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
In-Line Dielectric Sensor for Chemical Composition Measurements in Molten Polymers
Michael McBrearty, Anthony Bur, Stephen Perusich, May 1999
Resin producers and compounders use additives to extend and modify the properties of their polymers, and they increasingly use rugged dielectric sensors to measure additive concentrations in-line for automatic process control and quality monitoring. They need to control the concentrations of the additives they use as processing aids and to modify properties in plastics, elastomers, fibers, adhesives and coatings. This helps them meet demanding product quality specifications and ensure strong prices and market shares. Theory and experiments described here indicate that dielectric measurements in melts can quantitatively determine individual or total additive concentrations with an accuracy that depends on electrical contrast and can exceed 0.1 volume percent (1000 ppm) with polymers and compounds having one or possibly two dominant additives. In-line measurements of additive concentration facilitate automatic process control, which helps maintain product quality and manufacturing efficiency. In multi-component mixtures the measurements indicate on-aim conditions, provide automatic quality monitoring and accelerate transitions.
Hierarchical Assembly of Fibrous Proteins
Regina Valluzzi, Peter Avtges, Sandra Szela, Stefan Winkler, David Kaplan, May 1999
Fibrous proteins provide useful models with which to explore self-assembly processes from the molecular scale to the macromolecular scale. Silks and collagens are under study in an effort to understand the sequence of events involved in these assembly processes, as well as to explore options to direct this process toward different paths. Model peptides, the native proteins, and recombinant versions of these proteins are studied. Interfacial and bulk solvent environments are utilized in an effort to understand and direct these processes. The interplay between primary repeat sequence and solvent is essential in fostering a specific assembly pathway. Insights into these processes will be presented within the context of pattern formation in fibrous protein materials with implications for biomaterials and tissue engineering.
Case Studies of Plastics Failure Related to Improper Formulation
Myer Ezrin, Gary Lavigne, May 1999
Troubleshooting of plastics failures often requires chemical analysis to determine if the formulation is a contributing factor. Examples of failures in product performance or development associated with incorrect or improper chemical composition of formulations include (1) adhesive problem due to improper order of films in a multilayer system; (2) hardener left out of an adhesive; (3) delamination of tin coating from copper due to adhesive tape wrap; (4) stiffening of grease lubricating a moveable screw in a servo motor; (5) unintentional color in a portion of an electrical cable.
An Accurate Warpage Prediction for Injection Molded Part by Using Simulation Program
Shijun Ni, May 1999
This paper describes the computerized injection molding simulation of filling, post-filling, cooling and shrinkage and warpage phase analyses for an injection molded fiber-filled reinforced frame part used in a laser printer. Using C-MOLD ® simulation program, the part warpage was separately predicted by non-uniform shrinkage, fiber orientation, and unbalanced cooing effects. In the study, the frame part, as an example, the displacement components induced by different factors were investigated. The predicted shrinkage and warpage of the part are compared to the measurements of an actual production part. It was in good agreement with the actual injection molded part.
Modification of Thermoplastics for Density and Gas Permeability through Additives and Reactive Processing
M. Xanthos, May 1999
Transport properties of thermoplastics such as thermal conductivity and gas permeability are usually controlled through foaming and the formation of lamellar microstructures respectively. Production of low-density foams by extrusion in the presence of physical blowing agents requires materials with particular rheological characteristics. Reactor/post-reactor branching or controlled cross-linking is commonly carried out in the presence of multifunctional additives. Low vapor/gas permeability structures may be formed through the incorporation and subsequent orientation of impermeable lamellar fillers, or the in-situ formation of lamellar microstructures during processing of mixtures of immiscible polymers. Examples of available technologies in both areas and recent research results will be presented.
Visual Research of Melting Mechanism of Polymer Pellets in Intermeshing Co-Rotating Twin-Screw Extrusion
Linjie Zhu, Xiaozheng Geng, May 1999
With visualization co-rotating twin-screw extruder, the transition of polymer from solid to melt can be investigated on-line. Based on different states of polymer pellets along the screw in the experiments, several melting sub-stages, such as conduction melting, particle deformation, inter-particle friction melting and viscous dissipative mix-melting, were divided and defined in order to fully understand the melting process. Function of every stage was deeply discussed. It showed that dissipative mix-melting was an efficient way to polymer pellets melting, which depended on not only screw configurations but operational conditions and polymer properties as well.
Thermally Conductive Thermoplastic Materials
James M. Finan, May 1999
Thermoplastics have made steady gains in the replacement of metals in a wide variety of applications. One of the last areas in which thermoplastics have not been effective in replacing metals has been in applications where thermal conductivity is required. Central to the development of these materials is an understanding of the heat transfer requirements in these applications. A simple model will be presented in which the heat transfer requirements for thermally conductive materials can be understood. Through the use of various filler systems, materials have been developed with thermal conductivities from 1 to 10 W/m°K.
The Formation of Supermolecular Polycaprolactone (PCL) Spherulites in Polystyrene-Polybutadiene-PCL (PS-b-PB-b-PCL) Semicrystalline Block Copolymers
G. Kim, C.L. Jackson, V. Balsamo, M. Libera, R. Stadler, C.C. Han, May 1999
The morphological behavior of polystyrene (PS), polybutadiene (PB), and polycaprolactone (PCL) semicrystalline block copolymers as a function of annealing conditions is discussed. For this study, both bulk and thin films of (PS)0.35(PB)0.15(PCL)0.5 were cast from toluene solution and the morphologies were examined using transmission electron microscopy (TEM) and polarized light microscopy (PLM). The morphology of either as-cast or annealed bulk (1 mm) specimens is a lamellar-cylindrical morphology having PB cylinders at the interphase boundaries. The block copolymer thin film (5-10 µm) from fast solvent evaporation also shows a lamellar-cylindrical microphase-separated morphology without the formation of visible PCL spherulites using PLM. After the formation of the well-defined PCL spherulites by annealing, the micromorphology is no longer lamellar-cylindrical but instead the PCL lamellar crystals dominate the system.
Structure and Processing Control of Electrically Conducting Polymers
A.J. Epstein, W.-P. Lee, K.R. Brenneman, A.D. Gudmundsdottir, M.S. Platz, A. Saprigin, K. Bates, D. Tigelaar, M. Platz, P.K. Kahol, A.P. Monkman, May 1999
The electrical conductivity of doped conjugated polymers is very sensitive to their in-chain and interchain structure. We present results of an integrated study of the electrical and magnetic properties. Modifications examined include the role of oligomer length, substituent group, chirality of dopant and processing-induced orientation and crystallinity. The data show a systematic variation of the room temperature conductivity and its temperature dependence. The variation of magnetic behavior supports the important role of structural order and inhomogenity. New concepts such as the role of “fractal networks” in determining the electrical properties (and industrial applicability) of these polymers are introduced.
Corrosion Protection of Aluminum and Iron Alloys Using Polyanilines
A.J. Epstein, H. Guan, J.A.O. Smallfield, M. Fahlman, May 1999
Corrosion protection capabilities of polyaniline in the emeraldine base form and self-doped sulfonated polyaniline form have been studied for aluminum and Al 3003 and Al 2024-T3 alloys. The polyaniline is applied as a coating on the aluminum coupons which were exposed to a variety of corrosive environments, including 0.1M NaCl. The oxide layers that formed were studied by X-ray photoelectron spectroscopy depth profiling using argon sputtering. Potentiodynamic polarization studies were used to determine changes in corrosion current and corrosion potential as well as pitting potential. For Al and Al 3003 there were modest indications of potential corrosion protection capability of polyanilines. The coatings of emeraldine base (EB) and sulfonated polyaniline (SPAN) on Al 2024-T3 were effective at reducing the corrosion rate when these coated coupons were exposed to 0.1M NaCl environment. The XPS study suggests a reduction in the copper concentration at the surface of the coated coupons. It is suggested that the EB and sulfonated polyaniline coatings facilitate the extraction of copper from the surface of the Al 2024-T3 thereby reducing the galvanic couple between aluminum and copper that usually leads to accelerated corrosion for the Al 2024-T3 alloys.
Single-Site Supported Catalysts for Ethylene Polymerization
A. Muñoz-Escalona, L. Mendez, B. Peña, P. Lafuente, J. Sancho, W. Michiels, G. Hidalgo, Ma. Fca. Martinez-Nuñez, May 1999
The new family of single-site catalysts for ethylene polymerization are soluble organometallic compounds, which make them suitable to be used in solution or in high pressure processes. However, if they want to have an impact in the polyolefin industry they need to be heterogenized for dropping into large gas-phase and slurry production plants and to produce polyethylene with differentiated properties. In this paper we describe different approaches for the preparation of supported single-site catalysts. Special attention have been paid to the requirements of the catalysts for retaining the essential characteristics of the homogeneous analogs (e.g., single-site nature) after supporting them, as well as to the ability to control of morphology of the polymer particles (replication phenomena) and the properties of the resulting polyethylene
Instrumenting the Elmendorf Tear Test
C.N. Marzinsky, A. Lustiger, S. Ling, May 1999
The Elmendorf tear test is widely used to evaluate tear strength of blown and cast films. Yet, the tear strength value does not directly relate to toughness, energy, or, indeed, any other true material property. Development of structure-property relationships are very difficult when the property one attempts to measure is so ill-defined. Furthermore, the Elmendorf value does not differentiate between initiation and propagation events. In this paper we describe a setup for instrumenting the Elmendorf tear test so that the information that one derives from the test is analogous to an instrumented impact test.
Estimating Permeability of Compacted Fabrics and its Use in Modeling and Control of the RTM Process
E.M. Sozer, A. Gokce, S.G. Advani, May 1999
Permeability of compacted multi-layer fabric preforms is predicted by using an analytical code based on an approximated two-dimensional lubrication flow in open spaces between the fabric tows and one-dimensional transverse Darcy's flow within the tows. The distribution of microscopically measured tow architecture of compacted and resin-filled fabric samples is used in the code to predict the range of permeability and a weighted permeability. The predicted permeability values are compared with the experimentally measured values for some fabrics. The predicted value serves as input to a separate mold filling simulation code which can predict flow front location and pressure distribution. The experimental and simulation injection pressures are compared under constant injection flow rate boundary condition within molds with both uniform and non-uniform fiber volume fractions. This permeability predictor code is an alternative to the costly and time-consuming permeability measurement experiments in RTM process and empirical relations between permeability and fiber volume fraction. Besides the tow distribution analysis, the model is flexible enough to study the effects of in-plane shifting of layers of a multi-layer mat.
On-Line Measurement of Polymer Melt Specific Volume Using a Gear Pump
Simon Park, Chul B. Park, Dmitry Ladin, Hani E. Naguib, C. Tzoganakis, May 1999
This paper presents a newly developed experimental system that can economically and accurately measure the pressure-volume-temperature (PVT) properties of polymeric fluids based on an extrusion system. The density or specific volume of a polymer melt is determined by measuring the mass and volume flow rates of the melt. A positive displacement gear pump mounted on an extruder is used to measure the volume flow rate of the melt. In order to reduce the leakage across the gear pump, the difference between the upstream and downstream pressures is minimized by using a variable resistance die attached to the downstream outlet of the gear pump. The positive displacement volume of a gear pump was determined in calibration experiments with water and oil with the aid of a syringe pump. A critical set of experiments was carried out to measure the specific volume of a linear polypropylene as a case example. The measured results were compatible with the known PVT data of the polypropylene material, confirming the validity of the system.
Insights Regarding the Mechanism for Interfacial Polymer-Metal Oxide Reactions
J.M. Runge-Marchese, A.J. Pomis, May 1999
An anodic coating process for aluminum and aluminum alloy substrates has been theorized and experimentally proven which enables the formation of composite polymer-metal oxide films. Important to the process is the modification of the sulfuric acid electrolyte to include aniline monomer. The additive is made electroactive through ring substitution on the aminobenzene structure in the electrolyte [1- 4]. Autocatalytic side reactions were also noted during experiments to optimize electrochemical formation of composite metal oxide - polyaniline films. Analysis of the films formed through the electrochemical (anodizing) and autocatalytic reactions elucidated the mechanism for bonding at the polymer-metal interface. This paper discusses the reactions, analysis and the insights toward understanding the mechanism for polyaniline-metal interfacial reactions.
Comparison of Dry Blending-Based and Melt Compounding-Based Rotomolding Techniques for LLDPE Foams
Remon Pop-Iliev, Guobin Liu, Fangyi Liu, Chul B. Park, Sam D'Uva, John A. Lefas, May 1999
This paper presents a melt compounding based rotational foam molding technique for production of fine-celled LLDPE foams in comparison with the dry blending based technique. A chemical blowing agent (CBA) is well dispersed in the LLDPE matrix in a compounder while preventing the predecomposition of the CBA. The compounded pellets are then rotationally molded to produce foams. The morphology of the LLDPE foams obtained in such a way was investigated at various processing conditions. The quality of the cell structures obtained in melt compounding based rotational foam molding was superior to that of the dry-blended based in terms of cell size, cell population density and volume expansion ratio. The results indicate that the cell nucleation mechanism in the compounding based technique is superior and that the scheme of well distributing the CBA particles in the polymer matrix by compounding is effective to achieve better nucleation of cells compared to the dry blending technique.
Dynamics of Vulcanization Induced Phase Separation in Olefinic Elastomer Blends
T. Kyu, W. Kaewwattana, A. Ramanujam, H.-W. Chiu, May 1999
Blends of syndiotactic polypropylene (sPP) with ethylene propylene rubber (EPR), prepared through solvent casting, show no phase separation in the melt. Upon cooling, phase separation takes place in the vicinity of crystallization temperature of sPP. The phase diagram of the sPP/EPR blend is essentially an overlap of an upper critical solution temperature (UCST) and the melting temperature of sPP in the blends. In the case of sPP/ethylene propylene diene terpolymer (EPDM) blends, a lower critical solution temperature (LCST) was observed in the melt, i.e., about 30 K above the UCST. Vulcanization has been undertaken in the single phase using dicumyl peroxide (DCP) for EPR and DCP or phenolic resins for EPDM. Temporal evolution of structure factors and the emergence of phase separated domains in these blends have been investigated by time-resolved light scattering and optical microscopy. The temporal evolution of structure factors has been analyzed in the context of nonlinear dynamical scaling laws to elucidate mechanism(s) of vulcanization induced phase separation (VIPS) of sPP/EPR blends.
Determining Crack Growth Measurements for the Tear Resistance of Polyethylene Film
Misty D. Dawson, Cory P. Bowes, May 1999
Two methods are currently used to evaluate the tear resistance of polyethylene films, the Elmendorf and Dart tests. Often times these tests yield contradicting results, leaving much information to be desired on the properties of the film. Two tests that may provide more useful information are the Single Specimen J-Integral analysis and Crack-Tip Opening Displacement method. One important area in the determination of tear resistance is the measure of crack tip growth. It is crucial to observe and measure the growth of the initial crack as it is loaded constant extension. This was one of the main focal areas in development of the proper testing protocol.
A New Approach to Determining the Boundary between the Liquid and Gelatinous Zones in a Pultrusion Die
Sean Reymond, Rachid Boukhili, May 1999
The aim of this investigation is to propose an approach for the determination of the degree of cure at the gel point for a high reactivity amine cured epoxy pultrusion resin. To determine the gel time of the resin, two standard techniques have been adopted, with some modifications to suite the needs. The first is ASTM D-3056, Standard test method for gel time of solventless varnishes, and the second is ASTM D-4217, Standard test method for gel time of thermosetting coating powder. The results from these methods yielded a linear relationship, which is defined by kinetic theory. Secondly, the isothermal degree of cure profile's, are calculated from the kinematics equation. Using the two sets of data, the degree of cure at the gel point was found to be 54%. This result is verified using Flory's classical approach, which gave a degree of cure at the gel point of 58%. The degree of cure at the gel point can then be used as a fundamental parameter to model the pultrusion process.
New Polymer Blends by Reactive Compounding: Formulation, Generation and Property Profiles
H.G. Fritz, May 1999
Within this paper the generation of tailor-made thermoplastic materials by means of functionalization, blending and alloying is described. New strategies for the reactive compounding of innovative two-phasae polymers like heterophasic polypropylenes and polyurethane/polypropolene blends (TPU/PP) are presented. Process design, formulation parameters and resulting blend properties will be discussed in detail. An alternative concept for the generation of polylactides (PLA) by means of reactive extrusion and based on a ring-opening polymerization strategy guarantees high-quality and inexpensive PLA-types.
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