bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of Mixing Performance in a VIC Mixer
Authors: Yang Haur-Horng , Manas-Zloczower Ica 
Published: December 2013

Abstract
The VIC mixer is an intermeshing internal mixer, whose unique feature is its ability to vary the clearance between the two rotors. The flow field in the chamber of an internal mixer is difficult to analyze due to the complex geometry and transient character of the flow. Here, a fluid dynamics analysis package – FIDAP, using the finite element method was employed to simulate the flow patterns in a VIC 1.9 mixer. A 3D flow analysis was carried out for the whole mixing chamber. The problem of time dependent flow boundaries was solved by selecting a number of sequential geometries to represent a complete mixing cycle. The flow field was characterized in terms of velocity profiles, pressure contours, shear stresses generated and a parameter λ quantifying the elongational flow components. The last two parameters are the most important ones in analyzing dispersive mixing efficiency. Distributive mixing was studied numerically by means of tracking the evolution of particles originally gathered as clusters. The pairwise correlation function and the particle concentration were used to quantify the degree of mixing. The dynamic average flow field characteristics based on the particle tracking were also calculated. The effect of changing gap size on dispersive and distributive mixing was investigated.
Compatibilization and Dynamic Vulcanization of PA 6/Isobutylene Methylstyrene Elastomer
Authors: Kuwamoto K. 
Published: December 2013

Abstract
The effect of reactive polymer blending on the rheological properties and the deformation of dispersed phase in extruded films is described. Three types of polymer blends are studied: (1) a non-reactive blend of nylon 6 (PA 6)/isobutylene-co-para-methylstyrene elastomer; (2) a compatibilized blend of PA 6/brominated (isobutylene-co-para-methylstyrene) elastomer (XP-50); (3) a compatibilized, dynamically vulcanized blend of PA 6/XP-50 plus curatives. Mixing is performed with a Brabender mixer and a twin screw extruder. Rheological measurements were performed at 240 °C which is above melting temperature of PA 6. The storage moduli and complex viscosities of type (3) are the highest, those of type (2) are the next and those of the mechanically mixed non-reactive components are the lowest. The dispersed phases in extruded films show that the deformation of the dispersed elastomer in type (3) is the smallest. The sizes of the dispersed-elastomer domains in type (2) and type (3) are much smaller than those of type (1). There are large and highly deformed dispersed phases in the film of type (1). Also the interfacial bonding is poor.
Integral Constitutive Model (K-BKZ) to Describe Viscoelastic Flow in Injection Molding
Authors: Chang Rong-Yeu , Chiou Shiaw-Yuh 
Published: December 2013

Abstract
A novel theory which employs the K-BKZ viscoelastic integral constitutive model was developed in this study for simulating the non-isothermal injection molding filling process and the frozen stresses of a three-dimensional thin part. The simulation of viscoelastic model in such a problem has not yet been discussed in most previous works as a result of the complexity of this problem. A quasi-steady approximation concept was developed in the present investigation for solving the non-isothermal filling process via K-BKZ viscoelastic integral constitutive model. Additionally, the numerical method of flow field was based on the control volume finite element method. The flow field of generalized Newtonian fluid was used as the initial guess of flow kinematics. The quasi-steady state approximation was introduced for each element to calculate the flow kinematics and stress profile from the K-BKZ integral constitutive model. The finite difference method with streamline upwind characteristic was adopted here for calculating the temperature field of process. When the cavity is fully filled, the subsequent non-isothermal stresses would relax after cessation of flow. Thereby, the frozen stresses (or frozen birefringence) could be obtained.
Mechanical Effects in Extrusion: Slit Dies
Authors: Pittman J. F. T. , Sander R. , Schuler W. , Pick H. , Martin G. , Stannek W. 
Published: December 2013

Abstract
Simulations of the elastic deflection of a 1.2 m slit die under load during the extrusion process have been performed, using the commercial finite element package MARC. The melt pressure distribution needed to assign the loads to the MARC package was previously obtained by a Hele-Shaw based finite element program, and was thus not coupled with the deflection analysis. Existing analytical calculation methods for deflection are also examined. Experiments using production scale machinery have been conducted to record the die deformations under different melt pressures and compared with the computed data. Analytic deflection predictions are shown to be inadequate. The numerical results are fair, but it is clear that coupling of flow and deflection analyses is essential.
Structures and Properties of Injection Moldings of β-Crystal Nucleator-Added Polypropylenes
Authors: Fujiyama M. 
Published: December 2013

Abstract
An isotactic polypropylene homopolymer (PP) was added with 0 to 10000 ppm of γ-quinacridone, a β-crystal nucleator of PP. Flexural test specimens were injection-molded from the PP at cylinder temperatures of 200 to 320 °C and the structures and properties have been studied. The results can be summarized as follows: The crystallization temperature increases with γ-quinacridone content. The β-crystal content decreases with increasing cylinder temperature and shows a maximum at a γ-quinacridone content of about 100 ppm. The thickness of the skin layer scarcely depends on γ-quinacridone content. The orientation of β-crystals decreases with increasing cylinder temperature. It is high at the surface regions and decreases toward the interior. The Izod impact strength increases with γ-quinacridone content. The degree of the increase is higher as the β-crystal content is higher and reaches more than threefold in the highest case. The flexural modulus and strength decrease by about 10 % in the highest case. The heat distortion temperature increases with γ-quinacridone content. The mold shrinkage increases with γ-quinacridone content. From these results, it is concluded that the injection moldings of PPs containing γ-quinacridone are superior in impact strength and heat resistance.
Analysis of Polymer Flow through Coathanger Melt Distributors
Authors: Schläfli D. 
Published: December 2013

Abstract
Coathanger melt distributors are generally designed on the basis of one-dimensional flow models. These do not always have the desired performance, wherefore a 2-D flow analysis tool was developed based on lubrication approximation theory. This tool uses a contour adapted calculation grid and accounts for manifold side walls. Good agreement is observed for a variety of distributor designs. The integration of this tool into the design process permits to evaluate distributor geometries at design stage, reducing empirical corrections and adjustments.
Elastic Calculation of Residual Stresses in Injection Molding
Authors: Boitout F. , Agassant J. F. , Vincent M. 
Published: December 2013

Abstract
A calculation of residual stresses in injection molding using a 2-D description of the geometry is presented. The polymer follows an elastic behavior law. The thermal shrinkage and the frozen-in pressure when a layer solidifies are taken into account. A calculation of the pressure in the liquid areas after the gate is frozen is presented. A simplified mold deformation model is introduced and its influence on residual stresses is shown. Results are presented for a polystyrene injected in a square plaque.
Structure and Properties of Injection Moldings of β-Crystal Nucleator-Added Polypropylene
Authors: Fujiyama M. 
Published: December 2013

Abstract
Isotactic polypropylene (PP) with MFIs of 0.43 to 44.5 g/10 min were added with 0 to 10 ppm of γ-quinacridone, a β-crystal nucleator of PP. Flexural test specimens were injection-molded from the PPs at constant molding conditions and the structures and properties have been studied. 1) The crystallization temperature increases with γ-quinacridone content and MFI of the base resin. 2) The β-crystal content increases with γ-quinacridone content and MFI. 3) The thickness of the skin layer decreases with MFI and scarcely depends on γ-quinacridone content. 4) The orientation of β-crystals decreases with MFI. 5) The Izod impact strength increases with γ-quinacridone content for PP with MFI < 40 g/10 min, and decreases with MFI. However, little improving effect of γ-quinacridone is observed for MFI > 40 g/10 min. 6) The flexural modulus and strength decreased by about 10 to 20 % by the addition of γ-quinacri-done and the decrease is more significant for PP with higher MFI. 7) The heat distortion temperature increases with γ-quinacridone content and the increase becomes more prominent with increasing MFI. 8) The mold shrinkage increases with γ-quinacridone content and decreases with MFI.
Study on the Performance of Cooling Systems in Precision Injection Molds
Authors: Yang S. Y. , Chang H. C. 
Published: December 2013

Abstract
Mold temperature is one of the most important factors regarding the quality and production rate in injection molding. Enhancing the performance of mold as heat exchanger is expecially critical to precision molding. In this study, mold temperatures measured at four selected points are used to assess the effects of cooling channel layout and core material on the cooling performance of injection molds for precision molding. Measured data indicate that mold temperature is a complex function of space and time (in-cycle and cycle-to-cycle). Three performance indices based on the measured data are first established for comparing the cooling performance between molds with various design parameters. They are the response to reach equilibrium, the thermal uniformity, and the average mold temperature. Molds implemented with three typical cooling channel configurations and inserted with three core materials are constructed. Their cooling performances during injection molding of disks with steps have been compared. Information from computer-aided simulation of the mold cooling process further facilitates the evaluation of mold cooling performance. General guidelines for planning of cooling channel layouts and selection of core materials are drawn from this study. Experimental and theoretical results suggest that high thermal conductivity of the cores enhances the thermal uniformity, while high heat capacity retards the response of the system to reach thermal equilibrium. High convective area to mold volume improves the overall performance of mold as heat exchanger.
Modeling of Polymer Devolatilization in a Multi-vent Screw Extruder
Authors: Wang N. H. , Sakai T. , Hashimoto N. 
Published: December 2013

Abstract
A model for representing polymer devolatilization behavior in a screw extruder with multi-vent sections has been proposed. In this model, an overall film-interface geometry factor (OFIGF) comprised of several local film-interface geometry factors (LFIGF) is used as a measure for the devolatilizing performance of a screw extruder. Moreover, the OFIGF is related to screw geometries and open angles of open areas in vent sections, and dependent on the degree of filling or the flowrate of the fluid and the screw speed. An intermeshing co-rotation twin-screw extruder popularly used was taken as an example to discuss the effect of the OFIGF on its devolatilizing performance. For this purpose, a solution of how to calculate the local film-interface areas and their exposure time in a venthole unfitted zone (VUfZ) and a venthole fitted zone (VFZ) with an open area was presented. Furthermore, several interesting results about how the OFIGF is affected by flowrate, screw speed, lead, and number of tips were predicted and discussed. The results suggested that the devolatilizing performance of the VFZ is lower than that of the VUfZ due to decrease in the surface renewal effect there, and a plot of ln {(wout – w*)/(win – w*)} against (N1/2/Q) in generally used flowrate and screw speed ranges for a given screw geometry does not strictly satisfy a linear relationship due to the filling-degree dependence of the OFIGF.
Models of Flow and Experimental Studies on a Modular List/Buss Kokneter
Authors: Lyu M.-Y. , White J. L. 
Published: December 2013

Abstract
An experimental and theoretical study of the behavior of a List/Buss Kokneter is presented. The experimental study which uses polypropylene considers (i) the interaction of the Kokneter with a crosshead screw extruder, and (ii) distribution of polymer in the modular screw. A modeling study considers the dynamics of flow including the influence of screw oscillation. Calculations are made for various individual Buss elements. A model is developed for the total system including the crosshead screw extruder. It is shown that an oscillating length of fill in the crosshead screw extruder can account for the throughput oscillation stabilization characteristics of the composite machine. Predictions of pressure profiles and positions of starvation in a starved flow machine are made.
Analyses of Bowing Phenomena in Successive Transverse Stretching and Thermosetting Process for Biaxially Oriented Film
Authors: Yamada T. , Nonomura C. , Matsuo T. 
Published: December 2013

Abstract
Bowing distortion phenomena of bi-axially oriented film cause serious problems in practical application. Bowing distortion was conveniently defined to carry out the analysis. Bowing distortion profile throughout a tenter machine was observed. This profile was fairly successfully simulated by FEM using suitable anisotropic and heterogeneous elastic constant distributions, and a suitable initial shape of the elastic body. The mechanism of bowing distortion in relation with TD stretching was estimated by the above results and some experimental data. This leads to the forecast that the insertion of a cooling zone between the TD stretching zone and the thermosetting zone will be an effective way for decreasing bowing distortion of film. This forecast was experimentally verified. Despite the insertion of the cooling zone, a certain level of bowing distortion still remained. It was tried to give an explanation for the mechanism of the remaining distortion in terms of heat-shrinkage force in the thermosetting zone.
Evaluation of the FAN Technique for Profile Die Design
Authors: Huneault M. A. , Lafleur P. G. , Carreau P. J. 
Published: December 2013

Abstract
Die design is a daily concern in the manufacturing of extruded profiles. There are very few available Computer Aided Design (CAD) tools for profile die designers and considerable time and resources must be devoted to trial and error design procedures. This paper examines the applicability of the flow analysis network (FAN) to the design of profile extrusion dies. The FAN method is found to provide useful design information at a fraction of the computing cost required for 2.5 and 3D finite element methods. Experimental flow distribution obtained by extruding PVC compounds and polyethylene through simple profile dies are compared to model predictions. The numerical and experimental results provide evidence about the significant contribution of transverse flow to the flow distribution at die exit.
Devolatilization with Chemical Reaction in Polymer Solutions
Authors: Hu G.-H. , Chen Liqin , Lindt J. T. 
Published: December 2013

Abstract
It has been observed previously [1] that under the specific conditions prevailing in a reflux flask reactor, the overall rate of the transesterification reaction between an ethylene and vinyl acetate copolymer and 3-phenyl 1-propanol can be enhanced appreciably by the introduction of boiling inert hydrocarbon solvents. In the present study, the same reaction carried out under a controlled removal of vapors in a simulator emulating a non-intermeshing counter-rotating devolatilization twin screw extruder, a significant acceleration of the reaction rate has also been observed. In agreement with the previous work [1], the intrinsic reaction mechanism and the chemical equilibrium do not appear to be affected by boiling of the inert hydrocarbon solvents, nor does the additional mechanical agitation due to the rapid bubble growth contribute to the increase of the overall reaction rate. Theoretical analysis of the results confirms that the acceleration of the reaction rate originates from the localized mass transfer effect connected to the presence of the bubble vapor-liquid interface films induced by devolatilization.
Molecular Orientation in Polycarbonate Induced by Cooling Stresses
Authors: Wimberger-Friedl R. 
Published: December 2013

Abstract
The origin of the maximum of the birefringence at the surface of injection-molded polymer products is discussed. By systematic variation of the molding conditions with polycarbonate, it is shown that the maximum at the surface not only depends on the filling, but even more so on the packing conditions. The birefringence at the surface is equal in the flow direction and transverse to it. The height scales with the cavity pressure during compression and packing. This cannot be explained by stresses due to the classical fountain flow at the flow front. Instead, the dominating contribution comes from transient deviatoric stresses induced by the compression of the vitrifying polymer in combination with wall adhesion. The pressure-induced stress history in the vitrifying polymer leads to molecular orientation and residual stresses giving a birefringence maximum at the surface.
Upgrading Recycled HDPE by Rheometer-Controlled Crosslinking
Authors: Pillo A. , Dealy J. M. , Patterson W. I. 
Published: December 2013

Abstract
An in-line rheometer previously described was evaluated for use in the upgrading of post-consumer, recycled HDPE. Feed resin of variable melt index was brought to a preset, uniform viscosity by peroxide induced crosslinking in a twin-screw extruder. Closed loop control was demonstrated using the rheometer as a viscosity sensor. Set-point tracking was achieved using PID-IMC, Dahlin and minimum variance (MV) controllers. The Dahlin controller showed the best load rejection.
On the Simulation of Thermoplastic Injection Moulding Process
Authors: Titomanlio G. , Speranza V. , Brucato V. 
Published: December 2013

Abstract
The relevance of enhancement of crystallisation kinetics by effect of shear flow and rheology during polymer solidification to the phenomena taking place during the injection moulding process has been shown by means of simulations performed on the basis of Lord and Williams [1, 2] model and its recent extensions [3 to 5]. A key point of the simulation was the solidification criterion based on a critical crystallization index; on the basis of simple calorimetric and rheological tests in the limit of zero shear rate, values of a few percent were given to the solidification crystallinity value.
Many experimental features of pressure history both in the runner and in the cavity are recovered by model predictions, if both effects mentioned above are properly accounted for. However, predictions for gate sealing time, although improved, still have a sensitivity to gate thickness lower than that shown by the experiments. Similar conclusions, obviously, regard also the mass entering in the mould during holding.
Another mechanism which sums up to shear stresses to accelerate thin gate solidification has still to be identified.
On-Line Birefringence Measurement in Film Blowing of a Linear Low Density Polyethylene
Authors: Ghaneh-Fard A. , Carreau P. J. , Lafleur P. G. 
Published: December 2013

Abstract
Blown film properties depend on the thermo-mechanical history experienced by molten polymer during biaxial deformation. In this study on-line birefringence measurements along the length of the bubble in film blowing of a linear low density polyethylene (LLDPE) were carried out in order to assess the stress level in the melt zone and total orientation in the solid zone. Bubble temperature measurements were carried out to find out the onset and the end of crystallization. Strain rates were also determined from bubble diameter and axial velocity measurements. We have focused on the effects of key processing parameters on the thermo-mechanical history of polymers. The relations between the birefringence and temperature profiles are described. The birefringence value is shown to be very small in the molten zone and increases rapidly as crystallization proceeds. The birefringence of the solidified film is strongly dominated by the crystalline phase contribution. Stresses in the molten blown film were calculated using the data of birefringence and pressure inside the bubble. The birefringence technique appears to be a promising but limited tool to determine stresses occurring in film blowing.
Brittle Melt Rupture Phenomena in Polymer Processing
Authors: Ghijsels A. , Massardier C. H. C. , Bradley R. M. 
Published: December 2013

Abstract
In this contribution the various rupture mechanisms which can occur during the elongation of polymer melts will be briefly reviewed, with the focus on the cohesive brittle melt rupture. Observations of melt rupture phenomena during polymer processing operations will be discussed. The occurrence of brittle melt rupture is characterised by a constant value of the rupture stress in the order of 1 MPa. Published rupture stress data on various polymer melts are critically discussed, in particular those on polyethylenes and other polyolefins. Using the Rheotens technique a newly developed method will be described to measure the melt rupture stress of polypropylene (PP) melts. The measurement of the rupture stress of PP melts is hampered by the occurrence of the instability draw resonance. This problem was overcome by applying more pronounced cooling conditions. Initial data on the rupture stress of PP melts will be presented. It is shown that the rupture stress of PP melts is not a constant but increases with increasing molecular weight.
An Experimental Study of Rotational Molding of Polypropylene/Polyethylene Copolymers
Authors: Kontopoulou M. , Bisaria M. , Vlachopoulos J. 
Published: December 2013

Abstract
The objectives of this work are to assess the rotomoldability of rubber toughened polypropylene resins and to investigate how resin properties can influence the process of rotational molding and the final part quality. Four commercially available polypropylene/polyethylene copolymers were tested. The chemical composition and the powder, rheological and thermal properties of the resins were determined. Rotational molding experiments were carried out in a laboratory scale uniaxial machine which is capable of measuring internal mold temperature and which facilitates the visual observation of various transitions in the cycle. Impact and environmental stress cracking resistance tests, as well as thickness distribution and density measurements were performed on the roto-molded parts. It was found that increasing rubber content results in an improvement of the impact properties which is counteracted by difficulties in processing, presence of bubbles and uneven surfaces.