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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Flow-Induced Migration Phenomena in Polyethylene/Polyethylene-co-maleic Anhydride Blends
Flow-induced migration of polyethylene-co-maleic anhydride (PE-co-MA) additives in a polyethylene (PE) melt is investigated using long-chain branched polyethylene covering a range of melt index. Attenuated total reflection infrared (ATR FTIR) spectroscopy and interfacial tension measurements were used to characterize surface composition of copolymer additives processed by a melt extrusion. Experiments covering a range of shear rates, die length/diameter and extrusion temperatures are described. The surface concentration of copolymer additives were changed from the bulk to the surface of extrude depending on the shear rate and temperature due to the shear-induced diffusion of macromolecules. A mechanism based on stress-induced diffusion is proposed to explain the observed surface migration phenomena.
Blends of CO2 and 2-Ethyl Hexanol as Replacement Foaming Agents for Extruded Polystyrene
By the year 2010, HCFC 142b will be banned for use as a foaming agent for extruded polystyrene (PS) foam in North America. Many blends of foaming agents have been patented as replacements to expand PS. In this study the optimal concentration of a previously unexplored blend of CO2 and 2-ethyl hexanol (2-EH) is shown to allow the production of PS foam of 30 kg/m3 density. The glass transition temperature reduction of the PS, due to the incorporation of 2-EH, is believed to be an important contributor to the success of this foaming agent blend. In long-term use of the foams, the 2-EH does not measurably diffuse out of the PS whereas the half-life of CO2 diffusion out of the foam is measured in weeks.
PS Foam Moldings Expanded with HCFC 141b
Medium and high density polystyrene foam moldings were produced by compression and injection molding. Polystyrene (PS) was first impregnated with HCFC 141b and pelletized. These impregnated pellets became the feedstock in injection and compression molding, with cycles typically lasting between 1 and 30 minutes in duration. The compression molding cycles were studied to optimize the mold release method and the cycle times ascribed to heating, pressure release and sample cooling. The lowest foam density reached was 196 kg/m3. While residual foaming agent in the matrix negatively impacts on the mechanical properties of the foam, the results of this work demonstrate that a physical foaming agent is feasible for compression molding and short-shot injection molding of PS. It should however be pointed out that HCFC 141b will be banned for use in the U.S. by the year 2003 and in Canada by 2010.
Fracture Toughness Variations of Injection Molded Long Fiber Reinforced Thermoplastics
The fracture toughness, defined as Kc, of injection molded long fiber reinforced polypropylene with 50% E-glass and its variations is investigated. Rectangular plaques of different thicknesses at various sets of processing conditions have been fabricated. In order to assess the spatial variation of the fracture toughness, specimens aligned in the direction of the injection molding flow and perpendicular to it, have been obtained and tested at pre-selected locations. The morphology of the samples consisting of flow induced through-thickness layers was also evaluated experimentally and related to the fracture toughness, thus showing the effect of the part morphology on such mechanical property.
Method for Injection Molding a Crosslinkable Extrusion Grade of PEX
Crosslinkable Polyethylene (PEX) has been used in pipe extrusion for the unique properties obtained by crosslinking. The most important property being its elevated HDT (heat deflection test), which allows the material to be used in higher temperature applications. This paper is the development of a method for using PEX in an injection molding application. The factors of concern are property loss, cure time, temperatures, screw rpm, and residence time. This study will show that it is feasible to use PEX in injection molding. The cure time as well as processing conditions will be recommended.
New Routes to Market in the 21st Century
The plastics industry is hurtling toward the 21st century while undergoing remarkable changes that are completely reshaping the way business has been done previously. Restructuring, consolidations, portfolio swapping and joint ventures are taking place on an unprecedented scale and pace. E-commerce has added to globalized competition and new routes to market are emerging as old business models fade away. How will polymer manufacturers sell their goods in the future? Has the use of distributors peaked? Is the Internet the future? These changes will be analyzed and their impact on people and companies in the industry projected.
Color Effects of Modified Rubber on Black Colorant in Polypropylene
The primary use of modified rubber is to improve flexural modulus and impact strength. The disadvantage of using modified rubber is the distortion of color when used as an additive to a polymer. This study compared the color shifts of a black colorant with differing loadings of modified rubber.
New Fast Peroxides for PVC
Recent economic trends in the PVC market have pushed producers to reduce costs and improve productivity. Areas were sought where peroxide expertise can be utilized to develop new initiators that can help. Consequently a new developmental, fast peroxide for PVC, D-174, is being introduced which is reactive at lower polymerization temperatures, gives a more square heat profile and produces shorter polymerization cycle times for the PVC manufacturer.
Thin Wall Injection Molding of Thermoplastic Microstructures
Thin-wall injection molding is a key technology allowing the low-cost mass production of microstuctures, such as devices with surface-relief microcomponents widely applied in micro-optics, micro-fluidics, medical and biotechnology. Research was performed in order to gain better understanding of important parameters in injection molding of thin-wall microstructures. A series of injection molding experiments were conducted with PC and PMMA, which are common materials in bio-MEMS (Micro Electro Mechanical System) applications. The rheological properties were characterized through dynamic, and transient shear viscosity measurement using a Rheometrics Mechanical Spectrometer. Micro-channels of different lateral and depth dimensions were obtained on thin wall substrates. The Scanning Electronic Microscope (SEM) photos were used to measure the fidelity and roughness of the replicated plastics. Birefringence was used to qualitatively examine the amount of residual stresses in the molded parts.
Scratch Damage Mechanisms in Model Polymers
Fundamental scratch damage behavior in polymers was studied through investigation of a series of polycarbonate and polystyrene samples with different molecular weights. The constant load scratch test, based on a spherical indenter, was employed. Scanning electron microscopy and transmitted optical microscopy were performed to examine surface and subsurface damage during scratch. The plastic flow scratch pattern and the fracture scratch pattern are the two typical scratch patterns found in polymers. It is shown that shear yielding is the main mechanism for the plastic flow scratch pattern, while tensile-tear induced fracture on the surface and shear-induced fracture on the subsurface are the main damage mechanisms found in the fracture scratch pattern. The relationship between scratch resistance and material property relationship in polymers is discussed.
Digital Color Communication for Supply Chain Management: The Latest Technological Advancements to Impact the Plastics Industry
Everyone - color concentrate manufacturer, resin producer, compounder, molder, or extruder - understands delivering the right color the first time is crucial to customer satisfaction. Today, digital color communication technology ensures color specifications across approval points and within an increasingly complex cycle of tighter manufacturing tolerances and requirements, global competition, and just-in-time scheduling. By replacing physical sampling with digital, adjustments and approvals are made on screen, eliminating time, cost, and frustration among all points in the supply chain. This paper explores the profound implications this new technology has on the entire color cycle- from design to compounder to finished product.
Low Density Foaming of Poly(ethylene-co-octene) by Injection Molding
Low density poly(ethylene-co-octene) foams were produced by injection molding compounded formulations consisting of resin, chemical foaming agent, activators, cross-linking agent and nucleating agent. The effect of the formulation on the foam density and morphology was examined for one set of processing conditions. The concentration of cross-linking agent must be geared to the initial resin viscosity to allow proper bubble growth. The foam will otherwise collapse or show little expansion. The results show that an optimized formulation along with proper processing conditions yield fine-cell foam of low density.
Magnetic Materials Based on Polymers and Magnetical Fillers
In this paper the mechanical, magnetical and rheological properties are analyzed. The influence of different magnetic powders onto a plasticized polvinyl chloride) were studied. The magnetic characterization of isotropic plastic bonded magnets, based on strontium ferrite (SrFe12O19) and plasticized polyvinyl chloride, as a function of composition was analyzed in a magnetometer at room temperature. In order to explain the dependence of the volumetric density and the saturation magnetization with composition, an additive model for these properties is considered. The intrinsic coercivity shows a decrease with increasing strontium ferrite content, which is due to the increasing interaction between the magnetic particles. The maximum energy product is lower than 1 MGOe and increases with the second power of the strontium ferrite content. The rheological properties were studied in a capillary rheometer; it was found that viscosity increased as the magnetic powder concentration increased in the composite.
Assessment of Metallocene Propylene Polymers for Cast Film Applications
The entry of metallocene-based products into polypropylene cast film is at a stage where potential in various markets is only now being assessed. The current thrust is to bring forward a set of differential properties to complement effectively Ziegler-Natta based poly-propylene cast film products. This study reviews the structure features of metallocene polymers and reports some potential benefits in cast film applications.
Prediction of Temperature Profiles across Coating and Substrate in the Nip
An unsteady-state, one-dimensional heat conduction model is used to calculate the temperature profiles in the melt and the substrate(s) when they come into contact in the nip of the extrusion coating or lamination process. The model helps answer such questions as: • Is the melt totally quenched in the nip? • Will the substrate(s) be exposed to temperatures above which shrinkage occurs? Will the temperatures promote post-crystallization? The answers to these questions aid in the understanding of adhesion, curling and optical problems in extrusion coating.
High Molecular Weight Flexibilizers in Low Smoke Flame Retardant PVC Compounds
Ethylene copolymer resin (ECR) modifiers play an important role in low smoke PVC. As high molecular weight flexibilizers these resins reduce smoke and add strength and low temperature flexibility. This combination allows compounders to increase the flame-retardant additives without compromising strength or flexibility or by adding liquids which increase smoke. This paper is presented to demonstrate these attributes versus liquid plasticizers used in PVC compounds.
Microstructure and Electrical Conductivity of BR/EPDM/Carbon Black Blends
Important appliances have arised from the study of polymer composites containing conductive particles (e.g., EMI shielding, antistatics, wire coatings for overcurrent prevention). The present work is concerned with dynamic properties related to the microstructural arrangements, as observed by Transmission Electron Microscopy (TEM), in an elastomeric blend system consisting of Polybutadiene (BR), EPDM and Carbon Black (CB). Based on changes in the viscous component signals of BR and from micrographs of samples stained with osmium tetroxide it was found that the CB was located mainly in the BR phase. Final behavior of the conductivity was found to have great dependece on this fact.
Influence of Various Molding Conditions on the Uni-, Bi-, and Tri-Axial Impact Properties of Polyvinyl Chloride (PVC)
This study discusses the influence of molecular weight, melt temperature, mold temperature, and aging on the impact characteristics of molded PVC. Tensile impact (uni-axial), instrumented drop-dart impact (bi-axial), and Izod impact (tri-axial) methods were utilized to assess the impact properties of the material under investigation. It was found that the impact properties were affected by aging more than by the changes in the melt temperature or the mold temperature. Additionally, the molecular weight played a significant role in influencing the impact properties of PVC.
Incidence of Crosslinking Comonomer Composition in the Mechanical Properties of a Multilayer Reinforced Unsaturated Polyester Resin
In this work an improvement in mechanical perfomance of a general purpose reinforced unsaturated polyester resin, is attempted by using two different types of crosslinking systems to make composite materials by compression molding. Three resin layers separated by two glass fiber mat pieces conform the composites to be tested. Styrene, divinyl benzene and butyl acrylate in different proportions were used to crosslink the resin. Important variations in two formulation composition zones were found for tensile strength, impact resistence and dynamic properties. A formulation may be chosen to achieve enhanced performance in particular properties.
Rapid Tooling: The Rapid-to-Market Advantage
Industrial Technology is a field of study designed to prepare technical and/or management oriented professionals for employment in business, industry, education, and government. As a young industrial technologist it is my responsibility to understand both the technical aspects of world class equipment and more importantly, strategic application of these technologies for maximum corporate impact. Rapid prototyping and rapid tooling are technologies that if coupled with appropriate management strategies should allow companies to get their products to the market faster. This paper presents how a team of graduate students is using rapid prototyping and rapid tooling to reduce product changes and associated costs and accelerate product development.
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