bluuebunny/crossref_metadata_2025_split huggingface dataset:
Orientation and Mechanical Property Development in the Melt Spinning of Fibers from Polyetherimide and Polyarylate
Authors: Song S. S. , Cakmak M. , White J. L. 
Published: December 2013

Abstract
An experimental study of structure development in melt spinning polyetherimide (PEI) and polyarylate (PAR) is presented. PEI was melt spun at 320° and 350°C and PAR at 310° and 340°C to drawdown ratios of up to 1 000. The melt spun fibers were found to be totally amorphous but to have significant levels of birefringence which increased with draw-down ratio. The birefringence was found to vary linearly with the spinline stress for both polymers and the data was independent of the melt spinning temperature. The proportionality constants are interpretable as equivalent to stress optical constants for the corresponding melts and have values of 9 400 Brewsters for the PEI and 7 400 Brewsters for the polyarylate. The mechanical properties of the melt spun fibers were determined in uniaxial extension. It was found that Young's modulus and tensile strength increased with spinline stress or birefringence while elongation to break decreased. The mechanical properties were found to be similar to polyether ether ketone, poly-p-phenylene sulfide, and polyethylene terephthalate in similar correlations, but as compared to polypropylene at the same spinline stress had higher Young's modulus and tensile strength but lower elongation to break. We were not able to successfully draw these materials over a hot plate at temperatures above their glass transition temperature.
Non-isothermal Mold Filling and Curing Simulation in Thin Cavities with Preplaced Fiber Mats
Authors: Lin R. , Lee L. J. , Liou M. 
Published: December 2013

Abstract
A numerical model for non-isothermal mold filling and curing simulation in thin cavities with preplaced fiber mats was developed based on the control volume method. Both lumped temperature system (i.e. local thermal equilibrium between the resin and the fiber) and unlumped temperature system (i.e. thermal non-equilibrium locally) were considered. A Lagrangian coordinate system was used in the flow front region to improve the energy transfer calculation. Several molding simulation results were presented to show the effect of fiber mat presence (in the mold cavity) on the inlet pressure and temperaturedistribution.
Simulation of Flow in a Farrel Continuous Mixer
Authors: Kim M. H. , White J. L. 
Published: December 2013

Abstract
The Farrel Continuous Mixer has been an important compounding machine for a quarter century. There have, until this time, been no efforts to simulate flow in this machine. We apply a hydrodynamic lubrication theory-based analysis to this problem. We present a model of flow in a Farrel Continuous Mixer which predicts pressure and flux profiles for a fully filled machine. Calculations are reported for both Newtonian and non-Newtonian models.
Molecular Orientation in Injection-molded Polypropylene Copolymers with Ethylene
Authors: Fujiyama M. , Wakino T. 
Published: December 2013

Abstract
Flexural test specimens were injection-molded from random and block polypropylene copolymers with various ethylene contents at cylinder temperatures of 200 to 320°C. Properties such as flexural modulus (FM), flexural strength (FS), heat distortion temperature (HDT), Izod impact strength (IIS), and mold shrinkage (MS), and degrees of molecular orientation such as thickness of skin layer (ST) and crystalline orientation functions and their distributions in the flow and thickness directions were measured. The relationships between these properties and the degrees of molecular orientation were investigated. These properties decreased with increasing cylinder temperature. FM, FS and HDT were decreased by copolymerization with ethylene, in particular, by random copolymerization. IIS was increased by copolymerization with ethylene. MS was decreased by random copolymerization and slightly increased by block copolymerization. ST and crystalline c-axis orientation function fc decreased with increasing cylinder temperature and ethylene content and on increasing distance from the gate. fc is high at the surface region and decreases toward the interior. The higher the cylinder temperature and ethylene content, the lower is fc at the surface region. There are cases at high cylinder temperatures where a shoulder or a peak of fc is observed at a middle point in the thickness direction, which is assumed to be caused by secondary flow during cooling and pressure holding process. Rectilinear relationships between the properties and ST or fc were obtained for each sample. This means that the properties cannot be unified only with degree of molecular orientation and the character of sample still remains. The character of the sample is assumed to be originated from higher-order structures beside molecular orientation, for example, crystallinity, spherulite size, and thickness of lamellae, etc.
Numerical Study of Slip at the Walls in the Extruder
Authors: Ji Z. , Gotsis A. D. 
Published: December 2013

Abstract
Slip at the wall is often encountered during the flow of polymeric materials and during the mixing of multiphase systems, such as concentrated suspensions. This article is concerned with the development of a numerical method to simulate flows that show such slip. The flow of a generalized Newtonian fluid with Bingham-like viscosity curve is considered and a linear relation between the slip velocity and the shear stress at the wall is used. A novel method based on a penalty parameter is developed to implement the slip boundary conditions into the finite element method. The flow in the conveying elements of the extruder is used as an example of the application of this method. It is shown that the wall slip decreases the pressurization capability of the extruder and increases the leakage flow occurring over the flight tips, as well as its mixing efficiency by reducing the rate of recirculation and the stress levels. The technique developed in this article can be applied to many flows that show slip phenomena and may be used to gain better understanding of the dynamics of mixing of commercially important materials.
Elimination of Sag in Plastic Pipe Extrusion
Authors: Githuku D. N. , Giacomin A. J. 
Published: December 2013

Abstract
Plastic pipe is produced by extruding molten polymer through an annular die. As the pipe leaves the die, it passes through a sizing sleeve and then a cooling tank where it solidifies slowly. For thick walled pipe, the inside of the pipe remains molten for as long as ten hours causing downward melt flow called sag. Sag can cause serious non-uniformity in pipe wall thickness. The conventional way to reduce sag is by manually adjusting the die eccentricity, until an acceptable wall thickness profile is achieved. This tedious trial and error procedure can take up to four attempts to get the right profile. In this paper a new way has been proposed to reduce sag, by rotating the pipe during cooling. A numerical simulation of sag flow while pipe is rotating, predicts that for rotational speeds between 0.1 to 10 rad/s, sag is virtually eliminated for thick walled, large diameter HDPE pipe extrusion.
Melt-recrystallization of Talc-filled Polypropylene Injection Moldings
Authors: Fujiyama M. 
Published: December 2013

Abstract
Talc-filled polypropylene injection moldings show a peculiar crystal orientation, in which the plate planes of talc particles are aligned parallel to the molding surface, the c- and a*- axes of polypropylene crystals are bimodally oriented to the flow direction, and the b-axes are oriented to the thickness direction. If they are melt-recrystallized, although the orientation of talc and the b-axis orientation of polypropylene crystals are restored, the c- and a*-axes become unoriented in a plane parallel to the molding surface. This peculiar crystal orientation cannot be explained by any effect of an epitaxy caused by lattice matching between the cleavage plane of talc and (040) plane of polypropylene crystal, a crystallization nucleation effect, a concentration of stress or melt orientation, or their synergisms. From the facts that, even if talc-filled polypropylene injection moldings are melt-recrystallized, the b-axis orientation to the thickness direction is restored and that an injection molding of polypropylene filled with only 0.5 wt.-% talc already shows the peculiar crystal orientation, it is assumed that talc influences a remote interaction on the crystallization of polypropylene so that the (040) planes of polypropylene crystals pile on or the b-axes are oriented perpendicular to the plate planes of talc particles.
3D Flow Field Analysis of a Banbury Mixer
Authors: Yang H.-H. , Manas-Zloczower I. 
Published: December 2013

Abstract
Banbury mixers are widely used in polymer processing. 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. In this work, a fluìd dynamics analysis package – FIDAP, using the finite element method was employed to simulate the flow patterns in a BB-2 type Banbury 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 mixing efficiency. The influence of processing conditions (rpm, speed ratio, and initial relative position of the two rotors) on the flow characteristics was analyzed. The flow results from the 3D model were also compared with results previously obtained from a 2D model.
Two-phase Simulation of Tubular Film Blowing of Crystalline Polymers
Authors: Ashok B. K. , Campbell G. A. 
Published: December 2013

Abstract
Traditionally, modeling of the film blowing process consisted mainly of balances of the forces on a single layer of thin film and a mathematically defined freeze-line. In this publication we develop an alternative approach for the theoretical analysis for film blowing of crystalline polymer melts by treating the film as two layers, crystallized and amorphous. Therefore, a two-phase constitutive model is presented for the process simulation of the tubular film blowing of crystalline polymer melts. An upper convected Maxwell equation of state with a single relaxation time and the Oldroyd derivative is applied to the amorphous or liquid-like phase while a perfect plastic-elastic model with yield is used to describe the deformations of the crystallized phase. The model interpretations and predictions are obtained and found to be in qualitative agreement with published results. For polyethylene the model appears to help explain the interactions of the processing conditions and fluid-mechanics in the film blowing process of crystalline polymers.
A Basic Study of Applicability of Regrind Polyethylene in Rotational Molding
Authors: Song S. S. , Nagy T. , White J. L. 
Published: December 2013

Abstract
An experimental study on the use of regrind in rotomolded polyethylene parts is described. We investigated the introduction of 15, 30, and 100% reground polyethylene into the rotational molding operations. The number of regrind cycles varied from one to four. Rotational molding was done in air and nitrogen inner gas, respectively. The mechanical properties of the parts were investigated, including low temperature dart impact test, tensile test, and Izod impact test. Generally it was found that nitrogen atmospheres substantially improved the impact properties of rotomolded parts made with virgin polyethylene. With parts containing 15% and 30% regrind, the impact properties of boxes made in nitrogen are substantially higher than those molded in air. Also, adjustment of oven time to slight undercure for 15% regrind containing parts rotomolded in air gave good impact properties.
Analysis of an Alternative Extruder Screw Pump Design
Authors: Campbell G. A. , Sweeney P. A. , Felton J. N. 
Published: December 2013

Abstract
A new screw pump/extruder is analyzed with regard to the effect of the pump components on the pump output. The pump is constructed such that the barrel, screw core, and screw helix can all be rotated independently. Contrary to conventional wisdom, it is demonstrated that the major physical component of the pump which contributes to the output is the screw helix. A new theory is developed for pumping characteristics of this new pump and the theoretical analysis is compared with laboratory data. The theory compares quite well with the data.
Effect of Biaxial Stretching on Thickness Uniformity and Surface Roughness of PET and PPS Films
Authors: Iwakura K. , Wang Y. D. , Cakmak M. 
Published: December 2013

Abstract
Surface roughness and thickness uniformity are two of the most important parameters to control in the manufacture of polymeric films. In this paper, we present the results of a detailed experimental study on the effect of biaxial stretching variables on these parameters in polyethylene terephthalate and poly p-phenylene sulfide films. Decreasing processing temperature and increasing stretch ratio were found to improve surface smoothness and thickness uniformities of PET films. However, in the PPS films, biaxial stretching resulted in rougher surfaces. The main mechanism to improve these variables especially the thickness uniformity was found to be the strain hardening. In PET stretching this mechanism was present and in PPS it was found to be absent in the processing range investigated. This resulted in the improvement in surface roughness and thickness uniformities in the PET films with the increase of stretch ratio and with the decrease of stretching temperature. In PPS, increase of stretch ratios had an opposite effect on the surface roughness. This may be due to branching in the PPS.
Isothermal and Anisothermal Models for Cast Film Extrusion
Authors: Barq P. , Haudin J. M. , Agassant J. F. 
Published: December 2013

Abstract
In cast film extrusion, the polymer is extruded through a slit die, stretched in air and then cooled on a chill roll. Isothermal and non-isothermal models have been developed to predict the polymer melt behavior between the die exit and the chill roll. The mechanical resolution is based on the assumption of a uniform thickness in the film cross section. It takes gravity and inertia forces into account and is performed in two steps: the equilibrium equation for a small film element is first written in a curvilinear coordinate system and the stress tensor is then calculated in a local Cartesian system. The temperature field in the film thickness is determined using local heat transfer coefficients, whose calculation is based on a precise description of the radiation and convection phenomena. This local description requires the measurement of air temperature close to and far from the film. The coupling between mechanical and thermal equations is achieved by introducing the temperature dependence of the viscosity. An iterative scheme is used to adjust the stretching force, the length of the film and the contact point on the roll. The theoretical predictions (film profile, velocity, width, temperature) are compared with experimental measurements performed on a pilot line. The agreement is always good, except for the width, whose computed linear variation is in contradiction with the experimental observations.
A Process to Produce Microcellular PVC
Authors: Kumar V. , Weller J. E. 
Published: December 2013

Abstract
A novel process to produce microcellular PVC foams with a very homogeneous cell distribution and cell densities ranging from 107 to 109 cells/cm3 is described. Microcellular PVC foams with relative densities (density of foam divided by the density of unfoamed polymer) ranging from 0.15 to 0.94 have been produced. In this paper, experimental results on bubble nucleation and growth are presented. It was found that the bubble nucleation density increases with foaming temperature and eventually reaches a limiting value, while the average bubble diameter is relatively independent of the foaming temperature. A majority of the cell growth was found to occur in the early stages of foaming.
Development of Phase Morphology of a Polyethylene-Polyamide 6-Blend in a Modular Co-rotating Twin Screw Extruder
Authors: Lim S. , White J. L. 
Published: December 2013

Abstract
A basic study of blending two different polymers (polyethylene and polyamide 6) in a modular co-rotating twin screw extruder is presented. The development of phase morphology was observed along the axis of the modular screw. Five different modular screw designs are considered. We first look at a machine containing all right-handed screw elements. We then consider a machine with all right-handed elements plus a single left-handed screw element. The study then turns to machines with combined screw and kneading disc elements. The kneading discs play a key role in both melting polymers and in enhancing dispersive mixing. Increasing the number of kneading disc blocks gives enhanced dispersion.
A Slip Model for Linear Polymers Based on Adhesive Failure
Authors: Hatzikiriakos S. G. 
Published: December 2013

Abstract
Eyring's theory of liquid viscosity was adapted to the special case of polymer molecules at a solid interface. The resulting model gives the slip velocity as a function of wall shear stress, temperature, pressure, work of adhesion and the molecular parameters of the polymer. The work of adhesion is related, on the one hand, to the critical stress for the onset of slip, and on the other, to the surface tension of the melt on the surface of interest. The predictions of the model are compared with previously published data for the slip of polyethylenes on steel and on steel treated with processing aids, and the agreement is very good. Unlike previous power-law slip models, the new model provides for a smooth transition from no-slip to slip flow at the critical stress.
A Study on Flexural Properties of Sandwich Injection Moldings
Authors: Hamada H. , Maekawa Z. , Xia M. 
Published: December 2013

Abstract
In recent years composite materials have been widely used, largely because of their superior mechanical properties. Sandwich constructions can be suitably tailored to make use of each material's properties in the moldings, effectively (for example in honeycomb core constructions) in order to improve the mechanical properties of the moldings. In the injection molding process, however, it is quite difficult to fabricate sandwich constructions. A sandwich injection molding process in which the sandwich injection moldings are performed using two melt sources and one nozzle has been developed. At the present, there have been few investigations with respect to the mechanical properties of the sandwich structures produced by the injection moldings.
In this study, we tried to examine the sandwich construction made by the injection molding process. Three kinds of materials including polyamide resin, the short and the longer fiber reinforced polyamides were used as layer structural materials for the sandwich injection moldings. The flexural properties for the sandwich injection moldings were measured and their fracture surfaces observed to clarify the mechanical behaviors. Furthermore, the flexural moduli for the sandwich injection moldings composed of the polyamides reinforced with the different fiber lengths were predicted based on two-layer orientation model.
Experimental Study on Dewatering and Devolatilizing Operations Using Intermeshed Twin Screw Extruders
Authors: Sakai T. , Hashimoto N. , Kataoka K. 
Published: December 2013

Abstract
In this study, we have mainly discussed the dewatering and devolatilizing extrusion behavior of synthetic elastomers using intermeshed twin screw extruders. For these purposes, we utilized various twin screw extruders with long segmented barrels having several slitted sections and venting ports. Furthermore, we selected the optimum operational conditions using either the intermeshed co- or counter-rotation twin screw extruder depending on experimental purposes and raw materials. Some results obtained were compared between the co- and counter-rotation twin screw extruder.
On the Kinetics of Shear Induced Crystallization in Polypropylene
Authors: Liedauer S. , Eder G. , Janeschitz-Kriegl H. , Jerschow P. , Geymayer W. , Ingolic E. 
Published: December 2013

Abstract
With short term shearing at low degrees of supercooling a method has been developed by which nucleation during shearing can effectively be separated from the subsequent crystal growth, which, in these experiments, mainly occurs after the cessation of the flow. In this way the kinetics of nucleation by shear could be unravelled for isotactic polypropylene. The required measurement consists of the monitoring of the optical retardation which increases with the monitoring time and levels off by saturation. From these measurements conclusions could be drawn with respect to the modes of formation of the nuclei and of their type. Model predictions could be confirmed with the aid of electron micrographs.
Structures and Properties of Injection Moldings of Glass Fiber-filled Polypropylenes
Authors: Fujiyama M. 
Published: December 2013

Abstract
Two polypropylene (PP)-glass fiber (GF) compounds were injection-molded. One was a polypropylene filled with 0, 10, 20 and 30 wt.-% of an untreated glass fiber. A second was a compound filled with 20 wt.-% of a silane-treated GF plus 5 wt.-% of a maleic anhydride-grafted PP. Flexural test specimens were injection-molded from the filled PPs at cylinder temperatures of 200 to 320 °C. Properties such as flexural modulus, flexural strength, heat distortion temperature, Izod impact strength, and mold shrinkage as well as higher-order structures such as mean fiber length, crystallinity, ß-crystal content, thickness of skin layer, a*-axis-oriented component fraction, and crystalline orientation fraction were measured and structure-property relationships were studied. A simulation of molecular orientation was carried out from the viewpoint of growth of a melt orientation at the gate and its relaxation in the mold cavity.
Material Flow During Compression Moldings of Long Fiber Reinforced Thermoplastic Composites
Authors: Harnada H. , Sato T. , Maekawa Z. 
Published: December 2013

Abstract
Because of their many advantages, long fiber reinforced thermoplastic composites have been used in many industrial applications. However, because material flows during compression molding cause a large scatter in the mechanical properties of moldings, it is necessary to characterize the flow behavior during molding. A new experimental procedure, the “Mark Method”, was used to observe the flow in different layers during molding. Mold flow was found to be characterized by interlaminar slippage, which causes the core layer to flow to the edge of the panel.