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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Extrusion of Polystyrene Microcellular Foam with Supercritical CO2
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
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.
Developing Animations and Simulators for Plastics Education
Instructional technology, computer-based training, and multimedia are a few of the modern words associated with the wave of technological advancement in educational methods. The plastics industry is not only riding this wave, but has been a contributor in leading these advancements. This paper describes the development of several projects that expand the body of technology-based plastics education. These projects include animations used to describe machinery or present difficult polymeric concepts and simulators used to teach operational techniques. Hardware, software, and methods used in these projects are discussed.
Cover Part as an Application Example for Gas-Assisted Injection Molded Parts
The gas-assisted injection molding process is in use now for several years offering new technical and creative possibilities for injection molding. After a brief survey of the principle sequence of the process and basic process physics this paper comments on an application example for a cover part and provides solutions for the problem s found during the process of fixing existing issues on this tool.
Magnetic Resonance Imaging of Polymer Melt Flows
A tubular rheometry that is based on obtaining velocity profiles by nuclear magnetic resonance imaging (NMRI) and measuring pressure drop of the flow is used for the polymer melts. This technique allows one to get viscosity data potentially over many decades of shear rate region in a single measurement. In this study, we examined polyethylene melt as the flow medium. Despite the low shear rates attained, our results reveal that this non-invasive and non-destructive method is promising for constructing an on-line polymer melt rheometer.
Relaxation Model for FE Analysis of Plastic Product Behavior
The non-linear creep-based models cause numerical instabilities during FEA calculations because of the necessary inversion of stress-strain relations. From this point of view, the relaxation-based models are preferable for use within FEA. On the other hand, engineers avoid such models, due to complicated tests. Therefore, the goal was to develop the non-linear relaxation model, which uses the data of creep-recovery tests. In this way the model would be comparatively inexpensive and unconditionally stable in FE calculations.
Vibration Assisted Resin Transfer Moulding (VIARTM): A New Alternative Technique to Improve RTM Performance and Part Quality
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.
A Novel Ionomer for Nylon Modification
A new family of Surlyn® ionomers containing reactive functional groups is being developed for polymer modification, e.g., modifying nylon for blow-molding applications. Compared to existing ionomers, the new ionomers exhibit a higher degree of compatibility with nylon. One of the unique features of the new modifier is that the new ionomers can be dispersed in nylon in an extremely fine particle size and narrow size distribution. This has a profound effect on both the melt rheology and the mechanical properties of the modified nylon. Most significantly, the new ionomer imparts a truly shear thinning melt viscosity of the modified nylon 6. The paper discusses the dispersion of the new ionomer in nylon 6 as analyzed by SAXS and TEM and the melt rheology behavior of the modified nylon 6 and briefly highlights the effectiveness of the new ionomer to modify nylon 6 for the demanding blow-molding applications.
The Creep Behavior of Poly(ethylene terephthalate) Bottles
Room temperature viscoelastic behavior of PET beverage containers was studied. Internal pressures result in an increase of the container volume. By assuming a cylindrical geometry, stresses can be computed and linear strains can be estimated from the volumetric changes. A time-dependent creep compliance was determined for 2-L freestanding containers under various internal pressure loads. These values match favorably with uniaxial creep measurements. From isochronous plots, the viscoelastic behavior is shown to be linear over a limited range of pressures. The creep curves show all the characteristics of simple linear viscoelastic models such as instantaneous elastic response, retarded elastic response and permanent deformation.
Measurement of Layer Deformation in Coextrusion Using Unique Feedblock Technology
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. These layers should be uniform in thickness across the structure for best performance. However, layer thickness non-uniformities have been observed in many coextruded products. Previous work has shown these layer thickness variations can occur due to viscosity differences between the polymers in the layers and/or elastic effects that introduce secondary flows. The objective of this work was to experimentally measure the secondary flow velocities in a square channel using a unique coextrusion feedblock that produces annular rings instead of planar layers.
Enhanced Performance via Ester Lubrication of Rigid PVC Formulations Modified with Chlorinated Polyethylene
In traditional calcium stearate/paraffin wax systems, higher levels of wax leads to lower melt temperatures, higher gloss, and higher impact properties of the extruded sheet or profile. Unfortunately, higher levels of wax also leads to longer PVC fusion times, and an increased tendency to develop die plate out. However, recent work with ester lubricant systems, in PVC formulations using chlorinated polyethylene, have shown that lower extrusion temperatures, pressures and torque can be achieved without sacrificing fusion time or increasing the risk of die plate out. All while maintaining or enhancing gloss and impact properties.
A Study on the Poly(ethylene naphthalate)/Poly(ethylene terephthalate)-Poly(ethylene naphthalate) Copolymer Blends
Poly (ethylene naphthalate)/Poly (ethylene naphthalate)-poly (ethylene terephthalate) copolymer [PEN/(PEN-PET)] blends were investigated. It was found that introducing PEN-PET copolymer to PEN/PET blending system instead of using PET caused the lowering of transesterification reaction in melt mixing as compared to PEN/PET blends. As the duration of mixing gets longer, the transesterification difference between PEN/PET blends and PEN/(PEN-PET) blends becomes more evident. The increase of transesterification in PEN/(PEN-PET) blends with increasing mixing time resulted in the decrease of melting temperature, while glass transition temperature increased. In addition, our time resolved light scattering data shows that slower crystallization could be obtained in PEN/(PEN-PET) blends as compared to PEN/PET blends.
Warpage Analysis of Solid Geometry
The requirement to create a shell model on the midplane of the part for warpage analysis is at odds with the trend toward solid modeling. A method is introduced that enables warpage analysis without the midplane model. This ensures that the user interacts only with the solid geometry. In this paper we present results obtained with the new technique and compare them to those obtained on a midplane model.
Assessment of Opportunities to Produce Distributed Multilayer Film Microstructures in Thermoplastic Blends by Chaotic Mixing
Chaotic mixing of binary components has been recently used to produce and distribute fibers, multi-layer films, and fragmented sheets in melts. Formation mechanisms and means to promote one type over the other remain uncertain. In this study, in situ film formation and breakup in PS/LDPE blends was examined for differing extents of mixing. Results demonstrate new opportunities to develop distributed multi-layer films during blending processes.
A Novel Additive for PP Fiber
The purpose of this paper is to present the data on UV stabilization of flame retarded polypropylene fiber. The evaluation was conducted by exposure in the xenon arc weatherometer @ 63°C under dry conditions. Proprietary additives provided unique physical property retention for flame retarded polypropylene fiber.
Thermal Analysis during Epoxy Casting Process for Joint Units of High Voltage Cable
The temperature distribution and the degree of cure in an epoxy system during the casting process, which is used in the connecting unit of high voltage cable, have been simulated using the FE solver of MARC including the programmed routines. The curing kinetics of the epoxy system used in the casting process was determined by DSC test, which was used as material input data of the developed program. To verify the developed simulation program, we have compared the simulated results for the simple model problem with those simulated by C-MOLD. The simulation results of real epoxy system for the connecting unit of the 400 kV cable, which is currently under development, are also presented for various processing conditions.
Development of 0.5 mm Super SO DIMM Connector with Computer Simulation Tools
Super Small Outline Dual Inline Memory Module (SO-DIMM) is widely employed in the design of next generation notebook PC and portable electronic devices. The maximum warpage of the injection-molded connectors are required to be a low as 0.1mm in order to be compatible with the SMT (Surface Mount Technology) process. Design of Experiment method and computer simulation were utilized to investigate the complex interaction among final dimensions, mold design, grade of liquid crystalling polymer and injection molding conditions. By using the L9 orthogonal table, the most critical factor affecting the warpage was identified. The effects of other factors were also discussed.
A Novel Computer Simulation Technology for the Cooling Analysis of Complex Injection Molded Parts
Cooling analysis has been the biggest obstacle in the simulation of the injection molding process, mostly due to the loss of convergence and enormous computation efforts encountered in the conventional boundary element method (BEM) approach. However, cooling analysis is not only essential in designing cooling channel layout, but also in optimizing the overall accuracy of filling, packing and warpage analyses. Fast Finite Element Method (FFEM) has been proved to provide excellent computation efficiency over the conventional BEM. A case study of complex car panel with FFEM is discussed in this paper.
Cooling of Extruded Plastic Profiles
For the proper design of cooling equipment and its dimensions in profile extrusion, it can be very useful to know the temperature fields inside the profile. To be able to understand the cooling process, a physical - mathematical model of heat transfer in the extruded profile must be used and the temperature field solved by an analytical or numerical method. There are only very few problems that can be solve analytically. We can say that some one-dimensional problems (not all) and very few two-dimensional problems can be solved analytically. For example, it is possible to solve a problem of cooling an extruded film or a thin plate. If the profile shape is more complicated, it is necessary to use a numerical method. One peculiar variable in all heat transfer simulations is the heat transfer coefficient. Its setting is important for the absolute results of the simulations. On the other hand, an approximate, but close, value of such a coefficient can cause some errors in the absolute temperatures but will still show the relative temperature distribution across the profile. In the majority of problems, the overall picture of the process is more important than knowing the exact temperature in a certain position. If a designer has a good picture about the cooling process, he/she can easily design the lengths of calibrators, their appropriate placing, the length of the cooling bath and so on. It is also possible to judge where the walls of the profile will probably bend. The designer can also decide what should be the cooling conditions, about the possible placement of infrared heaters, the length of the water bath and so on. In the case of a complicated profile it is almost impossible to imagine the temperature distribution inside the profile. In profile extrusion, any uneven cooling can cause bending, if not collapsing, of the profile. Therefore, knowing the relative temperature distribution may be more important than knowing exactly the temperature values. This presentat
Thermoplastic Paint (a.k.a. Film Finish, Paint Film, Dry Paint): A Complementary Technology for Exterior Automotive Plastic
Thermoplastic film technology and a new plastic molding process, under development in a joint effort by ValTek and U Mass Lowell, combine to offer reductions in system cost, total emissions and weight for automotive Class A" exterior panels in the new millennium. The recyclable structural panels are fabricated using Class "A" film finishes in one step and targeted for vertical and horizontal automotive panels."
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