SPE Library

The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.

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Conference Proceedings

Multi-Component Injection Molding-Part 1: Interface and Microstructure Development
K.P. Palluch, A.I. Isayev, May 2000

The purpose of this paper is the physical modeling and numerical simulation of the interface and microstructure development during the multi-component injection molding process. A software has been developed based on the control volume finite element method to calculate the transient non-isothermal multi-phase flow of viscoelastic polymer melts and to predict the stress-induced crystallization within the semi-crystalline polymers. Based on the developed simulation software material selection and process optimization becomes possible.

Simulation of Shearing and Mixing Sections
H. Potente, W. Többen, May 2000

Three-dimensional finite-element-calculations on spiral shear sections and faceted mixing sections have been applied to test the influence of geometry onto pressure-throughput and mixing performance. Well-chosen dimensionless numbers described the geometrie of the elements so a statement about the process development could be reached. Residence time and the Flow Number ? were utilized to evaluate the mixing effect and its information value.

The Heating/Melting Mechanism of Plastic Energy Dissipation
Myung Ho Kim, Costas G. Gogos, May 2000

The Paper discusses the bulkwise heat source melting mechanism, we have termed Plastic Energy Dissipation (PED). When solid particulates are deformed in the melting section of polymer processing equipment, where melting occurs in a dissipative mix melting mode, part of the applied mechanical energy to deform solid particulates dissipates into heat. The amount of heat dissipation is quite large for both amorphous and semicrystalline polymers. A number of PED experiments were conducted as functions of strain rate, strain and temperature and the iso-temperature rise plots were obtained in temperature-strain space for commercial amorphous and semicrystalline polymers. A method to estimate melting length for Co-TSE was also developed.

Transesterification Reaction Kinetics of Blends of Poly(ethylene terephthalate) and Poly(ethylene naphthalate)
S.R. Tharmapuram, S.A. Jabarin, May 2000

Blends of poly(ethylene terephthalate)/poly(ethylene naphthalate), PET/PEN, have exhibited properties that are of commercial interest to the packaging industry. Melt processing of PET with PEN results in transesterification reactions. The blend properties are controlled by the kinetics of these reactions and these have been widely studied. Modifications to the chemical kinetic equations have been made to predict a theoretical processing temperature for different compositions of the blends to achieve critical transesterification. These values were found to be in close agreement with the experimentally observed values when blends were processed in a twin screw extruder.

The Influence of Morphology on the Impact Performance of an Impact Modified PP/PS Alloy
S.P. Bistany, May 2000

Brittle impact failures were observed at low temperature on blow molded parts made from a PP/PS alloy that is normally ductile for injection molded parts tested at same temperature. An investigation was launched to determine the cause of these failures. SEM analysis on the inside surface of the blowmolded part revealed the presence of micro-voids and large spherulites. Additionally, cross-sectional analysis of the inside surface showed coalescence of the impact modifier. These factors are believed to have contributed to the brittle failures. A test method was developed in an attempt to confirm these findings.

Shrinkage Behavior of Oriented Poly(ethylene terephthalate)
R. Mody, E.A. Lofgren, S.A. Jabarin, May 2000

The kinetics of thermal shrinkage of poly(ethylene terephthalate) films have been characterized and related to various parameters of the stretching process. Amorphous orientation functions and levels of crystallinity have been found to be of major importance to the shrinkage process. As film extension ratios increase, shrinkage behavior passes through five different regions. Shrinkage first increases with extension ratio, decreases with further extension to reach a minimum, and then increases again as extension is continued to higher levels. A schematic model has been proposed to describe molecular changes in polymer chain structures, within each of the shrinkage regions. Activation energies of shrinkage have been determined in addition to equilibrium shrinkage and shrinkage rate constants.

Filament Winding of Bicomponent Fibers Consisting of Polypropylene and a Liquid Crystalline Polymer
Jianhua Huang, Priya Rangarajan, Jay Sayre, Alfred C. Loos, Donald G. Baird, May 2000

Bicomponent fibers consisting of a sheath of polypropylene (PP) and a core of thermotropic liquid crystalline polymer (TLCP) were used in filament winding to form tubes suitable for transporting liquid oxygen. As the first step, the TLCP/PP bicomponent fiber was spun and the mechanical properties of the fibers were determined as a function of temperature to establish the conditions suitable for filament winding. Under these conditions the tensile modulus and strength of the filaments can be maintained in the filament wound products.

Dependence of Draw Resonance on Extensional Rheological Properties of LLDPE
Michael J. Bortner, Donald G. Baird, May 2000

The effect of extensional rheology on draw resonance during fiber melt spinning is studied. Two linear low-density polyethylenes(PE's) synthesized using metallocene catalysts are compared. The LLDPE's appear to have different amounts of long chain branching, resulting in differences in extensional rheology. However, both materials behave almost identically in shear. During melt spinning, the PE's exhibit different critical draw ratios at which the onset of draw resonance occurs. Furthermore, the period of resonance changes with increasing draw down ratio for both PE's.

Tooling Project Management of Injection Molding
Michael Yue, May 2000

Delivering good qualify mold on time is always a big issue for both mold maker and molder. Either of them could loss business if the tool is delayed and or in poor quality. How to avoid these? This paper starts with tooling flow chart and discusses tooling project management techniques. The problems encountered in tooling scheduling and manufacturing process are analyzed. Also, tooling qualification and cost reduction are discussed.

An Assessment of Weld Heterogeneities in PMMA Using Birefringence
R.J. Wise, R. Thomas, May 2000

This paper concentrates on the measurement of melt orientation of polymer chains and welding residual stress using birefringence. PMMA specimens were welded using four techniques, hot plate welding, laser welding, hot gas welding and ultrasonic welding. Measurements of birefringence made in transverse sections showed that levels of polymer chain orientation and some components of residual stress could be measured. These measurements were used as a basis for the assessment of heterogeneities introduced into PMMA during welding by the four techniques.

Foaming of Thermoplastic Elastomers with Water
Abdelhadi Sahnoune, May 2000

We present results on foaming of a thermoplastic elastomer (TPE) using water as the physical blowing agent. The TPE is a blend of polypropylene and fully crosslinked EPDM rubber made by a dynamic vulcanization process. The influence of the blowing agent content, and the processing conditions on foam density, cell nucleation, and foam structure are discussed. A brief discussion about the similarities and the differences between foaming in homopolymers and in TPEs is also included.

Heat Transfer in Extruder Screws
Stephen J. Derezinski, May 2000

In the study and modeling of the resin temperature in extruder channels, the screw is commonly assumed adiabatic. However, the resin begins as a cold solid and is melted and heated as it flows, which requires that the screw also be cold at the entrance and hot at the exit. Heat must, therefore, be conducted in the screw metal from the hot end of the screw to the cold end, which requires heat transfer with the melt. Also, the heat capacity, especially of larger extruders, can require significant time to attain steady-state operation. A model of transient heat conduction in the screw coupled to heat transfer with the resin feed, melting, and pumping is used to investigate these two phenomena.

Preventing Sink Marks of Injection Molded Parts Using CAE Analysis
Shijun Ni, May 2000

Sink marks on injection molded parts were caused mainly by part geometric design, mold design, and molding process conditions. This paper describes the dominant factors causing sink marks on injection molded part that can be predicted using CAE injection molding simulation programs. Sink marks on injection molded parts should be prevented for a new part design or solved for an existing one based on simulation results. In this study, a Bearing Bur, Laser printer part was chosen to illustrate how sink mark problems were solved using a commercial available C-MOLD® simulation program. The predicted sink marks of the Bearing Bur were compared to the measurements of an actual production part. Predictions were in good agreement with the actual injection molded part.

Apparent Viscosity Measurements for Determining Injection Molding Dimensional Variations
Gary L. Freiberg, May 2000

Injection molders presently use the Apparent Viscosity Curve" to determine the optimum fill time for a particular mold. Once the fill time has been determined the Viscosity Curve is set aside and the goal of the molder is to maintain the fill time. The motivation for my work is not only to determine fill time but also to quantify the melt viscosity using an injection molding machine/mold combination. The ability to determine the melt viscosity would assist the molder with "root cause" analysis when evaluating small dimensional shifts. The study will focus on determining if the derived viscosity using traditional rheological equations is of value when compared to dimensional or cosmetic changes."

A Transparent Barrel for Study of Reciprocating Screw Injection Molding
Furong Gao, Zhiming Jin, Xi Chen, May 2000

A transparent barrel system has been developed to assist in the understanding of polymer behavior in a reciprocating screw injection molding machine. This system allows the dynamic status of the polymer inside the injection barrel to be conveniently visualized though photography and video recording, and the corresponding material conditions can be measured via a computerized data acquisition system. Effects of different processing conditions on the melting behavior are analyzed. This system can not only assist in the understanding of the process but also can be used to quantitatively verify the modeling and optimization of injection molding system.

An On-Line Measurement Scheme of Melt-Front-Area during Injection Filling via a Soft-Sensor Implementation
Xi Chen, Furong Gao, May 2000

A constant melt-front velocity during the filling of an injection mold cavity is commonly believed to bring about more uniform part quality. To maintain a constant melt-front velocity, injection velocity can be set proportional to the melt-front-area which is, however, not directly measurable. An on-line soft-sensor scheme is developed through neural network to correlate on-line measurable process variables to the melt-front-area. Simulations indicate that the soft-sensor developed for the melt-front-area works reasonably well for some selected molds.

Characterization of Biaxial Orientation in Polyolefin Films
A. Ajj, K.C. Cole, May 2000

Among the most widely used orientation processes are those involving films; they include both film blowing (with a low level of orientation) and biaxial orientation or tentering (with a high level of orientation). Polyolefins (polyethylene, polypropylene, polystyrene, and their copolymers) represent a significant proportion of the polymers commonly used in these processes. The knowledge of the orientation developed in these films is critical for establishing the process conditions and the final properties of the films. In this study, we investigate the biaxial orientation developed in blown and biaxially oriented polyethylene films using Fourier transform infrared (FTIR) spectroscopy and birefringence. Biaxial orientation factors are determined for both crystalline and amorphous phases and discussed in relation with process conditions.

Evaluation of Layer Spreading in Coextruded Structures via a Modular Die
Joseph Powers, Joseph Dooley, Carl Reinhardt, Gary Oliver, May 2000

Layer spreading in coextruded sheet structures remains a problem solved more often with art than with science. A modular die, i.e. a die with inserts for the entrance channel and for the manifold, was designed and evaluated for a range of entrance shapes, manifold shapes, and resins. The results from these experiments lead to an improved selection process for die designs for coextruded sheet.

An Experimental Investigation of the Effect of Polymer Processing Additives (PPA) on the Melting and Gel Formation Mechanisms in a Single Screw Extruder
K.R. Slusarz, J.P. Christiano, Stephen E. Amos, May 2000

Much work has been published showing how the addition of a polymer processing aid (PPA) has improved the processing characteristics on the single screw extruder. This paper will give insight on how the PPA affects a single screw extruder. Solids conveying, melting, and melt conveying were experimentally studied to determine how the PPA affected these important processes during extrusion leading to improvements in the melt quality.

Effects of Varying Strand Length on Shielding Properties of Conductive Elastomers in Near-and Far-Field Experiments
Douglas Luther, May 2000

A new study examined the effects of varying the strand length of extruded conductive thermoplastic elastomer (TPE) pellets on the shielding efficacy of plaques molded of the material in both near- and far-field experiments. Results indicated that longer strand lengths yielded parts with higher shielding efficacy but at a cost of higher durometer and modulus. Data also indicated that far-field results were consistently higher than near-field values for the same materials and frequencies.

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