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
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.
A Study on Processing and Characterization of Short Glass Fiber Reinforced ABS/Nylon 6 Blends
Guralp Ozkoc, Goknur Bayram, Erdal Bayramli, May 2004
The properties of short glass fiber reinforced poly(acrylonitrile-butadiene-styrene)/Nylon 6 (ABS/PA6) blends were studied using the interfacial adhesion approach. Work of adhesion and interlaminar shear strength values were calculated from experimentally determined interfacial tensions and short beam flexural tests. APS was selected as the coupling agent for the glass fibers because of its compatibility with PA6. Increasing wt% of the PA6 in the short glass fiber reinforced blend increased the tensile strength and tensile modulus.
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.
Synthesis of Polyamide-Polyesters Base Random-Block Terpolymers in a Twin Screw Extruder via Reactive Extrusion: Process and Properties
In Kim, James L. White, May 2004
The synthesis of polyamide-polyester based random block copolymers were carried out in a modular co-rotating twin screw extruder via reactive extrusion process. These random block terpolymers have not been previously polymerized in a twin-screw extruder and these copolymers are very limited in open literatures. We used ?-lauryllactam , ?-caprolactam, and ?-caprolactone as monomers for synthesis of copolymers in a twin screw extruder. We also used sodium hydride as an initiator and N-acetylcaprolactam as a coinitiator. Simultaneously two lactams with initiator systems to make random copolymer and subsequently added the lactone without initiator to form a random block copolymers. All formation of random-block copolymers were studied in a twin-screw extruder as a chemical reactor. The thermal, mechanical, rheological, and structural properties of new synthesized random block copolymers were investigated and compared with homopolymers and Pebax® (Atofina) which consist of polyamide12- PTMEG (polytetramethyleneglycol)-polyamide12 block copolymer. It has the properties of a thermoplastic eslastomer (TPE).
Synthesis of Thermoplastic Polyurethanes by Chaotic Mixing
Chang Do Jung, Sadhan C. Jana, May 2004
The self-similar lamellar structures produced by mixing of aromatic or aliphatic diisocyanates, polyol, and butanediol chain extenders were utilized in this study in carrying out rapid conversion of isocyanate groups in the formation of thermoplastic polyurethanes. Chaotic mixing helped produce TPUs with narrow molecular weight distribution in the same system when the time scale of reactions was shortened by the use of tin catalyst and matched with the time scale of mixing. In addition, chaotic mixing distributed the exothermic heat of reaction homogeneously and, thus, helped minimize the extent of side reactions.
Analysis of the Effects of Flow Reorientation in Chaotic Mixing Flows on Coalescence in Blends of Polypropylene and Polystyrene
Jairo E. Perilla, Sadhan C. Jana, May 2004
A phenomenological model was developed to analyze the effects of flow reorientation on collision between droplets and drainage of fluids between colliding droplets in shear flows encountered in chaotic mixing devices. It was found that flow reorientation affects the possibilities of collision between the droplets depending on the local shear rate, reorientation frequency, and reorientation angle. It was found that the collision frequency is reduced due to time-periodic reorientation, with respect to unidirectional shear flows. The time-periodicity of chaotic flows also affects the drainage step, e.g., by increasing or decreasing the drainage rate depending on the local shear rate at the time of the collision. Experiments on coalescence using a blend of polypropylene and polystyrene carried out in a chaotic mixer consisting of a two-roll mill showed that the rate of coalescence reduced significantly. These results are of remarkable importance in establishing that chaotic mixing not only expedites the formation of fluid morphology in blends, it also reduces the rate of coalescence.
Invesigations of Linear and Non-Linear Stress Optical Regimes during Uniaxial and Simultaneous Biaxial Stretching of Poly Lactic Acid Films by Real Time True Stress-Strain-Birefringence Technique
Xuesong Ou, M. Cakmak, May 2004
Polylactic acid(PLA) films are stretched in different modes at different rates. Development of birefringence and true stress of the film during stretching are measured on-line. Effect of stretching rate and modes on stress-optical behavior at different stage of stretching and microstructures formed in each stage were studied. The uniaxially constraint width stretched samples exhibit multistage linear and nonlinear stress optical behavior. The first regime I is a linear regime exhibiting a rate and mode independent stress-optical constant which is found to be 2.5GPa-1. If low rates of stretching are employed, a second stage appears with steeper positive slope associated with stress-induced crystallization before the final stage with a negative deviation in stress-optical co-efficient. If faster stretching rates are used, the first linear stage expands to higher stress and birefringence levels and the stress-optical behavior reach the final regime III with a negative deviation without showing the regime II. A one-dimensional mesophase ( nematic structure) can be observed in samples showing negative deviation in stress-optical behavior under high stretching rates. In simultaneous biaxial stretching mode, regime I and regime III are also clearly observable.
Tensile Testing of Microtomed Sections from Molded Parts
Rachel M. Thurston, John D. Clay, May 2004
This paper describes a method to accurately measure the tensile properties of microtomed sections from molded parts. This technique has great utility in determining physical property changes from skin to core for a molded part. It can also be used to assess potential process-induced degradation. Microtomed sections are too thin for contact extensometer use. In this study, accurate modulus and strain measurements are obtained with the use of a non-contact video extensometer. This paper details the test methodology to accurately measure the tensile properties of microtomed sections from molded parts. It also compares tensile test results from microtomed sections to bulk sample results.
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