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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Shear Effects on Extruded Foam Products
Shear has been found an important nucleation parameter in the foam extrusion process. In this paper, further shear effects on foam properties are presented. At increased shear, foam expansion decreases, which suggests die swell promote competing mechanisms. Extension rate was found to correlate with expansion and compression strength. Also investigated was residence time at low shear to restore the shear thinning in the counter-rotating twin screw extruder. Shear and extension rate effects are addressed for foaming and foamed products.
Shrinking Control and Residual Styrene of Unsaturated Polyester Resins Cured at Low Temperatures
In low temperature molding processes, shrinkage control and residual styrene are important concerns. The presence of low profile additives (LPA) can reduce the shrinkage of unsaturated polyester (UP)/styrene (St) resins cured at low temperatures under proper processing conditions. A systematic study was carried out to investigate the effect of reaction temperature, initiator systems, and modification of the resin system on structure evolution, final resin conversion, and shrinkage control of UP resins with LPA.
Simulation of Microcellular Foaming in Injection Molding
We present a simulation model for the MuCell® injection molding process in which supercritical fluid such as carbon dioxide or nitrogen is mixed with molten polymer and injected into the mold. The model accounts for the development of cells in the melt, their effect on viscosity and compressibility and the subsequent expansion of the melt to fill the cavity. Simulation results and their comparison with experiments will be discussed.
Simulation Study of Polymer Flow through an Extrusion Blow Molding Head
The unequal flow of polymer, through a die, is a common problem in industry. This imbalance in flow is due to a non-uniform flow path resulting in different velocities at different points in the die. This problem is commonly fixed by adjusting the die or pin position to compensate for the uneven flow. In complex die shapes, compensating for uneven flow cannot be done as easily. Simulation software was used in a verification study to ensure that the results from the software matched the experimental results. This will be useful in industry's determining of the validity of such software.
Sintering of Thermotropic Liquid Crystalline Polymers
Two thermotropic liquid crystalline polymers were evaluated for use in rotational molding: Vectra A 950 and Vectra B 950. Material is typically prepared by grinding. When ground, even under cryogenic conditions, TLCPs tend to yield particles of high aspect ratio translating to low bulk density, poor granular flow, and incomplete densification. A process was developed to generate spherical particles of controlled size and distribution. Particle coalescence and densification characteristics were determined and compared against model predictions.
Size Does Matter: Minimization of Gate Wear
Previous work in flow simulation and runner system balancing has demonstrated the impact that small changes in gate size have on cavity filling. Gate wear affects shear rate and in turn, the viscosity of the melt. The flow of glass filled material has long been identified as a factor in tool wear. As part of the long-term wear studies of copper alloys and tool steels at Western Michigan University, careful scrutiny was given to wear of edge gates due to the flow of molten plastic. Certain hard coatings and alloys were shown to demonstrate superior resistance to wear.
Soft Contact Lenses: A Material Review
Soft contact lenses contribute up to 85% of the market for contact lenses in the U. S. The concept and the introduction of contact lenses, the history of the development of soft contact lenses and the materials currently used for contact lenses are discussed in this paper. The manufacturing method and the surface treatment are also briefly reviewed.
Solid-Bed Break-Up during Plastication in Injection Molding
Uniformity in polymer melting in the screw-barrel system has very important influences on the quality of injection molded products. An experimental study on injection plastication is conducted with HDPE in a visual barrel system. Solid-bed break-up phenomenon is observed and analysed under different processing conditions.
Spotlight on Plastics Joining Advances at K 2001
A large number of improvements in plastics joining technology have been stimulated by the end user. The influence of the car industry's suppliers and the car industry itself, along with the telecommunications and construction industries and medical technology were reflected in recent developments that have been presented at the K-fare in Düsseldorf/Germany at the end of October 2001.
Stability of Two-Stage Single-Screw Extruders
In two-stage extrusion, the pumping section must be sized to produce the needed delivery pressure of the extruder. A method of calculating the channel depth so that the desired pressure is achieved and that the stability of the flow is optimized has been developed. Data for an example are given.
Structure Development in Melt Spinning of Cyclopolyolefin Filaments
Melt spinning of cyclo-polyolefins is presented. The birefringences of the melt-spun filaments were determined and contrasted with spinline stress. These were found to be much lower than polycarbonate and polystyrene filaments melt spun under the same conditions. The birefringence was represented in terms of polymer chain orientation.
Structure of Nanocomposites Foams
Exfoliated and intercalated polymer/clay nanocomposites were synthesized and used to prepare nanocomposite foams, using CO2 as the foaming agent. The foam structure was observed by scanning electron microscopy (SEM), while transmission electron microscopy (TEM) was used to observe the detailed clay distribution. The effect of clay dispersion and clay concentration on the cell structure was investigated.
Studies on the Influence of the Holding Pressure on the Orientation and Shrinkage of Injection Molded Parts
The shrinkage is determinant on the final dimensions of technical parts. This feature of the injection moldings is dependent on the processing setup, namely the holding pressure and the molding temperature.In this paper results are presented on studies made on a semi-crystalline material and an amorphous material that were molded in planar and tubular moldings. The shrinkage was directly measured and related to the frozen-in orientation of the part. The orientation was indirectly quantified by the across-thickness variation of the birefringence.
A Study of Degradation of LLDPE under Accelerated Conditions
In order to use linear low density polyethylene (LLDPE) as external duct lining of oil pipes, we have evaluated the aging of this polymer. The experiment has been carried out under accelerated UV fluorescent lamps exposure, during 336 hours.We focused our investigation on changes on mechanical properties occurring over the aging process.The LLDPE studied was mixed with peroxide in order to modify its properties.
Study of PVC Stabilization Using Capillary Rheometry
Capillary rheometry allows monitoring PVC thermal and shear stress degradations separately. Based on testing of PVC compounds with a capillary rheometer, stabilizers can be efficiently optimized to reduce both degradation processes. Capillary rheometry is an important tool to improve productivity of PVC processing further at high shear rates.
Study of the Effect of Velocity-to-Pressure Transfer Method on Process Robustness in the Injection Molding Process
This study will compare the use of several different transfer modes during the filling phase of the injection molding process. These modes include screw position, hydraulic pressure, and melt pressures within the cavity and nozzle. The modes will be investigated by using cavity pressure consistency when regrind and check ring wear are introduced. There are 4 transducers located in different areas within the cavity that will measure the peak pressures.
Styrene Block Copolymer Modified Food Wrap Film
Stretch wrapping film has been used for over 30 years to protect and preserve food from moisture, dirt and abrasion. These films allow increased food shelf lives and give the package an appealing smooth and shiny appearance.Styrenic block copolymers can be blended with polypropylene and co-extruded with ethylene vinyl acetate to form multi-layer structures suitable for food wrap applications. These films offer an excellent balance of properties combined with a low density.
Synthesis and Characterization of Liquid Crystalline Polyamides
By creating a dynamic interaction between aromatic and aliphatic compounds, a novel liquid crystalline polyamide was produced. By mixing various ratios of the aromatic 4,4-dimethyl bibenzoate and the flexible aliphatic 18-carbon diacid, with a stoichiometric equivalent of a single diamine, a variety of properties were developed. The homopolymer for the m-xylylene diamine produced a liquid crystalline regime of nematic and thermotropic behavior, which was the goal. Each species of diamine used; hexamethylene diamine, m-xylylene diamine, and p-xylylene diamine produced unique and distinct novel polymers.
Taguchi Based Design of Experiments of HDPE and Granite Fines
Granite-filled HDPE had lower tensile strength, modulus and elongation than unfilled HDPE. The reduction in properties is attributed to large particles that serves as stress concentrators. The mechanical properties of HDPE are improved with the use of adhesion promoters and use of metallic granite. A Taguchi design of experiment determined that the metallic component of the granite fines had higher tensile strength, modulus, hardness, and elongation at yield than the bulk granite fines.
Temperature Sensitivity of the Linear Viscoelastic Properties of Long Chain Branched Metallocene Polyethylene
The effects of long and short chain branching on the thermorheological behaviour of polyethylene are described. Long chain branched homo -polyethylene is thermorheologically complex and is most sensitive to temperature at low frequency. A technique for determining the activation energy spectra of thermorheologically complex materials is proposed. Short and long branches in the same system synergistically increase the zero-shear rate activation energy.
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