepared by polyaddition of isophorone diisocyanate (IPDI) to poly(tetramethylene ether glycol) (PTMG) and dimethylolpropionic acid (DMPA), followed by neutralization of pendant COOH groups with triethylamine (TEA). The resulting prepolymer chain was then extended through reaction with an ethylenediamine (EDA) derivative bearing sulfonate groups. The effect of such preparation conditions as catalyst (dibutyltin dilaurate, DBTDL) concentration, the acetone/PU ratio, phase‐inversion temperature, agitation rate, and water‐addition rate on the average particle size of aqueous PU anionomer dispersions is systematically studied using fractional factorial design and response surface methodology. Fractional factorial analysis indicates that the effects of the acetone/PU ratio, phase‐inversion temperature, water‐addition rate as well as the two factor interactions of DBTDL concentration and phase‐inversion temperature, of the acetone/PU ratio and phase‐inversion temperature, and of acetone/PU ratio and agitation rate are the key variables influencing average particle size of PU dispersions. Empirical models for average particle size are fitted and plotted using central composite experimental design as contour diagrams in order to facilitate examination of the average particle size results. The results show that for a 100 g PU anionomer containing 0.311 wt % COOH and 1.51 wt % SO3H groups, a minimum number‐average particle size of the dispersion ∼ 25 nm can be obtained under an acetone/PU ratio, water‐addition rate, phase‐inversion temperature, catalyst concentration, and agitation rate of 3.65, 2 mL/min, 50°C, 150 ppm and 350 rpm, respectively.
Challenge of synthetic cellulose
Authors: Kobayashi Shiro 
Published: December 2004

AbstractThis article focuses on why and how the chemical synthesis of cellulose was accomplished. The synthesis of cellulose was an important, challenging problem for half a century in polymer chemistry. For the synthesis, a new method of enzymatic polymerization was developed. A monomer of β‐D‐cellobiosyl fluoride (β‐CF) was designed and subjected to cellulase catalysis, which led to synthetic cellulose for the first time. Cellulase is a hydrolysis enzyme of cellulose; cellulase, inherently catalyzing the bond cleavage of cellulose in vivo, catalyzes the bond formation via the polycondensation of β‐CF in vitro. It is thought that the polymerization and hydrolysis involve a common intermediate (transition state). This view led us to a new concept, a transition‐state analogue substrate, for the design of the monomer. The preparation of cellulase proteins with biotechnology revealed the enzymatic catalytic functions in the hydrolysis and polymerization to cellulose. High‐order molecular structures were in situ formed and observed as fibrils (cellulose I) and spherulites (cellulose II). In situ small‐angle neutron scattering measurements suggested a fractal surface formation of a synthetic cellulose assembly. The principle of cellulose synthesis was extended to the synthesis of other natural polysaccharides, such as xylan and amylose, and unnatural polysaccharides. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 693–710, 2005
Latex Particle Size Distributions from Multiwavelength Turbidity Spectra
Authors: Gulari Esin , Bazzi Ghassan , Gulari Erdogan , Annapragada A. 
Published: December 2004

AbstractAccuracy, range, noise tolerance and resolution of turbitidy spectra analysis as a particle sizing method are discussed with respect to simulated data and data on latex spheres. The fine structure in the turbidity spectra is used to measure multimodal distributions with no apriori assumptions about the distribution.
Comparison of the Size Distribution of Boron Powders as Measured by Malvern Diffractometer and Coulter Counter
Authors: Davies J. Alwyn , Collins Dilys L. 
Published: December 2004

AbstractAspects of measuring the particle size distribution and median diameters of fine boron powders have been investigated. It has been demonstrated that high concentrations, typically 20 w/o, of wetting agent are necessary in a predispersion stage, especially if the material has a wide range of particle size. Measurements were made with both Coulter counting and a light scattering technique from which it has been demonstrated that for particles of median diameter in the range 10–30 μm, the latter oversizes with respect to the former by as much as 30%.
Regeneration of Form by Fourier Technique and its Application in Powder Characterization
Authors: Paramanand  , Ramakrishnan P. 
Published: December 2004

AbstractConventional shape parameters have serious limitations because of their inability to capture finer surface morphology as well as to regenerate the particle form. This problem has been successfully circumvented by applying Fourier analysis technique to the projected image of the particle profile to obtain Fourier coefficients which have been shown to be size inveriant and insensitive to starting point for digitization. Synthesis technique to regenerate the particle profile from Fourier coefficients has revealed that gradual addition of higher order harmonics brings the regenerated form very close to its original counterpart. The regeneration of the form of particles of different shapes as well as application of few strategy to harmonic amplitudes have amply demonstrated the capability of the technique as a potential tool for characterization of powders.
Variations in, and Relationships of Surface Area, internal angle of friction and compact diametral fracture strength with degree of compaction
Authors: Stanley‐Wood Nayland , Sarrafi Majid 
Published: December 2004

AbstractThe progress of the compaction process to produce from an assembly of particles a coherent mass can be achieved by the application of shear and normal stress. The achievement of a densified coherent mass necessitates, together with the yielding of material, the movement of particles over and between each other. In uniaxial compaction the angle of internal friction, δE, is a projection of the unique critical state line which divides a three dimensional relationship between volume change (V), shear stress (ϕ) and normal stress (σ) into yield domains and surfaces. There is one region for failure and flow (the Hvorslev surface) and another region for failure and consolidation (the Roscoe surface).In this paper the concepts of the Roscoe and Hvorslev surfaces together with the Coulomb yield criterion have been applied to the uniaxial compaction, over a range of compactable stresses, of titanium dioxide (20–2000 kPa). The characteristics of applied and shear stress, angle of internal friction (δE), angle of shearing resistance (ϕ) and surface area (SBET) were measured and correlated with the compaction stress (σc) and diametral strength (σf) of the compacts to investigate the phenomena of uniaxial compaction.
Computation of the Frequency Distributions of Distances Between Particles Randomly Dispersed in a Fluid Flow
Authors: Raasch Jürgen , Umhauer Heinz 
Published: December 2004

AbstractPulse holography can be used as a method for the experimental investigation of transport processes that occur in flows of dispersed phases. Since a complete evaluation of a hologram involves the measurement and recording of the position of every individual particle, it delivers all the information about the spatial distribution of particles at the instant of exposure.An exact knowledge of the spatial distribution of the dispersed phase is particularly important for those chemical engineering processes which require the spatial distribution of particles to be as homogeneous as possible. Maximum homogeneity is achieved when the particles are distributed purely randomly. For this case, the distributions of distances between neighbouring particles are calculated. They represent a standard which can be adopted as the basis for the assessment of real particle distributions, such as exist momentarily in flows of dispersed phases and are determined by the evaluation of pulse holograms.
Applications of Prism‐Cell Light‐Scattering Spectrometer to Particle Sizing in Polymer Solutions
Authors: Chu Benjamin , Xu Renliang , Nyeo Sulong 
Published: December 2004

AbstractA prism‐cell light‐scattering spectrometer has been modified to accept both a diode‐array detector for measurements of angular distribution of scattered intensity and a photomultiplier tube for measurements of time‐dependent intensity‐intensity correlation function. This spectrometer permits the practice of light scattering at small scattering angles down to a few degrees. Here we make a brief study of the reliability of characteristic linewidth distributions obtained by several methods of analysis on the correlation data, which correspond to a reasonably broad unimodal distribution. Then the prism‐cell light‐scattering spectrometer is used to characterize a polymer solution consisting of two different molecular weights. To obtain characteristic linewidth distribution, the correlation data are analyzed by both the constrained regularization method (CONTIN) and the maximum‐entropy method (MEM).
Removal of Adhering Particles of Polystyrene Latex and iron oxide on a wall by shear flow in water
Authors: Niida Tohru , Kousaka Yasuo , Furukawa Teiji 
Published: December 2004

AbstractThe velocity for removal of particles adhering on a wall has been measured for polystyrene latex (PSL) and iron oxide particles at laminar and turbulent flow in a glass cell. The results indicate that larger particles detache at lower flow velocities and the width of the velocity range for removing adhering particles is wider when the particle size is smaller in the laminar flow regime. Both the viscous drag force for removing particles determined experimentally and the adhesive force obtained theoretically are proportional to the particle diameter, and the coefficients of friction were estimated to be 0.01–0.08 and 0.01–0.02 for PSL and iron oxide particles, respectively. The ranges of the viscous force, the adhesive force and the coefficient of friction are not so far from the values given by Kanaoka et al. [2].
A Sampler for Total Suspended Particulates with Size Resolution and high sampling efficiency for large particles
Authors: Holländer Werner , Dunkhorst Wilhelm , Pohlmann Gerhard 
Published: December 2004

AbstractFor a field intercomparison of various widely used dust samplers, a reference instrument was needed. Based on a Wide Range Aerosol Classifier (WRAC), several improvements were introduced compared with the original design including mass flow control of the samplers and the plenum air, brushless threephase blowers, hyperbolic inlets and generally a more compact design, allowing for more comfortable operation. In addition, for measurement of small particle size distributions, a Hauke high‐volume, low‐pressure impactor (LPI 150/0.15) was included, so that size distribution information with cuts at 0.12, 0.30, 1.19, 3.14, 10.2, 20.4, 37.4 and 60 μm could be obtained. In addition, the aspiration efficiency was measured under in situconditions and parallel measurements were performed with the two reference samplers built so that the performance was well characterized.
Report Joint Meeting of GVC Committees on “Particle Characterization” and “Crystallization”, Winterthur 1988
Authors: Schäfer Michael 
Published: December 2004

AbstractThis Committee stood under the banner of joint meetings with the Crystallization Committee. Further it was characterized by two aspects, namely technological innovation in connection with measurement methods and their (on‐line) application in engineering processes, whether for the sake of model formation or for process control or quality assurance in industry.
Improved Resolution and Accuracy in Electrical Sensing Zone particle counters through hydrodynamic focussing
Authors: Merkus Henk G. , Liu Houyuan , Scarlett Brain 
Published: December 2004

AbstractThe electrical sensing zone technique is long established, well researched and widely used. It is often used as a reference method against which others are compared or calibrated. This position should not be allowed to disguise the potential which exists for still greater accuracy and versatility. In this paper the use of the hydrodynamic focussing technique is evaluated and an experimental comparison is made with a normal Coulter stand for several samples. It is clearly shown that hydrodynamic focussing enables higher resolution and accuracy to be obtained for materials with narrow or unusual particle size distributions.
Particle Size Analysis by Interaction of Charged Particles with an Alternating Electric Field
Authors: Vanck Rainer M. , Bernigau Norbert G. 
Published: December 2004

AbstractA theoretical model for the interaction of charged particles with an alternating current field is developed. This model permits the determination of the particle size distribution by a numerical nonlinear iterative method. Results of numerical simulations are presented and discussed. Restrictions on the applicability of the model as an on‐line measuring system are pointed out.
Evaluation of a Commercial Instrument of Sedimentation Field Flow Fractionation
Authors: Mori Yasushige , Merkus Henk G. , Scarlett Brian 
Published: December 2004

AbstractThe analysis of particles in the sub‐micron range by sedimentation field flow fractionation (SFFF) is not new, but its commercial exploitation is recent. This inevitably will lead to a rigorous evaluation of the technique by many laboratories, for many applications, as well as to rapid development.This paper describes first an evaluation of the new commercial instrument using both ideal and real materials. These experiments lead to a discussion of the software package and of the influence of experimental conditions. A particular study is described of the combination of the SFFF technique with that of quasi‐elastic light scattering. The paper concludes that SFFF now offers the technology for realistically measuring particle size distributions at high resolution in the submicron size range. The analysis time is in the order of one hour, but can be reduced at the expense of resolution.
Constraints On The Size And Shape Of The Receiving Aperture in a phase/doppler system
Authors: Naqwi Amir A. , Durst Franz 
Published: December 2004

AbstractUsing computations based on Mie scattering theory, the influence of the size and shape of the receiving aperture on the signal properties of a phase/Doppler system is examined. For circular apertures exceeding a certain size limit, it is shown that the signal phase is non‐monotonic with respect to the particle diameter and exhibits abrupt changes of 180° at certain values of the diameter. This difficulty may be overcome by using rectangular apertures with appropriate aspect ratios.
Dispersion of Monosized Heavy Particles in Grid Turbulence Effects of Body Forces
Authors: Maquet Cecille , Trinite Michel , Ledoux Michel 
Published: December 2004

AbstractDispersion of monosized drops downstream a point injection in a grid‐generated turbulence is studied. Influence of extra bodyforces is also investigated by use of ferrofluid drops and magnetic field. Datas are obtained through LDV and given for fluid and particles mean and fluctuant velocities. Presence probability repartition for particles downstream the injection is obtained by LDV counting.
Velocity and Drop Size Measurements in Fuel Sprays in a direct injection diesel engine
Authors: Pitcher Graham , Wigley Graham , Saffman Mark 
Published: December 2004

AbstractHigh‐pressure injection fuel sprays have been investigated in a single‐cylinder research Diesel engine using the laser and phase Doppler anemometry techniques to measure fuel droplet velocities and sizes and their spatial and temporal distributions within the spray. The measurements relate to the determination of the droplets' axial velocity component and diameter on the spray centre line between 75 and 100 nozzle diameters downstream from a single‐hole injector nozzle. The experimental program covered the use of both Diesel and a non‐combusting alcohol fuel. Measurements at radial locations in the spray and at different fuel loads were also taken for the alcohol fuel. Temporally resolved measurements of droplet velocity and size are presented together with time — averaged values in such a way as to isolate the contributions from the leading and trailing regions of each spray and identify two different break — up mechanisms occurring as suggested by a conceptual model of the spray behaviour.
Prediction of Gas‐Particle Turbulent Free or Confined Jet Flows
Authors: de Azevedo Jaão Luis Toste , Pereira José Carlos Fernandes 
Published: December 2004

AbstractNumerical predictions of two‐phase turbulent gas‐particle flows are reported for two test cases: for a plane jet and for an axisymmetric free jet. The numerical algorithm uses an Eulerian approach for the fluid phase and the particulate phase is described by using a Lagrangian stochastic model. The k‐ε turbulence model was used to characterize the length and time scales of the fluid. In the plane confined jet the influence of the restitution coefficient on the statistical distribution of velocities was analysed. Particular attention was dedicated to the ε equation corrections regarding the problem of the free jet spreading rate overprediction. The influence of the particle tangential momentum equation on the prediction of particle concentration near the centre line in axisymmetric free jets was also analysed. Comparisons between predictions and experimental data are presented and shown to be satisfactory regarding the incomplete knowledge of turbulent multiphase flows.
A Statistically Conditioned Averaging Formalism for Deriving Two‐Phase Flow Equations
Authors: Aliod Ricardo , Dopazo C. 
Published: December 2004

AbstractA statistical formalism overcoming some conceptual and practical difficulties arising in existing two‐phase flow (2 PHF) formulations and modelling techniques is introduced. Basic theorems for the case of dispersed 2 PHF are presented. Phase interaction terms with a clear physical meaning enter the equations and this formalism provides some guidelines to avoid closure assumptions or to close those terms rationally. Continuous phase averaged continuity, momentum, turbulent kinetic energy and turbulence dissipation rate equations can be rigorously and systematically obtained with this methodology in a single step. These equations display a structure similar to that for single‐phase flows. It is also assumed that the dispersed phase is well described by a "Boltzmann‐type" equation and Eulerian "continuity", momentum and fluctuating kinetic energy equations for the dispersed phase are obtained. A k‐ε turbulence model for the continuous phase is used. A gradient transport model is adopted for the dispersed phase fluctuating fluxes of momentum and kinetic energy. Closure assumptions are proposed for the phase interaction terms. This model is then used to predict the behaviour of an axisymmetric turbulent jet of air laden with solid particles varying in sizes and concentrations. Numerical results compare reasonably well with available experimental data.