bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Crystallinity and Orientation in Poly-p-Phenylene Sulfide
Authors: Maemura E. , Cakmak M. , White J. L. 
Published: December 2013

Abstract
We present a basic characterization methods and parameters for poly-p-phenylene sulfide (PPS) which are necessary to interpret experimental studies on fabricated parts. In particular (i) we determined the heat of crystallization of 100% crystalline PPS from density and DSC data, this allows the use of DSC to determine the percent crystallinity (ii) devised a method of calculation of crystalline orientation factors from Wide-Angle X-ray diffraction experiments. The latter problem is non-trivial because of WAXS peak overlap. The methods and parameters developed were applied to uniaxially stretched and annealed PPS films. (iii) We theoretically computed the intrinsic birefringence Δ° from first principles, this allows interpretation of birefringence data.
Studies on High Speed Spinning of PET
Authors: Cheng J. , Guan X. , Wei R. , Ma H. 
Published: December 2013

Abstract
It is observed that preoriented yarn (POY) begins orientating crystallization near the area of sharp structural change through the measurements of stress, optical birefringence and density at the speed of 3600 m/min. The investigated relationship between optical birefringence (Δn) and stress (σ) of spinning line proposed by Hamana is, to some extent, deviated from our observation. This paper gives an empirical formulation as Δn = 13.18 × 10−3 + 6.32 × 10−10 σ with a deviation within 4%. It also provides a predicting method for controlling the change of PET structure of spinning line. Our tests have shown that the less the denier of POY single yarn, the greater the stress and crystallinity during the fiber formation, and that stress induced effect of the crystallization kinetics of PET high speed spinning is greater than that of the cooling rate.
Speckle Photography of the Rheological Measurements of Polymer Systems
Authors: Ivanov Y. , Hadjikov L. , Kavardjikow V. 
Published: December 2013

Abstract
The speckle photography method is used for measurement of the viscosity changes during curing of polymer composites. Subject of considerations are the changes in the reflective ability of the composite during the hardening, in the degree of polymerization and of the properties. A new relation for a time dependence of viscosity is proposed on the basis of the obtained specklegrams.
Temperature and Velocity Profiles in Drag Flow of a Temperature Dependent Power Law Fluid
Authors: Rauwendaal C. J. , Ingen Housz J. F. 
Published: December 2013

Abstract
This paper analyzes non-isothermal drag flow between parallel plates. First, non-isothermal drag flow is considered of a Newtonian fluid with a non-zero pressure gradient, assuming viscous dissipation is negligible. Second, non-isothermal drag flow is considered of a power law fluid with zero pressure gradient, again assuming viscous dissipation is negligible. Finally, pure drag flow of a temperature dependent power law fluid is analyzed, including the effect of viscous dissipation. When the temperature of the stationary plate is increased, the flow rate increases. Applying this analysis to screw extrusion, this means that increasing the screw temperature relative to the barrel temperature will increase the flow rate. Also, the temperature sensitivity of the flow rate reduces with increasing screw temperature and with increasing power law index. This points to useful benefits of screw heating. With shear thinning fluids increased channel depth raises the stock temperatures, even though the shear rates in the fluid will be reduced. The increased temperatures are due to longer heat transfer distances; the viscous heat generated is less easily conducted away to the walls. At high values of the Brinkman number, the heat flux at the lower plate reduces when the upper plate temperature increases, while at low Brinkman numbers the opposite is true. This is important in the analysis of melting in extruders. It indicates that while high barrel temperatures in the melting zone may be beneficial at low screw speeds, it can be detrimental at high screw speeds. At high screw speeds, therefore, lower barrel temperatures may be more appropriate to obtain efficient melting.
Injection Molding without Packing
Authors: Friesenbichler W. , Knappe W. , Rabitsch R. 
Published: December 2013

Abstract
By injection molding two kinds of frozen-in orientation will arise: During the filling phase the outer layers of the molding will be sheared and simultaneously cooled. This results in highly oriented layers at the outside of the molding (orientation by filling). During the packing phase the melt, forced into the cavity, gives rise to low rates of deformation in the molding, but since the viscosity has become high by cooling, high stresses and frozen-in orientation will also result (orientation by packing). This last kind of orientation can be avoided by high pressures in the filling phase, followed by immediate mechanical sealing of the cavity (injection molding without packing), and hereby a better quality of the moldings can be achieved. Some results with moldings of PS and PP are given.
Numerical Simulation of Wire-Coating Coextrusion
Authors: Heng F. L. , Mitsoulis E. 
Published: December 2013

Abstract
The wire-coating coextrusion process has been simulated numerically using the Lubrication Approximation Theory (LAT) and the Finite Element Method (FEM). The analysis includes both Newtonian and shear-thinning fluids under isothermal or nonisothermal conditions. Special Streamline-Upwind/Petrov-Galerkin schemes have been used for an accurate solution of the energy equation in highly convective flows. The determination of the unknown a priori interface and free coating surface was carried out through an iterative procedure that allows for no cross-flow along these surfaces. The analysis shows how an initial die design for high-speed wire-coating coextrusion can be modified to meet several criteria deemed necessary for better operation. These involve: (a) lack of recirculation everywhere inside the die, (b) the development of smooth stresses along the die wall, especially near the contact region of the two melts, and (c) the location of an interface that runs almost parallel to the wire. The improved die design that meets these criteria consists of moving the torpedo to a position of optimum “gum space” and also reducing the taper in the die region. Subsequent non-isothermal studies of two typical polymer resins, namely HDPE and PS, show that the initial melt and boundary temperatures do not influence so much the results and especially the interface location as do the individual flowrates (hence flowrate ratios) for a given total coating thickness. The analysis also provides a wealth of information regarding pressure and shear stress distributions, stream-line patterns and temperature fields, along with such overall quantities as pressure drops, wire tension, maximum temperature rise and maximum stresses.
Computer Simulation of Multi filament Air Jet Melt Spinning
Authors: Ishihara H. , Hayashi S. , Ikeuchi H. 
Published: December 2013

Abstract
Air jet melt spinning for multifilament system was studied both theoretically and experimentally. Basic equations describing the multifilament system of air jet melt spinning were derived by considering air temperature and velocity of cooling flow surrounding the individual spinlines. Numerical computations of the fundamental equations for air jet melt spinning were carried out for various spinning conditions. Steady-state solutions obtained give the spinline cross sectional area, spinline temperature, spinning tension and spinline velocity. These are described as a function of the distance measured downward from the spinneret. Air jet melt spinning experiments were conducted for poly-(ethyleneterephthalate) (PET) having an intrinsic viscosity of 0.61. The spinning variables were changed mainly in terms of throughput, distance from spinneret point to ejector and air pressure in the ejector. Good correlations between theory and experiment were obtained for the final spinline speed or as-spun fiber denier. Further, the molecular orientation of asspun fiber can be estimated using the computed stretching speed at the ejector point. It was found that the simulation program of multifilament air jet spinning is very useful in finding the appropriate spinning conditions for the industrial spinning process and in estimating fiber properties.
Cast Film Extrusion of Polypropylene Films
Authors: Cotto D. , Duffo P. , Haudin J. M. 
Published: December 2013

Abstract
In cast film extrusion, the polymer melt is extruded through a slit die, slightly stretched in air and then cooled on a chill-roll. An important part of the present work was devoted to the development and application of a thermomechanical model of stretching in air and of a purely thermal model of cooling on the roll, taking polymer crystallization into account. The structures and morphologies in a series of extruded polypropylene films were investigated using density and sonic modulus measurements, wide-angle X-ray diffraction, small angle light scattering and optical microscopy. These experimental results combined with theoretical predictions obtained from the model allow to discuss the respective effects of stretching in air and cooling on the roll. Stretching in air essentially affects spherulite nucleation and growth during subsequent crystallization on the roll. Dissymmetrical cooling on the roll induces an inhomogeneous microstructure within the film. The presence of a zone with a finer microstructure near the roll has been correlated with the cooling rates and thermal gradients calculated by the model.
Prediction of Birefringence for Optical Memory Disk
Authors: Kanai T. , Shimizu K. , Uryu Y. 
Published: December 2013

Abstract
Polycarbonate (PC) is considered to be a proper resin for optical memory disk, however PC resin shows high birefringence. It is very important to reduce birefringence of PC optical memory disk. This research is to obtain the relationship between birefringence and process conditions and to get the optimum condition for the production of low birefringence substrate of PC optical memory disk. The birefringence distribution of PC optical memory disk was theoretically predicted by the calculations of both the stress distribution caused by molecular orientation during the filling stage and the thermal stress caused by temperature difference during the cooling stage. The relationship between birefringence distribution and the process conditions such as rheological properties of PC resin, injection temperature, mold temperature, mold design and annealing condition is possible to be predicted theoretically by calculating shear stress during the injection process and thermal stress during the cooling process. The predicted results of birefringence distribution qualitatively agree with the experimental ones.
Experimental Investigation of Rotational Molding and the Characterization of Rotationally Molded Polyethylene-Parts
Authors: Iwakura K. , Ohta Y. , Chen C. H. , White J. L. 
Published: December 2013

Abstract
An experimental study of the rotational molding of polyethylene parts is presented. Specific attention is given to heating and cooling of the molding cycle and to the micro structuring and bulk characteristics. Experimental measurements of the heatup of the oven at the startup of the process is presented. The heatup of different molds in the oven is then measured and interpreted in terms of heat conduction theory and the Fourier number αt/L2. In the experiments, thick aluminium molds heated up more slowly than thinner steel molds. The cooling characteristics of mold subject to different quenching conditions were compared with water showers inducing the most rapid cooling followed by fan blowing and the slowest being in quiescent air. The order of cooling of the different molds studied followed the same order as their rates of heating as would be expected from the theory of heat conduction. Polyethylene parts formed in the molds were found to be crystalline, without orientation and to possess large spherulites. The size of the spherulites and the level of the crystallinity was highest where the cooling rate was the lowest. Uniformity of part thickness and warpage were measured. Warp age correlated with rapidity of cooling rate. This suggested a mechanism of thermal quench stresses.
Fabrication of Microstructures of Extreme Structural Heights by Reaction Injection Molding
Authors: Hagmann P. , Ehrfeld W. 
Published: December 2013

Abstract
For the fabrication of microstructures with minimum lateral dimensions in the micrometer range and structural heights of up to several hundred micrometers a new microfabrication technique has been developed by the Karlsruhe Nuclear Research Center. The so-called LIGA method is based on a combination of deep-etch X-ray-lithography, electroforming and plastic molding. High-quality micromold inserts can be prepared by deep-etch X-ray lithography and electroforming allowing an arbitrary choice of cross section of the microstructures. By optimization of the process parameters of the reaction injection molding process using casting resins on a methyl methacrylate base it has been shown that a yield of 100% can be achieved. For molding microstructures without any flaws, the mold material has to be degassed, the cavity of the mold must be evacuated and the shrinkage due to polymerization has to be compensated by applying a holding pressure. With an internal mold release agent which is a special salt of an organic acid, cycle times of about 12 min have been achieved in the micromolding process step which are very much shorter than the exposure and development times in the direct lithographic production of microstructures. Such plastic structures can represent the final product or, if microstructures are to be made of metal, they are used as templates in a subsequent electroforming process. Depending on the geometrical configuration of the microstructures, either a metallic gate plate or an electrically conducting plastic layer are used as the electrode for electroforming.
Non-isothermal Extrusion of Composite Materials
Authors: Alexandrou A. N. , Papanastasiou T. C. 
Published: December 2013

Abstract
Non-isothermal extrusion, of non-dilute fiber suspensions with solidification is analyzed by means of an integral constitutive equation for melt fiber suspension and a novel, streamlined inverse finite element method (IIFEM), to account for the solidification. Newton iteration is used to solve simultaneously the highly non-linear system of intergrodifferential equations for all the primary unknowns including the apriori unknown location of the solidification front and the free surface. The fiber orientation is computed using the orientation distribution function along selected streamlines of the melt suspension. It is shown that the final frozen-in orientation of the fibers in the resulting solid composite depends on the location of the solidification front. Thus by controlling the location of the solidification front by means of the flow, cooling rate and the capillary design may be possible to produce composites of several orientation patterns.
Optimal Cure Cycle Design for the Fiber Reinforced Composite Lamination Processing
Authors: Hou G. J. W. , Hou T.-H. , Sheen J. S. 
Published: December 2013

Abstract
Fiber-reinforced composite laminates are used in many aerospace and automobile applications. The magnitudes and durations of the cure temperature and the cure pressure applied during the curing process have significant consequences for the performance of the finished product. The objective of this study is to exploit the potential of applying the optimization technique to the cure cycle design. Using the compression molding of a filled polyester Sheet Molding Compound (SMC) as an example, a unified Computer Aided Design (CAD) methodology, consisting of three uncoupled modules, (i.e., optimization, analysis and sensitivity calculations), is developed to systematically generate optimal cure cycle designs. Various optimization formulations for the cure cycle design are investigated. The uniformities in the distributions of the temperature and the degree of cure within the specimen cured under the optimal cycles are compared with those resulting from conventional isothermal processing conditions with pre-warmed platens. Recommendations with regards to further research in the computerization of the cure cycle design are also addressed.
Flow Analysis in an Internal Mixer
Authors: Yagii K. , Kawanishi K. 
Published: December 2013

Abstract
An attempt has been made to predict flow behavior of the rub bery material in an internal mixer by means of finite element analysis. For the convenience of analysis, a simplified model for the mixer and some assumptions were introduced. The model consists of a circular cylinder and a rotor with uniform cross sectional shape along the axis which rotates around the axis located at the center of the cylinder. Rubbery material fills the void between the cylinder and the rotor. The assumptions are: the material is a power law liquid, the material is incompressible, and the viscosity is large enough to allow laminar flow.
Processing of ABS Latex in a Single Screw Extruder
Authors: Ghosh A. K. , Lindt J. T. 
Published: December 2013

Abstract
The feasibility of the continuous and direct conversion from latex to wet crumb through the coagulation process in an extruder has been demonstrated through this work. The coagulation efficiency in the extruder has been largely governed by temperature. The maximum rate of increase of the first and the second moments of the particle size distribution of the coagulated latex occur in the neighborhood of the polymer glass transition temperature. The particle densities showed no longer a one-to-one relationship to the specific surface typical of the batch coagulation experiments, as the material coagulated in the extruder did not reach the same degree of equilibrium. Although the basic trends remained the same as in the batch coagulation experiments, the addition of residence time distribution, inherently associated with the extruder operation, introduced some significant changes into the coagulation process.
Fibre Orientation Mechanisms for Injection Molding of Long Fibre Composites
Authors: Bailey R. , Rzepka B. 
Published: December 2013

Abstract
The development of skin/core fibre orientations in injection molded fibre reinforced compounds is considered, and the applicability of the Tadmor fountain-flow mold filling mechanism to long fibre reinforced is investigated. A disc and plaque mold cavity are used to consider the influence of each injection molding cycle parameter upon the skin/core structure. The influence of the flow path length is also considered. The independent orientation controlling mechanisms identified (the injection speed, melt temperature and the holding pressure cycle all of which influence the fibre orientation favourably) can be used in combination to achieve a optimised microstructure for the cavities under study.
Effect of Thermal History on Viscoelastic Properties of Thermotropic Liquid Crystalline Copolyesters
Authors: Masuda T. , Fujiwara K. , Takahashi M. 
Published: December 2013

Abstract
Dynamic viscoelastic properties of two samples of co-polyesters, PHB60 and PHB28, were measured over a wide range of temperatures. The copolyesters had been synthesized from polyethylene terephthalate (PET) and p-hydroxybenzoic acid (PHB). PHB60 and PHB28 contain 60 and 28 mol.-% PHB as the comonomer, respectively. PHB60 is well known as a thermotropic liquid crystalline copolyester. The effect of thermal histories on viscoelastic behavior of the copolyesters are discussed in terms of structure and liquid crystallinity of the copolyesters. A rheological transition in viscoelastic properties of the copolyester PHB60 was observed at about 270°C in the fluid state. The viscoelastic properties of the copolyester PHB60 strongly depend on thermal histories below the transition temperature, but not above the temperature. The transition behavior was attributed to a crystal-nematic transition by wide angle X-ray diffraction and differential scanning calorimetry. The attainable crystallinity was fairly low. Thermal history behavior found below the transition temperature is caused by slow crystallization and supercooling of the sample. PHB28 forms no liquid crystal phase, and is thermorheologically simple in the molten state: the sample showed no effect of thermal history in viscoelastic properties.
Molecular Orientation and Modulus of a Thermotropic Liquid Crystalline Copolyester
Authors: Fujiwara K. , Takahashi M. , Masuda T. 
Published: December 2013

Abstract
The relationship among processing parameters, molecular orientation, and modulus of a thermotropic liquid crystalline copolyester synthesized from poly(ethylene terephthalate) and 60 mol.-% p-hydroxybenzoic acid was systematically investigated so that the dominant processing factors to result in high orientation and high modulus were elucidated. Solid filaments were prepared by shear flow in capillaries and elongational flow by spinning from the liquid crystalline phase of the copolyester at various processing conditions. Superstructure, especially molecular orientation, of the filaments was analyzed by wide angle X-ray scattering (WAXS), scanning electron microscopy (SEM), and polarizing optical microscope (POM). Also, tensile modulus of the filaments was determined. Although filaments prepared by means of shear flow in capillaries had the Hermans orientation function of about 0.3, tensile modulus and morphology by SEM and POM did not exhibit the evidence of high orientation of the filaments even at high ratios of length over diameter and high shear rates. In the elongational flow by spinning, the dominant processing parameters for molecular orientation and increasing of tensile modulus are a spin-draw ratio and an initial diameter of the filament. The small diameter results in high orientation and high modulus. Enhancement of modulus was independent of the processing conditions related to a relaxation process of molecular orientation, such as spinning temperature, strain rate, and cooling. These results imply that there exists a size effect for the orientation process.
Frequency Analysis of Pressure Fluctuations in a Single Screw Extruder
Authors: Becker J. , Klason C. , Kubát J. , Sáha P. 
Published: December 2013

Abstract
This paper demonstrates the usefulness of frequency analysis in monitoring flow behavior in a single-screw extruder fitted with a capillary die with a length to diameter aspect ratio of 20. The melt pressure in the barrel and die was measured by a transducer, and the pressure fluctuations processed in a Fast Fourier Transform (FFT) frequency analyzer. The pressure fluctuations were studied under various processing conditions for high density polyethylene, linear low density polyethylene and polypropylene. In general, stable extrudate flow generates a noise spectrum with low intensity, the intensity increasing with the level of instability. The machine vibrations appeared to have a direct effect on flow stability. Also, unstable melting of the resin along the screw resulted in an increase in noise level. It seems probable that the frequency of the surface distortions can be related to the shape of the noise spectrum. In general, although more complex in nature, the noise results related to melt flow in the extruder were in agreement with data reported for capillary flow using a piston rheometer.