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

Screw Design for Cooling Extruders

Chris Rauwendaal, May 2004

This paper presents a theoretical approach to the prediction of melt temperature profiles in cooling extruders. The effect of screw design on cooling performance in discussed. A new screw geometry is presented will substantially improved cooling capability. Initial performance data on a 200-mm cooling extruder are presented.

Processing Polyethylene Terephthalate on a Single Screw Extruder without Predrying Using Hopper- and Melt Degassing

Walter Michaeli, Torsten Schmitz, May 2004

Conventional PET processing requires pre-drying, an energy- and cost-consuming process limiting production flexibility. The paper presents combined hopper- and melt degassing in a single screw extruder as a real alternative to predrying and investigates the influence of extrusion- and degassing parameters, screw-design and water content on both intrinsic- and melt viscosity.

Practical Approach to Screw Breakage and How to Avoid Failures

Jeff A. Myers, May 2004

The use of practical mathematical expressions can be used to evaluate the mechanical strength of a rotating shaft. Similar expressions can be used in the design of a feedscrew. The purpose of this paper is to investigate the factors that influence the mechanical strength of a feedscrew and to show how to use these expressions from a practical standpoint to avoid failure during operation.

Effect of Screw Surface Properties on Extruder Performance

Chris Rauwendaal, May 2004

The surface condition of the screw and die can have a significant effect on extruder performance; however, little information about these effects is available in the open literature. This paper discusses various aspects of the screw surface conditions and how these can change the characteristics of the process and extruded product quality.

Die Lip Sensitivity in Cast Film Dies

Gary Oliver, May 2004

Die designs for production of cast polymer films typically include a flex lip for varying the geometry of the lip opening. The cast film process requires die lip gaps ranging from 0.4 mm to 0.8mm. Flex lip gap and the adjustment of said gap becomes increasingly difficult to control as it is reduced. An examination is made of the issue of die lip sensitivity with different polymers extruded at different lip openings.

Metering Channel Flows and Troubleshooting Single-Screw Extruders

Mark A. Spalding, May 2004

The manufacturing costs for a process depend highly on the proper operation of the extrusion equipment. In general, proper operation requires that the metering section of the screw be the rate-limiting step. Using drag flow and pressure flow calculations for the metering section is a simple method to determine if the section is the limiting step. This paper shows how these types of calculations can be used to determine if the screw and process are functioning properly.

Reactive Extrusion of Starch-Polyacrylamide Graft Copolymers

J.L. Willett, V.L. Finkenstadt, May 2004

Graft copolymers of starch and polyacrylamide have been prepared using a twin screw extruder. The effects of monomer/starch ratio and moisture content on conversion, graft efficiency, graft molecular weight, and frequency of grafting are discussed. Conversion of monomer to polymer exceeding 90% and grafting efficiencies exceeding 60% can be achieved by this process, with residence times of approximately 250 seconds or less.

Compatibilizing of PET/PA Blends with a New Coupling Agent in a Twin Screw Extruder

Edmund Haberstroh, Stephanie Lambertz, May 2004

Polyethylene terephthalate (PET) and Polyamide (PA) can be compatibilized in one process step on a twin screw extruder using a novel coupling agent. This reagent is able to react with PET as well as with PA which leads to Copolyesteramids. Until now a compatibilisation was only possible in a three step process, this new reagent makes a one step process possible.

The Effect of Multilayer Rheology on Coextrusion Die Design

Joseph Dooley, May 2004

Multilayer coextrusion is a process in which two or more polymers are extruded and joined together in a feedblock or die to form a single structure with multiple layers. This paper will discuss the proper techniques for using rheology data to design coextrusion dies based on experimental rheology data for monolayer and multilayer structures.

The Effect of Process Aids on Interfacial Instabilities in Coextrusion Flows: Theoretical and Experimental Investigation

M. Zatloukal, J. De Witte, May 2004

In this paper, the effect of process aids on the interfacial instabilities in coextrusion flows is investigated theoretically via viscoelastic FEM simulations as well as experimentally. Theoretically determined processing/materials rules according to which a stabilization effect with process aids can be achieved are compared and discussed with experimental results.

Interlayer Adhesion of Co-Extruded Sheets before and after Biaxial Stretching

Hongyi Zhou, May 2004

In order to quantify interlayer adhesion of co-extruded sheets with strong interlayer adhesion, a test method was developed to first initiate delamination by uniaxial stretching and then measure interlayer adhesion by peel test. The method was applied to co-extruded sheets before and after biaxial stretching. Interlayer adhesion with peel force as high as 5330N/m (30lb/in) have been measured for the as co-extruded sheets. Reduction of interlayer adhesion as a function of biaxial stretching was revealed.

Ultrasonic Monitoring of Barrel Wear and Screw Status

C.-K. Jen, Z. Sun, M. Kobayashi, May 2004

Four types of high temperature (HT) ultrasonic sensors have been installed at barrels and a flange of a 30-mm twin-screw extruder to non-intrusively and non-destructively measure barrel and screw wear, as well as screw misalignment and deflection during polymer extrusion. The sensors included sol-gel sprayed ultrasonic transducers (UTs), non-clad and clad buffer rod sensors, and stand-alone HTUTs. This study has demonstrated the capability of these ultrasonic sensors in monitoring the barrel and screw statuses at the pumping, mixing and melting zones of the extruder.

The Determination of the Best" Viscosity Model for Shear Thinning Fluids from Capillary Rheology Experiments"

W.A. Gifford, May 2004

This paper describes an algorithm used to determine a single viscosity correlation from capillary rheometer experiments. One can choose any one of seven commonly used models for shear thinning fluids. The program then determines the constants in the chosen model which best describes all of the experimental data in a statistical (i.e., least sum of squares) sense. By comparing the results from several different models, one can determine in a matter of minutes the model, which best describes the measured rheology data.

High Performance Polyethylene Resins for the Thin Wall Injection Molding Market

J. Auger, A. Duff, M. Weber, C. Bellehumeur, May 2004

A new single-site catalyst and process technology has been used to produce resins for thin wall injection molding lid applications. The performance of the single-site resins is compared with conventional Ziegler-Natta resins. The single-site polyethylenes provide superior processability with less mold deposit and organoleptic concerns. Additionally, these resins possess equivalent or better stiffness and toughness versus competitor products along with an unusually high level of clarity in the final parts.

Effect of Cyclic Cooling on Power Consumption of the Injection Moulding Process

A.L. Kelly, P.D. Coates, R. Evans, May 2004

The performance of a cyclic mold cooling system has been investigated with particular emphasis on process power consumption. A highly instrumented proportional-hydraulic injection molding machine was used to produce tensile test specimens from HDPE. Mold temperature was monitored at high frequency during each cycle, as was nozzle melt pressure, temperature and power consumption. Reduced cycle times were achieved with cyclic cooling and savings in power consumption of up to 23% were recorded over conventional methods.

A Novel Microcellular Co-Injection Molding Process

Lih-Sheng Turng, Hrishikesh Kharbas, May 2004

This paper presents the development of a novel microcellular co-injection molding process that combines aesthetic and processing advantages of injection molding with the benefits and property attributes of microcellular plastics (MCPs). While eliminating the swirling patterns seen on surface of microcellular plastic parts, this process is capable of producing lightweight parts with lower energy requirements, better dimensional stability, reduced sink marks, and desirable microcellular structure with fine cells and high cell density.

Real-Time, Non-Intrusive and Non-Destructive Ultrasonic Monitoring of Injection and Co-Injection Molding Processes

Y. Ono, M. Kobayashi, C.-K. Jen, C.-C. Cheng, A. Derdouri, Y. Simard, May 2004

Integrated ultrasonic sensors directly coated onto mold inserts of a molding machine together with rugged ultrasonic system are used for real- time, non- intrusive and non- destructive monitoring of injection and co- injection molding processes. Monitoring of flow front arrival, flow speed, filling completion, solidification, part detachment and thickness of skin and core inside the mold has been demonstrated.

In-Line Activation with Atmospheric-Plasma Makes a Strong Bond in Multi-Component Injection Moulding

Simon Amesöder, Gottfried W. Ehrenstein, May 2004

In-line-activation of polymer surfaces by atmospheric-pressure plasma-treatment directly in the injection mould enables positive-joint composites to be made from polymer combinations that were hitherto unable to adhere to each other, significantly improves adhesion of compatible combinations and can be easily integrated into the process chain. The paper presents the technology, its advantages, and shows results for new compatible material-combinations.

Co-Injection Molding in Metal Injection Molding

Kenji Okubo, Shigeo Tanaka, Hiroyuki Hamada, May 2004

Metal Injection Molding (MIM) is a process to manufacture metal parts, combining powder metallurgy with plastic injection molding. With MIM process, it is possible to produce highly functional composite metal structures by insert molding, co-injection or double injection molding. In this study, co-injection molding was applied to manufacture composite component of dissimilar metals. The effect of injection speed on flow behavior of dissimilar metal powder was experimentally investigated.

Localized Material Effects Associated with Flow Control during Multi-Cavity Injection Molding Processes

Gregory S. Layser, John P. Coulter, Ahmet Pinarbasi, May 2004

This paper describes a numerical simulation based study of a new injection molding concept focused on locally controlling the filling of multi-cavity molds in real time. The concept is applicable to all runner system types and involves the utilization of controllable mechanical valves. Several types of valve designs in cold runners were modeled and the effects of various control scenarios on localized material conditions throughout the mold are presented.