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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Solids Compaction and Conveying in a Single-Screw Extruder by Discrete Particle Modeling
To improve our understanding of granular flow in the solids-conveying zone of a single-screw extruder, a discrete particle model has been developed. The discrete particle approach allowed us to simulate polymer compaction without using the isotropic stress assumption used by continuum models. An elastic-fully plastic contact force displacement model was validated by simulating HDPE and PS under compaction in a batch cell and comparing against reported data in the literature. The particle model and experimental results showed good agreement for PS which exhibited elastic behavior up to the tested limit of 12 MPa. The simulation for HDPE showed marked deviation above 4 MPa, over predicting the plastic dissipative losses. The extruder simulations showed exponential pressure development along the axial length of the screw, similar to continuum models, but indicated that bulk density in the screw was affected by attributes of the flow field besides just pressure. The nonisotropic stress distribution of the solids in the screw was examined, with the stresses found to be concentrated at different boundaries depending on pressure development.
Scale up Rules for Profile Geometries in Extrusion Dies and Options to Adjust Surrounding Flow Channels to Avoid Transverse Flow
The design of extrusion dies is frequently based on knowledge and experience of the designers. One very simple, rapid and low-cost means of designing a profile die is the use of scale-up rules. This paper deals with an approach to develop scale-up rules which make it possible to scale-up or scale-down existing profile geometries by means of simple equations. The following profiles are observed: rectangular channel, annular gap and pipe channel. Allowance is also made for a change in material properties in order to achieve the greatest possible variability in the die design. Neighboring areas are examined and revised by iterative procedures to avoid transverse flow between the flow channels.
Effects of Structural Constraint and Impact Energy on Fracture Behavior of a Flexible Composite Tubing
By using scanning electron microscopic analysis, we fractographically examine failure modes of flexible, braiding-reinforced composite tubes under impact energy pulses. The tubes are subjected to different extents of structural constraint imposed by other catheter components. The effects of impact energy pulses and structural constraints on failure modes are qualitatively evaluated. It is practically shown that under certain extents of structural constraint, minimal impact energy input can introduce catastrophic, brittle fracture mode dominant over either fatigue fracture mode or ductile failure behavior. In an attempt to identify the root causes for the formation of observed brittle fracture phenomena, various material characterizations, including differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) are conducted on the thermoplastic elastomer material of the tubes to attest material integrity after fabrication.
Melting Behavior of a Poly(Ether-Block-Amide) Copolymer Melt-Crystallized under Isothermal, Quiescent Condition
The melting behavior of a poly(ether-block-amide) copolymer melt-crystallized under various quiescent, isothermal conditions was studied using differential scanning calorimetry (DSC). The structure of the crystallized copolymer was characterized at ambient temperature using wide-angle X-ray diffraction (WAXD). It was found that the hard, crystalline microdomain of the melt-crystallized copolymer only exhibited ?- or (???) crystal form associated with hexagonal habits. It was determined based on the DSC and WAXD results that the multiple melting endotherms were attributive to different origins, including the short-range ordering effect at the late stage of crystallization and the melting-crystallization event that occurred during the DSC heating scan.
Generic Circuits by Conductive Epoxy/Ni Adhesives: Geometric Effects
Epoxy/Ni adhesives can be used as integrated circuit (IC) packaging materials due to their lower cost than epoxy/Ag adhesives with acceptable electrical conductivity. In this work, conductive epoxy/Ni adhesives were prepared by solution method and filled into holes connecting the multilayers of a novel prototype designed to be used in electronic components in circuit boards, in order to study the geometrical effects on the prototype's electrical resistance. An empirical equation was obtained for the contact resistance (Rc) measured after cure. We also show that Ohm's law adequately describes the effects of the bulk adhesive resistance (Rb) on prototype's electrical resistance.
Comparison of Crystallization between Water-Assisted and Gas-Assisted Injection Molding Part of Semicrystalline Polymer Based on Numerical Simulation
Water-assisted injection molding (WAIM) and gas-assisted injection molding (GAIM) are two innovative process based on the conventional injection molding. Because of the difference between water and gas, the crystallization of part manufactured by WAIM and GAIM has a discrepancy. In order to compare the difference, a simplified mathematics model was created. Moreover, the simulation code was completed and numerical simulation was carried out. The simulation result shows the WAIM parts of the semi-crystallizing polymer will scarcely crystallize and have a short cooling time because of the fast cooling effects of water.
The Effect of Temperature on the Modulus of Elasticity of Non-Linear Viscoelastic Materials
Understanding the effect of temperature is decisive to describe the deformation behaviour of viscoelastic materials. There is still no unambiguous evidence whether the elastic part of the deformation is influenced by temperature. Within the scope of this paper both viscoelastic properties and elastic deformation are investigated separately. Therefore, thermoreversible rearrangements (time-, temperature-, strain- and stress-dependent) based on dynamic, creep and relaxation experiments up to the nonlinear viscoelastic range are measured and modeled. A significant difference in the limit of linear viscoelasticity below and above the glass transition temperature is shown. These investigations can be the basis for a more effective use of thermoplastics in the future.
Recycled Vinyl Wallpaper- A New Composite
Mechanical recycling of waste polymeric based composites allows production of same or similar products, but in the case of vinyl wallpaper the quality of recovered material combines the cellulose component with the vinyl PVC resulting in a new composite which can have completely different applications compared with the original vinyl wallpaper.Vinyl wallpaper is generally composed of Polyvinyl chloride combined with cellulose fibre and with certain formulations a small percentage of different polymer based additives.It has been demonstrated and described in a previous presentation that this post industrial waste material can be recycled, the present paper will demonstrate that this recyclate can be claimed to be a new vinyl based composite. The present paper will also demonstrate advantages of using modified extrusion technology to recycle wallpaper continuously without degradation of base components. With properties characterisation and evaluation it will be demonstrated that this material can have different applications compared with vinyl wallpaper.
Highly Conductive Epoxy Composites for Application as Bipolar Plates in Proton Exchange Membrane Fuel Cells (PEMFCS)
Electrically conductive graphite-filled epoxy composites were developed by solution intercalation mixing of epoxy resins with expanded graphite (EG) and carbon black (CB), followed by compression molding and curing for application as bipolar plates in proton exchange membrane fuel cells (PEMFCs). High in-plane conductivity of 200-500 S/cm compared to DOE target value of 100 S/cm was achieved with good mechanical properties. The flexural modulus, flexural strength and impact strength were 2.08×104 MPa, 72 MPa, and 173 J/m respectively. The composites also showed high glass transition temperatures (Tg ~ 141°C) and high thermal degradation temperatures (T2 ~ 415°C). Hygrothermal effects on electrical, thermal, mechanical, and chemical properties were evaluated especially under acidic conditions. The maximum water absorption was found to be 1-2 % by weight for these composites, compared to 4-5% for cured EP resins without fillers. SEM micrographs suggested no change in morphology due to reflux in water and acid.
Production of a Tractor Cab Roof Module Using Direct In-Line Compounding of Long Glass Fiber Thermoplastics
Composite Products, Inc. continually adapts their Advantage In-Line Compounding Process to produce products that use novel composite molding tools and methods. In a recent agricultural application, a tractor cab roof combined long glass fiber thermoplastics with innovative tooling and molding methods to simultaneously maximize structure and aesthetic appearance. Additionally, significant cost and performance advantages were realized through part consolidation, material waste reduction, reduction in manufacturing steps at the OEM, and corrosion resistance. The launch of this product was achieved through the successful combination of materials, tooling and process.
Influence of Injection Molding Parameters on One-Stage Injection Stretch Blow Molding
The advantages of one-stage injection stretch blow molding (ISBM) are energy efficiency and high productivity as reheating is not necessary. However, due to the complexity of operation parameters from raw material through injection molding to the end products, a conventional trial-and-error method is ineffective to predict and control this process. Hence, how to correctly integrate injection and blow molding sequentially is in a great demand. In this study, a comparative investigation between one-stage and two-stage processes is performed firstly. Then in one-stage system, the influence of various operation parameters during the injection stage on product forming is conducted numerically.
Development of New Ionomers with Novel Gas Permeation Properties
Ethylene ionomers, such as Surlyn® from DuPont™, have been the premium sealant materials for packaging applications due to their excellent seal strength and process robustness. The ethylene ionomers achieve the unique property characteristics through the development of a network morphology. In this paper the development of new ethylene ionomers will be discussed. The versatile compositions and the unique morphology of the new ionomers will be presented together with the novel gas permeability properties. Their enhanced breathability to oxygen, carbon dioxide, moisture, etc., selective permeability, and smart barrier properties will be presented.
Improved Properties and Cost Efficiencies of Cyclic Olefin Copolymer Enhanced Forming Films
Cyclic olefin copolymers (COC) can provide film producers and packaging converters with an opportunity to create thermoforming films. COCs are amorphous thermoplastics with excellent moisture barrier, high temperature stability and stiffness. Mono- and multi-layer examples of LLDPE-based forming films, compared against commercially available products, clearly demonstrate how well the addition of COC improves physical properties, thermoforming and packaging performance. COC improves material distribution of LLDPE formed trays. These improvements enable the formed tray to withstand higher crushing force. Enhanced performance permits possibility of down gauging.
Determination of the Mechanical Properties of a PVC Coated Wire with a New Clamping Fixture for Rotational Rheometers
Car electronic components are potentially subjected to a very wide temperature range compared with electronic components in domestic appliances for example. In (very) cold regions temperatures can get as low a -60 °C and in the engine bay of a car temperatures of 100 °C and higher (near the engine) are easily reached. In cars these extreme temperatures not only put high demands on high tech components like printed circuit boards but also on the electrical wires in wire looms.We have studied the mechanical properties of PVC coated copper wire in a wide temperature range before and after subjecting the wire to an elevated temperature for a certain defined time.
Development of Polycarbonate Diffuser Films for Liquid Crystal Displays
In many current Liquid Crystal Display (LCD) systems, it is required to have light diffusing components. Light diffusing components are utilized to improve uniformity in illumination and increase viewing angle. They also serve to mask artifacts. For instance, the films are used to hide injection molded or printed patterns on the light guide pipe of the display or to reduce the appearance of moiré patterns generated by the interference of the LCD pixels with other regular structures within the system. In a typical LCD display, diffusion of light is introduced into the backlight assembly by adding separate films (i.e., a stack) that are comprised of a non-diffusing substrate to which a highly irregular, diffusing surface treatment is applied or attached. In this study, we present GE’s polycarbonate film systems to generate diffuse light in a monolithic film structure utilizing bulk diffusing additives. The relationship between the material properties of the bulk diffuser and the functional properties of the films is discussed.
Photoinitiated Grafting of N-Vinylpyrrolidone onto Poly (Lactic Acid) Film
Polylactic acid (PLA) film with good wettability and versatile reactivity was produced by photoinitiated grafting of N-vinylpyrrolidone (NVP) onto its surface using benzophenone (BP) as the initiator. The PLA film was melt extruded and a known amount of monomer solution containing the photoinitiator BP was deposited between two films, the assembled unit was irradiated under UV light at room temperature under nitrogen. The surface photografting parameters- grafting percent (Gp) and grafting efficiency (Ge) were obtained. The films resulting from this treatment were analyzed using differential UV spectroscopy, and water contact angle.
Bamboo Fiber Reinforced Eco-Composites by Wetlay Processing
Hammer-mill processed bamboo fibers were used as the reinforcement fiber for an eco-composite made from wetlaid non-woven mats using polyethylene terephthalate (PET) fibers as the binding fibers. These eco-composites, containing up to 70 wt.% bamboo fibers, were compression molded and tested using dynamic mechanical analysis (DMA) in three-point-bending mode. The thermal behavior of the consolidated PET matrix was analyzed using a DSC. While all composites exhibited very good mechanical properties, the one with 40 wt.% bamboo fibers displayed the highest modulus. The glass transition activation energy calculated from time-temperature superposition suggests that some components from bamboo or moisture lowered the activation energy as the bamboo content increased.
Polyphenylene Ether Macromonomers. I. Property Enhancements in Thermoset Resins via Novel Telechelic Oligomers
Unique low molecular weight polyphenylene ether telechelic copolymers were designed specifically for use in a variety of thermosetting resins. These macromonomers have high solubility in common solvents and monomers and tailored functionality to co-polymerize via step-growth or chain-growth polymerization. The incorporation of these copolymers in epoxy and styrene based thermoset resins results in single-phase thermoset materials with enhanced performance. Noticeably, the glass transition temperature and toughness increase, the dielectric constant and loss factor decrease with increasing PPE content. These new materials thus show a property set very well suited for next generation electronic materials.
Preparation and UV Weathering of Polyethylene Nanocomposites.
Polyethylene / montmorillonite (PE/MMT) nanocomposites films were prepared by blending in the molten state: Low-density polyethylene (LDPE), montmorillonite clay, and polyethylene grafted maleic anhydride (LDPE-g-MA) or zinc neutralized carboxylate ionomer (Surlyn B) as compatibilizers. A chemically modified clay Closite 20A has been used. Nanocomposites were prepared by melt blending in a twin-screw extruder by using two-step mixing. Characterization of the nanocomposites was performed by X-ray diffraction, infrared spectroscopy (FTIR) and transmission electronic microscope (TEM) techniques. Changes in UV irradiated nanocomposites film samples were characterized by FTIR. The results were analyzed in terms of the effect of the compatibilizing agent in the clay dispersion, and UV degradation of the nanocomposite.
Effects of Melt Rotation on Warpage Phenomena in Injection Molding
Shear induced imbalanced filling in a geometrically balanced runner system is always a difficult problem to handle in injection molding. Moreover, the shear-induced temperature variation across the cross section also affects the warpage result. Previous research proposed that the melt rotation apparatus could control the warpage phenomena of parts. In this paper, we have proposed a new methodology to analyze this injection process. The comparison between the simulation and experiments can demonstrate and verify the warpage phenomena. The results show that the proposed methodology is a highly valuable tool to understand the melt rotation effects.
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