bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow of a Generalised Power-Law Fluid in Triangular Dies for Rubber Extrusion
Authors: Kakouris A. P. , Freakley P. K. 
Published: December 2013

Abstract
A theoretical and experimental study of the flow of a rubber compound through dies of equilateral triangular cross-section is presented. To determine the pressure drop in these sections both the variational approach and the finite difference method are used. Velocity profiles for different non-Newtonian indices have been obtained under the assumption that rubber compounds conform to the generalised power-law equation of state. Comparisons between the two methods adopted and experimental data are made. Memory effects which contribute to extrudate swelling are also considered; and a quantitative analysis is carried out in which these effects are used to calculate a minimum die land or preform length. Experimental trials were carried out with an ethylene propylene ter polymer (EPDM) compound and a fair agreement was obtained with theoretical predictions. Also the assumed isothermal conditions were found to conform well with experimental results.
Flow Visualization and Performance of a Non-Intermeshing Counter-Rotating Twin Screw Extruder
Authors: Min K. , Kim M. H. , White J. L. 
Published: December 2013

Abstract
A laboratory modular twin screw extruder with transverse and tangential apex windows for flow visualization is described. The machine is operated as a tengential twin screw extruder with right- and left-handed screw elements. Screw characteristic curves, Q-Δ p, were measured and compared for polyethylene in matched and staggered flight screw configurations with right-handed screw elements. Configurations with matched screw elements are better pumps. We have introduced left-handed screw elements into each screw configuration. This reduces the total pressure developed. Again matched screw element configurations are better pumps. Pressure profiles are measured along the length of the extruder. For right-handed screws, the pressure rises monotonically. Left-handed screw elements produce regions of decreasing pressure. Flow visualization investigations allow us to locate the position and follow the mechanism of the melting process. Using colored markers, we were able to see that in most (but not all cases) there was no inter-screw transfer of material.
System Analysis and Morphological Classification of Procedures and Molds for Injection Molding
Authors: Čatić I. , Raos P. , Razi N. 
Published: December 2013

Abstract
The theoretical foundation of system analysis is given after historical development of the problem. The key concepts and the technical systems of things are discussed. Based on investigated procedures of injection molding of polymers and other matters a general definition of injection molding is given. This enables us to work out the general model of injection molding of matter, as well as the system analysis of molds for injection molding. From this analysis, it follows that the mold has different functions: primary shaping of the product as well as structuring on the molecular and supramolecular level. The mold is at the same time a very complicated and complex technical system of things. The morphological classification of different systems gives the basis for better process control.
New Developments in Fiber- and Filmextrusion
Authors: Hensen F. 
Published: December 2013

Abstract
The demands of the fiber and film producers, the result of scientific polymer research studies and the ideas and work of machine manufacturers determine the trends and developments in fiber and film extrusion. The main goal is the improvement of the fiber- and filmproduct-quality and of the process efficiency. Judged by their results, we believe the most significant new developments in the fiber and filmextrusion are: Polymer cleaning by melt filtration, polymer blends by dynamic polymer mixing, coextrusion of different polymers, product specific orientation, precision in melt metering, high speed spinning resp. high speed film extrusion, inline processes with automatic process control.
Modifying Threadline Dynamics in the High-speed Melt Spinning Process
Authors: Cuculo J. A. , Tucker P. A. , Chen G.-Y. , Lin C.-Y. , Denton J. 
Published: December 2013

Abstract
Polyethylene terephthalate (PET) was spun into fibers in the speed range of 3000 to 5000 m/min. Threadline dynamics was modified by altering the threadline temperature profile. This was achieved using a combination of on-line zone cooling and heating(OLZCH). Experimental results showed that the structure development in the threadline was significantly influenced by the OLZCH conditions. The orientation, crystallinity and crystal dimensions of the resulting fibers were greatly increased by the introduction of OLZCH in the take-up speed range of 3000 to 5000 m/min. Various characterization techniques confirmed that the fiber structure was obviously changed with OLZCH. The fiber tensile properties were noticeably improved via this approach. It is concluded that the fiber structure development may be dominantly enhanced by modifying the threadline dynamics in the high speed melt spinning process.
Transient Compressible Flow in Injection Molding Runner**
Authors: Amon M. 
Published: December 2013

Abstract
The transient flow of a compressible polymer melt in an injection system consisting of a ram, a runner, and a shutoff valve is studied. Experimentally, the exit flow rate is found to have an initial value determined mainly by the precompression level and a steady state determined mainly by the ram speed. This flow rate can fall before it rises again, or it can overshoot its steady state. Such complex behavior is predicted qualitatively by a simplified mathematical model, which neglects elasticity but accounts for the finite compressibility and bulk viscosity. Four dimensionless parameters governing system dynamics are identified and their effects investigated by computation.
Optical and Mechanical Measurements to Characterize Injection Molded Polypropylene Plates
Authors: Fleischmann E. 
Published: December 2013

Abstract
By the determination of birefringence and elongation at break as functions of the distance from the surface detailed informations are obtained about the states of orientation of the molecules in injection molded polypropylene plates. Both, the birefringence profile and the profile of elongation at break in the cross-section of the plates, exhibit the skin/core structure typically for injection molded polypropylene articles. An analysis of the results of two polypropylene grades molded at different processing conditions shows a good agreement of both methods.
Blow Molding of Thermotropic Liquid Crystalline Polymers
Authors: Blizard K. G. , Baird D. G. 
Published: December 2013

Abstract
The process of extrusion blow molding was considered in an attempt to obtain biaxial orientation and properties in two thermotropic copply esters: hydroxybenzoic acid/polyethylene terephthalate (HBA/PET) and hydroxybenzoic acid/6-hydroxy-2-naphthoic acid (HBA/HNA). Some degree of biaxial properties and orientation was obtained in blow molded samples in which the die temperature was maintained below the melting temperature. However, the biaxial orientation was present as a layered structure in which the orientation and texture varied from the outside to the inside surface of the blow molded article. Tensile and flexural properties, as well as the morphology and orientation as determined by scanning electron microscopy (SEM) and x-ray diffraction (WAXS), attested to the resulting structure in the blown parison. The orientation and properties were strongly dependent on the thermal and deformation histories during the process. For liquid crystal polymers with relatively slow crystallization kinetics, blow molding in the supercooled state represents a possible processing method to obtain multidimensional properties.
Foam Processing with Rigid Polyvinylchloride
Authors: Kim K. U. , Kim B. C. , Hong S. M. , Park S. K. 
Published: December 2013

Abstract
Rheological and processing studies have been performed on the extrusion of neat and expandable polyvinylchloride (PVC) compounds. Processing additives greatly change both rheological and physical properties. In the normal PVC processing temperature range, the neat compound exhibits very small values of power-law index, which increase with temperature. The usual usage level of dioctylphthalate (DOP), a plasticizer, and Acryloid K-125, a processing aid based on polymethylmethacrylate, increases the power-law index, whereas BTA, an impact modifier based on terpolymer of methylmethacrylate-butadiene-styrene, decreases it. DOP normally decreases viscosity and first normal stress difference. On the other hand, Acryloid K-125 and BTA increase them. Plotting first normal stress difference against shear stress, however, eliminates the effect of DOP and BTA level. Inclusion of a blowing agent increases the powerlaw index, and produces a substantial reduction in viscosity. At high shear rates, all the viscosity data of the expandable PVC compounds fall onto the single viscosity curve of the neat PVC compound. Two blowing agents, azodicarbonamide (ADCA) and sodium bicarbonate (SBC), yield similar reduction of the torque on a screw, but ADCA brings about much larger viscosity reduction than SBC. Further, ADCA shows more rapid bubble expansion rate on leaving the die exit and produces more uniform cells. On the other hand, SBC requires induction time for bubble expansion after leaving the die exit and gives a wider cell size distribution. Particularly in the foaming process with SBC, skin formation is considerably promoted by incorporating small quantities of DOP along with BTA, suggesting a strong potential for manufacturing rigid PVC structural foams with thicker skins by a single extrusion process.
Structure Development in Melt Spinning and Drawing of Nylon-11 and Nylon-12 Fibers
Authors: Shi Y. , White J. L. 
Published: December 2013

Abstract
A basic study of the development of crystallinity and polymer chain orientation in melt spinning and drawing nylon-11 and nylon-12 fibers is presented. The fibers were examined using wide angle x-ray diffraction, differential scanning calorimetry and optical retardation (birefringence) measurements. Melt spun nylon-11 fibers possesses an α-triclinic structure, while melt spun nylon-12 forms a γ-structure. Orientation factors were computed from wide angle x-ray diffraction measurements. These were correlated together with birefringence as a function of spinline stress. The influence of annealing and solid state drawing on fiber structure was investigated.
Naphthalene-ring Containing Thermotropic Copolyester and its Blends with PET
Authors: Zhou Z. , Wu X. , Yu M. 
Published: December 2013

Abstract
A series of thermotropic liquid crystalline copolyesters based on p-acetoxybenzoic acid, 2,7-diacetoxynaphthalene, terephthalic acid and polyethylene 2,6-naphthalate were prepared via melt transesterification. Their thermotropic liquid crystalline behavior was studied by visual observation on the hot stage of a polarized light microscope. The dependence of the crystallizability and melting temperature of the copolyesters on the 2,7-diace-toxynaphthalene content was examined by x-ray diffraction and differential scanning calorimetry. A blend sample was prepared by physically mixing 40% thermotropic copolyester and 60% polyethylene terephthalate and the phase-separated charackter of the copolyester and PET in the blend was proved by TOT and dynamic mechanical measurements. The SEM micrographs of the as-spun fibers of the blend show separation of the two phases. The highly oriented macromolecules and the fibril alignment of the mesomorphic copolyester in the blend has also been revealed after the dissolution of the PET phase in a solvent.
Rheological Properties and Morphological Structure of Blended and Filled Nylon-6
Authors: Wu D. , Tang N. , Gu D. , Wen W. 
Published: December 2013

Abstract
Rheological properties and morphological structure of PA 6/NBR and PA 6/EVA blends with and without CaCO3 fillers are studied. It is found that viscosities of samples investigated can be described approximately by the power law. The rheological behaviour of PA 6/NBR blends slightly deviates from the so-called logarithmic additivity law of the relation between viscosity and composition. The viscosity-composition curve of PA 6/EVA blends shows a positive deviation at the range of low shear rate and changes to the manner of negative deviation after the shear rate is greater than a certaine value. All the samples fabricated in the experiment perform very satisfactory in their processing. An unique morphological structure is found for them, which may be presented by the model of “sea and island”.
Film Blowing of Thermotropic Liquid Crystalline Polymers
Authors: Blizard K. G. , Wilson T. S. , Baird D. G. 
Published: December 2013

Abstract
The process of film blowing was considered in an attempt to obtain biaxial orientation and properties for two thermotropic copolyesters: p-hydroxybenzoic acid/polyethylene terephthalate (HBA/PET) and p-hydroxybenzoic acid/6-hydroxy-2-naphthoic acid (HBA/HNA). Tensile properties of the blown film were exceptional for these materials: tensile strengths of 300 to 400 MPa and moduli of13 GPa were observed in the axial direction, for example. This result if believed due to the absence of a skin-core texture in which the core often remains relatively unoriented. Despite some improvement in the transverse direction with increasing blow up ratio (B UR), properties did not exceed 20 to 25% of those in the machine direction. Wide angle x-ray scattering measurements confirmed the predominantly axial orientation in the films, which was believed to be generated in the annular die gap and not significantly disrupted during the subsequent blowing process. The properties and morphology of the blown film were compared to those ofuniaxially drawn films. It was found that in the machine direction the properties were similar, while significantly higher properties were obtained in the transverse direction for the blown film.
Structural Gradients in Injection Molded PPS
Authors: Hsiung C. M. , Cakmak M. , White J. L. 
Published: December 2013

Abstract
The processing-structure-property relationships in injection molded poly-p-phenylene sulfide (PPS) has been investigated. The structural gradients developed in the molded parts were characterized using optical microscopy, differential scanning calorimetry and wide angle X-ray diffraction techniques. Generally amorphous parts are produced with cold molds and crystalline parts with hot molds. At intermediate mold temperatures the parts produced exhibit a glassy surface and core and a crystalline annular ring sandwiched in between. The characteristics of this crystalline ring formation were studied as a function of processing conditions and position in the molded parts. Tensile and impact properties of the injection molded parts were correlated with the processing conditions and structure. The samples containing crystalline rings were found to exhibit greater toughness and tensile strength as compared to the samples that are uniformly amorphous or uniformly crystalline.
Flow Analysis in an Internal Mixer
Authors: Kawanishi K. , Yagii K. 
Published: December 2013

Abstract
A modified laboratory mixer (Banbury-type; batch volume is 250 cm3) with transparent front windows was used to observe the flow of silicone rubber. A pair of specially designed rotors was used in order to estimate the influence of rotor design upon the behavior of silicone rubber. Five parameters were picked up in designing the rotors. The rotor consists of a number of thin plates of identical shape. The plates are designed so that they can construct a double-winged rotor. By assembling the plates properly, the angles of twist of longer and shorter wings and lengths of wings can be varied, i. e. the overlap ratio of longer and shorter wings can be controlled. The rotor tip clearance is also variable. Batch homogenization times were measured with torque and unit-work for all experiments, observing the flow of silicone rubber through the front window at the same time. The torque and unit-work increase as rotor tip clearance decreased and as overlap ratio of wings increased. The twist angle of wings had little influence on torque and unit-work. The batch homogenization time became shorter with increases of rotor tip clearance, overlap ratio of wings and twist angle of wings and with the decrease of rotational speed ratio.
Modelling Flow in Tangential Counter-rotating Twin Screw Extruders
Authors: Kim M. H. , White J. L. 
Published: December 2013

Abstract
The flow of Newtonian fluids in a (modular) tangential counter-rotating twin screw extruder is analyzed using hydrodynamic lubrication theory and a modified Flow Analysis Network Method. The flow in systems with (i) forward puming screws and (ii) backward pumping screw pairs is investigated. For forward pumping screw elements we analyze the extent of back flow between the screws for different levels of screw flight staggering. The ratio of backflow to net flow is the highest when the flight staggering angle is 180°. The computed flow fields of backward pumping screw elements shows backward helical flow along the screw channel and forward flow between the screws. Screw characteristic curves of backward pumping screw elements are shifted by a factor of 2 Δp/L Q=0 from the forward pumping screw characteristic curves. The flow and pumping characteristics of modular systems have also been considered.
Influence of Melting Zone and Melt Homogeneity on Extrusion and Injection Molding Processes
Authors: Sakai T. 
Published: December 2013

Abstract
In this study, the melting behavior and melt homogeneity in a single screw extruder have been investigated to obtain better products in quality and higher productivity for extrusion and injection molding. For the analysis of the melting behavior, so-called “cooling experiments” were used. For the melt homogeneity evaluation, furthermore, molten polymer temperature fluctuations at the exit of a single extruder and injection molding machine were measured. As a result of these analyses, we have concluded that the melting process in extrusion and injection molding played an important role on improving product quality and its productivity. Based on experiments and analyses on the melting mechanism, we have developed a mixing and kneading screw configuration with a new melting process, in which the compulsory circulation flow in solid bed accelerates rapid melting of raw materials and melt homogeneity.
Instability Phenomena in Film Casting Process
Authors: Barq P. , Haudin J. M. , Agassant J. F. , Roth H. , Bourgin P. 
Published: December 2013

Abstract
This paper deals with instability phenomena in PET film casting. An experimental investigation makes it possible to confirm the occurrence of draw-resonance above a critical draw ratio, and to show interesting coupling effects between thickness and width fluctuations. A theoretical model is developed on the basis of some important assumptions: constant width, vertical film, isothermal regime and Newtonian behavior. It allows to calculate the response to a sudden increase of the chill roll velocity and to predict the critical draw ratio (DR = 20.3). Other types of perturbations of the roll velocity (sinusoidal oscillation, random fluctuations) are also treated using this model.
Influence of Stretching and Cooling Conditions in Cast Film Extrusion of PP Films
Authors: Duffo P. , Monasse B. , 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 to study the effect of the roll temperature on the polymer crystallization in the thickness of extruded films. A thermomechanical model of the whole process taking into account the polymer crystallization was used to determine the mean stretching stress in air, local temperature, local cooling rate and local crystallization development. The morphologies in the thickness of the films were observed by optical microscopy on microtomed slices and the crystalline structures were investigated by wide-angle X-ray diffraction and DSC measurements. From DSC melting curves of thin sections it is possible to know the local crystallization temperature and to check the thermomechanical model. The model is validated and explains the influence of the roll temperature on the formation of structures and morphologies. Nevertheless neither the existence of three different zones in the thickness nor the high p phase concentration are predicted by the model, which needs new developments.
Multilayer Injection Molding
Authors: Vos E. , Meijer H. E. H. , Peters G. W. M. 
Published: December 2013

Abstract
Visualization of the fountain flow in a piston driven non-Newtonian flow is studied by means of experiments and numerical computation. The result will be applied to the multilayer injection molding technique, where an accumulator is used, to store the polymer melt. The discontinuity at the contactline of the piston and the wall of the cylinder appears to have considerable influence on the total deformation history.
Flow Analysis of Sheet Molding Compounds in Compression Molding
Authors: Lee L. J. , Fan J. D. , Kim J. , Im Y.-T. 
Published: December 2013

Abstract
A series of experiments and a numerical simulation were carried out to investigate the flow of silly putty and sheet molding compound (SMC) at various processing conditions in compression molding. The flow resistance and the interface friction of both materials were characterized by using a squeeze flow rheometer and the ring compression test, respectively. Molding experiments were carried out on an instrumented mold and the finite element code ALPID (Analysis of Large Plastic Incremental Deformation) was used for numerical simulation. The flow front shape, temperature profile, and pressure change obtained by numerical simulation compared well with experimental results.
Modeling of Reactive Filling in Complex Cavities***
Authors: Garcia M. A. , Macosko C. W. , Subbiah S. , Güçeri S. I. 
Published: December 2013

Abstract
The flow of reacting monomers into thin planar cavities of irregular geometry is analyzed. The Hele-Shaw approximations are used to simplify the momentum and mass balances. At each time step, the flow domain is mapped onto a rectangular domain using elliptic expressions. The transformed governing equations are solved using finite-differences. The transient three-dimensional energy and species balances are solved using an explicit marching scheme coupled to the flow. Viscosity is modeled as a function of temperature and extent of reaction. Castro's model is used to compare several fountain flow approximations. A simplified algorithm was found to capture the essence of the fountain flow kinematics. The fountain flow approximations described here can also be used in thermoplastic injection molding modeling. Results for a rectangular end gated mold and for an irregular mold geometry are presented.
Dynamic Modelling of Internal Mixers Using System Identification Techniques
Authors: Stoten D. P. , Moore J. M. 
Published: December 2013

Abstract
Dynamical modelling techniques are presented that facilitate the derivation of transfer function models between key inputs and outputs of internal mixing processes. Tests to model the mastication of natural rubber in a Francis Shaw Intermix at two levels of fill-factor are described. The derived models will form the basis for closed-loop control strategies.