bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of fluid decoupling on viscous mixing
Authors: Bigio David I. , Young Dave 
Published: December 2004

AbstractFlow in a three‐dimensional channel with a sinusoidally‐wavy, vertical wall is examined for the case of applied down‐ and cross‐channel velocity components. An important parameter for the analysis of the nature of laminar mixing in the flow field occurs when the changes in the downstream direction can be decoupled from the changes in the cross‐channel direction, thereby allowing for a two‐dimensional solution of the system of equations. This paper shows the effect on the nature of laminar mixing when the decoupling of the momentum equations from a fully three‐dimensional case to one where a two‐dimensional solution can be performed. Experiments are performed on a channel with sinusoidally varying vertical walls that cover the range of decoupling criteria. Silicone pigmented either white or black was run in the apparatus, cured, and cross‐sectioned. The cross sections embody a local, detailed history of the state of mixing as it proceeds down the mixer. The amount of mixing is presented as a function of position at each cross section for the different channel configurations. The nature of mixing changes from a linear growth rate in the amount of interfacial area to an exponential rate as the amplitude of the wave is increased. Results demonstrate the existence of chaos, islands, and the factors affecting the mixing behavior.
Analytical and experimental study of the die drawing of circular rods through conical dies
Authors: Motashar F. A. , Unwin A. P. , Craggs G. , Ward I. M. 
Published: December 2004

AbstractAn analysis is presented of the process of die drawing isotropic polymers, in the form of circular rods, to produce highly oriented materials with enhanced mechanical properties. The stresses in a small element of material undergoing the drawing process have been analyzed using a force‐equilibrium approach and the initial yield and flow stresses in the material have been predicted from the von‐Mises yield criterion. The stress‐strain‐strain rate characteristics of the polymer used in the analysis were deduced from uniaxial tensile test data obtained at the same temperature at which the die drawing occurred. Experimental results are presented of the stress in polypropylene GSE‐108 rods when die drawn at 90°C in a purpose‐built die drawing facility. Novel techniques were used to determine the stress and strain distributions along the die. A comparison of the experimental results and the analytical predictions shows good agreement.
Flow induced phase inversion agglomeration: Fundamentals and batch processing
Authors: Akay G. 
Published: December 2004

AbstractA novel agglomeration technique, based on flow induced phase inversion (FIPI) is described and applied to the batch preparation of polyethylene‐bound abrasive calcite agglomerates. Water soluble polymers are used to agglomerate the needle‐like crystals of tetraacetylethylene diamine and also sodium chloride crystals. In a typical isothermal FIPI agglomeration process primary particles are dispersed in the molten binder, which is subsequently inverted by the addition of sufficient amount of primary particles, which also defines the critical filler concentration at phase inversion, Cc. Agglomerate particle size is primarily a function of Cp – Cc where Cp is the mean concentration of filler. Cc decreases with increasing binder molecular weight and primary particle surface area. Agglomerate size distribution is affected by processing, mainly by the mixing time after phase inversion. For the non‐isothermal FIPI agglomeration process, phase inversion is induced locally, by the addition of fine particles in the molten binder. Phase inversion is then propagated by cooling the dispersion during mixing. Agglomerate characteristics such as particle size, particle size distribution, binder concentration distribution in each agglomerate size range, agglomerate topology, binder morphology in the agglomerates, agglomerate strength, and agglomerate dissolution rate in water were evaluated. These agglomerate characteristics are related to the binder and filler properties as well as to the processing conditions.
A nonlinear dynamic model of a servo‐pump controlled injection molding machine
Authors: Wei Jong‐Hwei , Chang Chian‐Chiunn , Chiu Cheng‐Ping 
Published: December 2004

AbstractThis paper presents the development of a nonlinear mathematical model and a microcomputer controlled servo‐pump system for the study of the dynamics of a servo‐pump controlled injection molding machine (IMM). The model is formulated by the Reynolds transport theorem which is applied to describe the polymer flow dynamics in the nozzle. The comparison between the simulation results and experimental investigations indicated that the nonlinear dynamic model is a reasonable representation of a servo‐pump controlled IMM. The output flow rate and working pressure of a servo‐pump controlled IMM can be reasonably represented by the nonlinear model when the acrylonitrile‐butadiene‐styrene (ABS) is injected.
The influence of surface heating on the birefringence distribution in injection molded parts
Authors: Jansen K. M. B. , Flaman A. A. M. 
Published: December 2004

AbstractIn order to reduce the frozen‐in orientation, which is usually present in injection molded products, the effect of high‐performance mold surface heaters was investigated. The heaters are capable of changing their surface temperature by 70°C within a few tenths of a second typically, which minimizes their effect on the cooling time. The effects of the heating time, the instant of heating, and the heating power on the birefringence distribution of a polystyrene resin were studied. Reductions of the birefringence peak by a factor 4 to 7 were observed. The birefringence is removed most effectively by heating briefly before and during the injection stage. A heating pulse of about one second and with a power density of 20 W/cm2 then seems to be sufficient. A minimum power density of 10 W/cm2 is needed for the relaxation to occur in this specific system.
Investigation of cure in epoxy acrylate resins using rheological and dielectric measurements
Authors: Hayward D. , Mackinnon A. J. , Radhakrishnan S. , Pethrick R. A. 
Published: December 2004

AbstractDielectric and rheological measurements are reported for the cure in a series of mixtures of an epoxy‐acrylate with n‐butyl methacrylate. The level of the initiator and properties of the epoxy acrylate and n‐butyl methacrylate influence the cure characteristics and morphology of the film formed. Analysis of the rheological data indicates that during the curing process, microphase separation occurs within the mixture. The changes in the dielectric relaxation behavior with composition of the completely cured material is also consistent with microphase separation occurring in these resins while they are cured.
Screw optimization of a co‐rotating twin‐screw extruder for a binary immiscible blend
Authors: Vainio Tommi P. , Harlin Ali , Seppälä Jukka V. 
Published: December 2004

AbstractThe effect of the screw configuration of a closely intermeshing co‐rotating twin‐screw extruder on residence time and mixing efficiency was studied for an uncompatibilized immiscible PA6/PP (80:20) bend. Alternative screw configurations were investigated systematically. The residence time distribution (RTD) was found to be a poor indicator of the total mixing efficiency, whereas the mixing intensity function yielded considerably better information. High shear stress, sufficient residence time, and high fill ratio in the melting section of the screw were the most important factors in achieving good dispersion of the minor phase. The evolution of morphology along the screw axis depended strongly on the screw configuration. The downstream flow characteristics after the screw end determined the final morphology of the blend.
Effects of inserts on the injection molding process
Authors: Rezayat Mohsen , Jantzen Brian 
Published: December 2004

AbstractInjection molds often contain blocks of dissimilar material for improved cooling; they may also contain blocks of movable metal as a means of ejecting large parts from the mold. In this case, the blocks of metal are made of the same material, but the resistance at the interface between them has a marked influence on the cooling in the local area near the interface. In many other cases, inserts may be required because of wear in a particular mold section, or because efficient mold design is needed to produce similar parts. Hence, any mathematical model for analysis of heat transfer in injection molds must be general enough to apply to interfaces with and without gaps (i.e., with and without resistance to the flow of heat at the interface) for similar, as well as dissimilar, materials. A new and accurate model for prediction of heat transfer in heterogeneous (zoned) molds is presented in this paper. Through the solution of real problems with this model, the effects of differing material properties and interfacial thermal resistance are studied and the results are reported. It is observed that inserts have both local and global effects on the injection molding process; the overall ejection time for a part may be shortened, and the surface appearance of a part may be improved by correct placement of inserts.
Nonisothermal bubble growth in polymeric foams
Authors: Arefmanesh A. , Advani S. G. 
Published: December 2004

AbstractThe dynamics of a large number of bubbles separated by distances of the order of their radii in highly viscous fluids with specific application to foams is investigated. The growth of bubbles is due to diffusion of gas from the fluid and the momentum transfer between the fluid and the bubbles. Equations governing the growth of a single bubble in a shell of fluid containing limited dissolved agas are coupled with the transport equations for the fluid under non‐isothermal conditions. The resulting set of equations are solved numerically for a system of bubbles growing along the axial direction in a mold. The results predict a bubble size distribution along the axial direction with large bubbles close to the melt front and smaller bubbles close to the gate, which results in a density distribution in the molded article. Experimental studies on structural foam under nonisothermal conditions are performed. The transient bulk foam density is measured by monitoring the melt front as the foam expands. The predicted values of the foam density are compared with the experimental results and the sources of error are discussed.
Mechanical response of beams of a nonlinear viscoelastic material
Authors: Wineman Alan , Kolberg Raymond 
Published: December 2004

AbstractA constitutive equation for nonlinear viscoelasticity is used to model the mechanical response of solid polymers such as polycarbonate. The nonlinearity arises from a reduced time which causes stress relaxation to accelerate with increasing strain. The constitutive equation can account for the occurrence of yield in a homogeneous uniaxial constant strain rate test. The constitutive equation is used in a study of the pure bending of beams. It is assumed that the classical assumption of beam theory is valid, i.e., plane sections remains plane. At each fixed time, the strains vary linearly through the depth of the beam. At a fixed material element the strain varies in time with the curvature. This spatial variation of the strains combined with the nonlinear dependence of the reduced time on strain leads to a significantly different response from that given by traditional beam theory. The implications of this for the bending moment history, stress distributions, and other factors that relate to beam design are discussed.
An investigation into the three‐dimensional stress‐birefringence‐strain relationship in elastomers
Authors: Arruda Ellen M. , Przybylo Phillip A. 
Published: December 2004

AbstractThe statistical theory of the birefringence of an individual non‐Gaussian elastomer chain is used together with a chain network description of rubber elasticity to develop a relationship among the strain, birefringence, and stress in elastomers, valid for large deformations under generalized strain states. The result is a fully three‐dimensional internal variable based constitutive model of rubber elasticity in which measurement of the elastomeric birefringence during straining in one deformation state characterizes the optically anisotropic response of the elastomer. Simultaneous measurement of the stress vs. strain response provides the rubbery modulus and limiting network extensibility properties needed to completely characterize the mechanical anisotropy of the material. Once characterized using the single, large deformation experiment, the birefringence and stress responses of the elastomer in other deformation states may then be predicted without adjusting any model parameters. The theory is compared to experimental studies from the literature of large strain deformations of elastomers in uniaxial tension and compression for which the exhibited birefringence and stress responses of deforming elastomers have been simultaneously recorded.
Kinetics modeling and time‐temperature‐transformation diagram of microwave and thermal cure of epoxy resins
Authors: Wei Jianghua , Hawley Martin C. , Demeuse Mark T. 
Published: December 2004

AbstractStoichimetric mixtures of a diglycidyl ether of bisphenol A (DGEBA)/ diaminodiphenyl sulfone (DDS) and a DGEBA/meta phenylene diamine (mPDA) were cured using both microwave and thermal energy. Fourier transform infrared (FTIR) was used for the measurement of the extent of cure and thermal mechanical analysis (TMA) was used for the determination of the glass transition temperature (Tg). The cure kinetics of the DGEBA/mPDA and DGEBA/DDS systems were described by an autocatalytic kinetic model up to vitrification in both the microwave and thermal cure. For the DGEBA/mPDA system, the reaction rate constants of the primary amine‐epoxy reaction are equal to those of the secondary amine‐epoxy reaction, and the etherification reaction is negligible for both microwave and thermal cure. For the DGEBA/DDS system, the reaction rate constants of the primary amine‐epoxy reaction are greater than those of the secondary amine‐epoxy reaction and the etherification reaction is only negligible at low cure temperatures for both microwave and thermal cure. Microwave radiation decreases the reaction rate constant ratio of the secondary amine‐epoxy reaction to the primary amine‐epxy reaction and the ratio of the etherification reaction to the primary amine‐epoxy reaction. Tg data were fitted to the DiBenedetto model. A master curve and a time‐temperature‐transformation (TTT) diagram were constructed. The vitrification time is shorter in microwave cure than in thermal cure, especially at higher isothermal cure temperatures. For the DGEBA/mPDA system, the minimum vitrification time is two to five times shorter in the microwave cure than in the thermal cure. For the DGEBA/DDS system, the minimum vitrification time is 44 times shorter in the microwave cure than in the thermal cure.
Enhanced polycarbonate toughness. II: Mechanisms
Authors: Kim S. W. , McGarry F. J. , Riew C. K. 
Published: December 2004

AbstractGlassy shell‐rubbery core polymer particles, 0.1 to 0.2 μm in diameter, increase the plane strain JIC values of 3.175 mm thick polycarbonate from 3.05 kJ/m2 (no particles) to 9.5 kJ/m2 (7.5 phr particles) at 23°C. Some modest decreases in these values are caused by tests at −20°C in samples 9.525 and 3.175 mm thick. If only the particle concentration is varied, JIC increases monotonically to 7.5 phr (by wt), then levels off or decreases slightly at 10.0 phr. The total volume of 1 to 2 μm diameter cavities formed in the matrix by the apparently unbonded particles behaves similarly; cavity volume and JIC are directly related. With increasing particle concentration the tensile modulus is unchanged, the yield stress and strain decrease modestly, the strain at fracture decreases appreciably, and the heat recoverable orientation in the fractured samples decreases. Few cavities are formed. The particles reduce the extent of shear deformation in the tensile samples.
The copolymerization of methacrylates in a counter‐rotating twin‐screw extruder
Authors: Jongbloed H. A. , Mulder R. K. S. , Janssen L. P. B. M. 
Published: December 2004

AbstractThe copolymerization of n‐butylmethacrylate with 2‐hydroxypropylmethacrylate was studied in a closely intermeshing counterrotating twin‐screw extruder. The average molecular weight of the product can be increased by increasing the screw rotation rate or the die resistance or by decreasing the throughput or the barrel temperature. The conversion can be improved by decreasing the throughput, increasing the die resistance, and (within limits) increasing the barrel temperature, as well as through post‐initiation. Compared with various classical polymerization processes, this situation requires that particular attention be paid to the occurrence of a gel effect, the existence of a thermodynamic ceiling temperature, and the reactivity ratio of the monomers used.
Residence time distribution in non‐intermeshing counter‐rotating twin‐screw extruders
Authors: Chen L. , Hu G. H. , Lindt J. T. 
Published: December 2004

AbstractThis paper deals with the residence time distribution (RTD) in a non‐intermeshing counter rotating twin screw extruder.The RTDs were measured in three vent zones of the extruder sparately, and in the adjacent zones combined, using a soluble dye as the tracer. Assuming that the RTDs in the adjacent zones are independent of each other, the overall RTD was also calculated using a previously developed statistical theory. The theory has also confirmed the consistency of the present measurements.A predictive RTD model for the non‐intermeshing twin screw extruder, based on the flow analysis of the individual screw zones and their statistical superposition, was also developed. The predictions are in good agreement with experiment.
The flow‐induced phase morphology of fluoroelastomer and polycarbonate blends during extrusion
Authors: Tsai Hsien Yin , Min Kyonsuku 
Published: December 2004

AbstractThe flow‐induced phase morphological development under different extrusion conditions was studied in terms of the rheological property and interfacial tension of various elastomers and thermoplstics. The interfacial tension for elastomers and thermoplastics was investigated by using a breaking thread method (1‐4). We found that the method is suitable for measuring interfacial tension without degradation. The droplet‐fibrillation transition phenomenon was observed in various extrudates of fluoroelastomer/polycarbonate blends. The criteria for the flow‐induced morphology, in particular the droplet‐fibrillation transition, are critically discussed in this paper.
Master curve approach to polymer crystallization kinetics
Authors: Chan T. V. , Shyu G. D. , Isayev A. I. 
Published: December 2004

AbstractNonisothermal crystallization kinetic data obtained from differential scanning calorimetry (DSC) for a poly(ethylene terephthalate) are corrected for the effects of temperature lag between the DSC sample and furnace using the method of Eder and Janeschitz‐Kriegl which is based on experimental data alone without resort to any kinetic model. A method is presented for shifting the corrected nonisothermal crystallization kinetic data with respect to an arbitrarily chosen reference temperature to obtain a master curve. The method is based on experimental data alone without reference to any specific form of kinetic model. When the isothermal crystallization kinetic data for the same material are shifted with respect to the same reference temperature, a master curve is also obtained which overlaps to a large extent the corresponding master curve from nonisothermal data. It follows that nonisothermal DSC measurements provide the same crystallization kinetic information as isothermal DSC Measurements, only over a wider range of temperatures. The shift factors obtained from experimental data alone are compared in turn with the corresponding values calculated from the Avrami equation, the Hoffman‐Lauritzen expression, and the Nakamura equation as a means of evaluating these models individually. It is concluded that the Avrami equation is very good at describing isothermal crystallization kinetics, the Hoffman‐Lauritzen extrapolation of the limited isothermal data to a wide range of temperatures is quite good, and the Nakamura equation yields reliable crystallization kinetic information over a narrower range of temperatures than nonisothermal data alone without using any specific model.
Finite element analysis modeling of powder injection molding filling process including yield stress and slip phenomena
Authors: Kwon T. H. , Park J. B. 
Published: December 2004

AbstractFor a science‐based design of the Powder Injection Molding (PIM) process, it would be desirable for designers to have a numerical analysis tool capable of predicting the PIM filling process as a design aid. In this regard, the present study is aimed at developing a numerical analysis system to simulate the PIM filling process based on a new physical modeling taking into account rheological characteristics of powder/binder mixtures, namely the yield stress and the apparent slip phenomena. In particular, two different slip models were employed to represent the apparent slip phenomena. In accordance with the new physical modeling, the numerical simulation of the PIM filling process was accomplished by combining a finite element method and a finite difference method. It was found that the slip layer plays a role of not only a lubricating layer but also a thermal insulation layer. In this aspect, the slip layer model seems to represent the apparent slip phenemena better than the slip velocity model with regard to both the momentum and the thermal transport phenomena. The present paper presents the physical modeling, numerical scheme, and some numerical analysis results showing the effect of the yield stress and slip phenomena.
Effect of matrix ductility on the fracture behavior of rubber toughened epoxy resins
Authors: Chen Teng Ko , Jan Yi Hung 
Published: December 2004

AbstractThis paper investigates the effect of matrix ductility on toughness in a carboxyl‐terminated butadiene‐acryionitrile copolymer (CTBN) toughened diglycidyl ether of bisphenol‐A (DGEBA)‐piperidine system. Two kinds of epoxides were blended separately into this system to change the matrix ductility. One was a rigid and polyfunctional 4,4′‐diaminodiphenol methane (MY720), and the other was a flexible diglycidyl ether of propylene glycol (DER732). The matrix Tg was significantly changed, but without alteration of the microstructure of the dispersed rubbery phase. The result of fracture energy tests reveals that the toughness of the neat epoxy resins increases slightly with the increase in the resin ductility. The toughness of the rubber‐modified epoxy resins increases strongly with matrix ductility. Studies on the morphology of the toughened systems and their fracture surfaces indicate that the size of the plastic deformation zone under constant rubbery‐phase morphology is determined by the multiple but localized plastic shear yielding. Increasing matrix ductility increases the size of the plastic deformation zone by inducing more extensive shear yielding. In addition, fracture surfaces reveal that as the matrix rigidity is increased, an increasing proportion of the fracture energy is dissipated by rubber cavitation during crack initiation.