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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
Design of a Foaming Simulation System with a High Pressure Drop Rate
Qingping Guo, Jin Wang, Chul B. Park, Masahiro Ohshima, May 2004
The pressure drop rate is one of the most important parameters used to control the cell density of foams for a given processing pressure, temperature, nucleating agent content, and blowing agent content. In this paper, we concentrate on the experimental and theoretical analysis of the pressure drop behaviors in an experimental foaming simulation system using a visualization window. Both CO2 and N2 were used in the experiments and the simulation. It was observed that the maximum pressure drop rates obtained were 2.5 GPa/s and 0.4 GPa/s for CO2 and N2, respectively. Some simulation results at high-pressure drop rates are also shown.
Microporous Films from Polymer Blends and Composites - Processing/ Structure/Property Relationships
M. Xanthos, J. Wu, May 2004
This presentation will cover recent advances on selected inorganic and organic micron or sub micron fillers, which in addition to their primary functionality of modifying bulk mechanical properties provide also unique secondary functionalities. Inorganic particles (e.g. surface coated CaCO3) dispersed in polyolefins and organic particles (e.g. polystyrene with or without adhesion promoters) particles dispersed in polypropylene may promote the formation of micro/nano porous structures by post extrusion stretching of flat precursor films. The effects of filler concentration and process conditions on the resulting morphology and properties are discussed with applications in separation membranes and water breathable films.
Analysis of Solubility and Spinodal Decomposition for Thermoplastic Foams
Chien-Yueh Huang, Lining Zhu, Jenny Jun, S.T. Lee, May 2004
Using Sanchez-Lacombe Theory, we have calculated the solubility and spinodal surfaces for solutions of inert gases dissolving in thermoplastics. The gas solubility surfaces are compared to known experimental data and can be used for simulating the kinetic path of foaming on the pressure-temperature plane in batch or continuous extrusion processes. Relations of experimental data of cell density and the pressure superheat are studied and are compared with the classic nucleation theory. A critical superheat surface is suggested for explaining the gap between theoretically predicted and experimental measured nucleation rates.
Microcellular Wood Fiber Reinforced Polypropylene Composites: A Comparative Study between Injection Molding and Extrusion Processes
Andrzej K. Bledzki, Omar Faruk, May 2004
Microcellular processing techniques have been applied at a experimental level to both extrusion and injection molding plastics processing, using wood fiber as a reinforcing filler. The focus of the current research is the investigations of these processes using chemical foaming agents and comparative studies of physico-mechanical properties of materials. Results of using different chemical foaming agents (endothermic and exothermic), the variation of their content for producing wood fiber-polypropylene microfoamed composites and the effect of a coupling agent on the composites are presented. Microcells morphology, cell size, shape and distribution were investigated using scanning electron micrographs.
Validation of Shrinkage Predictions for Injection Molded Parts
Shubha Prasad, Satish Sharma, Mihir Jariwala, Carol M.F. Barry, May 2004
Shrinkage predictions from a commercial simulation package were compared with shrinkage of parts molded from neat and glass-filled grades of polycarbonate, poly(butylene terephthalate) (PBT), polyamide-6, and polyamide-6,6 various over a range of processing conditions. For both the neat and filled materials, the simulations overpredicted in-flow shrinkage and cross-flow shrinkage near the gate. Cross-flow shrinkage at the end of fill was underpredicted for glass-filled materials, did not correlate with values predicted for neat materials. The validation of shrinkage prediction for thin walled parts was also done using PC+PET blends.
Effect of Decompression Rate and Foaming Temperature on Cell Density
Keiichi Muratani, Minoru Shimbo, Yasushi Miyano, May 2004
The polystyrene specimens were foamed under various foaming temperatures and decompression rates, and the equivalency of decompression time that can obtain from decompression rate and foaming temperature about cell density was examined. As results, it was found that cell density has time and temperature dependence that cell density increases with a decrease in decompression time and foaming temperature, and cell density decrease with an increase in decompression time and foaming temperature. And it was found that the time-temperature equivalency seems to be held to the decompression time and foaming temperature, which affect cell density.
Mechanical and Fracture Behavior of Rigid-Rod Self Reinforced Polymers
Nick Malkovich, Romana Chavers, Kevin Battjes, Robert Bubeck, May 2004
Recently, a novel family of processable rigid-rod polyphenylenes with outstanding mechanical properties was introduced (Parmax® SRPs). These materials possess strength and stiffness superior to other thermoplastics while retaining reasonable notched Izod values (65 J/m). To understand this better, the mechanical behavior of these materials, focusing on fundamental fracture mechanisms, was investigated. The materials appear to generate weak crazes at crack tips combined with a multiplanar step-deflection mechanism for crazing/cracking behavior during the crack propagation stage.
Fabrication, Processing and Tensile Properties of Weft-Knitted Hybrid Composites Combining Microbraiding and Compression Molding Techniques
Omar A Khondker, Tatsuro Fukui, Xinyu Yang, Asami Nakai, Hiroyuki Hamada, May 2004
The presence of fibre/matrix interfaces strongly influences the overall mechanical properties of composites. This paper reports investigations on the fabrication process and tensile behaviour of weft-knitted thermoplastic composites by combining micro-braiding and compression moulding techniques. Aramid/Nylon66 (AF/PA66) microbraid yarns (MB) were produced using a tubular braiding machine and these MB yarns were subsequently used to produce weft-knitted fabrics having 1×1 rib architecture. Three types of MB hybrid knitted composites were fabricated and tensile test was conducted to evaluate tensile properties. Properties were also compared with those of the Aramid/Epoxy and Aramid/Nylon filmstacked knitted composites. Cross-sectional observations on the selected AF/PA66 MB hybrid knitted specimens by optical microscopy have confirmed that moulding condition at 290°C under 2 MPa for 20 minutes was ideal for achieving better matrix fusion and improved state of resin impregnation. The overall changes in the mechanical properties were found to be broadly related to several factors such as, continuity of reinforcing fibres in the knitted preforms, processing techniques and parameters, pre-tensioning prior to consolidation and the fibre/matrix interfacial adhesion.
Compatibility and Mechanical Property in Polymer Blends of ?-MSAN/SMI
Jaewook Lee, Jaehyug Cha, Seung-Hoon Chae, Seong-Lyong Kim, Chan-Hong Lee, May 2004
Improved heat resistance, chemical resistance and mechanical properties have been consistently demanded for ABS polymers to widen its application. To improve heat resistance of ABS several approaches have been taken. From the industrial point of view, one of the most useful approach is to prepare copolymers of poly (?- methylstyrene-co-acrylonirile) (MSAN) or poly (styrene-co-maleimide) (SMI) and to blend with grafted ABS (g-ABS).In this study, the miscibility and mechanical properties of the MSAN/SMI blends were investigated which contained various kind of styrene copolymers such as a styrene-coacrylonitrile with controlled AN content, styreneco- maleicanhydride and styrene-co-acrylic polymer. The MSAN/SMI blends samples were prepared using a twin screw extruder.Miscibility was investigated from Dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC). Mechanical property was investigated by measuring the tensile elongation and impact strength.
Mixing and Compatibilization of Polymer Blends by Solid-State Shear Pulverization: Effects of Microscopic Composition, Processing Aids, and Pulverization Parameters
Andrew H. Lebovitz, John M. Torkelson, May 2004
Solid-state shear pulverization (SSSP) has been shown to achieve compatibilization of immiscible polymer blends by the in situ formation of block copolymer resulting from coupling of polymer radicals made via low levels chain scission. Here we describe the impacts of microscopic dispersion of a blend prior to SSSP, processing aids (trace levels of polyethylene wax), and various SSSP process parameters on the ability to achieve intimate mixing as well as compatibilization. These studies also reveal that optimization of SSSP of polymer blends can result from focusing on only several of the many SSSP processing variables.
A Model to Predict the Development of Particle Morphology in Seeded Emulsion Polymerizations
S. Mendoza-Fernández, Carlos F. Jasso-Gastinel, Luis J. González-Ortiz, May 2004
Polymer blends can be obtained from two-phase polymer particles synthesized by seeded emulsion polymerization, whose properties depend on their particle morphology. Here, a mathematical simulator is presented to predict the development of particle morphology during the seeded stage and after the reaction (aging period). Two experimental systems previously reported showing as the only difference the type of initiator used (AIBN or KPS) were simulated, as an example, and an acceptable agreement between predictions and experimental morphologies was obtained.
Power Ultrasonic Irradiation Effects on the Mechanical Properties of Polymer Blends
Joung Gul Ryu, Seong Ho Kong, Hyungsu Kim, Jae Wook Lee, May 2004
Polymer blends were prepared with ultrasonic assisted mixing in an internal mixer. The influence of the ultrasonic irradiation time, blend ratio, and rotor speed on the mechanical properties of the polymer blends was carefully examined. The morphology of the polymer blends was examined under scanning electron microscope for domain-size measurements. Also, for confirmation of the mechanical properties, we performed the impact and tensile test. The effect of the ultrasonic irradiation on the polymer blends morphology was investigated. It was observed that the most significant reduction of domain-size occurred at an increase of ultrasonic irradiation time.As a result, mechanical properties of polymer blends prepared by ultrasonic assisted mixing were extraordinarily increased with sonication time compared to the polymer blends prepared by simple mixing. And the important relationship between ultrasonic irradiation time and mechanical properties was revealed.
Effect of Blending Sequence on the Modulus, Toughness, and Structure of PC/PBT/Talc Ternary Composites
Wade DePolo, Donald G. Baird, May 2004
Ternary blends based on polycarbonate (PC), poly[butylene terephthalate] (PBT), and talc are typically mixed in one step having a talc composition in the range of 6-12% by weight. This gives rise to flexural properties in the range of 3 GPa and lower thermal expansion which is advantageous for the production of exterior body panels but the high talc loading levels also significantly reduce the impact strength (toughness) and add to the overall weight of the composite. In an effort to increase the toughness while maintaining flexural properties, three different blending sequences of the above ternary composite were prepared: (1) melt blend PBT with talc first and then dry blend the PC with the PBT/talc, (2) melt blend the PC, PBT, and talc in one step, and (3) melt blend PC with talc first and then dry blend PBT. It was found that the blending sequence of the ternary PC/PBT/talc composites significantly influenced the toughness while maintaining a flexural modulus of around 3.0 GPa. The ternary composites generated by blending sequence (1) showed about a 20% increase in toughness compared to blending sequences (2) and (3). The higher toughness that was observed for blending sequence (1) was attributed to keeping the talc particles primarily in the PBT phase of the composite, better dispersion of the PC and PBT phases, and less degradation of the PBT.
Properties of Injection Moldable Blends of {Latex/Wood Flour recipes} and Polypropylene
Sophie Morneau, J.P. Ibar, May 2004
We prepare recipes of wood flour, from maple and pin tree, and latex, in various proportions, and disperse them with Polypropylene in a TekFlow processor in order to produce various conditions of disentanglement (viscosity reduction) for PP and for the blend. In particular, dispersion temperature is reduced to below wood degradation temperature.The dispersed blends are submitted to a series of rheological, mechanical and thermal analysis tests, to compare their properties with those of pure PP (controls). It is shown that for certain wood flower/ latex recipes, the blends with PP present favorable characteristics, both in terms of improved fluidity (they can easily be injection molded) and improved mechanical properties at room temperature and at -40 °C.
Modification of Nylon 6,6 and Metallocene Linear Low-Density Polyethylenes Blends Using Ethylene-Methacrylic Acid Ionomers
F. Gribben, G.M. McNally, W.R. Murphy, T. McNally, May 2004
Polymer blends of polyamides and polyethylenes are immiscible and highly incompatible. These blends are characterised by high interfacial tension, a two-phase morphology and poor physical characteristics due to reduced interaction across the phase boundaries. The focus of this work will involve the use of various amounts of ionomers based on ethylene-methacrylic acid copolymers as compatibilisers, which will physically be miscible with the polyethylene phase and will chemically bond with the polyamide phase. The use of this material was investigated for its abilities as a suitable impact modifier for these blends. The influence of the composition of the blends and the effect of the addition of the compatibiliser were both investigated for their affect on the mechanical and rheological properties.
Modelling Mechanisms of Brittle Oxidative Degradation to Ensure Plastic Pipe Material Performance
S. Chung, J.D. Kim, M. Toro, P. Vibien, K. Oliphant, May 2004
With material evolution, the projected service lifetimes of plastic piping materials continues to increase. This has led to an increasing interest in characterization of the brittle-oxidative resistance of these materials to define the ultimate lifetime. In this paper, the mechanisms associated with brittle failure of polyolefin piping materials are examined. The competing mechanisms of oxidative and mechanical crack initiation and propagation are found to control the ultimate mechanism of failure. Four different possible failure modes are identified and examples of the failure modes observed in laboratory testing are provided. Identification of the different failure modes and methodologies for forecasting and validating pipe oxidative performance are discussed.
Structural Design of Polypropylene Stormwater Chambers
Phillip A. Sharff, Jesse L. Beaver, Timothy J. McGrath, May 2004
Environmental Protection Agency requirements for control of stormwater runoff are increasing the need to provide on-site stormwater storage as part of site development projects. Underground stormwater storage is one solution to this need. Open bottom thermoplastic chambers make use of profile design theories established for thermoplastic pipe and allow maximum area at the bottom for natural seepage of the stored water into the ground. This paper reports on analysis and testing of archshaped, open bottom, corrugated polypropylene stormwater storage chambers that have spans of 1270 mm (50 in.) and are supported on a flat, turned-out foot. Computer analysis included finite element, soil-structure interaction models of chambers with 450 mm (18 in.) and 2440 mm (8 ft) of fill with AASHTO HS20 design axle load. Field-testing included chamber installations at shallow cover from 150 mm (6 in.) to 600 mm (24 in.) with vehicle live loads and at deep cover with 3500 mm (11.5 ft) fill. Design calculations were based on the new AASHTO procedures for profile wall thermoplastic pipe. Using prescribed installation procedures, the factor of safety is greater than the required AASHTO factor for thermoplastic pipe of 1.95.
Melt Residence Time Distributions in Smart Blenders and Continuous Chaotic Mixers
A.S. Joshi, D.A. Zumbrunnen, May 2004
Devices that utilize chaotic advection to controllably form polymer blend morphologies or arrange solid additives into functional structures (i.e., smart blenders) have been demonstrated. In relation to this new technology, a numerical study has been performed with the aim of characterizing melt residence time distributions (MRTDs) in an idealized smart blender. A numerical model was constructed by the superposition of flows given by an analytical blinking rotlet model and a Poiseuille velocity profile through a cylindrical pipe. The use of analytical models reduced numerical error associated with tracing pathlines of individual particles while allowing general characterization of parametric effects. Since each particle could be tracked independently, the numerical model was implemented on a parallel computer to reduce computational times and give accurate results. Results are also generally applicable to related chaotic mixers that operate in a continuous flow mode where the focus is on mixing in lieu of controllable in situ structure development.
The Effects of Nanoclay on Morphology Development in Immiscible Polymer Systems by Chaotic Mixing
Dhawal Dharaiya, Sadhan C. Jana, May 2004
Chaotic mixing has been utilized in the past to produce an array of microstructures, such as lamella, fibrils, and droplets, in the blending of two immiscible polymers. In the present work, we studied the effect of nanoclay on morphology development in chaotic mixing of polyamide-6 (PA6) with polypropylene (PP). The organically modified nanoclay was first pre-compounded with PP and the PP-clay mixture was blended with PA6. All morphological forms, e.g. lamella, fibrils, and droplets were seen as in blends without clay. However, the following distinct observations were made: (1) Nanoclay particles migrated into PA6-phase throughout the mixing period, (2) The conversion of the PP-phase into droplets was delayed, and (3) the size of the PP droplets were much smaller than those obtained in absence of clay.
Controllable Morphology Development by Chaotic Advection in PP-LDPE Blends with a Smart Blender Prototype
A.V. Dhoble, D.A. Zumbrunnen, May 2004
Most polymer blends are currently produced with machines intended to mix so the variety of obtainable blend morphologies has been constrained. The relation of structure (i.e., blend morphology) to properties at fixed compositions has as a consequence remained largely unknown. In this paper, a new smart blending technology (www.ces.clemson.edu/mmpl) that is based on chaotic advection has been implemented to assess the various types of morphologies producible in polypropylene (PP) - low density polyethylene (LDPE) blends for LDPE volume fractions of 10, 20 and 30%. Tensile properties of extruded films are related to morphologies and blend composition. Results indicate that morphologies other than droplet morphologies typically obtained with present compounding equipment can impart the best combined property enhancements.


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