bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulation of Core Deflection in Powder Injection Molding
Authors: Ling D. , Gupta M. , Myers P. R. , Upadhyay R. K. 
Published: December 2013

Abstract
Core deflection in powder injection molding is one of the main causes of the structural defects in the molded part. Simulation of the core deflection in the injection molding process requires solution of the fluid-solid interaction problem, in which the fluid flow and solid deformation problems are coupled along the fluid-solid interface. A three-dimensional finite element program was developed in this work for a non-isothermal injection molding simulation including the fluid-solid interaction effects. With the assumption of small deformation in the solid structure, the fluid flow problem is formulated in an Eulerian frame-work, whereas the solid structure problem is formulated in a Lagrangian framework. Numerical simulation of the filling stage of injection molding for an airfoil-shaped part is presented and compared with the experimental data. The predicted melt-front advancement as well as the pressure is in good agreement with the corresponding experimental results. The predicted core deflection during the filling stage of the injection molding process is also compared with the measurements on a molded part.
Utilization of Rheology Control to Develop Wood-Grain Patterned PVC/Wood Flour Composites
Authors: Joo Yong Lak , Cho Myung Ho 
Published: December 2013

Abstract
The effects of wood flour and plasticizer on the rheology and extrusion of polyvinyl chloride (PVC) based wood—plastic composites are investigated. The intention of the study was to determine an optimal pair of PVC based wood—plastic composites that should exhibit substantially different rheological behaviors so that patterns similar to grain of wood can be developed inside and on the surface of the product when two selected wood—plastic compounds are extruded at once. The rheological study reveals that the shear viscosity and shear thinning behavior of the composites can be controlled by varying the contents of wood flour and plasticizer. It is also found that the depression of glass transition temperature due to the addition of plasticizer is substantially reduced by the loading of wood flour. In addition, various wood—plastic composites were compounded into different colors, and several pairs of the compounds with different rheological properties were extruded in single and twin screw extruders to see whether any wood-patterns are developed. When the differences in the shear viscosity and the glass transition temperature of the two compounds were too large, the incomplete plasticization of the higher viscosity component was observed due to the premature plasticization of the lower viscosity component. It is shown that distinct wood-patterns were developed both inside and on the surface of the extruded products only for the pairs of the composites with an optimal differences in both viscosity and plasticizer content.
Modeling Non-isothermal Mixing in a Rotor Mixer
Authors: Malkin A. Ya. , Baranov A. V. , Balinov A. I. 
Published: December 2013

Abstract
A mathematical model of the mixing process in a two-rotor mixer is proposed. The model developed takes into account the interrelations among the following essential features of the process: non-isothermal effects due to heat exchange and energy dissipation in flow, non-Newtonian behavior of a material and dependence of its properties on temperature and the degree of filler agglomerate destruction, kinetics of changing carbon agglomerate sizes due to mechanical distraction. The system of governing equations is formulated and the procedure of its solution is described.
The theoretical model is compared with experimental data obtained in real technological process of mixing of a rubber compound. In all cases quite satisfactory results of comparison were obtained. It means that the model proposed can be used for analysis of real technological processes of mixing and choice of optimal technological regime and geometrical sizes of a mixer (primarily size of the gap between a rotor and the wall of a chamber) as well.
Structure Development in Melt Spinning Polypropylene-EPM Blends and Dynamically Vulcanized Polyolefin TPEs
Authors: Yu Y. , White J. L. 
Published: December 2013

Abstract
Polypropylene blends, both mechanical blends and a dynamically vulcanized blend, have been melt spun into fibers. Melt spinning was carried out through air and in ice water. Melt spun filaments were characterized by wide angle x-ray diffraction (WAXS), birefringence and differential scanning calorimetry (DSC) measurements. Generally, the polypropylene crystalline orientation-spinline stress relationship is the same for the homoploymer, the blends and the dynamic vulcanizate. However, the blends and the dynamic vulcanizate have much lower birefringence apparently due to a lack of orientation in the rubber phase. It was shown that the PP contribution to the birefringence for all the systems is the same at the same spinline stress.
Compressive Squeeze Flow of Generalized Newtonian Fluids with Apparent Wall Slip
Authors: Lawal A. , Kalyon D. M. 
Published: December 2013

Abstract
The compressive squeeze flow is encountered in various processes like compression molding and in rheometry. It involves a complex deformation field driven by both shear and normal stresses. Here the flow and deformation field generated during the compressive squeeze flow of generalized Newtonian fluids, subject to wall slip, was analyzed using both numerical simulation based on the 2-D Finite Element Method and the 1-D analytical model, which is based on the lubrication assumption. The agreement between the analytical and numerical solutions deteriorates with increasing Navier's wall slip coefficient and the increasing yield stress value of the viscoplastic fluid. The lubrication assumption is valid under various squeeze flow conditions but numerical analysis in conjunction with experimental studies are necessary to determine the ranges of material parameters and operating conditions for which the lubrication assumption is valid.
Experimental and Numerical Study of Rhomboidal Mixing Sections
Authors: Rios A. C. , Gramann P. J. , Osswald T. A. , Noriega M. del P. , Estrada O. A. 
Published: December 2013

Abstract
The rhomboidal mixing section is becoming very popular among processors to provide distributive mixing. Currently, several different designs are used but the details of the flow behavior and mixing efficiency is not well understood. This information is needed to be able to design and find the most efficient rhomboid geometry. In this investigation nine different geometries with various pitches (helix of rhomboids) were analyzed using a 3-dimensional boundary element method (BEM). The geometries were compared according to mixing efficiency, pressure and energy consumption. The results were compared to experiments performed with a conventional single screw extruder that was fitted with three different rhomboidal mixing sections. The investigation led to the conclusion that the most effective distributive mixing sections were those with neutral rhomboids (pine-apple mixer). However, the neutral rhomboidal mixing section consumes the most pressure in the extruder. It was also concluded that rhomboidal mixing sections deform the material by shear, making them poor dispersive mixing sections.
Production of Pipe with Uniform Wall Thickness: How to Compensate for Gravity Sag
Authors: Pittman J. F. T. , Farah I. A. 
Published: December 2013

Abstract
A detailed simulation of the cooling process in the production of plastic pipes has been used to gain insights into the problem of gravity flow or sag, which can lead to troublesome wall thickness variations in thick walled pipes. It is shown how the simulation can be used in an iterative, forward-backward calculation, based on the time reversibility of the creeping gravity flow problem, to calculate the initial extru-date wall thickness profile that the die must deliver to precisely compensate for sag. For pipes with particularly thick walls, this calculation shows that no compensating initial profile exists whilst conventional cooling arrangements are used. Reduction of the cooling rate of the lower part of the pipe promotes wall thickness uniformity and the existence of a compensating profile. Means for achieving the required initial profiles are discussed, and the need for an integrated view of the design and operation of the die and cooling line in understanding and overcoming the effects of sag is emphasised.
A New Polymer Processing Technology for Polymer Blends with Unmatched Viscosity: Solid-State Shear Pulverization (S3P)
Authors: Khait K. , Torkelson J.M. 
Published: December 2013

Abstract
Solid-State Shear Pulverization (S3P) is a new polymer processing technology capable of efficient mixing blends with different component viscosities (which are unprocessable by conventional melt extrusion due to the phase separation). S3P sub ects polymers to compression and shear, resulting in fracture into a powder of various particle size and particle size distribution. S3P also allows modification of properties by compatibilization of ordinarily incompatible polymers without adding premade copolymers or conventional functional groups. Additionally, because S3P produces powder, it is suitable for a solid-state dispersion of pigments, curing agents, catalysts and other additives without melting (unlike conventional compounding).
After reviewing the S3P concept, this paper discusses recent experimental data. The research focuses on mixing like polymers such as virgin polypropylene (PP) with unmatched viscosity, resulting in blends with improved processability and a significant increase in elongation at break. A comparison with a conventional melt mixing by twin-screw extrusion is provided to demonstrate uniqueness of S3P processing. An additional example involves the mixing of dissimilar, ordinarily incompatible polymers such as recycled high-density polyethylene (PE-HD), low-density polyethylene (PE-LD), PP, polystyrene (PS), and polyvinyl chloride (PVC) with very different viscosities. Once again, the S3P-made material exhibited exceptionally high elongation at break as compared with that of the conventionally melt-mixed blend.
Polymerization of ∊-Caprolactone in a Twin Screw Extruder
Authors: Poulesquen A. , Vergnes B. , Cassagnau Ph. , Gimenez J. , Michel A. 
Published: December 2013

Abstract
The purpose of this work is to model the bulk polymerization of ∊-caprolactone in a corotating twin screw extruder. Starting from kinetic data and rheological laws previously defined, we use a twin screw flow modelling software to calculate the progress of the polymerization along the extruder. Experiments are performed to assess the influence of processing conditions (feed rate, screw speed, barrel temperature, initiator concentration) and to validate the model. They put in evidence the control of the polymerization process by the temperature and the residence time in the extruder. It is shown that a good correlation between theoretical and experimental results can only be obtained if accurate kinetic and rheological data are used in the model.
The Mapping Method for Mixing Optimization Part I: The Multiflux Static Mixer
Authors: Kruijt P. G. M. , Galaktionov O. S. , Peters G. W. M. , Meijer H. E. H. 
Published: December 2013

Abstract
The development of the mapping method [1, 2] and its application to viscous flow in a (multiflux) static mixer [3] is discussed. The mapping method describes the repeated transport of fluid from one domain to another and computes the concentration distribution, yielding a unique mixing measure, like e.g. the intensity and/or scale of segregation [4,5], the residence time distribution and structure parameters like e.g. the area tensor [6].
In the multiflux static mixer, the domain is a (two dimensional) cross-section of the flow channels at the beginning and end of a single element. Since static mixers are build of a sequence of similar elements, we only need to determine one mapping matrix (a computationally expensive operation). To simulate the complete mixer, the mapping matrix is repeatedly applied (a computationally cheap operation). Three different geometries are analyzed. It is shown that an approach like the mapping method is a prerequisite in order to obtain meaningful results after a number of mixer elements. Moreover, it enables optimization of industrial mixers.
Compatibilization of SBR/NBR Blends Using Chemically Modified Styrene Butadiene Rubber
Authors: Ramesan M. T. , Kuriakose Baby , Pradeep P. , Alex R. , Varghese S. 
Published: December 2013

Abstract
The effect of dichlorocarbene modified styrene butadiene rubber (DCSBR) as a compatibilizer in blends of acrylonitrile butadiene rubber and styrene butadiene rubber (SBR/NBR) has been studied. The cure characteristics, physical properties, crosslink density, FTIR studies and low temperature transitions of the blends were determined as a function of chlorine content of DCSBR. Compatibilizing efficiency depended on the chlorine content of DCSBR and composition of blend constituents. Effective compatibilization was achieved when chlorine content of compatibilizer was 25% and SBR content of blend was either 50% or lower. FTIR studies, glass transition behavior measured by DSC and DMA showed that an appreciable extent of molecular level miscibility has been achieved in SBR/NBR blends by using DCSBR as a compatibilizer. Improvement in mechanical properties such as tensile strength, tear strength, resilience, hardness and compression set were achieved both when DCSBR was added and chlorine content of DCSBR increased up to 25%. The resistance of the vulcanizate towards air and oil aging improved with compatibilization. The change in technological properties correlated with crosslink density of the blends assessed from swelling studies and stress-strain data.
PA612 Double Bubble Tubular Film Process – Processability and Structure Development
Authors: Rhee S. , White J. L. 
Published: December 2013

Abstract
Biaxially oriented Polyamide 612 (PA612) films made by double bubble tubular film extrusion were characterized. The processing characteristics of the polymer in the double bubble process were investigated. The development of crystallinity and orientation in the films was clearly considered. First bubble PA612 films showed a low level of crystallinity (X = 7.7%). Differential scanning calorimetry (DSC) indicated that the first bubble PA 612 films experienced a considerable increase in glass transition temperature (Tg), cold crystallization temperature (Tc) and crystallinity during aging at room conditions. The second bubble films were more highly crystalline (X = 22 to 28%) with poorly grown β unit cells. The WAXD and SAXS patterns showed that the crystallites of double bubble PA612 films became more perfect by annealing in a boiling 20% formic acid solution, resulting in a well-developed triclinic α crystals coexisting with minor proportion of β phase. The WAXD and SAXS patterns indicated that crystallography planes and lamellae in the second bubble films were oriented depending on SBUR × SDDR (second blow-up ratio x second draw down ratio). White-Spruiell biaxial orientation factors were calculated with the WAXD pole figure data. The hydrogen bonding (0k0) planes of biaxial double bubble films were found by WAXD to be aligned parallel to the sheet surface before and after annealing.
Flow Instabilities of Linear PE in Capillary Dies
Authors: Larrazabal H. J. , Hrymak A. N. 
Published: December 2013

Abstract
Flow instabilities of linear polyethylenes have been studied in capillary dies. The effects of shear stress, temperature, molecular weight and material of construction of the dies on both the critical shear stress for the onset of slip and slip velocities have been evaluated. Flow curves were obtained using capillary dies with constant L/D and different diameters. Slip velocities were calculated using the Mooney technique [1] as a function of shear stress. The onset of slip and slip velocity are affected by the material of construction of the capillary die. Flow instabilities were eliminated when brass dies were used under specific conditions. Instabilities persisted when naval brass and copper capillary dies were used.
Extrusion Coating with Metallocene-Catalysed Polyethylenes
Authors: Toft N. , Rigdahl M. 
Published: December 2013

Abstract
During recent years, the interest in metallocene-catalysed polyethylenes has been steadily increasing. These polymers are generally characterised by a narrow molecular weight distribution and a uniform comonomer distribution. In extrusion coating, the interest in these polymers is mainly related to the enhanced physical performance of the resulting film. However, from the processing point of view, the metallocene-catalysed polyethylenes can present problems. In this study, a number of metallocene-catalysed linear low-density polyethylenes (m-LLDPE) were characterised with regard to their viscous and elastic properties. Conventional grades of LDPE and LLDPE were included as references. The same grades were used in pilot scale extrusion coating experiments. The processability of the polymers was primarily expressed in terms of neck-in (NI), which describes the lateral reduction of the film width as the film is drawn down into the coating nip, and the draw-down ability (DD), which provides a measure of the ability of a thin film to be drawn into the nip at a high machine speed. A lower NI-value, which is desirable, was noted when the polymer melt exhibited a higher elasticity, expressed in terms of the steady state compliance, the extrudate swell and Trouton's ratio. Factors that had a positive effect on the NI-value tended in general to reduce the draw-down ability. A relation between NI and DD was established, which in principle makes it possible to optimise both NI and DD, based on finding the optimal values of the shear and the elongational viscosities. The results obtained indicate that a low shear viscosity and a high Trouton's ratio provide optimal processability with regard to NI and DD. It was noted that m-LLDPE-grades could be chosen to match the processability of more conventional polymers (expressed in terms of NI and DD). Rheology can be an important tool for such a selection.
Simultaneous Calculation of Roll Deformation and Polymer Flow in the Calendering Process
Authors: Mewes D. , Luther S. , Riest K. 
Published: December 2013

Abstract
Calender units with rotating rolls are used to produce foils or sheets from polymer material with viscous or elastomeric flow properties. Up to now, the design process of calender units, the calculation of flow and pressure fields in the calender gap and the calculation of resulting deformations of the rotating rolls are implemented with different computer programs. In this work a design concept that integrates design and calculation programs is being developed in order to achieve integrated design and calculation. With this concept, it is possible to design calenders and calculate flow fields and deformations. After designing the rolls with the Computer Aided Design program Pro/Engineer, the flow field in the calender gap is calculated with the Finite Volume Method program CFX4, and the deformation of the rolls is calculated with the Finite Element Method program ANSYS. The iterative process of design, calculation and modification of shape is continued until sheets or foils of constant thickness leave the calender gap. The design concept has an object-oriented operational structure. The data transfer between the programs takes place via a central data base in STEP format.
As examples, calenders with combinations of solid rolls are designed. The flow field in the calender gap is calculated for Newtonian and for viscoelastic fluids with use of an integral rheological equation of state. The flow field is compared to a measured flow field. The resulting deformations of the rolls are calculated and represented graphically. Furthermore, a design process for elastomer-coated rolls is implemented and their deformations as well as the interior stress fields are calculated.
Stress Induced Crystallization in Elongational Flow
Authors: Swartjes F. H. M. , Peters G. W. M. , Rastogi S. , Meijer H. E. H. 
Published: December 2013

Abstract
Stress-induced crystallization is studied in an extensional flow device (a cross-slot flow cell) for an isotactic Polypropylene (iPP) by measuring the micro-structure that develops after flow. Birefringence and Wide Angle X-ray experiments were performed. The birefringence experiments with flow below the melting temperature showed the occurrence of a fiber-like structure around the outflow centerline and, later in time, of ‘streamlines’. The latter are explained by the influence of shear gradients close to the optical windows. The WAXS experiments also showed the fiber-like structure around the outflow centerline, having orientations in the (110), (040) and (130) reflections, with a width of about 80 μm. This dominance of the elongational flow around the stagnation line could not be observed in experiments with flow above and subsequent crystallization below the melting temperature.
Structure development in this cell was numerically predicted using the Leonov and the extended Pompom (XPP) model. The oriented structures can be predicted. Moreover, process conditions are found with less influence of the (unwanted) shear gradients. Finally, it was concluded that the strain hardening behavior in the Leonov model over-estimates the first component of the Finger tensor, and thus the number of flow-induced nuclei. Therefore it is recommended to use the extended Pompom model as a more realistic basis for a quantitative flow-induced crystallization model.
Improved Spinnability of Metallocene Polyethylenes by Using Processing Aids
Authors: Vogel R. , Hatzikiriakos S. G. , Brünig H. , Tändler B. , Golzar M. 
Published: December 2013

Abstract
Melt spinning is a polymer processing technique that is strongly influenced by the extensional flow behaviour of polymer melts. Therefore only a few polymeric materials are usable for this kind of processing with sufficient take-up speeds. When approaching critical conditions of deformation most polymers show either fibre break in the molten state either by a brittle cohesive rupture or a ductile failure. During the melt spinning of pure and modified metallocene poylethylenes additional flow instabilities occur within the spinning die. Namely, wall slip, ‘sharkskin’ and pressure oscillations (gross fracture) may be obtained dependending on the volume flow rate. Pressure oscillations lead to diameter oscillations of the melt extrudate, which create local increase of tensile stress in the spin line. This effect immediately causes fiber break in the spinline.
Therefore, melt spinning of polyethylenes was only possible up to a critical molecular weight or its relating melt viscosity. The limitation of the molecular weight restricts the mechanical properties of the melt spun fibres. This paper reports on an attempt to find out appropriate processing aids for suppressing ‘sharkskin’ effects and pressure oscillations in an attempt to overcome the limitation of a critical molecular weight. At first, the critical conditions for the onset of flow instabilities for higher molecular weight polymers were analysed. Further experiments concerned with the use of processing aids for melt spinning of metallocene polyethylenes of higher molecular weights. A combination of boron nitride powder and a fluoroelastomer was found to be an effective processing aid for this process.