bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical simulation and experimental verification of nonisothermal flow in counter‐rotating nonintermeshing continuous mixers
Authors: Ishikawa Takeshi , Kihara Shin‐Ichi , Funatsu Kazumori , Amaiwa Teruo , Yano Kazunori 
Published: April 2004

AbstractWe have developed non‐Newtonian and nonisothermal flow simulation codes in twin screw extruders using the finite element method. These codes can simulate the fully filled part of several kinds of screw elements, such as full flight screws, kneading discs, rotors, and their combinations. In this paper, we describe how we applied them to simulate a counter‐rotating nonintermeshing continuous mixer, LCM100G, by Kobe Steel, Ltd. The LCM100G is a Farrel‐type continuous mixer that has two mixing stages. We focused on the second mixing stage, since the flow domain of this stage is almost filled by polymer melts. Numerical simulations at various flow rates were performed. We also carried out experimental observations to verify the numerical simulations. Pressure and temperature profiles from the simulations were found to be in good agreement with the experimental results.
Mechanical properties of acrylic based latex blend coatings
Authors: Agarwal N. , Farris R. J. 
Published: April 2004

AbstractA complete characterization of the mechanical properties of acrylic based latex blend coatings comprising hard (Tg = 45°C) and soft (Tg = −5°C) phases is presented. Although clear and transparent in appearance, these blends remain phase separated through the entire range of compositions based on their hard phase content. Blends with less than 50% hard phase (soft blends) show a typical rubber‐like behavior with large elongation to break and low stiffness, whereas those with more than 50% hard phase (hard blends) exhibit a progressively glassy behavior. The values of effective Young's moduli and Poisson's ratios lie within the bounds calculated from Hashin‐Shtrikman models and exhibit a sigmoidal shaped profile as a function of composition, in close agreement with the solutions of Hill‐Budiansky equations. These results, along with interpretations based on a percolation theory, indicate that a phase inversion to a continuous hard matrix from the soft one occurs around 30–40% hard phase content, a conclusion further supported by scanning electron micrographs of the fracture surfaces.
The Izod impact strength of modified methyl methacryate/styrene copolymer molding and the toughening mechanism
Authors: Takaki Akira , Yamazaki Kaoru , Narisawa Ikuo 
Published: April 2004

AbstractTo better understand the Izod impact strength of modified poly(methyl methacrylate‐co‐styrene), the fracture mode and whitened state of molded specimens were studied. The Izod impact strength was closely related to the amount of whitened area, and the degree of whiteness improved with increasing whitened area and degree. The whitened area was strongly related to the transition rate for shear yielding in tensile testing. The degree of whitening was strongly related to the elongation at break in low‐speed tensile testing. Transmission and scanning electron microscopy were also used to develop an understanding of the mechanisms of energy absorption and the fracture process.
Effects of coupling agents on the oxidation and darkening of cellulosic materials used as reinforcements for thermoplastic matrices in composites
Authors: Urreaga J. Martínez , Matías M. C. , De La Orden M. U. , Munguía M. A. Lechuga , Sánchez C. González 
Published: April 2004

AbstractOxidation and darkening occur during the processing of composites made from thermoplastic matrices and cellulosic reinforcements. We have studied the effects of several coupling agents on both the oxidation and darkening of cellulosic materials at temperatures close to those used in the processing of cellulose‐reinforced thermoplastics. A maleated polypropylene wax (Epolene E‐43TM) and two silanes (N‐2‐aminoethyl‐3‐aminopropyltrimethoxy silane and methyltrimethoxysilane) were used as coupling agents. Oxidation was measured by Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy. Standard colorimetry was used to measure darkening. Coupling agent effects depend on the nature and extent of cellulose modification achieved by treatments and the nature of the coupling agent. Epolene wax E‐43 produced scarce effects on both the oxidation and darkening of cellulosic materials at 200°C. Only for longer oxidation times was an increase in oxidation and darkening observed in E‐43‐treated samples. Silane coupling agents inhibited the formation of carbonyl and carboxyl groups for shorter oxidation times. The diaminosilane produced a stronger darkening, probably due to a chemical reaction that generated new chromophores containing CN bonds.
Chemorheological analysis of an epoxy‐novolac molding compound
Authors: Hsieh T. H. , Wang T. L. , Ho K. S. , Wang Y. Z. 
Published: April 2004

AbstractThe chemorheological behavior of an epoxy‐novolac molding compound was studied by a combination of differential scanning calorimetry and dynamic rheological measurements. Based on a modified version of Kamal and Sourour's kinetic expression, a procedure aiming at the phenomenological description of cure kinetics was developed. In combination with our kinetic study, an empirical Arrhenius‐type expression was adopted for the description of the dependence of complex viscosity on temperature, frequency, and conversion by allowing the pre‐exponential factor and the flow activation energy to be frequency‐ and conversion‐dependent. At low conversions (α < ∼0.05), the system behaves approximately as a thermoplastic material; at higher conversions, the rheological behavior of the system was dominated by the extent of cure reaction.
Morphology and mechanical properties of blends of polycarbonate and segmented copolyetherester
Authors: Gaztelumendi M. , Nazábal J. 
Published: April 2004

AbstractThe solid state features and the mechanical properties of melt mixed polycarbonate (PC)/segmented copolyetherester (CPEE) blends were investigated over the full composition range. The partially crystallized blends were composed of two amorphous phases but with only small composition differences in most blend compositions. The specific interactions, and the free volume decreases observed, gave rise to a decrease in the γ relaxation strength. The dependence on composition of both the decreases in the γ relaxation strength and in the free volume, as well as that of the modulus of elasticity and yield stress, were very similar to those of miscible blends. The nature of the amorphous phases of the blends at room temperature, changed from glassy to partially rubbery as the CPEE content was increased. As a consequence, to discuss the plots of the properties against composition at room temperature, the properties of the rubbery materials in the glassy state had to be determined. The synergistic modulus and yield stress behaviors appeared to be mainly determined by the γ relaxation strength and specific volume decrease, and that of ductility additionally by the Tg change.
The effect of strain rate, temperature, and molecular mass on the tensile deformation of polyethylene
Authors: Hillmansen S. , Hobeika S. , Haward R. N. , Leevers P. S. 
Published: April 2004

AbstractConventional tensile testing applied to high density polyethylene can lead to erroneous impressions of the tensile response of the material due to a local reduction in cross section of the sample. Several workers have developed novel tensile testing techniques to measure the response of a small element as it deforms. The true stress true strain curve that results describes tensile deformation of the material in a geometry‐independent manner. Here, results from previous workers, together with some of our own, are interpreted in terms of the Haward‐Thackray spring‐dashpot model, in which the spring defines a strain hardening process according to the theories of high elasticity and the dashpot describes a strain‐independent viscous process. The effects that temperature, strain rate, and molecular mass have on each process are investigated. For a pipe‐grade, modified high density ethylene copolymer, sufficient data have been measured to interpret the effects of strain rate and temperature in accordance with an Eyring flow process, where the parameters for the two mechanisms are found to be similar.
Thermal expansivity and thermal conductivity of amorphous thermoplastic polyimide and polymer liquid crystal blends
Authors: Brostow Witold , D'Souza Nandika Anne , Gopalanarayanan Bhaskar , Jacobs Elizabeth 
Published: April 2004

AbstractLinear thermal expansivities αL and thermal conductivities of polyimide (TPI) and polymer liquid crystal (PLC) blends were studied. The glass transition temperatures Tg of our amorphous TPI and the PLC are, respectively, 240 and 220°C. The addition of the PLC induces orientation through the channeling process, as predicted by an extension of the Flory statistical‐mechanical theory of PLCs (27). Channeling was observed at PLC concentrations as low as 5 wt%. Thermal conductivity decreases with the addition of the PLC to the TPI. The anisotropic expansivity of the blends shows a strong dependence on PLC concentration and orientation direction. The pure PLC shows a maximum on the along‐the‐flow expansivity vs. temperature curves and also negative αL values. TPI addition moves the expansivities to positive values, but the maximum persists, even for 5% PLC only.
Preparation and properties of thermoplastic starch‐polyester laminate sheets by coextrusion
Authors: Wang L. , Shogren R. L. , Carriere C. 
Published: April 2004

AbstractThe effects of extrusion and formulation variables on the structure and properties of starch‐polyester laminates were examined. Three‐layer polyester/starch/polyester sheets were prepared using a twin‐screw extruder for the starch/water center layer, a single screw extruder for the outer polyester layers and a feedblock and coathanger type sheet die. Overall sheet and coating thicknesses were more uniform as coating polymer (poly(ε‐caprolactone), PCL) viscosity decreased (lower molecular weight), starch melt viscosity increased (lower moisture) and feedblock/die temperature increased. Peel strengths were 1 to 2 orders of magnitude larger for high than low molecular weight PCL. High peel strengths were associated with rough, wavy interfaces (interfacial instability). Addition of plasticizer such as glycerol and sorbitol to the starch decreased peel strengths. Peel strengths varied little with type of polyester coating, except, perhaps, for polylactic acid and polyesteramide, which were more difficult to peel. Some possible applications of laminated starch sheets include food packaging and controlled release of drugs, pesticides, insect diets, etc.
Numerical simulation of pressure and velocity profiles in kneading elements of a co‐rotating twin screw extruder
Authors: Bravo V. L. , Hrymak A. N. , Wright J. D. 
Published: April 2004

AbstractThe objective of this work is to validate, via comparison with available experimental data, the results obtained from the numerical simulation of polymer melt flow in the kneading disc section of an intermeshing co‐rotating twin screw extruder. A quasi‐steady state 3‐D solution of the conservation equations via the finite element method was obtained, and comparisons were made with experimental pressure profiles measured by McCullough and Hilton (1) on various kneading block elements. These measurements helped provide understanding of the flow patterns developed within the unit and provided a comprehensive approach of validating the numerical model. Results confirm the importance of a fully 3‐D model for this type of geometry, where the model predicts the development of flow patterns in the radial directions and within the intermeshing region. The influence of inlet and outlet boundary conditions was studied and it was determined that they play an important role in the physical significance of the model solution. Comparisons of the simulation results with experimental data by McCullough and Hilton (1) for two different configurations of kneading discs showed good agreement, with some differences in the peaks of pressure produced at the narrow clearances encountered in intermeshing co‐rotating twin screw extruders. Differences between simulation and experiments are attributed to a number of factors. It is difficult to measure the very steep pressure gradients generated over small lengths. The assumptions of isothermal flow and quasi‐steady state may cause an over‐prediction of the pressure peaks. Simulation results describe the general trends and produce good quantitative agreement in most of the kneading disc region.
Isothermal transient startup of a starved flow modular co‐rotating twin screw extruder
Authors: Kim Eung Kyu , White James L. 
Published: April 2004

AbstractA model for flow start‐up of a Newtonian liquid in an initially empty modular selfwiping co‐rotating twin screw extruder is developed. The changes of length of fill in front of the die and kneading disc block elements and output flow rate with time were predicted for various modular screw configurations. Experiments were also carried out on a laboratory modular machine with windows to verify predictions. Generally, good agreement with the flow analysis was found.
Melt viscoelasticity of polyethylene terephthalate resins for low density extrusion foaming
Authors: Q̧uintans J. , Xanthos M. , Dey S. K. , Yilmazer U. 
Published: April 2004

AbstractThe rheological properties of conventional polyethylene terephthalate (PET) resins are not particularly suitable for low density extrusion foaming with physical blowing agents; as a result, chemically modified resins through chain extension/branching reactions are often used. Such resins have overall higher melt viscosity and higher melt strength/melt “elasticity” than unmodified materials. In this work, following a review of the prior art on PET chemical modification, an unmodified and a chemically modified resin were selected and characterized for their melt viscoelastic properties including shear and dynamic complex viscosity over a broad shear rate/frequency range, storage and loss modulus, and die swell. Certain rheological models were found to provide better fits of the entire viscosity curve for the unmodified vs. the modified resin. Foamed extrudates having variable densities (from about 1.2 to 0.2 g/cc), were prepared by carbon dioxide injection in monolayer flat sheet extrusion equipment. Foams with increasingly lower density, below 0.5 g/cc, were obtained by increasing gas pressure only in the case of the chemically modified resin. The effects of variables such as concentration of the physical blowing agent, resin rheology, resin thermal properties and choice of process conditions are related to product characteristics including density, cell size and crystallinity.
Morphology–mechanical property relations in syndiotactic polypropylene (sPP) fibers
Authors: Loos Joachim , Schimanski Tilo 
Published: April 2004

AbstractMechanical properties of melt‐spun syndiotactic polypropylene single filament fibers were studied in relation to their formation conditions. Depending on the processing parameters, fibers with rubber‐elastic properties can be prepared. Dynamic mechanical studies show almost unchanged rubber‐elastic properties after 1000 test cycles. A model of the fiber morphology is introduced to explain the rubberelastic behavior: small micel‐like crystals containing molecules in the planar alltrans conformation act as physical crosslinks in the amorphous matrix.
Engineering analysis of crosslinking polymerization of diallyl lsophthalate
Authors: Znoj Bogdan , Matjažkrajnc  , Barborič Franci , Golob Janvit 
Published: April 2004

AbstractA kinetic model for crosslinking free radical polymerization of DAIM (monomer diallyl isophthalate) with initiator CHPC (dicyclohexyl peroxydicarbonate) is developed. An improved version of Batch and Macosko's model was used to describe the initiator efficiency (f) and the active radical fraction (Fact). The experimental data of allyl and carbonyl group consumption are used for the optimization of the model and calculating of f and Fact. From the developed kinetic model and experimental results, obtained by FT‐IR measurements of monomer conversion, the introduction of the Fact was proved. Application of this model may be of use in process modeling of DAIM and other crosslinking polymerizations with CHPC as initiator.
Simulation of a mold‐cooling process for gas‐assisted injection molded parts designed with a top rib on the gas channel
Authors: Chen Shia‐Chung , Hu Sheng‐Yan , Chao Sher‐Meng , Chien Rean‐Der 
Published: April 2004

AbstractThe same CAE model used for the filling and packing stage in the gas‐assisted injection molding (GAIM) process simulation was also applied to simulate the cooling phase. This was made possible by using the line source method for modeling cooling channels. The cycle‐averaged and cyclic transient mold cavity surface temperature distribution within a steady cycle was calculated using the three‐dimensional modified boundary element technique similar to that used in conventional injection molding. The analysis results for GAIM plates of a semicircular gas channel design attached with a top rib are illustrated and discussed. It was found that the difference in cycle‐averaged mold wall temperatures may be as high as 10°C, and within a steady cycle, part temperatures may also vary by about 15°C. The conversion of the gas channel into equivalent circular pipe and further simplification into two‐node elements using the line source method not only affects the mold wall temperature calculation very slightly but also reduces the computer time by 93%. This indicates that it is feasible to achieve an integrated process simulation for GAIM under one CAE model, resulting in great computational efficiency for industrial application.
Relationship between isothermal and dynamic cure of thermosets via the isoconversion representation
Authors: Atarsia A. , Boukhili R. 
Published: April 2004

AbstractThis study deals with the cure of thermoset resins used in the pultrusion of fiber reinforced composites. The objective was to predict the degree of cure under non‐uniform time‐temperature profiles. A simple procedure using differential scanning calorimetry results was developed for predicting the degree of cure vs. time under isothermal conditions from dynamic DSC tests and vice versa. The principal feature of the procedure is the transformation of the degree of cure vs. time curves obtained under isothermal or dynamic DSC conditions into isoconversion curves as time vs. temperature or time vs. heating rate diagrams. The proposed procedure is validated with isothermal and dynamic DSC results from epoxy and polyester resin formulations used in the pultrusion of fiber reinforced composites. The agreement between predictions and experiments was very good and the extension of the procedure for predicting the cure under non‐uniform temperature profiles as in pultrusion seems to be feasible.
Fatigue crack growth in polyethylene: Material dependence. II: Effects of time “off‐load”
Authors: Harcup J. P. , Duckett R. A. , Ward I. M. , Capaccio G. 
Published: April 2004

AbstractFatigue crack growth rates have been determined for a series of polyethylenes through the application of various periodic loading and unloading programs in which the load was held constant for tON seconds and unloaded to a lower constant value for tOFF seconds in each cycle. The crack growth rate, da/dN, was given by

where the parameters γ, k, β and n are material dependent and β and n are also geometry dependent. It was found that β and n described the closure of the crack during the unloaded period as well as the kinetics of the increase in crack growth rate. It is proposed that this equation is consistent with a mechanism in which the crack growth rate increases because of damage sustained by the craze during the unloaded period as it closes and is compressed under the recovery of the surrounding material.
Correlation and modeling of the occurrence of different crystalline forms of isotactic polypropylene as a function of cooling rate and uniaxial stress in thin and thick parts
Authors: Choi Cheol‐Ho , White James L. 
Published: April 2004

AbstractA study of structure development in thin melt spun isotactic polypropylene filaments is described, which is then applied to the prediction of the behavior of thick parts. Conditions under which different crystalline forms of polypropylene are obtained as a function of cooling rate and spinline stress were investigated. Continuous cooling transformation (CCT) curves are developed. This also allows us to develop a map of crystalline form as a function of these variables. We have applied the CCT curves and this map to predict the development of cross‐sectional variation structure in thick filaments and rods. This is applied in particular to the quenching of a cylindrical rod and the structural characterizations observed through the cross section are compared with predictions from the CCT curves and solutions of Fourier's transient heat conduction equation.
Dynamic mechanical modeling of PEI/dicyanate semi‐IPNs
Authors: Kim Yu‐Seung , Min Hyun‐Sung , Choi Woo‐Jin , Kim Sung‐Chul 
Published: April 2004

AbstractThe dynamic mechanical behavior of polyetherimide(PEI)/dicyanate semi‐interpenetrating polymer networks (semi‐IPNs) was analyzed by using the conventional Takayanagi model for the sea‐island morphology (PEI content of 10% or below) and a polyhedron model, which we developed for the dicyanate nodular structure (PEI content of 20% or above). The model parameters for the Takayanagi model were determined by the volume fraction of the PEI dispersed phase and Kerner's equation, while the model parameters for the polyhedron model were simply calculated by introducing a phase continuity factor. Both models correlate well with the morphology revealed in the micrographs except near the transition temperature of the PEI‐rich phase. The additional shift toward higher temperature found in the nodular structure was due to the intermixed phase composition, and the effect was quantified by measuring the calorimetric transition temperature. The dynamic mechanical modeling for the dual‐phase morphology (PEI content of 15%) and for the semi‐IPNs showing a morphology spectrum were also successfully accomplished by combining the Takayanagi model and the polyhedron model.
Polyurethane and unsaturated polyester hybrid networks: Chemorheological and dielectric study for the resin transfer molding process (RTM)
Authors: Maazouz A. , Dupuy J. , Seytre G. 
Published: April 2004

AbstractThe kinetic, rheological and dielectric behavior of a polyurethane‐unsaturated polyester hybrid system was studied with a view to control the RTM process. The kinetics of the polyurethane reaction (which governs the viscosity evolution during injection) was satisfactorily modeled with a simple second order model. The rheological study enabled complex viscosity and gelation time (tanδ crossover) at different curing temperatures to be obtained. Furthermore, dielectric data and viscosity measurements have been interpreted with respect to kinetics. It was shown that the modified percolation law equation suggested by Macosko et al. can be used to describe the viscosity as a function of temperature and extent of reaction by using a temperature and conversion dependent critical exponent. Dielectric properties such as ionic conductivity were related to viscosity with a Stockes based equation, and to conversion with an empirical equation.