bluuebunny/crossref_metadata_2025 huggingface dataset:
Reactive Ion Etching of Polymer Films
Authors: Dems B. C. , Rodriguez F. , Solbrig C. M. , Namaste Y.M.N. , Obendorf S. K.
Published: December 2013

The need for nanometer-sized features in integrated circuits calls for the use of dry-etching techniques using glow-discharge plasmas. The reactive ion etching (RIE) mode in which there is a large difference in potential between the gas phase and the solid surface yields particularly desirable, straight-walled etched structures. The design of processes and materials for RIE requires a knowledge of the effects of operating variables on various parameters. In the present work, the parameter emphasized is the etch rate. A novel aspect of the apparatus used incorporates a laser interferometer for in situ measurements of etch rate. Some observations on operating variables are: i. Chamber pressure is more critical when a fluoride-oxygen plasma is used than when oxygen alone is used. This is due to polymer deposition that occurs with the former along with etching. 2. The etch rate in the oxygen/RIE mode is almost the arithmetic sum of the oxygen/plasma mode together with the nitrogen/RIE mode except at low incident power levels where etch rate with oxygen/RIE is much greater than the sum of the other two. 3. Aromatic polymers etch more slowly than aliphatic polymers. 4. The oxygen/RIE rate of polyvinylchloride, PVC, decreases on addition of a compatible organotin compound. A 1:1 mixture of PVC with a tin compound etches at i/10 the rate of PVC alone.
New Aspects in the Design of Extruders with a Forced Feeding Section
Authors: Potente H. , Koch M.
Published: December 2013

New aspects in the design of forced feed section extruder (FFSE) screws are presented which are based on the understanding of the pressure profiles along the screw. The pressure at the end of the grooves correlates with the throughput characteristics in so far that when the maximum build up of pressure in the solid is exceeded, a kink in the throughput curves occurs due to high energy dissipation. This leads to partial melt film friction in the groove section. This can be avoided by the consequences shown in the paper for the design based on a reduced pressure consumption in the zones subsequent to the feeding zone. All criteria are dealt with analytically so to calculate and predetermine the process behaviour as a function of screw geometry. By the way, the main disadvantages of the FFSE can be kept under control as this new understanding is consequently applied to process as well as to screw design. The results of the process analysis are prooven by experimental work.
Continuous Melt Polymerization of Polyetherimides
Authors: Schmidt L. R. , Lovgren E. M. , Meissner P. G.
Published: December 2013

A new process for continuous melt polymerization of aromatic dianhydrides and diamines has been developed. The process consists of several integrated stages: feeding, melting, devolatilization, mixing, and advanced polymerization. The transport phenomena and coupled reaction rates have been studied in a corotating, intermeshing twin-screw reactor/extruder. Each stage in this process has been analyzed. The results show the importance of viscous heat for melting monomers, free surface generation in mass transfer, total shear strain in distributive mixing, and back mixing for extended residence time and advanced polymerization. High molecular weight polyetherimide (Mw 50 × 103) was obtained with this process for a variety of conditions. The reactions were run with 3 mole % of monofunctional anhydride to cap the polymer ends at a specific molecular weight for the most desirable balance of mechanical and physical properties.
The Synthesis of Polymer Processing Machines
Authors: Tadmor Z.
Published: December 2013

In this paper a methodology is proposed by which new geometrical configurations of polymer processing machines can be conceived. The methodology involves a process of analysis which uncovers the conceptual ‘building blocks’ of the machines. These, in turn, can be systematically converted into desirable new machine configurations.
Effect of Spinline Quenching on Structure Development in High-speed Melt Spinning of PET
Authors: Kikutani T. , Morinaga H. , Takaku A. , Shimizu J.
Published: December 2013

In the high speed melt spinning of polyfethylene terephthalate), the spinline was quenched with a water-bath and diameter profiles were measured. The filament diameter measured just above the water-surface was much thicker than that of the asspun filament and the deformation of filament after it was immersed in the water was suggested. At a take-up velocity of 6000 m/min without a water-bath, neck-like deformation was observed. When the water-bath was set farther from the spinneret than the position of neck-like deformation, the diameter at the water-surface was still thicker than that of as-spun filament. In other words, neck-like deformations disappeared. The friction stress applied to running filament by the water was estimated from the measurement of spinline tension. The calculation of the temperature distribution in the filament cross-section revealed that cooling behavior in the water is governed not by heat transfer from a filament surface to the water but by heat conduction in the polymer. Rapid increase of spinline tension due to high friction stress by the water and relatively slow cooling of filament due to low heat conductivity of the polymer lead to the deformation of filaments in the water and disappearance of neck-like deformation.
Compression Mold Filling Simulation for Non-Planar Parts
Authors: Osswald T. A. , Tucker C. L.
Published: December 2013

We describe a simulation of compression mold filling that combines a Galerkin finite element solution of the governing equations with a control volume scheme for tracking the moving flow front. The method can model thin shell-like parts in three dimensions, single or multiple charges, and multiply-connected domains. Either the generalized Hele-Shaw formulation or the thin-charge limit of Barone and Caulk's model can be used for the governing equations. The numerical techniques are explained, with special attention to the recovery of approximate flow front shapes. Predictions compare favorably to experiments, including laboratory experiments on model fluids as well as two large commercial parts molded from sheet molding compound. The simulation is most accurate when the initial charge thickness in uniform, but can also model multi-thickness charges.
Thermoforming of Amorphous PET Sheet
Authors: Birley A. W. , Haworth B. , Ola A. O.
Published: December 2013

A novel practical approach has been used to study the processability of a commercial grade of poly(ethylene terephthalate) during vacuum forming, in order to derive statistical models to relate some physical properties of containers to the thermomechanical nature of the process. Two-variable and three-variable Factorial Experimental designs were chosen to model the practical vacuum forming, and plug-assisted forming techniques, for process draw ratios of 1:1 and 2:1. Response measurements included container thickness distribution, and high temperature dimensional stability. Coefficients for a simple polynomial model have been experimentally determined: statistical correlations were apparent throughout the study, showing that the process environment determined the properties of vacuum formed containers through the morphological changes which occur by deforming in the thermoelastic region. Thickness distribution is improved when the plug assist mode is utilised. However, further optimisation is apparent when stress-induced crystallisation in PET is promoted (for example, when forming at a relatively low sheet temperature), especially for deep-drawn containers deformed beyond the natural draw regime. Whilst the temperature of the PET sheet primarily determines component thickness distribution, high-temperature stability is promoted by increases in the degree of crystallinity which occur when vacuum forming using super-ambient molding tool and plug temperatures.
Effect of Various Parameters on Residual Stresses in Transparent Polymeric Tubes
Authors: Mittal R. K. , Khan I. A.
Published: December 2013

Using the photoelastic technique for the measurement of residual stresses in rods and tubes of transparent polymers, the effect of some processing parameters such as the initial and final temperatures of quenching, type of cooling medium and the tube wall thickness is examined. These parameters have been shown to influence the magnitude and distribution of residual stresses. Also, a simplified version of the technique has been suggested to assess the magnitude of stresses in such tubes during fabrication itself. This simplified version yields necessary information about the stresses within an accuracy of approximately ± 10%.
Modified Flow Analysis Network Method for Analysis of Extrusion and Molding
Authors: Brzoskowski R. , Kumazawa T. , White J. L.
Published: December 2013

An improved form of the numerical FAN method of Tadmor, Broyer, and Gutfinger for solving hydrodynamic lubrication theory problems in flow through molds and dies has been developed. The new procedure takes into consideration transverse shearing in two rather than only one direction. It is also applied to the class of problems considered by Szydlowski, Brzoskowski, and White which involved applying this technique to situations when one surface is stationary and the other moves, such as in screw sections of extruders.
Throughput characteristics of Tightly Intermeshing Co-rotating Twin Screw Extruders
Authors: Potente H. , Ansahl J. , Wittemeier R.
Published: December 2013

This paper presents a mathematical-physical model for tightly intermeshing co-rotating twin screw extruders which describes the throughput and pressure characteristics of these extruders in the sections filled with molten plastic. With the equations that have been compiled, it is possible to calculate pressure profiles and back-pressure lengths for individual sections of isothermal and two-dimensional flow with non-Newtonian melts, making allowance for the screw geometry and for the parameters of relevance to the process. A comparison of the results supplied by the formulated theory and those obtained from the experiment shows that good computed results are obtained for various materials and different points of operation, although no allowance is made for the leakage flow that occurs in reality.
A 3D Mold Filling Study with Significant Heat Effects
Authors: Tanguy P. A. , Lacroix R.
Published: December 2013

A three dimensional finite element methodology is presented for the modelling of complex injection mold filling, using an extension of the Flow Analysis Network method coupled to a three dimensional solution of the thermal equations with phase change. The method allows the computation of the propagation of the polymer melt front with time as well as the prediction of the frozen skin which occurs during filling. Illustrations are presented in the context of an industrial mold, and simulation results are validated against experimental data showing a reasonable agreement.
Plastics Magnet Manufacturing Process: Mixing, Kneading, and Injection Molding
Authors: Sakai T. , Nakamura K. , Morii A.
Published: December 2013

To manufacture anisotropic plastic magnets with higher magnetic power, the compounding of Strontium Ferrite powder / plastics binder and injection molding processes should be optimized. In this study, we have carried out the optimization of injection molding machine design, and the mechanism analysis of the compounding operation. As a result, to generate effective strong magnetic fields during injection molding, the coiling system, mold structure, and pole shape were very important elements. Better Ferrite powder dispersion accelerated the particle orientation, which lead to higher magnetic power of the molded product when strong magnetic fields were applied. And then, particle dispersion depended on specific energy of the compounding machine unless excessive shearing force degraded Ferrite and plastics binder.
Prediction of Optimum Process Conditions for Rotomolded Products
Authors: Crawford R. J. , Nugent P. , Xin W.
Published: December 2013

This paper describes analytical and experimental work which has been carried out to identify optimum process conditions for rotomolded products. The mechanical performance of the moldings has been assessed using tensile impact tests. It has been found that changes in the oven temperature or oven time cause a very significant shift in the ductile-brittle transition for the SCLAIR 8504 grade of polyethylene used in the work. Optimum combinations of process variables can be clearly defined and used to establish a processing window for the material.

The ROTOSIM computer simulation for the rotomolding process has been used to establish the best (most economic) combinations of process conditions to obtain the optimum mechanical properties. A single equation is presented to relate pool depletion time to some of the process variables.
Observation and Analysis of Carbon Black Agglomerate Dispersion in Simple Shear Flows
Authors: Rwei S.-P. , Horwatt S. W. , Manas-Zloczower I. , Feke D. L.
Published: December 2013

Experiments aimed at detecting agglomerate dispersion were performed in a rotating concentric cylinder device mounted in a light scattering monophotometer. The dispersion of carbon black agglomerates suspended in various media (e.g. water, squalene, poly (dimethyl siloxane)) was inferred by measuring changes in turbidity under the application of a controlled simple shear field. In a given suspension the turbidity was observed to be constant for shear rates less than a threshold value. At shear rates in excess of this value, the turbidity was observed to increase monotonically in time to a steady state value. The effects of particle size and fluid viscosity on the critical shear rate necessary to induce agglomerate breakage were examined. Also, the change in the nature of the agglomerate size distribution upon shearing was studied. The results obtained indicate that the breakup of highly structured agglomerated solids such as carbon black does not proceed by a halving process. Also, the initial breakup process was observed to be irreversible.
A Model of Flow in the Mixing Section of the List KoKneader
Authors: Brzoskowski R. , Kumazawa T. , White J. L.
Published: December 2013

In this paper, an analysis for a whole section of the List KoKneader is presented. The analysis is restricted to the isothermal flow of a Newtonian fluid and uses a modified Flow Analysis Network method of simulation. This paper continues our efforts to analyze the flow of polymer melts in screw extruders containing pins.
Drag and Pressure Flow in Twin Screw Extruders
Authors: Todd D. B.
Published: December 2013

Staggered arrays of kneading paddles in co-rotating intermeshing twin screw extruders have drag and pressure characteristics similar to those in conventional screws. The pressure flow term was determined by measuring pressure drop as a function of flow rate in a non-rotating configuration. The drag flow per revolution was estimated as half of the product of lead length and open barrel cross section. The preliminary determinations were subsequently confirmed in a flooded operating extruder.
Fluid Mechanics of Distributive Mixing in a Modular Intermeshing Corotating Twin Screw Extruder
Authors: Monies S. , White J. L.
Published: December 2013

A theory of distributive mixing in a modular intermeshing corotating twin screw extruder is described. This is based on the Spencer – Wiley premise of representing mixing through interfacial area increase and its relationship to shear strain. The increase of interfacial area in both screw elements and kneading disc elements is analyzed. The flow in screw elements has a figure eight configuration but basically is analogous to flow in a single screw extruder. The primary mixing mode in these machines is within the kneading disc elements. A model for increase of interfacial area, which includes backflows through kneading disc tips, is developed. The kneading disc and screw element models are combined to compute interfacial area development in modular twin screw machine. We consider that modular twin screw extruders often have regions of starvation. To apply this model it is necessary to know flow configurations such as may be determined by a composite model of the total flow such as has been developed by the authors and their coworkers in earlier papers.
A Fundamental Experimental Study of the Mechanisms of Warpage and Shrinkage of Polyethylene in Rotational Molding
Authors: Chen C. H. , White J. L. , Ohta Y.
Published: December 2013

An off-line experimental simulation of cooling and warpage of rotationally molded parts is described. Slabs of polyethylene rotationally molded parts containing thermocouples and monitored by displacement transducers are placed on a metal surface representing a mold wall. This is cooled by varying methods such as simulated water showers, fan blown air, and natural convection cooling. Temperature profiles in the mold wall and through the polymer are determined as a function of time. The position of crystallization and the development of warpage are observed. Warpage is attributed to thermal quench stresses and release of the polymer from the mold surface.
Production and Characterization of Fine-dispersed Mixtures of Liquid Crystalline with Conventional Polymers
Authors: Meretz S. , Kwiatkowski M. , Hinrichsen G.
Published: December 2013

By investigation of adhesion following the harmonic mean method after Wu a suitable pair out of seven liquid crystalline (LCP) and conventional polymers was established in order to produce a LCP-matrix compound. Using a bidirectional piston mixer with a steel wire mesh with mesh size of 63 μm, 5% of the picked out PHB-PET copolymer was finely dispersed into the PET matrix polymer in the molten state. As a result a dispersion of the initial volume of the LCP granules of 1 mm3 into small particles of 0.5 to 1.0 μm3 as well as a very uniform local distribution was achieved which can be considered as an argument for the compatibility of the selected pair and as a confirmation of the usefulness of the preceding investigations of adhesion.
Dimensionless Non-Newtonian Isothermal Simulation and Scale-up Considerations for Modular Intermeshing Corotating Twin Screw Extruders
Authors: Chen Z. , White J. L.
Published: December 2013

Dimensionless calculations for throughput and pressure gradients are reported for flow of non-Newtonian fluids in screw and kneading disk elements of a modular intermeshing self-wiping corotating twin screw extruder. These calculations are applied to compute pressure and fill factor profiles along the axis of commercial twin screw extruders of varying scale. The used twin screw geometries are found to allow scaling for both the double threaded/tipped and triple threaded/tipped screw/kneading disc families. Dimensionless calculations are presented and applications to modular machines design are described.
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

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

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

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

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

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

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

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

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

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

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.
New and Unconventional Methods for Recycling Mixed Plastic Scrap
Authors: Menges G. , Fischer R. , Lackner V.
Published: December 2013

Waste from polymer materials – no matter whether filled or unfilled, extremely impure or mixed – can be divided more or less into their molecular components by chemical means.
Analysis of an Alternative Extruder Screw Pump Design
Authors: Campbell G. A. , Sweeney P. A. , Felton J. N.
Published: December 2013

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

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

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

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

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

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

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

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

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

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

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.
Reactive Extrusion of Styrene Polymers
Authors: Michaeli W. , Frings W. , Höcker H. , Berghaus U.
Published: December 2013

Reactive extrusion is the term used to denote a plastics processing method in which an extruder is used as a reactor for the continuous synthesis and modification of polymers. This paper describes the manufacture of polystyrene and styreneisoprene copolymers by a reactive extrusion process: anionic “living” s-butyl lithium initiated bulk polymerization was performed in a co-rotating closely intermeshing twin screw extruder. The results of the process analysis show that living polymerization of styrene can be performed in a screw-type reactor, despite the high reaction temperatures of over 200 °C. The polystyrene melt can be modified in bulk with comonomers or coupling reagents immediately after polymer synthesis. Depending on the raw material, formulation, and process parameters, the process variants developed and analyzed (homopolymerization of styrene, copolymerization of styrene-isoprene mixtures, sequential polymerization of styrene and isoprene) resulted in styrene polymers with widely differing structural characteristics and properties. For example, the copolymerization or styrene-isoprene monomer mixtures produced poly [(isoprene-co-styrene)-b-styrene]. The sequential polymerization of styrene and isoprene led to poly(styrene-b-isoprene) contaminated with partly crosslinked low molecular weight polyisoprene. The polyisoprene content is presumably formed by side reactions due to the high reaction temperatures.
The Role of Process Parameters in Blow Molding and Correlation of 3-D Finite Element Analysis with Experiment
Authors: deLorenzi H. G. , Taylor C. A.
Published: December 2013

The paper describes a series of blow molding trials on two different polymers under a variety of processing conditions. The tests were performed to investigate factors that affect the variation of wall thickness in a blow molded part. In addition, a numerical analysis was performed to predict the wall thicknesses. A major outcome of the tests was that the relative thickness distributions in the parts were independent of processing conditions and of the material used to form the part. The primary influence of the processing conditions was to put more or less material into the part, but they did not significantly affect the relative distribution of the polymer. The analysis gave a good overall prediction of wall thickness distributions.
Image Simulation and Evaluation of Fiber Orientation Distribution
Authors: Hamada H. , Maekawa Z.-I. , Xia M. , Nakeno I.
Published: December 2013

A new method is presented for analyzing fiber orientation distribution in fiber reinforced composites. A fiber orientation state in fiber reinforced composites is first obtained from soft X-ray image by making contract micro-radiograph (CMR). The distribution of the fiber orientation is measured by a fiber orientation index G(θ) as proposed in this paper. Furthermore, a computer simulation for the fiber orientation distribution is carried out in order to evaluate the fiber orientation index G(θ). It has been found that the value of the fiber orientation G(θ) decreases with an increase in the scatter of the fiber orientation distribution. Not only the direction but also the degree of the fiber orientation can be shown from the curve of the fiber orientation index G(θ). The result shows that this method is easy and useful to evaluate the fiber orientation distribution in fiber reinforced composites.
Flow Visualization and Residence Time Distributions in a Modular Co-rotating Twin Screw Extruder
Authors: Kim P. J. , White J. L.
Published: December 2013

A flow visualization study is reported for the motions of a mineral oil and a thermoplastic polymer individually in a modular co-rotating twin screw extruder. Flow in particular elements and combinations of elements is described. Experiments were also carried out to determine the residence time distribution. The influence of modular screw configuration and screw speed on residence time distribution has been determined. It was found that replacing screw elements with kneading discs or left handed screw elements increases residence time and broadens the residence time distribution. Increasing screw speed at fixed feed rate reduces both the mean residence time and the variance σ2 of the residence time distribution. Increasing feed rate at fixed screw speed has a similar effect. The variation of σ2 with position along the screw axis was measured. The results are interpreted in terms of the fluid mechanics of twin screw extruders including the Akro-Co-Twin Screw program.
Short Glass Fiber Reinforced PA 6 and ABS Blends
Authors: Kannan K. , Misra A.
Published: December 2013

A 70:30 blend of polyamide 6 (PA 6) and acrylonitrile butadiene styrene terpolymer (ABS), with and without a compatibilizer, was used as the matrix for reinforcement with short glass fibers. The compatibilizer used was a copolymer of styrene maleic anhydride (SMA) and its level was kept at 5 wt.-% in the blend. The glass fiber content was varied from 10 to 30 wt.-%. The blends and corresponding composites were compounded using a single screw extruder and test samples were prepared by injection molding. Tensile, flexural and impact properties were determined using the injection molded test samples according to ASTM standards. Morphological studies were carried out on fractured tensile test specimens using scanning electron microscopy (SEM). In general, the mechanical properties improved by the addition of glass fibers to the blend matrices and increased with increasing glass fiber content. The compatibilizer (SMA) has no favorable effect on the mechanical properties of the composites although it has a significant effect on the blends of PA 6 and ABS. SMA increases the melt viscosity of the blend and its addition to the blend results in greater damage to the fibers in the composite during processing. The fiber-matrix adhesion appears to be better in the absence of SMA. The morphological observations have been correlated with mechanical properties.