SPE Library
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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Conference Proceedings
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.
The Early Use of Process Simulation to Optimize the Wall Thickness of Blow Molded Plastic Parts
The variable method of extrusion blow molding is widely used for the production of plastic hollow bodies. The primary target of the paper is the early and complete use of computer aided techniques in advance for the development of new commodities. The use of the new tool PreBlow" for the calculation of realistic wall thickness distributions using machines under recognition of different wall thickness adjustment methods will show realistic simulations. Conclusions are provided together with industrial examples."
New Technology to Vary the Thickness of the Parison in Circumferential Direction during the Blow Molding Process
The complexity of blow molded parts grows steadily. Accordingly the technology must keep space with the raised requirements of the market. Thus to improve the thickness distribution of complicated blow molded parts such as tanks for cars it becomes necessary to alter the thickness distribution of the parison not only in axial direction but also in circumferential direction. Encouraged by the success of the introduction of Membrane Dies for film and sheet extrusion the idea was born to design also dies with an extreme flexible outer wall for blow molding machines. This flexible wall can be locally deformed by adjusting screws which are located around the circumference of the die. The basic steps to reach this goal and the possibilities of the new technology are described.
Rapid Tooling and Plastics - Where the RT Industry Stands in 2001 on Better Alternative Tooling Methods
Rapid tooling (RT) has been surveyed, talked about, praised and condemned by users, promoters and bystanders since the development of alternative tooling methods debuted. However, RT processes are improving, with newer direct metal deposition and spray metal methods addressing concerns by plastic molders about size, durability, and molded materials. This paper outlines the state of RT industry for users already familiar with prototyping and RT. Setting the group of commercialized RT products which can be used in standard injection molding machines against P20 CNC produced tooling standards for density, cosmetics, thermal conductivity, cost and lead-time, feature definition, and others shows the evolving technology and the gaps that persist. By and large, the RT industry has been redefining acceptable boundaries for rapid tooling, and listening more to customer concerns. Several experimental technologies and limited use technologies exist that may be used to produce molded plastic parts, but are not available for placement on a conventional injection molding machine. Experimental and noncommercial technologies are not covered in this paper, and discussion is limited to three commercialized processes that show more commercial and mainstream acceptance by custom molders, KelTool™, LaserForm™, and DMD™.
Metallocene Plastomer Based Thermoplastic Olefin Compounds Designed for Roof Membrane Applications
This paper discusses the use of ethylene octene (EO) copolymers made with metallocene catalysts in thermoplastic polyolefin (TPO) compounds designed for single-ply roofing. The performance of two neat EO copolymers is first compared with a polypropylene (PP) based Reactor TPO (RTPO) currently used in single-ply roofing. The more crystalline EO copolymer displays superior thermal and physical properties compared to RTPO. Formulations comprising the EO polymers were designed and optimized using mixture design of experiments. The optimal compounds contain about 50 % EO, 20 % PP and 30 % magnesium hydroxide (MH), a flame retardant additive.
Structure Performance of Thin-Wall Injection Molded Parts
Influence of processing conditions, part thickness and residual stress on the structure performance of 3C thin-wall injection molded parts were investigated. Thin-wall tensile test specimens were molded. A computer dictionary (CD), with 1.6 mm thick housings, was also used for structure evaluation of bending strength and drop-impact performance. It was found that as part becomes thinner, residual stress becomes higher and affects both part tensile strength and weld-line strength more significantly. Higher melt temperature and mold temperature, lower packing pressure and faster injection speed would reduce residual stresses, increase weld-line strength and improve associated properties. When CD housings were redesigned to 1 mm thick keeping sidewall 1.6 mm, both its bending strength and drop-impact performance were only slightly decreased.
Effect of Different Nucleating Agents on the Degassing Conditions as Measured by Ultrasonic Sensors
Ultra sonic sensors have proven to provide valuable information on the thermoplastic foaming process in polymers. Measurement of the attenuation of the ultrasonic signal can be easily related to the nucleation process, i.e. the onset of bubble formation in the foam matrix. The ultrasonic sensors can be installed in-line, on the extrusion line, and thus allow direct access to the prevailing processing conditions. In this work, the degassing conditions (pressure and temperature) of a mixture of polystyrene and a physical blowing agent, HCFC 142b, are determined for two different nucleating agents. The resulting cellular structure of the extruded foams is correlated to the degassing conditions determined by the ultrasounds. The results are discussed in light of other observations on the nucleation process.
The Use of EVOH in Automotive Applications
Regulations for automobile emissions are stiffening in the U.S., requiring reductions by 75 percent or more. Polymers used in automotive fuel systems are a source of evaporative fuel emissions as they have poor barrier properties to fuels. New barrier polyolefins containing EVOH have been developed for injection molded automotive applications so that evaporative emissions can be reduced. A new EVOH has been developed to allow for down gauging and reduced cycle time of the current plastic fuel tank. This new EVOH will allow for cost savings in fuel tank production.
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