bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fracture toughness of acrylonitrile‐butadiene‐styrene byJ‐integral methods
Authors: Lu Ming‐Luen , Lee Chang‐Bing , Chang Feng‐Chih 
Published: December 2004

AbstractThe fracture toughness of acrylonitrile‐butadiene‐styrene (ABS) was determined by threeJ‐integral methods, ASTM E813‐81, E813‐87, and by hysteresis. The criticalJvalues (J1c) obtained are fairly independent of the specimen thickness, ranging from 10 to 15 mm. ASTM E813‐81 and hysteresis methods result in comparableJ1cvalues, whereas the ASTM E813‐87 was ∼40% to 50% higher. The critical displacement determined from the plots of hysteresis (energy or ratio) and the true crack grow length vs. displacement are close. This indicates the critical displacement determined by the hysteresis method is indeed the displacement at onset of crack initiation, and the correspondingJ1crepresents a physical event of crack initiation. The elastic storage energy. The input energy minus the hysteresis energy, is the most important factor in determining the onset of crack initiation. The critical elastic storage energy (at the beginning of crack growth) was found close to theJ1cobtained from the E813‐81 or the hysteresis method.
Interfacial structure in reacting poly(methyl methacrylate)/polycarbonate polymer blends
Authors: Yoon H. , Han C. C. 
Published: December 2004

AbstractThe snall angle neutron scattering (SANS) technique has been used to study the interfacial structure development in poly(methyl methacrylate)/polycarbonate (PMMA/PC) blends through transesterification. We found: (1) Development of interfacial structure through transestrification at the phase separated domain interfaces are observed at T ≤ 200°C. At T ≥ 215°C, because of a higher transesterification rate, the melting of domains is observed together with very weak scattering by interfacial structure. (2) Interfacial thickness ti increases with time and reaches a plateau value of ti at 32.5 ± 2.4 Å and 29.6 ± 3.7 Å for 180°C and 200°C, respectively. (3) The internsity profiles at 190°C and long times shows the formation of spherical domains similar to those reported by Rabeony et al. (1). These may be caused by the crosslinking effect of the transesterification reaction between PMMA and PC.
Curing of thermosetting polymers by an external fluid
Authors: Reboredo M. M. , Vazquez A. 
Published: December 2004

AbstractA theoretical model is proposed for curing thermosetting polymers. The following heat transfer mechanisms are taken into account: convection through the heated fluid‐mold interface, conduction through the resin, and heat generated by chemical reaction. To study the influence of the convective heat in the curing step of the polymers, different external heating fluids are considered. Several chemical systems are used in the simulation. The results show that an apoxy requires precise control of thermal runaway. Criteria for processability are established and they provide a cycle time without promoting a damaging exotherm.
Mixing in reactive extrusion of low‐density polyethylene melts: Linear vs. branched
Authors: Polance R. , Jayaraman K. 
Published: December 2004

AbstractThe melt flows of linear low‐density polyethylene (LLDPE) and branched low‐density polyethylene (LDPE) have been compared in a fully intermeshing co‐rotating twin‐screw extruder. The polyethylene melts were selected in order to investigate the effects of the melt rheology on the mixing. Their shear vicosity curves are quite similar, but the LDPE has a markedly higher apparent extensional viscosity over a wide range of stretch rates. The stagger of the paddles in the mixing zone of the extruder creates axial pressure‐driven axial flow can have significant extensional strain components. Residence time distributions obtained in the melt zones of the extruder with tracer dye reveal that the LDPE has a narrower residence time distribution than the LLDPE over a wide range of operating conditions. The axial dispersion for the LDPE is significantly lower than the axial dispersion for the LLDPE. This is attributed to the greater extensional viscosity of the LDPE. During the reactive extrusion process, solid maleic anhydride and polyethylene were added at the feed port but the peroxide provides better control of the crosslinking reaction. Residence time distributions measured for the chemically more reactive LLDPE melt indicate reduced levels of axial mixing with reaction. The reduction in mixing is due to a crosslinking reaction that occurs in parallel to the grafting reaction. This change in mixing is smaller than the difference in mixing between LDPE and LLDPE.
The control of miscibility of PP/EPDM blends by adding lonomers and applying dynamic vulcanization
Authors: Kim Youngkyoo , Cho Won‐Jei , Ha Chang‐Sik , Kim Wonho 
Published: December 2004

AbstractThe control of miscibility for isotactic polypropylene (PP) and ethylene‐propylene‐diene terpolymer (EPDM) has been attempted by adding poly(ethylene‐comethacrylic acid) (EMA) ionomers and by applying dynamic vulcanization. The rheological properties, crystallization behavior, and morphology of the dynamically vulcanized EPDM/PP/ionomer ternary blends were investigated with a Rheometrics dynamic spectrometer (RDS), a differential scanning calorimeter (DSC), and a scanning electron microscope (SEM). Two kinds of EMA ionomers neutralized with different metal ions (Na+ and ZN++) were investigated. Blends were prepared on a laboratory internal mixer at 190°C. Blending and curing were performed simultaneously, i.e., EPDM was vulcanized with dicumyl peroxide (DCP) in the presence of PP/ionomer. The composition of PP and EPDM was fixed at 50/50 by wt% and the contents of EMA ionomer were vaired from 5 to 20 parts based on the total amount of PP and EPDM. It was found that the addition of ionomers and the application of the dynamic vulcanization were effective in enhancing the miscibility of PP and EPDM. The structure of the blends was controlled by the following three component phases, i.e., the phase of the dynamially valcanized EPDM, PP, and Zn‐neutralized ionomer. The ternary blends showed more miscibility than the PP/EPDM binary blend. This is due to the thermoplastic interpenetrating polymer network (IPN) of the ternary blends. The structure and properties of the ternary blends differed, depending on the types and contents of ionomer, i.e., the ternary blend containing Na‐neutralized ionomer did not show a thermoplastic IPN structure clearly, even though the blend was prepared by dynamic vulcanization. The ternary blend containing Zn‐neutralized ionomer clearly showed the behavior of a thermoplastic IPN when the contents of ionomer and DCP were 15 parts and 1.0 part, respectively.
Transesterifications in a polyblend of poly(butylene terephthalate) and a liquid crystalline polyester
Authors: Jo Byung‐Wook , Chang Jin‐Hae , Jin Jung‐Il 
Published: December 2004

AbstractTransesterfication between a liquid crystalline polyster and poly(butylene terephthalate) was followed quantitatively by analyzing 13C‐NMR spectra of the 50:50 blend after heat treatmetn at 290°C for varying lengths of time. Differential scanning nalysis was employed to follow the interchange reactions. From analysis of triad sequences of the transesterified blends, it was clear that measurable exchange reactions occurred when the blend was kept at 290°C for 20 min. The distribution of sequences tends to approach that of a statistical binary copolymer as the heat treatment period is increased. The results ontained from this investigation show that polyblends between an LC polyesterand conventional polyesters must be handled carefully. Otherwise, ester interchange reactions are inevitable.
Effect of die geometry on the structural development of a thermotropic liquid crystalline polymer in a thermoplastic elastomer matrix
Authors: Seo Yongsok , Hwang Seung Sang , Hong Soon Man , Park Tae Suk , Kim Kwang Ung 
Published: December 2004

AbstractThis study investigates deformation of a thermotropic liquid crystalline polymer (TLCP) in different die geometries. Blends of aTLCP with a thermiplastic elastomer of EPDM were made in a twin‐screw extruder. Morphological observation of the extruded blends demonstrates the complimentary effect of shear in the die exit on dispersed phase deformation and fibril formation. Shear strain can affect fibril formation for a relatively large dispersed phase in the region close to the die wall. However, the main role of shearing is in breaking up the larger particles and initial polydomain structure. A strong elongational deformation on the blended melt after the die exit is required, and fine microfibrils normally obnserved in in situ composites were not easily formed by shear deformation only in the die.
Mixing and morphological transformations in the compounding process for polymer blends: The phase inversion mechanism
Authors: Shih Chi‐Kai 
Published: December 2004

AbstractThis study reports on the progression of processes occurring in polymer blends during mixing. For the polymer pellet blends studied, an abrupt phase inversion was observed simultaneous with attainment of maximum torque in the batch mixer. A four‐step phase inversion mechanism is described as predominant where dissipative mix‐melting of the polymer system occurred in the mixing process.
A simple model for heat transfer inside an extrusion die
Authors: Wu Ping‐Yao , Huang Lee‐May , Liu Ta‐Jo 
Published: December 2004

AbstractA simple model based on the lubrication approximation has been developed to analyze heat transfer of power‐law fluids inside an extrusion die. This model can effectively predict the influence of temperature variations and other production alterations on flow uniformity. The predictions of this model are compared with those based on three‐dimensional finite element simulation, and the agreement is satisfactory. The optimal design concept can be incorporated into this model so that a specially designed choker bar can be inserted into the extrusion die to reduce flow nonuniformities. The shape of the choker bar is initially suggested by the lubrication model; minor corrections through the three‐dimensional finite element simulation are then introduced so that a choker bar can be properly constructed to eliminate flow nonuniformities.
A unified K‐BKZ model for residual stress analysis of injection molded three‐dimensional thin shapes
Authors: Chang Rong‐Yeu , Chiou Shiaw‐Yuh 
Published: December 2004

AbstractThe flow‐induced and thermally induced residual stresses during injection molding of a thin part with complex geometries are predicted. The injection molding precess was considered to consist of a filling and a post‐filling stage (packing coupled with cooling). Additionally, the analysis were applied to successive stages of the process. The model takes into account the viscoelasticity of the molding polymer, which has been neglected in most previous works, because of the complexity of its inclusion. A unified K‐BKZ viscoelastic constitutive model, capable of modeling both the fluid‐rubbery state and the glass state of amorphous polymers, was employed for simulating this problem. For the flow‐induced residual stress predictions of the filling stage, a quasi‐steady state approximation was employed for each element of the part, for the calculation of stress profile and subsequent stress relaxation after cessation of flowf. Stress calculations were provided for the thermally induced residual stress predictions of the post‐filling stage. These explicit calculations led to the results of pressure and temperature distributions of the part during the post‐filling stage into the viscoelastic constitutive model. Additionally, the pressure and asymmetric temeprature profiles of the post‐filling stage were based on finite element packing analysis coupled with a boundary element cooling analysis of the molding process. Finally, the total residual stress in the part was obtained via superposition of the flow‐induced and thermally induced residual stresses. An example is provided to demonstrate the entire concept. The results indicate that thermally induced residual stress is higher than the flow‐induced residual stress by one to two orders of magnitude.
Stretch and inflation of hyperelastic membranes as applied to blow moldiing
Authors: Khayat R. E. , Derdouri A. 
Published: December 2004

AbstractThe free and confined inflation of isotropic homogeneour membranes of general shape are considered. The material is assumed to obey the Mooney‐Rivin constitutive model, and the resulting partial differential equations, governing the deformation field, are solved using a Galerkin based finite‐element procedure. The method is illustrated through examples of both free and conflined inflation, as well as simulationeus stretch and inflation. Measurements were carried out on the final thickness distributionof containers blow‐molded inour laboratory. These containers typically cover a wide range of geometry adn size, including bottles with handles. Comparison between theory and experiment leads generally to good agreement, despite the limitation of the membrane hypothesis.
Theory of competition between breakup and coalescence of droplets in flowing polymer blends
Authors: Fortelný Ivan , Živný Antonín 
Published: December 2004

AbstractThe Smoluchowski equation for the breakup and coalescence of dispersed droplets has been solved for flowing polymer blends. A scaling form for the distribution of droplet sized derived and published for a system of clusters with fragmentation and coagualation was used in our dervation. Equations are developed here for the average droplet size and for the characteristic time of transition to steady state flow of blends with a high content of the dispersed phase. Expressions reasonably describing the average size of droplets for all concentrations were obtained by a theory modification. Measured dependences of droplet size on the blend composition can be matched only if simultaneous collisions of three and more droplets are considered. The results of the theory indicate that the mechanism of droplet breakup (formation of pieces with the same or different volumes) has only a small effect on their average size in concentrated systems. The dependence of droplet size on the shear rate in flow is determined by properties of the blend components, and is generally nonmonotonic.
Impact testing of polypropylene blends and comosites
Authors: Pukánszky Béla , Maurer Frans H. J. , Boode J.‐W. 
Published: December 2004

AbstractPolypropylene (PP) composites containing 0.30 vol% of talc filler, in addtion to blends modified with an ethylene‐propylene copolymer (EPR) elastomer were prepared and their fracture resistance was determined by the standard Ixod impact test and by a fracture mechanics technique. Effects of composition, type of modification, specimen size, and temperature were studied. The validity of linear elastic freacture mechanics (LEFM) conditions were checked: It was shown that under the conditions applied they can be satisfied even twith specimens of reasonable size (4 × 10 × 80 mm) prepared by conventional processing techniques. Calculations of minimum specimen thickness must be carried out, with material properties obtained under the conditions of impact. For heterogeneous blends and composites yield stress should be corrected for the effect of decreasing load‐bearing cross section. Linearity of the fracture energy (U) vs. BDϕ or U vs. B(D ‐ a) plots is not a proof for either elastic of plastic fracture. The composition dependence of fracture properties proved to be practicaly independent of specimen size, temperature, or measurement technique.
Dry Etching of Electronic Oxides, Polymers, and Semiconductors
Authors: Pearton Stephen J. , Norton David P. 
Published: December 2004

AbstractSummary: A review is given of commonly used plasma etching techniques and typical plasma chemistries for patterning electronic oxides, such as SiO2, HfO2, MgO, Sc2O3, and ZnO, polymers, and several important semiconductors (Si, GaAs, and InP). Issues that affect the reproducibility and manufacturability of etching processes, such as loading effects, endpoint detection, and etch selectivity, are also discussed. Finally, disruption to the etched surface in the form of polymer deposition, plasma residues, ion‐induced displacement damage, or preferential loss of one of the lattice elements during the etch process are covered.SEM micrograph of features etched into a ZnMgO/ZnO structure using a BCl3/Cl2/Ar ICP plasma.imageSEM micrograph of features etched into a ZnMgO/ZnO structure using a BCl3/Cl2/Ar ICP plasma.
Surface Modification of PET Films Using Pulsed AC Plasma Polymerisation Aimed at Preventing Protein Adsorption
Authors: Ademovic Zahida , Wei Jiang , Winther‐Jensen Bjørn , Hou Xiaolin , Kingshott Peter 
Published: December 2004

AbstractSummary: We utilise pulsed AC plasma polymerisation to create thin films that either contain reactive acid functional groups (by deposition of maleic anhydride (MAH) followed by hydrolysis) or are poly(ethylene glycol) (PEG)‐like in nature (by using diethylene glycol vinyl ether (DEGVE) as monomer). The MAH films were further modified with PEG chains using a two‐step wet chemical method. For the DEGVE films the plasma power was varied in order to change the degree of monomer fragmentation and thus retention of PEG‐like character. The chemistry of the surfaces was determined using Fourier‐transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and time‐of‐flight secondary ion mass spectroscopy (ToF SIMS). Significant reduction (up to 90%) in protein adsorption was achieved by the plasma polymer surfaces as determined using 125I‐radiolabelled fibrinogen adsorption experiments.AC plasma experimental setup.imageAC plasma experimental setup.
Confederated Miniature Sieves as an Alternative to Nest Sieving
Authors: Kaye Brian H. , Clark Garry G. 
Published: December 2004

AbstractMiniaturized sieves (1/2 inch diameter) can be mounted in a spinning riffler system to obtain small representative powder samples which eventually can be sieved in situ without removing the miniature sieves from the riffler system. By mounting several different aperture sieves around the riffler a confederation of miniature sieves could replace nest sieving. The sieving surface for these new sieves is so small compared to that of the traditional eight inch sieve that one could consider using the more expensive electroformed sieving surfaces for all test sieves in the quality control laboratory.
Particle Size Analysis of Some Difficult Measurable Systems
Authors: Hoffmann Brigitte , Bernhardt Claus 
Published: December 2004

AbstractKnowledge of the granulometric behaviour of dispersed systems is vital for a full and complete characterisation. Despite the variety of methods and devices which have been developed for this purpose, difficulties frequently arise in the practical determination of particle size distribution. In this paper it is shown, by means of examples, how measurements for surface modified and porous particles can be influenced by the behaviour of the material, and which approaches exist to obtain accurate values by taking this into account.
Model‐Based On‐Line Analysis of Disperse Systems on the example of digital fourier spectroscopy
Authors: Weiss Martin , Schmidt Marc , Bottlinger Michael 
Published: December 2004

AbstractWith progress in the advancement of measuring techniques and information processing, it is increasingly possible to analyse even complex signals with on‐line methods. After fundamental considerations concerning the evaluation of such signals, digital Fourier spectroscopy is explained as an example of a new development. With this method the image of a particle collection will be transformed by the Fourier transformation. Methods such as used with laser diffraction spectrometry are applied to calculate back to the particle size distribution. After a description of the principles of the procedure, its application is demonstrated by different examples. It can be shown that digital Fourier spectroscopy is superior to conventional image analysis methods especially if the particle density in the image is high and the particles overlap. In a further development step it should be possible to determine the particle size distribution of the bulk from an image of its surface.
Non‐Invasive Size‐Control of Pneumatically Conveyed Particles
Authors: Block Franz Rudolf , Obst Heike‐ursula 
Published: December 2004

AbstractInvestigations on the size control of pneumatically conveyed coarse particles were carried out using a microphone which detects the structure‐borne sound caused by the impact of the particles on the pipe wall. Modes of eigenvibrations of the pipes are excited up to a maximum frequency, which decreases with increasing particle size. In an assembly of different sized particles, the lower frequencies are more stimulated as the fraction of larger particles increases. Changes in the particle size distribution are detected by analysing the intensities of the vibration modes which are set up in the walls of the tube by particle impact. One application is the monitoring of the upper range of a particle size distribution.
Global Analysis of Dynamic Light Scattering Autocorrelation Functions
Authors: Provencher Stephen W. , Štêpánek Petr 
Published: December 2004

AbstractDynamic light scattering has become a standard technique of investigating colloidal suspensions and polymer solutions. The experimental field autocorrelation function ĝ1(t) can often be well modelled by a Laplace transform relating ĝ1(t) to a distribution of decay times A(τ). In simple systems A(τ) can usually be directly related to a distribution of molecular weights, particle sizes, diffusion coefficients or other physically relevant quantities, With constrained regularization methods, the parameter‐free estimation of A(τ) has become straightforward. In complex systems, the resulting A(τ) may contain several components the identification of which is not always obvious. The problem often originates in a superposition of diffusive and angle‐independent components that have different variations of their respective decay times with the scattering vector. A method is presented based on a simultaneous fit of several autocorrelation functions measured at several different scattering angles, which, using simple and reasonable assumptions, yields a robust analysis of the spectra of decay times. The application of the method is illustrated on simulated autocorrelation functions and also on real experimental data obtained on a variety of different polymer systems.
The Interaction of the Efflux of Solid Propellants with Nozzle Materials
Authors: Klager K. 
Published: December 2004

AbstractProgress in obtaining solid composite propellants with highest specific impulse caused severe problems with materials such as graphite used in the construction of insulation and nozzles in solid rockets. Refractory metals provide relief but at the expense of the desired and gained performance increase in propellants. On the basis of data obtained by experimental firings and thermodynamic analysis it was demonstrated that the primary cause of graphite removal in solid rocket motor nozzles is dependent on pressure and on chemical attack by certain species of the exhaust gas. The most damaging gases are those which react with carbon to form carbon monoxide. The chamber flame temperature does not directly affect graphite removal. Analysis of data indicates a good correlation of propellant composition and oxygen balance of the initial propellant from which the exhaust gases are generated. Application of these findings make it possible to select propellant formulations with minimum corrosive action on graphite.