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
The Extrusion of Multi-Layer Barrier Tubing from Cross Linked Polyethylene (PEX)
John A. Colbert, May 2000
The use of multi-layer tubing, based upon PEX, is growing substantially especially in hot water plumbing applications. Improvements in Oxygen barrier, thermal stability and durability, are the major properties that are driving this growth. Whilst papers have been presented on the cross linking process, and long term durability of PEX, very little has been published on the process of producing five layer PEX tubing. This paper covers the process and methods used to achieve consistently high quality. It looks at extrusion conditions, screw design, die technology, control of layer thickness and centricity, and vacuum sizing techniques and how they can influence factors such as surface finish and ovality. It also looks at measurement of layer thickness and the overall tube dimensions. All aspects are illustrated with actual results from production scale work based upon a 90mm extruder line.
Incompressible Model of Solids Conveying in a Single-Screw Extruder
Shibo Zhang, Valentinas Sernas, May 2000
Experiments in corn meal extrusion [18] have shown that the flow of solids in the screw channel of a single-screw extruder has a helical pattern. This observation implies that there is a cross-channel velocity component in the solids conveying zone of the extruder. Existing solids conveying models [2,5,6,9] treat the solids moving in the channel as a plug flow without a cross-channel velocity component. The two-dimensional powder conveying model proposed in this paper contains both a down-channel component and a cross-channel component. The stress generating mechanism is much more complicated in a powder flow than in a fluid flow. The incompressible model incorporates a constitutive equation for the powder flow with slip boundary conditions. The energy equation with appropriate boundary conditions is also included in the model. The numerically solved model shows that the predicted down-channel pressure development, velocity and temperature distributions are all reasonable.
Carbon Black (CB) Distribution in Binary Immiscible Polymer Blends
Jiyun Feng, Chi-Ming Chan, May 2000
Carbon Black(CB) distribution in binary immiscible polymer blends was elucidated by computer simulation and experimental observation (scanning electron microscopy (SEM) and optical microscopy (OM)). It has been found that the predictions of CB distribution by computer simulation based on a thermodynamic model are in agreement with microscopic observations when the viscosity of the two components is in a similar range. However, when the viscosity of one component in binary immiscible polymer blends is extremely high, the predictions are not valid due to incomplete wetting of CB particles by the high viscosity component.
Morphology Identification of a Polymer Blend by Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) Chemical Imaging
Jiyun Feng, Chi-Ming Chan, Lu-Tao Weng, May 2000
The bulk morphology of a multi-component polymer blend of PC/PMMA/PVDF(50/20/30) was elucidated in detail by ToF-SIMS negative and positive chemical imaging. Based on the characteristic negative or positive secondary ions generated from different polymers under a 69Ga+ beam, bulk morphology can clearly be identified. A combination of negative and positive ion chemical imaging directly revealed that PMMA is distributed in the PVDF phase. Our results indicated that even though ToF-SIMS is a special technique used in surface and interface studies, it is also a powerful tool in the study of bulk morphology of polymer blends.
Relaxation of Residual Stress in a PPS High Precision Part
Lee E. Hornberger, Lilia A. Sanchez, May 2000
Glass filled polyphenylene sulfide (PPS) is a preferred material for many electronic applications because it is known to be dimensionally stable when exposed to elevated temperatures for short periods of time. The presence of residual stress, however, significantly affects the dimensional stability of this material. In this study, a new testing method, holographic interferometry, was used to monitor the relaxation of residual stresses in the molded actuator arm of a hard drive due to exposure to elevated temperatures. With this method, permanent deformation was detected in the arm at temperatures ranging from 40-80°C. This deformation is enough to cause significant problems in the high precision components of the hard drive.
Electrical Static Dissipative Composites Made from Coated Fillers
Brian P. Grady, W. Berlin Genetti, May 2000
A novel polymerization technique, admicellar polymerization, was used to coat alumina with a thin layer of polypyrrole. A polyethylene composite made from the uncoated material had a conductivity of approximately 10-9 S/cm, well below the useful conductivity range for most applications. However, the conductivity of the composite made with the coated material was approximately 10-5 S/cm, which is in the conductivity range of many electrically static dissipative applications.
Permeation of Thermoplastics through Random Fiber Mats
Jurron Bradley, John Muzzy, May 2000
The permeation of fiber mats by thermoplastics has not been studied in depth. In order to address this issue, the permeation of nylon 6 and polypropylene through random glass, carbon, and sisal fiber mats has been studied. A transverse Kozeny constant of 4.6 was calculated for the permeation experiments, and a non-Newtonian permeation model was found to predict the permeation rate of the thermoplastics into the fiber mats well.
An Integrated Process for Medical Design Success
Robert L. Braido, May 2000
Customer driven medical product development is a process to shorten the development cycle time and drive speed to market. It focuses on the product concept and the design freeze to develop a manufactureable assembly with built in quality while lowering manufacturing costs.
Benchmarking STL-Based Plastic Analysis
Geoffrey Engelstein, May 2000
New software packages allow for full dynamic analysis of plastic filling and cooling using a finite-element mesh derived from an STL model. The elimination of the need to create a midplane mesh holds out the promise of getting analysis results much faster and with less training and specialized knowledge. Does the reality stack up? This presentation examines the new meshing process and compares analysis results obtained through both the STL and traditional midplane mesh methods. Guidelines will be offered to assist in the proper usage of this tool to help enhance its effectiveness and avoid pitfalls.
Metal Injection Molding: Simulation of Three-Dimensional Flow with Free Surface Boundary and Experimental Comparison
Florin Ilinca, Jean-François Hétu, Abdessalem Derdouri, Brian Holmes, Craig Scott, James Stevenson, May 2000
A three-dimensional transient finite element flow analysis code that includes inertia and free surface boundary conditions is used to predict uniform (axisymmetric) and nonuniform (nonaxisymmetric) filling patterns in a thick-walled tool with a diaphragm gate. The simulation for a powder injection molding compound, which is strongly influenced by thermal effects, predicted several observed flow patterns: initial annual free surface flow, bypass and folding flow to form internal weld lines, and the transition from uniform (axisymmetric) flow to nonuniform (nonaxi-symmetric flow) with increasing fill time. The effects of inertia, yield stress, and wall slip on the filling patterns were assessed.
A Three-Dimensional Analysis of Coextrusion in a Single Manifold Flat Die
W.A. Gifford, May 2000
The coextrusion of two polymers through a single manifold flat die is examined. The three components of velocity and the pressure are determined in each layer along with the interface between the layers. It is shown that even when the viscosity ratio is one (i.e., single layer), flat layers" entering the die will not remain flat but will be distorted by the die. For coextrusion of two polymers the distortion of the interface profile at the exit of the die and thus the uniformity of the layers depends upon the viscosity and flow rate ratios of the two polymers as well as the geometry of the die."
Influence of Temperature, Molecular Weight and Molecular Weight Dispersity on the Surface Tension of Polystyrene (PS): Experiment and Theory
José Carlos Moreira, Nicole Raymonde Demarquette, May 2000
In this work, the influence of temperature, molecular weight (Mn) and molecular weight dispersity (MWD) on the surface tension of polystyrene (PS) was evaluated using the pendant drop method. The discrete interface cell model (DICM) theory was used in conjunction with the Flory, Orwoll, and Vrij (FOV) equation of state theory to predict surface tension (?) with bulk pressure-volume-temperature (PVT) data. It was shown that surface tension of PS decreases with increasing temperature for all PS studied. The surface tension of PS increased when the molecular weight of polystyrene was varied from 3,000 to 40,000. When the molecular weight of PS was further increased the surface tension was shown to level off. The surface tension was shown to decrease with increasing molecular weight distribution. The theoretical predictions of DICM theory corroborated with the experimental results as far as the influence of temperature, molecular weight was concerned.
Computer Aided Design for Rotationally Molded Parts
John Fawcett, May 2000
3D Cad software is improving new product development in many plastic fields including rotational molding. These improvements are leading to better products that are developed faster with fewer down stream changes. Because a 3D Cad electronic file gives a more complete design that can be viewed as a 3-dimensional model or represented as a 2D drawing, everyone involved with the project has a better understanding of the final product. Some features of 3D Cad can improve the development process in ways that are unique to rotationally molded products. The use of 3D Cad is also creating new opportunities for the use of rotationally molded products because tighter tolerances can be achieved when the 3D electronic file is used to create the tooling models and/or molds.
The Role of Phosphites in Stabilization of Non-Polyolefin Polymers
Henry C. Ashton, William Enlow, Tim Nelen, May 2000
The use of organophosphites as stabilizers for polyolefins has been well described and documented(1). This paper deals with the use of phosphites as stabilizers in non-polyolefin applications such as PVC and also in condensation polymers e.g. Polyesters, polyamides, and polycarbonates. A key point in understanding the application of phosphites in such materials is that the process of polyolefin thermooxidative degradation begins with thermomechanical scission of a carbon-hydrogen bond that yields a polymer based macroalkyl carbon-centered free radical. This free radical is highly reactive with molecular oxygen yielding a peroxy radical which can by interaction with the polymer substrate generate other free radical species such as alkoxy radicals and the highly detrimental hydroperoxides (see Figure 1).
Blends of Tetrabromooligocarbonate with Polycarbonate
James Y.J. Chung, Winfried Paul, May 2000
Tetrabromooligocarbonate (TBOC) was melt-blended with Bisphenol-A polycarbonate (PC) in various ratios to determine their miscibility with PC. According to the glass transition temperature (Tg) of the blend, TBOC can be miscible with PC, depending on the molecular weight of TBOC and its amount in the blend.
Joint Performance of Mechanical Fasteners under Dynamic Load
Axel Tome, Gottfried W. Ehrenstein, Frank Dratschmidt, May 2000
Threaded Inserts in either brass or plastic or rather economic self-tapping screws can be used to join different polymers or polymers to metal at high loads. Usually joints are subjected to dynamic loads as well as temperature variations. In this paper the static and dynamic load limits of mechanical fasteners (insert/self-tapping screw) will be discussed.
Application of Pulsed Electrochemical Machining to Micromold Fabrication
Blaine Lilly, May 2000
Pulsed electrochemical machining (PECM) is an effective method for removing EDM surface damage from tool steels, while maintaining the surface geometry to close tolerances. Mold steels show improved fatigue life after PECM when compared to steel machined by EDM. Because the tool does not wear during machining, PECM also shows promise as a method for machining micromolds. This paper reports on mold finishing research using PECM, and ongoing work applying the technology to micromachining of mold cavities.
Understanding Color Technology
Scott A. McCabe, May 2000
The production of custom colored thermoplastic elastomers often involves the use of color concentrates provided by a color house. In order to effectively communicate color requirements, a good understanding of the principles of color technology is a necessity. The basic principles of color theory will be discussed and current industrial practices of measuring color will be presented. Proper selection of color tolerances will be illustrated with several case studies.
Influence of Thermal History and Molecular Weight on the Mechanical Properties of High Density Polyethylene
C. Albano, R. Sciamanna, G. Delgado, D. Kaiser, May 2000
Several variables affect the plastics solidification process, being the thermal history given to the polymer and its molecular weight the more important. Therefore, this paper is mainly aimed at establishing a relationship between thermal history, mechanical properties and molecular weight of HDPE based on mathematical models of the following type: mechanical property =f(molecular weight, crystallinity) through a multivariable non-linear regression method and three-dimensional views of the surfaces generated by the mathematical expressions were obtained to have a better view of the results and models developed, concluding that these models are very useful for the industry.
The Use of Thermomechanical Indices to Establish Straightforward Processing-Mechanical Properties Relationships
J.C. Viana, A.M. Cunha, N. Billon, May 2000
The thermomechanical environment imposed to the melt in injection molding is quantified by two thermomechanical indices estimated from computer simulations of the mould filling. These indices are associated to the onset conditions of the microstructure development, and aim at interpreting its final state. As the microstructure determines the mechanical properties, straightforward relationships between those and the thermomechanical indices can be obtained. In this work, axisymmetric specimens were injection molded with systematic variations on the melt and mold temperatures and the flow rate. The mechanical properties were assessed in tensile tests at cross-head velocities of 2, 10, 500 mm/min and 3 m/s. They were related to the thermomechanical indices. Their variations were interpreted in terms of the expectable microstructure of the moldings.
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