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

Melting Phenomena and Mechanism in Polymer Processing Equipment
Costas G. Gogos, Myung Ho Kim, May 2000

The research work presented here examines the heating and melting phenomena taking place, when individual polymer particulates or compacted polymer particulate systems are subjected to stresses which force them to deform and flow. The heating/ melting behavior in compression experiments of single polymer cylinders and in co-rotating twin screw extruders was examined. Different polymers and different polymer particulate solid systems were used, over a range of processing conditions. The results of this work shed light on the important roles that solid dissipative deformation and interparticle frictional phenomena play in generating the heat necessary to melt polymer particulate systems. This paper also attempts to deal with the modification of the Thermal Energy Balance Equation, so that it includes the above heat generating dissipative source terms.

Rheological and Mechanical Properties of Recycled Polycarbonate
Ruifeng Liang, Rakesh K. Gupta, May 2000

Polycarbonate (PC) is used in computer and electronic housings, and here it was sought to reuse this polymer after having been separated from electronic shredder residue. The separated stream was not pure PC; there was some cross-contamination. The separated polymer was characterized by rheological, thermal and mechanical methods; the measured properties were only slightly inferior to those of comparable virgin materials. Recovered plastic and virgin polymer were blended using a TSE to determine the minimum virgin content needed to mask the effects of addition of recycled material on the rheological and mechanical properties of the blend. Differences in processing behavior and mechanical performance of the blends as a function of composition are discussed in relation to potential material recycling strategies.

Characterizing Scrap Vinyl Flooring to Determine Feasible Reuse Options
Andrew Lawrence, May 2000

The manufacturing waste generated during the production of vinyl floor tiles is typically sent to landfills, rather than recycled, because of a lack of reuse options for this material. This waste is typically PVC loaded with approximately 80% limestone. The goals of this research are to characterize this material to determine the feasibility of reprocessing it and to measure the mechanical properties of the processed material. This study will also attempt to suggest an injection molding or extrusion application for the mixture.

A Method to Characterize the Impact Properties of Hand Tools
John Stanko, John Kennerknecht, May 2000

There does not currently exist a method for the characterization of the impact properties of hand tools, specifically screwdrivers. Without a scientific method of collecting data for various designs, it is difficult for manufacturers to determine the effect of material or design changes on the impact properties of the product. The most demanding application for these hand tools can often be a hammer blow to the handle of the product, and therefore this abuse must be strongly considered in the design criteria.

Predicting Creep in Bottle Design
Ivan McCracken, May 2000

Experimental creep is data collected to drive an FEA program, ultimately used to predict bottle deformation caused by an internal pressure. The results indicate that it is possible to predict bottle deformation using existing creep data, but it is a highly manual process. The FEA program is beneficial in determining stresses caused by internal pressures, which can then be used to calculate deformations. True deformations can be calculated for segments of a bottle using FEA, but a new approach has been suggested, which will allow the FEA program to calculate the deformations along the entire sidewall of the bottle.

Crystalline but Fully Transparent - A New Polyamide with Outstanding Properties
Hans-Peter Hauck, May 2000

Requirements for chemical resistance and transparency are usually mutually exclusive in plastics, especially for polyamides. While aromatic constituents are used to produce most amorphous polyamides, this new transparent polyamide (designated according ISO 1874: PA PACM 12, herein PA means polyamide, PACM = Bis(p-aminocyclohexyl) methane) is based on aliphatic monomers. The monomer building blocks form very small crystallites that do not scatter visible light, so consequently parts made of this polyamide are clear as glass. This so called microcrystalline structure counts for a well-balanced combination of properties, e.g. good UV-stability, high level of impact behavior, low water absorption and isotropic shrinkage. Especially its chemical resistance is superior to other transparent materials such as polycarbonate, polymethacrylate or all amorphous polyamides.

Small-Scale Testing for Brittle-Tough Transitions of Rapid Crack Propagation in PE Pipelines
Paul Davis, Stuart Hillmansen, Patrick Leevers, May 2000

The resistance to Rapid Crack Propagation (RCP) of extruded PE pressure pipe undergoes a well defined brittle-tough transition with increasing temperature. Material developers need to correlate the transition temperature with property data measured using coupon-sized samples. This paper discusses mechanisms underlying transitions in pipe specimens before presenting efforts to correlate transition temperatures of pipe with small-scale test results. A non-mechanical thermal analysis technique appears to correlate the phase transformation behaviour of raw materials with transition temperatures of extruded pipe.

The Effect of Boron Nitride on the Processability of Metallocene Based LLDPE
Sang Myung Lee, Jung Gon Kim, Jae Wook Lee, May 2000

Melt fracture of a various shapes and related processing instabilities continue to limit processing rate in many commercially important polymer processing industries such as fiber spinning, film blowing and extrusion. Therefore, the occurrence of melt fracture needs to be limited in order to produce high quality products, which have the desired physical properties. In an effort to investigate increasing the processing rate and improving the quality of the final product, a commercial LLDPE was modified by the addition of small amount Boron Nitride (BN). BN was added to the virgin LLDPE at 180°C at concentrations of 0.05, 0.1, 0.5, 0.75 and 1.0 wt %. Also, the processability of capillary flow was investigated as functions of temperature, applied shear rate and L/D for the virgin LLDPE and LLDPE containing BN. The equipment used in this study include capillary rheometer, parallel-plate rheometer and universal test machine (UTM). The degree of processability in the capillary flow was found to depend on boron nitride concentration. The relationship between the apparent characteristic relaxation time and the critical shear rate for the onset of melt fracture and slip is also discussed.

The Comparison of Newly Proposed Cavity-Variable-Based Full Factorial Design and Artificial Neural Network in Injection Molding Process
Jung Gon Kim, In Ho Shin, Jae Wook Lee, May 2000

The statistical experimental design has been used to generate useful information for injection molding process, where more precise models based on physical laws and linear relations are not available. Until now, attempts at applying traditional full factorial design have resulted in creation of many problems, due to the selection of experimental variables from the machine rather than the cavity mold. Injection molding process has plenty of variables to be carefully observed concerning parts quality. Among these, cavity pressure and temperature are the ideal candidates for process monitoring and quality control role, thanks to their capability to present the dramatic changes inside the mold.

Comparison of Experimental and Predicted Data for Conventional Single Screw Extruders
Petra Samsonkova, Jiri Vlcek, May 2000

Single screw extrusion is widely used in the processing of thermoplastic materials. Good understanding of the extrusion process can save time and capital investments. Simulation programs capture the solids conveying, melting and pumping behavior to help us study the process and eventually to fit the screw design to a particular thermoplastic material. From such a study, the best processing conditions may be determined. There is still a considerable lack of understanding of the physical process in an extruder particularly with regards to the solids conveying. Our objective is to contribute to the understanding of this process, which should lead us to an improvement of the solids conveying model. In this paper we present a set of experimental data measured on various screw designs, for varying properties of different PE resins. Further more, the comparison of measured and predicted data is presented. This comparison is used to evaluate the physical model used during simulation of the extrusion process.

A Study of the Tensile Creep Behavior of Wood Flour Filled HDPE in Aqueous Mediums
John Raybuck, Daniel Heuer, May 2000

Wood flour filled polyethylene can be used as a replacement for conventional lumber in the waterfront structure industry. The effect of large amounts of moisture and submersion in fresh and salt water on the long term mechanical properties of these materials is important to understand. This study will examine the tensile creep behavior of wood flour filled high density polyethylene in air, fresh lake water, and salt water. An apparatus for aqueous tensile creep testing has been designed and built, and will be used to gather data for this study.

Modeling Gate Freeze in Hot Runners Using CAE
James J. Chiamardas, May 2000

When using computer flow simulation software to predict gate freeze time in hot runners it is hard to know how to correctly model the hot drop tip to accurately correlate the gate freeze time. This study will attempt to use computer flow simulation to correlate the gate freeze time of hot runners predicted by the simulation to actual gate freeze times. This will be done by changing a model to make the gate freeze prediction match an actual molded part, and observing how these changes affect the rest of the model.

Color Effects of Modified Rubber on Black Colorant in Polypropylene
Eric B. Hunt, May 2000

The primary use of modified rubber is to improve flexural modulus and impact strength. The disadvantage of using modified rubber is the distortion of color when used as an additive to a polymer. This study compared the color shifts of a black colorant with differing loadings of modified rubber.

Simulation of the Micro Injection Molding Process
Oliver Kemmann, Lutz Weber, Cécile Jeggy, Olivier Magotte, François Dupret, May 2000

To predict the filling process of micro injection moldings, a dedicated 3 dimensional software is under development. The algorithm is based on automatic re-meshing of the varying flow domain. Currently, viscous flow calculations are performed, while visco-elastic effects will be addressed at a later stage. To verify the results, micro injection molding trials with different polymers were carried out. Therefore, new test structures, realized by means of the LIGA technique, were designed. Visco-elastic effects like unique shapes of the frozen flow fronts have been observed, which leads to a new interpretation of micro mold filling.

Vacuum Stamping of a Refrigerator: Identifying Problems through Numerical Simulation, Solving Them and Validating the Solution on the Production Line
Nikos G. Pantelelis, Thierry M. Marchal, Prodromos Megisidis, Laurent Fondin, Andreas E. Kanarachos, May 2000

Thermoforming is gaining more and more applications because of its comparatively easy and fast process. With thermoforming either small (yoghurt pots) or large (refrigerator panels) flat parts can be moulded and a complete description of the process can be found. On the other hand, to simulate the thermoforming process is a real challenge, as various factors have to be investigated and taken under consideration if we want to achieve a realistic simulation. At the present paper, a very complicated thermoforming process is simulated using finite element and other numerical tools and the results are compared to the real process. Moreover, problems occurred in the real process are solved using the simulation tool.

Extrusion of Polystyrene Microcellular Foam with Supercritical CO2
Xiangmin Han, Kurt W. Koelling, David Tomasko, L. James Lee, May 2000

The continuous production of polystyrene foam with supercritical CO2 is achieved by injection of CO2 into the extruder barrel at a certain pressure and rapid pressure release in the die. The effects of temperature, pressure, and die shape, are analyzed in detail. Fundamental work related to the foaming process is accomplished by modeling the phase equilibrium with the Sanchez-Lacombe equation of state and combining the equations of motion, the energy balance and the Carreau viscosity model to characterize the flow behavior. The experimental parameters were selected according to the Tg and phase equilibrium. The position of nucleation in the die was studied according to the simulation results via a computational fluid dynamics code (FLUENT).

Processing Glass-Filled Polyethylene on a Twin-Screw Injection Molding Extruder
David Bigio, Rajath Mudalamane, Yue Huang, Saeid Zerafati, May 2000

The mechanical properties of glass-fiber reinforced thermoplastics depends largely on the post-processing fiber length distribution. The traditional method of compounding in an extruder followed by injection molding causes considerable fiber attrition. In this study, the benefits of using a novel type of machine -the Twin-screw Injection Molding Machine (T.I.M.E.) - is investigated. The effects of operating conditions such as screw speed, glass-fiber content and extent of screw fill, on the final fiber lengths and distribution are studied. Optical microscopy and image analysis methods were used to analyze the processed parts.

Vibration Assisted Resin Transfer Moulding (VIARTM): A New Alternative Technique to Improve RTM Performance and Part Quality
Nikos G. Pantelelis, Athanasios Bikas, Andreas E. Kanarachos, May 2000

At the present paper a new system with the aim to improve the RTM process has been developed and presented. The system is based on the assistance of the resin flow with mould-inducing mechanical vibrations. Potential advantages of the proposed method are the improvement of the quality of the composite part (reduction of voids and reach areas), decrease of the filling time and/ or the maximum applied flow pressure. A test apparatus has been set up at NTUA to study the various mechanisms that relate the resin flow through the preform mat, the curing and the external vibrations. The project is progressing well and initial results are very promising and will be presented at the conference.

New Fast Peroxides for PVC
Kenneth W. Dixon, May 2000

Recent economic trends in the PVC market have pushed producers to reduce costs and improve productivity. Areas were sought where peroxide expertise can be utilized to develop new initiators that can help. Consequently a new developmental, fast peroxide for PVC, D-174, is being introduced which is reactive at lower polymerization temperatures, gives a more square heat profile and produces shorter polymerization cycle times for the PVC manufacturer.

Assessment of Metallocene Propylene Polymers for Cast Film Applications
Charlie Y. Lin, Michael C. Chen, Aspy K. Mehta, May 2000

The entry of metallocene-based products into polypropylene cast film is at a stage where potential in various markets is only now being assessed. The current thrust is to bring forward a set of differential properties to complement effectively Ziegler-Natta based poly-propylene cast film products. This study reviews the structure features of metallocene polymers and reports some potential benefits in cast film applications.










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