bluuebunny/crossref_metadata_2025_split huggingface dataset:
Injection Moulding of a Commercial β-Nucleated Polypropylene
Authors: Varga J. , Breining A. , Ehrenstein G. W. , Bodor G. 
Published: December 2013

Abstract
In a recent paper [1], the preparation techniques, structural features, crystallization, melting characteristics, and certain properties of the β-modification of isotactic polypropylene (β-IPP) were reviewed. Possible uses of β-IPP were demonstrated through example applications. The problems involved with the processing of β-nucleated polypropylene were analyzed and the conditions of the processing technology of β-IPP end-products were discussed. In the present paper, the results of the studies on the injection moulding technology of a commercial β-nucleated polypropylene are addressed.
Modeling the Distributive Mixing in an Internal Batch Mixer
Authors: Hutchinson B. C. , Rios A. C. , Osswald T. A. 
Published: December 2013

Abstract
Mixing has been the focal point of many experimental studies in recent years, but advances in modeling and simulation now allow for fast, accurate and useful simulation analysis. Numerous mixing indices have been developed but the majority are tailored to experimental studies. In this study, a new mixing index is developed to analyze the particle position history of the mixer. Due to its simplicity when dealing with moving boundary problems, the boundary element method is employed to model the fluid flow and track particles.
Numerous geometries can be modeled and compared on a basic workstation. First the mixing index is applied to Couette flow. Analytical and boundary element simulation results compare well. Next the method is used to analyze the mixing capabilities of a Banbury mixer with different speed ratios. Further the mixing index is used to compare the mixing capabilities of triangular mixing lobes versus typical Banbury type.
Profile Die Design Based on Flow Balancing
Authors: Švábík J. , Plaček L. , Sáha P. 
Published: December 2013

Abstract
This paper presents a methodology for the design of profile dies based on the Cross Flow Minimization Method. The flow balancing is described for cases where the flows are balanced by varying the die land length combined with the flow separation. Three different approaches were utilized in the die analysis. First, the flow in two proposed profile dies was calculated by substituting the flow domain by a set of simple geometries. The second approach applied the Cross-Sectional Calculation method, while the last method is a fully 3D FEM non-isothermal calculation. The results are verified by comparison with experimental data. It is shown that each of the calculation procedures may be the choice of preference depending on the geometrical complexity.
Comparative Study of Ziegler-Natta and Metallocene Based Polypropylenes in Injection Molding
Authors: Isayev A. I. , Churdpunt Y. , Guo X. 
Published: December 2013

Abstract
Injection molding of the isotactic polypropylenes polymerized using metallocene and Ziegler-Natta catalysts and having the same molecular weights was performed. Rheological properties and shear-induced crystallization kinetics were measured and their comparative analysis is made. These data are fitted to the equations necessary for simulation of the injection molding process. Numerous injection molding runs were carried out and pressure measurements during molding were performed. The gapwise distribution of crystallinity, spherulite size and thickness of flow-induced crystallized layer in moldings were measured. The effect of various processing conditions on these values was determined. The measured values were compared with the results obtained from the simulation of injection molding process using unified theory of crystallization proposed earlier. Comparative analysis is made between flow conditions and crystallization behavior of these polymers and their effect on the pressure development and structural characteristics of the moldings.
Non-Isothermal Transient Startup of A Starved Flow Modular Co-Rotating Twin Screw Extruder
Authors: Kim E. K. , White J. L. 
Published: December 2013

Abstract
A model for non-isothermal Newtonian flow startup in an initially empty modular self-wiping co-rotating twin screw extruder is developed. A viscous Newtonian fluid is considered to gradually fill a modular co-rotating twin screw extruder with viscous heating and heat transfer to the barrel (and screw). The build up of the axial cup mixing temperature profiles with time was calculated for various modular screw configurations.
Polymer Flow Velocity in the Helical Channel in Dependence of a Coordinate System
Authors: Sikora R. , Sasimowski E. 
Published: December 2013

Abstract
Taking into consideration the extensive literature we conducted our own studies of polymer flow velocity in the helical channel of the plasticating system. They included the following subjects: studies conditions in rectangular and helical coordinate systems—a model with a rotating barrel and a model with a rotating screw (theoretical principles); computational verification on the concrete example for different screw channel depths; comparison of the models with regard to drag flow velocity, pressure flow velocity, longitudinal flow velocity (resultant), shear rate and polymer viscosity.
The thesis that both models of a screw-based plasticating system with a rotating barrel or a rotating screw differ fundamentally was confirmed in the same conditions in two coordinate systems—rectangular and helical. In connection with this theoretical investigations at a rotating barrel and next their experimental verification at a rotating screw, which is a common practice, are unsuitable.
Polymer Melt Rheology at High Shear Rates
Authors: Haddout A. , Villoutreix G. 
Published: December 2013

Abstract
The importance of polymer flow properties during processing has required the development of new on line measurement systems, able to work under rates encountered during industrial processes. This paper will describe a rheometer which is able to study the thermorheological behavior of polymers within industrial injection or extrusion machines. Its main feature is to work at high shear rates which are experimented during production processes; it is equipped with dies of different diameters and lengths, allowing shear rates between 102 to 107 s−1. Some results concerning viscosity and first normal stress differences are presented for high density polyethylene (HDPE), polypropylene (PP) and polypropylene/polyarylamide blends (PP/PA). The plot of viscosity and first normal difference against shear rate for these materials are not linear. Two non Newtonian regions and a third one similar to Newtonian behavior were observed in the wide range of shear rates up to 8.106 s−1.
Dynamic Analysis of Melting in Injection Extruder
Authors: Yung K. L. , Xu Y. , Lau F. 
Published: December 2013

Abstract
Melting is one of the most important process in plastics processing. Admit the extensive use of plastic injection moulding machine in industry, most studies were on extruders which were simpler to model. This paper studies the melting process and derives its transient (dynamic) model for predicting the characteristics of melting in feeding stage of injection extruder. Based on this transient model, factors affecting the melting speed in injection extruders are exposed. Simulation results agree with the results from experiments.
A New Approach in Offline-Optimization of the Injection Molding Process
Authors: Kuhmann K. , Meckbach S. , Zhao G. , Ehrenstein G. W. , Jeltsch-Fricker R. 
Published: December 2013

Abstract
For the purpose of process optimization of the injection-molding process a robust processing point is determined, at which specified characteristics of the parts are met and the process is insensitive to disturbances. The idea of the new optimization concept is to ensure that also around the robust processing point, within the so-called robust processing window, the part geometry is in tolerance and a low standard deviation respectively a high SN-ratio is achieved. Instead of reducing the optimization task to a one-dimensional problem by combining the target functions, in this approach one defines lower and upper bounds for the characteristics to be optimized. These bounds must be fulfilled in the range of the robust processing window and, if necessary, might be sharpened or relaxed during the optimization procedure. The corresponding response surfaces are generated by means of new Scattered Data Interpolation-methods.
Radially Dependent Stress and Modeling of Solidi cation in ilament Melt Spinning
Authors: Henson G.M. , Bechtel S.E. 
Published: December 2013

Abstract
When polymer fibers are manufactured by melt spinning, axial velocity is nearly uniform across any cross section but temperature and stress vary significantly across the fiber radius. Thus, the fiber solidifies from the outside in, with the fiber being solid on the outside but molten on the inside for some distance before complete solidification, and stress near solidification, the controller of mechanical properties of the spun fiber, has radial variation. We present a computationally 1D melt spinning model which recognizes the radially inhomogeneous solidification region, and computes axial and radial dependence of stress in the spinline. With this radial resolution, stress near solidification is now the stress evaluated on a surface near the solidification boundary. In simulations of melt spinning processes, we investigate features of the solidification boundary and stress near solidification, and examine how these change as material properties and process conditions change. As part of this study, we propose and investigate a solidification criterion that is a function of both stress and temperature.
Numerical Study of Internal Bubble Cooling (IBC) in Film Blowing
Authors: Sidiropoulos V. , Vlachopoulos J. 
Published: December 2013

Abstract
Numerical simulation of turbulent airflow emerging from an Internal Bubble Cooling (IBC) stack and directly impinging on the internal surface of a blown film bubble has been carried out. The streamline pattern and heat flux are determined through a finite volume numerical technique using a version of k-∊ turbulence modeling. It is shown that balancing the airflow between the multiple slits of the stack is useful to increase the internal cooling rates, but may require more elaborate designs of the inlet pipe. As the air flows towards the internal bubble surface there is significant deceleration which diminishes the effectiveness of the heat removal mechanisms. Depending on the flow rates and geometrical configurations the airflow may induce compressibility effects at the exhaust pipe. The numerical results suggest that Internal Bubble Cooling (IBC) equipment introduces distinctive design and operation challenges.
Comparison Studies of Anionic Polymerization of Caprolactam in Different Twin Screw Extruders
Authors: Lee B. H. , White J. L. 
Published: December 2013

Abstract
There is a study on the comparison of twin screw extruders and a batch mixer in the polymerization of caproiactam. A sodium metal initiator and 4–4'-diphenylmethane diisocyanate (MDI) as the activator were used. Our attention is given to (i) a modular intermeshing co-rotating twin screw extruder, (ii) a modular intermeshing counter-rotating twin screw extruder and (Hi) a modular tangential counter-rotating twin screw extruder. We consider the variables of screw configuration, temperature profile, screw speed, and throughput on polymer characteristics. It was found that the conversion of twin screw extruders with proper mixing segments is much higher than the internal mixer at low mixing times. This was seen as higher conversion in twin screw extruders than an internal mixer for the same mean residence time considered.
Microstructure and Prediction of Stress-strain Behaviour of Cold-rolled PP Sheets
Authors: Wu S. Z. , Lee W. B. 
Published: December 2013

Abstract
A constitutive equation for cold-rolled polypropylene is presented based on a modified two-phase model for semicrystalline polymer, which combines the crystalline network that obeys the Langevin based theory and the entangled network with slip-linked character. The microstructure of the rolled semicrystalline polymer consists of packed crystalline inclusions which are separated by adjacent amorphous regions. A theoretical description of the stress strain behavior is obtained by the sum of the stress effects from crystalline and entangled networks. The microstructural observations by scanning electron microscopy X-ray pole figures and differential scanning calorimetry show that polymer chains are aligned along the rolling direction. The stress-strain equation can be obtained from the modified two-phase model and verified by experimental results.
Effects of Process Conditions on the Dissolution of Carbon Dioxide in PS in Foaming Extruders
Authors: Zhang Q. , Xanthos M. , Dey S. K. 
Published: December 2013

Abstract
The effects of the main processing conditions on the dissolution behavior of CO2 in polystyrene melt were studied using a novel in-line method in connection with both single and twin-screw foaming extruders. Apparent solubility data obtained from the twin-screw extrusion experiments showed better consistency compared with those obtained from the single screw experiments, indicating the importance of enhanced mixing in affecting the gas dissolution and solubility behavior during an extrusion foaming process. Gas dissolution inside a twin-screw foaming extruder was further studied for CO2 in the polystyrene melt. The measured gas up-take was compared with the values calculated assuming equilibrium conditions in the gas injection zone in an effort to elucidate possible mechanisms for gas dissolution inside a foaming extruder during the actual foaming process.
An Empirical Study of the Surface Blush in Gas-Assisted Injection Molded Parts
Authors: Liu S.-J. , Lin I.-H. 
Published: December 2013

Abstract
Gas-assisted injection molding of thermoplastic materials has become an important process in industry, because of its capability of producing parts that have thick and thin sections with a good structured rigidity. However, there are some unsolved problems that confound the overall success of this technique. Surface blush of the molded parts caused by glossy difference of the materials is one of them. An L'18 experimental matrix design based on the Taguchi method was conducted to investigate the surface blush of gas-assisted injection molded thermoplastics. The material used was black-pigmented polypropylene. Experiments were carried out on a 4.1 oz reciprocating injection-molding machine equipped with a high-pressure nitrogen-gas injection unit. A plate cavity with gas channels of different geometry was used to mold the parts. After molding, the surface quality of the parts was characterized by a gloss-meter. For the factors selected in the main experiments, mold temperature and gas pressure were found to be the principal factors affecting the surface quality of gas-assisted injection molded parts. The surface glossy difference increases with the content of the pigment in the materials. In addition, a trapezoidal gas channel of small width was found to mold the parts with the least glossy difference. An aluminum mold helps reducing the surface blush in molded parts.
Estimation of Residence Time Distribution in two Elements of a Ko-Kneader
Authors: Mehranpour M. , Nazokdast H. , Dabir B. 
Published: December 2013

Abstract
An attempt has been made to estimate the resident time distribution (RTD) in the KE and EZ elements of the Buss Ko-Kneader. The effects of both rotating and reciprocating motions of the screw were taken in to account in the flow analysis as well as in a simplified mathematical model developed for the RTD estimations. The basic function employed in the present work was F(t) = ∫ f(t) dt, where f(t) dt defined as dq/q was evaluated as a function of the channel depth. Due to the periodic nature of the system averages of minimum resident time was considered as tmin in the above equation. The computation of the model was carried out to evaluated the F(t) as a function of time for both KE and EZ elements. These results demonstrate that the residence time distribution in KE element is slightly narrower than that in EZ element.
Direct Measurement of Fiber Temperature in the Continuous Drawing Process of PET Fiber Heated by CO2 Laser Radiation
Authors: Okumura W. , Yamaguchi T. , Ohkoshi Y. , Gotoh Y. , Nagura M. 
Published: December 2013

Abstract
Poly(ethylene terephthalate) (PET) fiber was heated by carbon dioxide laser radiation during the continuous drawing process. Numerical calculation shows that the PET fiber can be heated much more rapidly and uniformly by heat radiation than by convective heat transfer through the fiber surface. During CO2 laser heated drawing, temperature in the vicinity of a neck-like deformation can be measured on-line with high precision, because the neck-like deformation is located within a range of 0.5 mm. We measured the fiber temperature profiles on the drawing process by IR thermometer that has a range resolution of 0.355 mm. The temperature at which neck-like deformation of the fiber initiates is higher than Tg when draw ratio is less than 4.5, but lower than Tg when draw ratio is more than 5.5. The maximum fiber temperature in the drawing process increases with draw ratio, up to 208°C for a draw ratio of 6.0. The rate of orientation-induced crystallization in the drawing process was estimated by comparison of measured temperature profiles with calculated temperature profiles.
A New Method for Simulating the Conveying of Solid Pellets
Authors: Yung K. L. , Xu Y. , Lau K. H. 
Published: December 2013

Abstract
A new method for simulating the solid conveying process in plasticating machine is proposed in this paper. The new simulation method is superior to previous ones by having the ability in modeling the movements, in any direction, of solid pellets of any geometry or whether it is densely or sparsely packed. New normal and tangential contact force models are introduced. With the new method the solid conveying process are simulated more realistically. In the simulation, the effects of velocity of the barrel, the sliding frictions of the pellets against the barrel and the screw walls with respect to the solid conveying speed are studied, which coincide with empirical results.
Tensile Strength Characteristics of Polymer Melts
Authors: Zatloukal M. , Štach P. , Liu P. , Sáha P. 
Published: December 2013

Abstract
Two different methodologies were employed to determine tensile strength properties of two LDPEs and two metallocene LLDPE resins through capillary and Haul-off (Rheotens-like) measurements. It has been shown that the tensile strength properties obtained by both methods yield almost the same values. Moreover, these values can be correlated to the drawability in tubular film blowing for corresponding materials.
Residual Stress and Warpage Models for Complex Injection Molded Parts
Authors: Young W.-B. , Wang J. 
Published: December 2013

Abstract
In the postfilling stage of an injection molding process, thermal induced residual stress usually develops during the solidification of the melt with non-uniform through thickness temperature distribution. Furthermore, the packing pressure is applied through the gate, and will be different in different locations. Since the local melt pressure varies with time due to the change of melt viscosity, the material solidifies under different frozen-in pressure. The stress relaxation behavior of the plastic materials also complicates the stress field. This study uses a simple thermoviscoelastic model to calculate the residual stress developed in the postfilling stage and a elastic model to determine the warpage after demolding for three dimensional complex parts. Based on the calculation of the injection molding process, the temperature and pressure histories in the postfilling stage can be determined, and used to calculate the developed stress field. The model divides the thickness into two regions, liquid and solid phases. Residual stress calculation is applied in the solid region, while the liquid region is kept at the melt pressure without any strain. The resulted in-mold stress fields are used to calculate the part warpage after demolding.
Crystallization and Orientation Development in Melt Spinning Isotactic PP of Varying Tacticity
Authors: Choi D. , White J. L. 
Published: December 2013

Abstract
We investigated the effects of tacticity on crystallization and orientation development in melt spinning isotactic polypropylene (iPP) through air. Melt-spun fibers were characterized by wide-angle X-ray diffraction (WAXD), birefringence and differential scanning calorimetry (DSC). The melt-spun fibers usually exhibited the monoclinic α-crystalline form, but the mesomorphic form was found under certain processing conditions. The mesomorphic structure was formed more readily in low tacticity fibers. We found certain amounts of hexagonal β-crystalline form in all of the α-form fiber samples. The amouns were generally negligibly small, but the low tacticity fibers spun at high draw-down ratios exhibited significant amounts of β-form crystals. At low spinline stress levels, some low tacticity fibers exhibited lower birefringence and chain orientation than high tacticity fibers due to a less perfect crystal structure. At certain high spinline stress levels, low tacticity fibers exhibited much higher birefringence and chain-axis orientation levels than expected. This was attributed to a reduction in epitaxial lamellar branching (a*-axis oriented group in bimodal orientation). However, the extent of lamellar branching in low tacticity fibers appeared to increase again at higher stress levels. This led to a significant decrease in birefringence and crystalline orientation.
A New Style Single Screw Extruder with Improved Plastification and Output Power
Authors: Grünschloβ E. 
Published: December 2013

Abstract
A single-screw-extruder is presented, consisting of a barrel with grooved feed zone (helical grooves), a grooved melting zone (axial or helical grooves) and a barrier-screw with mixing and shearing elements. Compared with extruders with a smooth melting zone, significant process improvements are achieved regarding mass throughput, pressure build up, melt temperature, melt homogeneity, feed-zone cooling, processing wall-slipping polymers, abrasive wear, residence time, total degree of efficiency and economy. The processing principles of the new extruder are explained. Experimental results confirm the theoretical predictions. The system has proven to be very worthwile in more than 100 extrusion blow molding machines since 3 years.
Investigation of Bubble Instabilities in Film Blowing Process
Authors: Laffargue J. , Parent L. , Lafleur P. G. , Carreau P. J. , Demay Y. , Agassant J. F. 
Published: December 2013

Abstract
This paper describes an original on-line video device developed in order to study bubble instabilities occurring in the film blowing process, taking into account their three-dimensional behavior. For a linear low-density polyethylene, two forms of instabilities and combination have been observed: draw resonance and helical instability. These instabilities could be quantitatively described and differences in behavior could be assessed using real objective measurements and criteria. The influence of key processing conditions was investigated and the results showed that the instabilities are enhanced by increasing the draw ratio, blow up ratio and frost line height. These first results are in agreement with the majority of the results reported in the literature, but allow for a more accurate analysis of the phenomena.