Published by De Gruyter

Volume 19 Issue 2

Issue of International Polymer Processing

Contents
Journal Overview

May 2, 2013

Page range: 93-93

Editorial

May 2, 2013

DuPont, IG Farbenindustrie, ICI and Japanese PA Fiber Manufacturers Polyamides 66 and 6

Fifth in a Series: Pioneering Polymer Industry Developments

J. L. White

Page range: 94-94

Screw Extrusion

May 2, 2013

Modeling the Flow in the Metering Zone of Single Screw Extruders Using a Helical Geometry Model

M. H. R. Ghoreishy, M. Razavi Nouri

Page range: 95-100

Abstract

This research work is devoted to the development of a finite element model for the simulation of the flow of polymer melts through the metering zone of single screw extruders. The sets of the governing equations (flow and energy) were solved using the continuous penalty scheme and a streamline upwinding Petrov-Galerkin method, respectively. The non-Newtonian rheological behavior of the fluid was also taken into account by the use of the power-law model. The novelty of this work is the application of this model on the flow of a polypropylene melt through the helical geometry of a single screw extruder. To validate this model, the results of the computer simulations were compared with experimentally measured mass flow rate and also results from a previous model, which was based on the simulation of the flow in a flat flow domain. Comparisons showed that not only there are very good agreements between the model predictions and actual data but also inclusion of the curvature of the screw flights has an important influence on the accuracy of the results.

May 2, 2013

Engineering Analysis of Devolatilization of Various Additives in Intermeshing Co-rotating Twin Screw Extruders

J. Keum, J. L. White

Page range: 101-110

Abstract

An experimental study of devolatilization of nonane, xylene and 1-hexanol from molten polyethylene in a modular co-rotating twin screw extruder is described. Various modular screw designs, as well as different feed rates, screw speeds, and barrel temperatures were used. It was found possible to correlate the extent of devolatilization in different modular screw designs with a mass transfer coefficient which depends on screw speed and LDPE feed rate. The mass transfer coefficient depended on the liquid being devolatilized, being highest with 1-hexanol and lowest with nonane. In addition, the values of the mass transfer coefficient were obtained through experiments on the twin-screw extrusion of PE with nonane, xylene and hexanol. Interpretations of these results are described.

Die Extrusion

May 2, 2013

Novel Extrusion Dies with Rotating Rollers for CO₂-Plastic Foam Production

H. Benkreira, M. Gale, R. Patel, M. Cox, J. Paragreen

Page range: 111-117

Abstract

This paper describes a new roller die design capable of generating high pressures to allow the direct injection of liquid carbon dioxide into polymer melts and produce low density foams. The novelty of the design lies in the counter-flow action of a pair of rotating rollers separated by a gap to build up pressure. A mathematical model of the flow in the extrusion-roller die system is described and tested against experimental data with PS, LDPE and PP under a wide range of roller speeds and gaps. The study shows that this new design is feasible but more comprehensive CFD simulations and experiments are required to optimise design and operation to obtain the low-density polymer foams sought.

May 2, 2013

Experimental Investigation of the Development of Interfacial Instabilities in Two Layer Coextrusion Dies

R. Valette, P. Laure, Y. Demay, J.-F. Agassant

Page range: 118-128

Abstract

The stability of two-layer flow of polyethylene and polystyrene is experimentally studied in different flow geometries and for various flow rate ratios. A first coextrusion device allows to stop the coextrusion flow in a very long slit channel, to cool down the polymer sample and to dismantle the die in order to extract extrudate which is then carefully analyzed. A second device allows to observe the whole slit flow through transparent lateral walls and to record the interfacial waves in both spontaneous and controlled unstable conditions. Both devices point clearly out that the interfacial defect begins to grow after a specific flow distance and is then quickly amplified. This demonstrates the convective character of interfacial wave. Controlled unstable processing conditions in transparent die allow to measure accurately growth rate of defect in the linear regime and show quick occurrence of non linear regime.

May 2, 2013

Detachment of the Polymer Melt from the Roll Surface: Calendering Analysis and Data from a Shear Roll Extruder

D. M. Kalyon, H. Gevgilili, A. Shah

Page range: 129-138

Abstract

The detachment behavior of a polymer melt from the hot roll surface/s during roll-driven processes affects the maximum production rates achievable in various processes including calendering, embossing and shear roll milling. Here the continuous shear roll milling process is used to investigate the conditions that lead to the detachment of the polymer melt from the surface of one or both heated rolls. During the shear roll milling process the polymer melt needs to continuously stick to one roll and periodically to stick and then to detach from the other roll (at the nip). Different roll speeds, surface roughness and temperatures are used to facilitate continuous stick to one roll and periodic stick and detachment from the other roll. Shear roll mill process fails to convey the melt in the forward direction under conditions for which the melt detaches from both rolls. The shear roll mill processing of a high density polyethylene revealed the detachment of the melt from both rolls under various combinations of operating parameters. A calendering model enabling the use of different roll diameters and roll velocities for incompressible generalized Newtonian fluids under isothermal and lubrication flow conditions was developed and used to understand the detachment dynamics. The detachment of the melt from both rolls was revealed to occur when the maximum shear stress at the roll surface exceeds the critical wall shear stress at which the onset of macroscopic wall slip is observed in simple shear flow. These findings suggest that the processing window for roll-driven processes is affected by the wall slip characteristics of the polymer melt and that the processing window can be widened using a better understanding of the wall slip behavior of the materials being processed.

Reactive Extrusion

May 2, 2013

Reactive Extrusion of SAN/EPDM Blends

Z. Hrnjak-Murgić, L. Kratofil, Z. Jelčić, J. Jelenčić, Z Janović

Page range: 139-146

Abstract

The blending of styrene-acrylonitrile copolymer (SAN) and three different types of ethylene-propylene-diene terpolymer (EPDM) by reactive extrusion was studied and the free radical initiators: 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane (Luperco 101 XL), 2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3 (Luperco 130 XL), α,α′-di(t-butylperoxy)diisopropyl-benzene (Peroximon F40) and 2,2-azo-di-(2-acetoxy)propane (Luazo AP) were used. Besides, structural characteristics of the obtained blends, some rheological and mechanical properties were also established. The rheological behavior was determined using rheometer and corotating extruder. Measurements of mechanical properties included: tensile strength, impact strength and elongation at break have been made. Blends were separated on its structural components SAN, EPDM, graft (EPDM-g-SAN) and gel content, which were further characterized by solution viscosimetry and IR spectrophotometry. The obtained results elucidate the reactions that occur during extrusion process. The dominant grafting reaction was observed in blends prepared by using a Peroximon F40 as an initiator also showing outstanding mechanical and processing characteristics.

Film

May 2, 2013

Easy Tear Film of Biaxially Oriented PA 6/MXD 6 Blend by Double Bubble Tubular Film Process

M. Takashige, T. Kanai, T. Yamada

Page range: 147-154

Abstract

In the market, a film which adapted to environmental and barrier problems is desired. This report discusses the stretching stability and physical properties for biaxially oriented PA 6/ MXD 6 blending film produced by double bubble tubular film process. As MXD 6 blending ratio increased, the stretching stress decreased. Hydrogen bond is due to be suppressed by the steric hindrance of the MXD 6 resin. Blending film can be stretched stably and oxygen gas permeability is more excellent than PA 6. Further the film blended between 20 % and 40 % as MXD 6 blend ratio has the property of easy straight line cut. It is found that the plate-like cylinder structure was formed in the observation of TEM. However, thickness uniformity deteriorates when MXD 6 blending ratio exceeds 40 %. To improve the thickness uniformity, the influence of the kneading conditions was studied. When the melting point of MXD 6 decreased, the stretching stability deteriorated and mechanical properties drastically lowered. The excess reaction of the blending resins is not desirable. Stretchability, easy tear property and oxygen gas barrier property are maintained by following process conditions. In case of dry blending, MXD 6 30% is proper content. And in case of premixing, MXD 6 melting point keeps over 236°C. It was confirmed that there is the condition satisfying all properties. The blending film keeps the compatible performance of strength and easy tear property. Namely, the material and production technology of a film could solve environmental and barrier free problems.

May 2, 2013

Deformation Behavior, Processability and Physical Properties for Biaxially Oriented Film of LLDPE

H. Uehara, K. Sakauchi, T. Kanai, T. Yamada

Page range: 155-162

Abstract

The bubble deformation behavior of double bubble tubular film (DBTF) of linear low density polyethylene (LLDPE) is experimentally analyzed. Also investigated is how the bubble deformation behavior of the stretched films are changed by stretching conditions, especially stretching temperature, and how the properties of stretched films are influenced by stretching conditions. From the results, the optimum conditions required to obtain a stable bubble and good properties for the DBTF of LLDPE are indicated. The relationship between the DBTF and laboratory tenter stretched film (LTSF) is investigated in order to predict the processability and the properties of the DBTF by using the laboratory tenter biaxial stretcher. This method is not only more time efficient, but also reduces overall costs of developing the DBTF.

May 2, 2013

Stretchability and Properties of LLDPE Blends for Biaxially Oriented Film

H. Uehara, K. Sakauchi, T. Kanai, T. Yamada

Page range: 163-171

Abstract

In order to improve the stretchability of linear low density polyethylene (LLDPE) for double bubble tubular film (DBTF), the blending of LLDPEs have been investigated. Three LLDPEs of varying densities were blended, and several films having different densities, molecular-weight distributions and composition distributions were produced. The stretchability and properties of these films were investigated and the relationship between the stretchability and the material properties were also discussed. The material properties of LLDPE which showed better stretchability were reported. Furthermore, the stretchability of LLDPE by using the laboratory tenter stretched film (LTSF) and the DBTF were compared. The prediction of the stretchability for the DBTF by using the LTSF was reported.

May 2, 2013

Stretchability and Properties of Various LLDPE for Biaxially Oriented Film

H. Uehara, K. Sakauchi, T. Kanai, T. Yamada

Page range: 172-179

Abstract

Stretchability and properties of linear low density polyethylene (LLDPE) blends for biaxially oriented film was investigated in the previous report [1]. That report focused on changing the film density by blending three different densities of LLDPE. The relationship among stretchability, film density and the composition distribution was explored. In this report, several different densities and melt flow indices (MFI) of LLDPE were examined. A film with a density of about 0.915 g/cm 3 displayed the best stretchability, while films not less than 2 g/10 min MFI had poor stretchability. The most suitable composition distribution for stretching was reported. The properties of biaxially oriented films were also evaluated. Furthermore, the relationship between the laboratory tenter stretched film (LTSF) and the double bubble tubular film (DBTF) was investigated. There was a correlation between the density in film over 0.910 g/cm 3 and the stretchability of the DBTF and LTSF.

Molding

May 2, 2013

Microinjection Molding with LIGA-Like Process

S.-P. Yang, W.-B. Young

Page range: 180-185

Abstract

Injection molding process is used to mold component with microstructures in this study. The mold insert with microstructures having an aspect ratio around one is fabricated by the LIGA-Like process. This LIGA-Like process combines the UV-Lithography and electroplating to define the microstructure on a steel substrate. The method provides a cost effective way for molding a microstructure without the X-ray lithography. In fabrication of the mold insert, well-defined draft angle of the sidewall at the structure is a crucial factor for successful molding. The molded component has a good replication of the microstructures in the mold insert.

Thermoforming

May 2, 2013

On the Use of the Heating Stage to Control the Thickness Distribution in Thermoformed Parts

F. M. Duarte, J. A. Covas

Page range: 186-198

Abstract

This work investigates the influence of the heating stage of roll-fed and sheet-to-sheet thermoforming on the thickness uniformity of the final parts produced. Modeling of the heat transfer process involved in each case is carried out. An inverse methodology capable of setting the temperature of the heaters that produce a prescribed sheet temperature at the end of the heating stage is presented. The sensitivity of this differential heating technique to moderate perturbations of the individual set values is analyzed.

PPS News

May 2, 2013

PPS News

Page range: 199-203

About this journal

International Polymer Processing offers original research contributions, invited review papers and recent technological developments in processing thermoplastics, thermosets, elastomers and fibers as well as polymer reaction engineering. For more than 25 years International Polymer Processing, the journal of the Polymer Processing Society, provides strictly peer-reviewed, high-quality articles and rapid communications from the leading experts around the world.
All articles are subject to thorough, independent peer review.
Editor: Polymer Processing Society

Volume 19 Issue 2

Issue of International Polymer Processing

Contents

DuPont, IG Farbenindustrie, ICI and Japanese PA Fiber Manufacturers Polyamides 66 and 6

Fifth in a Series: Pioneering Polymer Industry Developments

Modeling the Flow in the Metering Zone of Single Screw Extruders Using a Helical Geometry Model

Abstract

Engineering Analysis of Devolatilization of Various Additives in Intermeshing Co-rotating Twin Screw Extruders

Abstract

Novel Extrusion Dies with Rotating Rollers for CO2-Plastic Foam Production

Abstract

Experimental Investigation of the Development of Interfacial Instabilities in Two Layer Coextrusion Dies

Abstract

Detachment of the Polymer Melt from the Roll Surface: Calendering Analysis and Data from a Shear Roll Extruder

Abstract

Reactive Extrusion of SAN/EPDM Blends

Abstract

Easy Tear Film of Biaxially Oriented PA 6/MXD 6 Blend by Double Bubble Tubular Film Process

Abstract

Deformation Behavior, Processability and Physical Properties for Biaxially Oriented Film of LLDPE

Abstract

Stretchability and Properties of LLDPE Blends for Biaxially Oriented Film

Abstract

Stretchability and Properties of Various LLDPE for Biaxially Oriented Film

Abstract

Microinjection Molding with LIGA-Like Process

Abstract

On the Use of the Heating Stage to Control the Thickness Distribution in Thermoformed Parts

Abstract

PPS News

Novel Extrusion Dies with Rotating Rollers for CO₂-Plastic Foam Production