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
Screw Cooling Effects in Single Screw Extruders
Screw cooling has been used on occasional single screw extruder applications for many years. Most screws today are set up for cooling (have holes drilled down the screw shaft for some distance), but these days the cooling is seldom utilized. It would be helpful to have a general study of this parameter to prove where possible gains in performance are expected, or to obtain data to support why we should not be cooling the screw in some instances. This paper will give the results of a study of screw performance on several polymers where screw cooling was tested. The results of the non-cooled screw will be compared to screw cooling along the early portion of the screw as well as a fully cooled screw shaft. The tested screw will be one of today's barrier type screws and will allow conclusions as to the performance altering affects of screw cooling. The need to have this information documented in a concise form will be satisfied by this study.
Business Opportunities in the Czech Republic
The Czech Republic, a country with a population of 10 million has a formidable chemical industry with a long tradition. The polymer processing industry is its important part and represents a number of unique technologies. One of the prime candidates for the European Union, expected to be admitted in 2005, it is a stable partner ready to be part of the global economy. With a highly skillful and productive workforce it represents a very good opportunity for trade offering a great variety of unique products. Because of this country's location in the center of Europe, it is an attractive partner for investment. This paper will deal with current trends and provides details about the industry.
The Influence of Rotational Shear Pultrusion on Fiber Concentration and Wet out of Long Glass Polypropylene
New technology was developed to impregnate continuous glass fiber with molten thermoplastic polypropylene for manufacturing long fiber compounds. A composite with a polypropylene matrix and glass fiber reinforcement was made by rotation of a die orifice chamber about an axially directed roving of continuous fiber in the presence of the thermoplastic melt. The rotation reduced the melt viscosity of the polymer by shear thinning, while dragging and directing the polymer into the fiber, thereby wetting and dispersing the fiber. Fiber concentration was strongly influenced by the rotational speed of the die in conjunction with the line speed of the strand. Fiber wet out, measured by the shear strength of the strand, was improved at higher rotational speed and line speed.
The Processing and Performance of Nylon 4.6, Polypropylene Oxide/ Polyamide (PPO/PA) and Polyetherimide (PEI) in Automotive Fuel Handling Applications
This present work investigates the rheological properties and the effect of immersion in standard automotive fluids (an extension of SAE J2027) on the mechanical performance of a range of Nylons, Polypropylene Oxide/Polyamide (PPO/PA), and Polyetherimide (PEI). The rheological characteristics of Nylon 4.6., PPO/PA and PEI were investigated and the results showed significant decrease in shear viscosity at dwell times in excess of three minutes for Nylon 4.6. and PPO/PA. Injection moulded samples of the Nylon 4.6., impact modified Nylon 4.6., Nylon 12, PPO/PA and PEI were immersed in the standard automotive test fluids, Fuel C, zinc chloride solution and aggressive water. Subsequent mechanical analysis of the various specimens showed only slight decrease in the tensile modulus of the Nylon 4.6. after immersion in Fuel C, however significant weight gain and deterioration in tensile modulus were recorded after immersion in aggressive water. Dynamic Mechanical Thermal Analysis on the Nylon 4.6 showed only slight decrease in storage modulus (Log E') and Tg, after immersion in Fuel C. However a significant decrease in Tg by up to 80°C was recorded for samples immersed in aggressive water.
A Rational Way to Reduce Number of Colorants Used
The number of colors or colorants used in your operation takes on a life of its own, ever growing in size and complexity. There are valid reasons for the growth; to better match colors, satisfy a key customer, gain more heat or light stability, improve cost or processing properties, more reliable supply or to provide a specialty product. At the time each one is introduced we are typically under some driving force to satisfy a tactical need, what the heck its just one more item, and we lack the time to take a more strategic view. Next thing you know the number has grown from 80 - 100 items to 300 or more! So, do you really need that many colors? If you had fewer colors, your operations would be much simpler and simplicity implies better, less costly more reliable operating. So why not do the job with 50 colors. Well why stop there, why not 20 or maybe 16, shucks the rainbow only has 7, ROYGBIV. You know, we see all the colors on a TV screen or CRT & they are made from just Red Green & Blue, why not 3 colors? This paper will deal with the issue of what is the right number of colors, how you can go about getting there (and maybe staying there) and finally some of the benefits you might expect.
Chlorine Resistance Testing of Cross-Linked Polyethylene Piping Materials
The chlorine present in potable water as a disinfectant has been reported to reduce the lifetime of some plumbing system components. In this study the nature of the failure mechanism of a commercial cross-linked polyethylene (PEX) pipe material exposed in the laboratory to chlorinated potable water is examined. Water quality, or more specifically, chlorine level, is seen to have a significant impact on material performance. Test lifetimes are seen to be noticeably lower for chlorinated potable water, even at chlorine levels as low as 0.1 mg/L (ppm), than for non-chlorinated water. Through accelerated testing at multiple temperature and pressure conditions and the use of the Rate Process Model, a model to estimate the test lifetime of the PEX pipe material at end use conditions is developed. Based on this analysis the PEX pipe material examined in this study appears to have good resistance to chlorinated potable water.
Development of a New TPV for Bonding to Rigid Thermoplastics
The development of a new flexible thermoplastic vulcanizate (TPV) that bonds to a number of different rigid polymeric substrates is introduced. Detailed bonding values will be given for this new material to ABS, polycarbonate, PC/ABS alloys, polystyrene, and polyester. Physical properties will be presented and compared to other bonding elastomeric materials. The processing recommendations are given for over molded or insert molded applications for this flexible bonding TPV. Potential applications for this flexible bonding material include bumpers for vacuum cleaners, soft touch grips for tools and utensils, and flexible housings for instruments.
The Use of Scanning Probe Microscopy to Determine the Surface Morphology and Mechanical Properties of Latex and Polymers
An overview of Scanning Probe Microscopy (SPM) and it applications to polymeric materials will be presented. The SPM is a mechanical technique capable of both imaging and making physical measurements. The images provide rapid comparison of surfaces, while image reduction to a surface roughness value (Ra) allows numeric comparisons. Additionally, the interaction of the imaging tip with the surface, using the phase modulated mode, provides details on relative compliance of the surface. Images of compliance can be used to differentiate the spatial location of the different materials that make up the materials surface. The combination of the two techniques, topography and phase modulated, provides a very powerful tool for surface characterization.
Modeling Drop Size Distribution in Polymer Blend Injection Molding
An approach for modeling the drop size distribution in the injection molding of polymer blends is developed. The simulation directly uses experimental data correlated to functional forms in the FIDAP fluid dynamics package. As an example, experimental data for droplet size and shape in a Polyisoprene /Polybutadiene system was measured using an in-situ optical microscopy instrument designed for studying complex fluids under simple shear flow. The data is collected in the flow-vorticity plane as a function of temperature and shear rate. Size and shape distributions were calculated from the digitized micrograph using standard image analysis software. The shear viscosity of the blends, as well as that of the pure components, was measured as a function of shear rate and temperature using a commercially available parallel-plate rheometer. From theoretical considerations, the simulation is expected to provide good estimates of drop size distribution for flows with large aspect ratios of flow length to thickness where entrance effects are expected to be negligible, and there are no regions of recirculation.
Investigation of Structure Development of Polyamide 11 and Polyamide 12 in Single Bubble Tubular Film Blowing
The processibility of single bubble PA11 and PA12 films was investigated. The development of crystalline structure and chain orientation of polyamide 11 and polyamide 12 films in single bubble film blowing was studied by differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXS), infrared (IR) spectroscopy and birefringence. DSC measurements of both films exhibited a spontaneous increase in glass transition temperature (Tg) and cold crystallization temperature (Tc) during aging at room condition with crystallinity and melting point remained constant. Single bubble PA11 and PA12 films exhibited triclinic and monoclinic ? crystals, respectively. The level of biaxial orientation was evaluated by calculating White-Spruiell biaxial orientation factors with pole figure data.
Structure Development in Uni- and Bi-Axial Stretching of Extrusion Cast Polyamide 12 Film
Development of crystal structure, orientation and morphology in both uniaxial and biaxial stretching of extrusion cast polyamide 12 (PA12) films was carefully investigated. According to DSC measurements, aging of unstretched extrusion cast PA12 film at room condition raised both glass transition temperature (Tg) and cold crystallization temperature (Tc) without any considerable changes in crystallinity and melting point. The crystals of unstretched and stretched extrusion cast films were mostly monoclinic ? form. Stretching was carried out at various temperatures. By examining birefringences and WAXS flat films and pole figures, we found that the direction and level of molecular orientation was largely dependent on the extension ratios. SAXS showed that an increase in stretching temperature raised long spacings of lamellae. Annealing of PA12 films in formic acid solution raised crystallinity, melting point, level of chain orientation and long spacing of lamellae.
Drop Deformation and Breakup in Viscoelastic Polymer Blends
A three-dimensional finite element code is developed for simulating viscoelastic two-phase flows. The viscoelastic fluid is modeled via the Oldroyd-B model. The exact governing partial differential equations are solved using the Marchuk-Yanenko operator-splitting technique. The two-fluid interface is tracked using the level set method. The code is used to study the deformation of drops in simple shear flows and bubbles in gravity driven flow. The effects of Deborah Number (De) and capillary number (Ca) on deformation is analyzed for De values ranging from 0.0004 to 16, and Ca ranging from 0.06 to 1.2. The numerical results show that the viscoelastic stresses near the drop surface increase deformation of a Newtonian drop in a simple shear flow as compared against Newtonian shear flow. For the case of a viscoelastic drop in a Newtonian shear flow the deformation is smaller than that for the corresponding Newtonian drop. The effect of viscoelasticity on deformation is more pronounced when De<~O(1). For a Newtonian bubble rising in a quiescent viscoelastic fluid, the extensional viscoelastic stresses pull out the trailing edge and the bubble develops a cusp like trailing edge in one view and a broad edge in the orthogonal view. The trailing end of a Newtonian bubble rising in a Newtonian liquid, on the other hand, is pulled inwards which leads to the drop taking an umbrella-like shape.
Direct Simulation of Sedimentation of Solid Particles in Viscoelastic Fluids
The sedimentation of rigid spherical particles in viscoelastic fluids is studied by using 3D direct numerical simulations, in the simulation, a Galerkin finite element formulation is used to solve the fully coupled motion of the solid particles and the fluid that is governed by an Oldroyd-B model. The movement of the particles is handled with an arbitrary Lagrangian-Eulerian technique in conjunction with a mesh update strategy. Effects of the parameters controlling the particle motion, which are the flow/particle Reynolds number, the Deborah number, and the solid-liquid density ratio are investigated. This work was supported by NSF through grant CTS-9873236.
Rheological, Morphological and Interfacial Properties of PP/HDPE Blends
In this paper the linear viscoelastic properties of polypropylene (PP)/high-density polyethylene (HDPE) immiscible blends were measured as a function of frequency for different blend composition and temperatures. The morphology of the blends was studied by Scanning Electron Microscopy. The interfacial tension between the components of the blends was evaluated using small amplitude oscillatory shear analysis. The results seem to indicate that there is a range of compositions for which it is possible to use Gramespacher and Meissner analysis in order to calculate interfacial tension between polymers using small amplitude oscillatory shear measurements.
Predictive Model Helps Develop New High-Performance HDPE for Barrier Film Application
As the blown film industry has matured, the need for decreased cost has become paramount. The most attractive means of reducing cost is by down gauging film thickness, which inherently reduces the toughness of the film. This paper describes how a predictive model was used to develop a new homopolymer HDPE resin, which produces films with significantly improved mechanical properties without sacrificing barrier properties. The improved properties are the result of modifying the molecular weight and molecular weight distribution of the resin. Detailed blown film results demonstrate the performance improvement and the downgauging potential of the new resin compared to conventional HDPE.
Effect of Interdiffusion Regions on Barrier Properties of Multilayer Films
Barrier properties of polymer films can be improved in various ways, such as formation of multilayer structures by coextrusion, surface treatment, and coatings. This work explores the use of thousands of alternating layers of polymer (xyxy...) to alter the resistance to permeation. A model is presented to predict the number of layers needed in a laminate to change the flux of a permeant by a given amount. An important feature of the model is the species transport across the interdiffusion regions at the polymer-polymer interfaces where diffusivity of the penetrant is assumed to be a function of the volume fractions of the interdiffusing polymers. Our modeling results show that increasing the number of interfacial regions decreases the flux for a given condition, and a large number of layers are required to achieve appreciable barrier enhancement.
Temperature Monitoring of Capillary Rheometry Using a Fluorescence Technique
A non-contact temperature monitoring technique based on fluorescence spectroscopy was used to measure the temperature of a polymer resin during capillary rheometry testing. Polyethylene doped with a fluorescent dye, perylene, was used in experiments that were designed to measure resin temperature changes due to shear heating as shear rate in the capillary increased from 10 to 10000 s-1. Resin temperature at the exit orifice of a 1 mm diameter capillary die was found to increase monotonically with increasing strain rate reaching 25°C above the capillary set point temperature at the highest shear rates. The implications regarding rheometry testing are discussed.
New Solidification Models for the Simulation of the Injection Molding Process
In order to predict shrinkage and warpage in injection molded products, the thermal contraction and the residual stress have to be calculated. Therefore the temperature distribution in the injection mold has to be simulated during the fast cooling in the cavity. For semi-crystalline polymers this implies the incorporation of the latent heat of crystallization into the heat equation by means of an adequate crystallization model. Furthermore, properties such as the specific volume and the heat capacity and conductivity need to be modeled. The models for the crystallization and the thermal properties presented here are physically motivated. Simulations are presented of the temperature distribution during the fast cooling of semi-crystalline polymers with and without glass fibers. The calculations are compared to experimental results, which have been obtained with an apparatus designed especially for very high cooling rates.
A Preliminary Investigation into the Use of Wood Fibers as a Filler in the Rotational Molding of Polyethylene
There has been no known work carried out on the use of wood fibers as a filler in the Rotational Molding (herein also referred to as rotomolding) of Polyethylene. It is reported though that the extrusion industry has noticed a 100% increase in wood fiber profiles over the past two years. (1) It is only a matter of time before this diversity of materials will find itself being used in Rotational Molding. This paper presents investigative results of the characteristics of the molded parts in terms of molding conditions, percentages of wood fiber used and the type and size of wood used. Potential for novel product design and the uses for the wood/ plastic composite will also be discussed.
Natural Fiber Reinforced Polypropylene Composites – an Approach on Thermoforming Processing
This work has been performed at Mercedes-Benz of Brazil in a partnership with its suppliers aiming the replacement of fiberglass in polypropylene matrix composites by natural fiber reinforcements. The process that has been chosen for this purpose was Vacuum-forming. This choice took into account the large application that this technique represents in the company's commercial products. The results expected for this new material is cost and weight reduction besides the friendly environmental aspect that this change introduces. Jute fiber reinforced polypropylene sheets at constant thickness and fiber content were prepared in order to evaluate the feasibility of the application. The preliminary results have shown that this material has a great potential of application because of the low fiber costs.
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