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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Mass Transfer between a Slender Bubble and a Variable Diffusion Coefficient Liquid in an Extensional Flow
Mass Transfer between a slender bubble and a Newtonian liquid in a simple extensional and creeping flow has been theoretically studied. The liquid is a solvent-polymer solution, having a variable diffusion coefficient, which depends exponentially on the solvent concentration. Assuming a thin concentration boundary layer thickness and applying the method presented by Levich for a constant diffusion coefficient, the differential binary mass balance was transformed into an ordinary differential equation, which was numerically solved. The final result was also compared with an approximated analytical solution developed by Polyanin and Dil'man.
Can DSC Fractionation Be an Alternative Technique to CRYSTAF for Determination of Comonomer Distribution in Polyethylene?
The use of differential scanning calorimetry (DSC) fractionation techniques as a possible alternative to temperature rising elution fractionation (TREF) and/ or crystallization analysis fractionation (CRYSTAF) technique for the determination of comonomer distribution in polyethylene has been a topic of enduring interest in the polymer literature over the last ten years. In this paper, we demonstrate a surprisingly good correlation between CRYSTAF and the two most popular DSC fractionation techniques, the segregated fractionation technique (SFT) and the successive self nucleation and annealing (SSA) Technique for metallocene based polyethylenes.
Composite Tooling for Injection Molding
Aluminum, ceramic, and high conductivity carbon fiber have been used to cast composite injection molds with superior thermal and mechanical properties. Heat transfer and dynamic mechanical analysis experiments showed improved conduction and glass-transition temperature compared to traditional epoxy and stereolithography-based tooling. The master pattern was produced using stereolithography and multijet prototyping technologies. In injection molding experiments, the composite tools required less total cycle time than a comparable stereolithography tool.
Fracture of a TPE Catheter
A nylon/polyether TPE catheter fractured during the final stages of childbirth in a British hospital. The catheter supplied an epidural anaesthetic to the patient, and part of the tip was left in her spinal fluid. She sued the hospital and manufacturer. The catheter showed brittle behaviour, and research showed that it was probably caused by a combination of UV and gamma radiation of the polymer, initiating chain degradation. ESEM of the fracture surface showed no cut marks, as suggested by another expert witness. FTIR microscopy showed traces of esters near the fracture, confirming degradation.
Double Foam-In-Foam Polymer Materials
Reticulated 100% open-pore low density (20 kg/m3) flexible polyurethane (PUR) foams with various pore sizes (1-8mm) were used as three-dimensional fillers to reinforce low-density closed-cell PUR flexible foams. The final materials represent the double foam-in-foam" structures where one foam "impregnates" another one. Compared to the "single" closed-cell PUR foam the double material exhibit considerable improvement of mechanical properties: for the same low density the compressive modulus increased up more than 10 times. Marketing aspects of a new family of the developed foams are discussed such as cushioning and packaging application."
3D Solid Brick Element Injection Molding Simulation - A Time Effective Solution
The model preparation for the current mid-plane shell element type flow/pack/shrinkage/warpage and cooling analysis is time consuming and tedious. Many attempts have been made to automate the process, but most have proven to be inadequate. The obvious solution of moving to solids based analysis programs was limited by unacceptably long calculation times. This paper describes the results of three years of experimentation, to develop a proprietary technique to quickly and easily create a user controlled hexahedral mesh from STL files and reduced the solid model calculation times.
Perspectivies of the East European Plastics Food Packaging
This paper is an attempt to analyze, in the limits of available space, the existing situation and development tendencies of the plastics food packaging, i.e. raw material resources, market structure and forecast for seven former Soviet influence zone states from Eastern Europe, not enough known to the American plastics market. Also presented here are the opportunities for American and Western European investors, with emphasis on the small and medium size production units already in place, benefiting from skilled work force, low production costs and increased market demand. Recommendations for changes in the western trade policy are also made.
Effect of Maleic Anhydride Content on the Rheology and Phase Behavior of Poly(Styrene-Co-Maleic Anhydride)/Poly(Methyl Methacrylate) Blends
The thermo-rheological properties of lower critical solution temperature (LCST) poly(styrene-co-maleic anhydride) (SMA)/polymethyl methacrlylate (PMMA) blends, with varying amounts of maleic anhydride (MA) content (8%, 14% and 32% by weight) in the SMA component have been investigated, using differential scanning calorimetry and small amplitude dynamic oscillatory rheological methods. The effect of MA content on the phase behavior of SMA/PMMA blends has been determined. The resulting phase diagrams have been modeled using Flory-Huggins theory.
Processability Studies of Silane Treated Silicas and Carbon Blacks in EPDM Matrix
Treated silica particles with different silane chain lengths were compounded in ethylene-propylene-diene terpolymer (EPDM) using an internal mixer, and their viscosity, agglomerate sizes, and extrudate swell were investigated and compared to carbon black filled systems. The treated silica compounds exhibited lower viscosity, smaller agglomerate size, and lower swell reduction than untreated silica compound after equivalent mixing times. The silica treated with shortest aliphatic chain length silane exhibited smallest agglomerate size compared to other silane treated systems. Silane acted as dispersing and processing aids in silica/EPDM compounds. Treated silica systems exhibited higher agglomerate size and viscosity than carbon black filled systems.
The Influence of Screw Design on the Stability of a Reactive Twin-Screw Extrusion Process
The pressure fluctuations that occur during the reactive twin-screw extrusion of polymers that contain solvents or solvent-borne reactants can be suppressed by closing off the reaction zone with low-pitch, reverse (so-called left-handed") screw elements. We suspect that the average down-channel velocity of the melt inside these screw elements is so high that the destabilizing effects of melt foaming occur only after the pressure is reduced. The time elapsing between the pressure drop below the boiling pressure and the end of the left-handed screw elements is the crucial parameter for controlling the stability of the process."
Rheological Characterization of the Molecular Weight and Molecular Weight Distribution of Linear Polyethylenes
It has been known for many years that the rheology of linear single phase polymer melts depends strictly upon their molecular weight and molecular weight distribution. Recently, theoretical relationships have been developed that permit transforming rheological data into molecular weight information. Rheology has several advantages over GPC or LC in determining the molecular weight distribution of linear polymers. For one, rheology is highly sensitive to the high molecular weight tail, which is usually excluded in chromatographic separations. These fractions dominate the elasticity of the polymer melt, which greatly affects processing behavior. Generally, in order to determine the entire molecular weight distribution of a polymer, the rheological data must characterize the complete range of relaxation times between the plateau and terminal regions. In practice, such measurements are very tedious and time consuming, and can involve multiple tests run at several different temperatures, with different sets of conditions. A solution to this problem has been developed by Mead et. al. that allows incomplete rheological data to be combined with appropriate mathematical models to produce the molecular weight distribution curves. This paper reports on the transformation of the frequency dependent viscoelastic material functions to molecular weight and molecular weight distribution curves of LLDPE samples using this method. These results are compared with the molecular weight distribution curves obtained from GPC.
Meeting Global Trends for Automotive Coatings
The paper deals with both macro trends in the way global business is done today and specific trends in functional and decorative coatings. Today's economics and system trends are driving unified products, universal quality, one-performance criteria, shortened life cycles, and local production for supply and technical service. Alliances are used to gain additional resources and to reduce overall R&D costs. The goals and benefits of Alliances are described. Plastics substitution is driving new applications for coatings. Global performance and appearance trends will influence these new applications.
Heat Transfer Decorating: Past - Present - Future
This paper will provide a close look at how and why heat transfers are being used as a way to decorate plastic components. I will start with the history of heat transfers and then look at the advancements in the manufacture and application of heat transfers. I will review the tooling, supplies, and equipment required for successful application of heat transfer programs and discuss the various industries that they are used in today.
Rheology of Polytetrafluoroethylene as Related to Paste Extrusion
The rheology of polytetrafluoroethylene (PTFE) pastes has been studied using an Instron capillary rheometer. Four different grades of PTFE have been tested. Three of them had a homopolymer structure with different molecular weights. The fourth polymer had a slight degree of branching due to the incorporation of less than 0.5% by weight of another perfluorinated monomer. The investigated parameters included those related to the die design (contraction angle, capillary diameter and length to diameter ratio), extrusion conditions (temperature, and extrusion speed) and the molecular weight and structure of PTFE. It was found that these parameters significantly affect the capillary extrusion pressure, which is important in the creation of fibrils during paste extrusion. Quantification of fibrils in the extrudate has been attempted by the use of Raman microscopy. An attempt has also been made to correlate the degree of fibrillation with the tensile strength of the extrudate.
Calculation of Melting Performance of Injection Molding Screws by an Easily Applicable Model
The plastication of solids in the reciprocating screw of an injection molding machine is a transient process, and consists of two phases. During the stationary phase of the screw, melting takes place mainly by conduction heat transfer from the barrel. The melting during the screw rotation phase of the molding cycle is similar to that of an extrusion screw, however the screw undergoes translation. Starting from the relationship for conduction melting and extending it to include a simplified model for the extrusion melting, a set of equations which can be easily solved for the solid bed profile in the reciprocating screw is derived. Using this extended model, simulations of the effect of the barrel temperature, screw speed, screw rotation time, screw geometry and resin properties on the melting performance of the screw are presented. Predictions of the model agree well with the experimental observations in practice. The easy applicability of the model is illustrated by worked-out examples.
New Developments in Plastics Packaging the next Ten Years
Packaging is the largest application of polymers, in all countries, at all levels of development, 30 to 40 % of total plastics consumption, boosted by very strong facts and trends. Past present and forecast figures show diversified plastics growth in packaging, and new competition between plastics. The narrow link of packaging with food products makes packaging a stronghold of resistance, even in recession. The fast development of emerging countries generates demand for improvement of the food supply and packaging; Research goes on, for smarter, simpler, thinner packaging, of higher performance and easier on the environment.
Waste Management of PET Bottles in Croatia
Waste management is gradually becoming a priority within an integrated approach to nature conservation. Croatia has taken a number of good steps during the recent years. The first life-cycle and economy analyses in Croatia were made for managing of glass waste in 1997, but no serious study of plastic waste was made until recently. Among all types of plastic waste, only PET-bottles are collected in Zagreb (within the OHO system - Croatian Recycling System), so it was logical to make the first life-cycle analysis of PET-bottle. The results have shown the evaluation of PET-bottles' impact on the environment and the critical points" of PET-recycling were pointed out."
Experimental Validation of a Mold Filling/Cooling Software
With the aim to establish some guidelines in the use of injection molding simulation programs as a predictive tool when designing a mold, an experimental validation of an injection mold was performed. Amorphous and semicrystalline materials were injection molded, and their corresponding process windows were established. C-Mold software was employed to simulate the experimental conditions. It was found that the software temperature predictions agree very well with the experimental results, but pressure predictions do not. The material properties seem to be strongly influencing the simulation results. Filling and packing times could be extrapolated from the simulation, but shrinkage predictions should be considered carefully.
Supercritical Fluid Assisted Polymer Processing
The plasticising action of supercritical carbon dioxide in polymer melts will be demonstrated using in-line rheometry applied to a single screw extruder. By optimising processing conditions, gas dose rate, temperature and pressure, it will be shown that significant viscosity reductions can be achieved, enabling enhancement of process performance. The application and potential use of this effect to different polymers will be considered, including highly filled compositions used in ceramic fabrication. Means for achieving foam-free product will be discussed in extrusion and injection moulding processes.
Use of Selective Laser Sintering for the Function Testing of Snap-Fits
Snap-fits have been a popular method of mechanically attaching plastic parts. Design of snap-fits, however, is still a very high-risk activity since testing cannot be done until first article parts are molded. This paper presents the authors experience in using SLS prototype parts for the design and testing of snap-fit assemblies. Examples cited include an automotive fuel system component, an optical lens housing, and two novel snap-fit topologies. The success and limitations of these efforts are discussed as well as typical experimental data.
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