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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Applicability of Advanced Constitutive Equations for Coextrusion Flows of Polyolefin Melts
The fitting/predictive capabilities of three models (eXtended Pom-Pom, PTT-XPP and modified Leonov model) are tested for both, steady as well as transient shear and uniaxial extensional flows of mLLDPE and HDPE. The applicability of these constitutive equations has been investigated from the coextrusion flow modeling point of view. Finally, the FEM and modified Leonov model has been employed for the stress analysis in the coextrusion flow domain and predicted stress fields have been compared with the stress measurements from the flow coextrusion visualization cell.
Effect of Die Geometry on Foaming Behaviors of High Melt Strength Polypropylene with CO2
A systematic study is conducted to investigate the effect of die geometry (i.e., pressure and pressure-drop rate) on the cell-nucleation and growth behaviors of noncrosslinked high melt strength (HMS) polypropylene (PP) foams blown with supercritical CO2. The experimental results show that the cellular morphologies of PP foams are sensitive to the die geometry. The initial expansion behavior of the foam extrudate at the die exit is recorded using a high-speed CCD camera, which allows the study of die geometry effect on both initial expansion behavior and final cellular morphology. The effect of die temperature on the cell morphology is also studied.
Shape Memory Elastomers Prepared from Ionomer/ Fatty Acid Salt Compounds
Shape memory elastomers were prepared from mixtures of a sulfonated EPDM ionomer and fatty acid salts, FAS, (ZnOleate),. Physical crosslinks in the ionomer that arise from inter-chain ionic interactions provide a permanent shape, while the crystalline low molecular weight FAS provides the means for a temporary shape. The material can be deformed above the melting point (Tm) of the FAS and the new shape can be fixed by cooling the material under stress to below Tm of the FAS. Polar interactions between the ionomer and the FAS stabilize the dispersion of the FAS in the polymer and provide the continuity between the phases that allows the crystals of the FAS to provide a second network of physical crosslinks.
Patterning of Conducting Polymers on Flexible and Insulating Polymeric Substrates
In this work, we report the electric field assisted patterning of a conductive polymer, polyaniline (PANi), on an insulated and prepatterned template, followed by transfer of the pattern to a secondary substrate. Conducting PANi was selectively assembled on the negative electrodes of the template. After deposition, it was demonstrated that by compression molding, patterned PANi can be transferred to a polyurethane film. Unlike transfer by solution casting, however, the transfer of patterned PANi by compression molding was not complete. This may be the result of poor mobility of the polymer molecules. This work provides a promising nanomanufacturing approach for cost effective and high performance flexible nanoelectronics and biosensors.
The Effect of the Injection Point Location on the Fiber Glass Length
The objective of this study was the development of a methodology to evaluate the influence of the fiber glass length contained in injection molded, flat PP specimens. The initial fiber length used was 12 mm. Flat specimens with 1mm of thickness were injected varying the injection conditions (injection velocity, melt temperature and cycle time). The mechanical properties were evaluated in longitudinal and cross-sectional sense respect to the flow direction in a universal testing machine, varying the position with respect to the injection point. When the cycle time and melt temperature were increased, variations in the size and fiber length distribution were not observed.
Polyvinylidene Fluoride Containing Long Chain Branching for Blown Film Applications
In this work the effect of long chain branching in polyvinylidene fluoride on its rheology and blown film processing is investigated. Branched samples prepared by a conventional polymerization process were compared to commercial resins in terms of their rheological properties in shear and extensional flows. The branched samples showed an enhanced elasticity allowing a higher melt strength as well as strain hardening when subjected to extensional deformation. The enhanced rheological properties in the branched samples resulted in better processing performance in a blown film application where higher blow-up ratios and thinner films were achieved.
High Melt Strength Polyvinylidene Fluoride for Thermoforming Applications
This paper discusses the properties of high melt strength polyvinylidene fluoride (HMSPVDF) and their correlation with the thermoforming process. Resins having different molecular weights and extents of chain branching (CB) were prepared and compared to commercial resins considered linear polymers. The presence of chain branching enhances in the melt strength of the branched samples while the melt viscosity remains identical to the reference samples. HMSPVDF also shows a significant improvement in sag resistance over the reference samples and suggests better performance in thermoforming.
Interfacial Interpretation of Autohesion of Ethylene/1- Octene Copolymers by Atomic Force Microscopy
The T-peel fractured surfaces of bonded ethylene/1- octene copolymer films were characterized using atomic force microscopy (AFM) and analyzed by fractal analysis. A stitch-welding" autohesion mechanism was proposed on the basis of that fractal analysis results suggesting that amorphous chains interdiffused while unmelted interfacial crystal structures remain essentially unaltered during the autohesion process. The fractal dimensions and the characteristic sizes determined from the fractal analyses are strongly dependent upon 1-octene content bonding temperature and peel rate."
Numerical Simulation and Moldability Investigation of Micro-Features
In micro-injection molding, the preservation of precise micro-feature is one of the most important indications to ensure proper functionality and quality. A new technique, Induction Heating" which is advanced in heating up the mold quickly and accurately is adopted to control mold temperature during filling phase. This paper aims to analyze the technique specifically for a part with micro-feature of a high aspect ratio. Meanwhile it probes into the result of numerical simulation and actual experimental investigation. The result shows that some critical factors have a dominant effect on the molding mechanism and this result will be beneficial to the development of micro-injection molding technology."
Numerical Simulation and Experimetal Investigation of Fiber in Injection Molding
A lot of plastic parts are made of fiber-reinforced engineering materials for its superior mechanical properties. Since the flow induced fiber orientation is complex 3D behavior, the final properties of the injected parts become very complicated. In this research, a ribbed flat plate geometrical model is conducted to examine the effect of fibers with various design consideration on injected parts both numerically and experimentally. Results show that the flow induced fiber orientation both numerically and experimentally in a good agreement. Also, it shows the fiber orientation will affect the final injected parts significantly.
CO2 and Water Vapor Permeability in Polymer Nanocomposites and Foams
Permeation properties are important for the design and implementation of polymer nanocomposites and polymer nanocomposite foam products. The literature is quite limited regarding permeation studies on these materials. In this paper, we focus on permeation properties of polystyrene nanocomposites (two types of nanoclay and carbon nanofiber) and their respective foams. Commercial instruments (PERMATRAN-C Model 4/41 and PERMATRAN-W Model 3/33 from Mocon) were used to measure steady state permeability coefficients of CO2 and water vapor at three temperatures: 10°C, 25°C, and 40°C. From these data permeation rates and permeation activation energy are compared based on nanocomposite morphology.
Collaborative Navigation System for Concurrent Mold Design
As products become ever more diversified, their life cycles are growing shorter. To reduce production costs, increased process automation and concurrent design are priorities. Therefore, a collaborative integrated design system is crucial in the mold design and manufacturing process.This research develops a collaborative navigation system for concurrent mold design within the CAD browser, using Pro/Web.Link as the core tool. Providing both concurrent engineering and collaborative design functions, the navigation system is capable of assisting designers in accomplishing 3D mold development efficiently and accurately. Results show significant time savings over other mold design process methodologies.
A 3-D Thermal Model of Laser Transmission Contour Welding for a Lap Joint
The paper presents a three-dimensional (3-D), transient, thermal finite element model of a scanning laser transmission welding (LTW) process for a lap-joint geometry. The model incorporates an accurate representation of a laser beam which accounts for its spatial intensity distribution as well as scattering by the semi-crystalline polymer. The laser heating is treated as a time- and space-varying internal heat generation source. Laser energy absorption is considered in both the laser-transparent and laser-absorbing parts being joined. The absorption coefficient for the transparent part is derived from data in open literature. Absorption by the soot in the absorbing part is based on theoretical predictions of soot particle absorption using Rayleigh theory. Available experimental evidence (weld line width observations) supports the validity of the temperature distributions predicted by the model.
Microfabrication of Polymer Substrates for Lab-On-A-CD Applications
It has been demonstrated and studied by several investigators that embossing with localized heating of conventional polymer substrates can generate relatively high quality features, but in all cases, flash is generated. In this work, foamed substrates were studied using localized heating and the resulting features were free of flash. In this study, ultrasonic heating was selected and features embossed on several different microcellular foamed polymer substrates. Samples were fabricated to mimic standard compact discs (CD) that could be used for bio-sensing. Patterns of micro features were designed and developed to function as devices such as valves, mixing chambers for sample/reagent loading.
A Knowledge-Based Navigation System for an Integrated Mold-Design Process
Efficiency and quality are essential demands in mold and molding manufacturing. Most related enterprises have already expanded from 3C (Computer, Communication, Consumer Electronics) to 4C (3C, Car) products, characterized by small quantities and variety. For many firms, the shortened life cycle of products presents an unprecedented challenge.This research aims at developing a knowledge-based navigation system for an integrated mold-design process. Based on both customizable and standardized procedures, the system not only prevents probable engineering mistakes and accumulates valuable knowledge, but also shortens mold-design processes from 7~10 days to 2~3 days. It includes conceptual mold-design, core and cavity design, mold-base design, and 2D drawing.
Use and Design Considerations for Using an Industrial CO2 Laser for Trimming Thermoformed Parts
This Paper explores the use of a CO2 laser to trim thermoformed parts. Traditionally thermoformers trim their parts with saws, router, or die cutting. These methods can be costly and hazardous, particularly for small volume parts. Many accidents occur in factories and other workplaces using saws and other cutting machines. Because of the high accident rates associated with these activities, factories are looking for safer alternatives.Results from experiments using an industrial laser to trim two different parts are reported and conclusions are drawn about the types of parts best suited to this technology.
Molecular Dynamics Simulation of Deformation Behavior of Carbon Nanotubes under Generic Modes of Loading
Molecular dynamics (MD) simulation of single walled carbon nanotube (SWCNT) was carried out under generic modes of loading. All calculations have been performed on an (7, 7) armchair SWCNT. The diameter of SWCNT was ~1 nm while its length was ~6 nm. In modelling the SWCNT, the Tersoff-Brenner potential was used for bonded interactions and L-J potential was used to account for non-bonded interactions. The displacement boundary conditions were applied at top four rings of the nanotube while other end was kept fixed during simulation. A good agreement was observed in the results obtained through MD simulation with the analyses done using continuum shell theory for compression and bending. The Young’s modulus under these modes is ~ 5±0.6 TPa.
Effects of Processing Conditions on the Foaming Performances in the Polyolefin Insulated Coaxial Cable Extrusion
Coaxial cable is the cable that transmits electrical energy and singal from the receiver evices to the antenna in the base station. Nowadays, as the telecommunication technology develops, demand of high signal quality is required in coaxial cable. To meet this market requirment, it is necessary to develop a new cable which has a reduced signal power loss. The attenuation is attributed mainly to the copper in low frequency, and as the freqeuncy increases, occurs from the insulation. Therefore, the most effective method to reduce the attenuation in cable at high frequency is to improve the dielectric properties of insulation. In this study, a new lowloss cable was developed by improving the foaming degree of PE insulation. An optimization of resin compositions and foaming processing conditions was performed. The newly developed coaxial cable has 6~8% lower attenaution values compared to the conventional cable.
Influence of Screw Elements on the Processing of Preparing LDPE-g-MAH by Reactive Extrusion
The effects of screw configurations upon grafting of low density polyethylene with maleic anhydride initiated by dicymyl peroxide in a co-rotating twin screw extruder have been investigated. Grafting degree of the samples collected from three different positions on the screw and the exit of the die was evaluated by titration. The results showed that the screw configuration has a significant impact on the grafting process. The effects of the screw element structure upon reaction could be interpreted in two terms: conveying ability and mixing capability. Small conveying ability (i.e. large conveying resistance, uch as in reversed kneading blocks) would lead to a high degree of fill in the screw channel, resulting in a long residence time and a high degree of reaction. Intensive mixing, especially elongational mixing (such as in the long lead elements), tends to enhance the ingredient uniformity in the reactive system, and facilitate the grafting process.
Effect of Polarity on Electrospinning Polycaprolactone Tissue Engineering Scaffolds
Electrospun polycaprolactone (PCL) fabric was affected by the electrospinning voltage polarity. The tensile test breaking strain and breaking stress of negative polarity spun samples was half that of positive polarity samples. The differences were investigated using XRD, DSC, scanning electron microscopy (SEM), and mercury porosimetry. XRD found a peak of a different magnitude, but DSC found no significant differences in crystallinity. The SEM show few differences, but the porosimetry shows a different distribution.Recent articles by P. Supaphol (2), (3) challenged the assumption that there is no effect of high voltage polarity on the electrospinning (Espin) process and product. This study examined the effect of polarity on the mechanical and physical properties and processing of Espun polycaprolactone (PCL) in acetone. The ultimate tensile test results were startling: the negative polarity samples broke at one half the elongation, 28% vs. 60%, and only achieved a UTS of 0.23 MPa, one half the positive polarity’s 0.51 MPa. While the total porosity of the samples was insignificantly different (74.5%+/-1.3% positive and 77.4% +/-1.8% negative), the distribution of pore sizes determined by mercury porosimetry was less uniform for Positive samples ,with a strong peak at 5 ?m. The Espin process differed also: more (39%) of the PCL was attracted to the target and its edges when the polarity was positive vs. only 31% when the polarity was negative. However, the negative polarity put more PCL onto the front of the target, 45% vs. 39% for positive, leaving the front samples of similar thicknesses and average porosities. These properties of the fabric were significantly different in ways that may affect its use as a tissue engineering scaffold.
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