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Conference Proceedings
Electrical Conductivity Changes of Silicone or Polyurethane Rubber/Carbon Black Composites during Cyclic Pressure Deformation
J. Vilcakova, A. Lengalova, P. Saha, O. Quadrat, T. Kitano, May 2002
Elastic composites consisting of a non-conductive matrix and conductive filler change their electrical properties under deformation, which enables them to be used as pressure sensors. For this purpose change in electrical conductivity of carbon black/silicone or polyurethane rubber composites during cyclic pressure deformation has been studied. The findings revealed that the character of conductivity changes depends on the filler concentration. While below the percolation threshold the conductivity decreases with the pressure deformation, above this critical filler content conductivity increases. This behaviour is explained as a result of the different space structure of conducting particles in the composite matrix. Cyclic pressure experiments showed that even a small deformation causes irreversible changes in the composite structure and, consequently, non-reproducibility of the repeated loadings.
Electrical Conductivity of a Graphite Based Composite as Affected by the Degree of Mixedness of Graphite in the Elastomeric Matrix
Dilhan M. Kalyon, Elvan Birinci, May 2002
The development of the electrical properties of composites as a function of the degree of mixedness of graphite distributed into a plasticized thermoplastic elastomer (Kraton with mineral oil plasticizer) is investigated. A wide-angle x-ray diffraction (WAXD) based quantitative phase analysis method was used to characterize the variations of the concentrations of the elastomer and the graphite particles around their mean values as a function of mixing time in an intensive batch mixer. Increasing the specific energy input during the mixing process results in a more homogeneous spatial distribution of graphite in the elastomer. The increasing specific energy input alters the rheology of the composite suggesting that significant structural changes do occur. Indeed the degree of mixedness of the graphite in the matrix is quantitatively determined to be improved, generally resulting in better coating of the individual graphite particles. This improved coating effectiveness in turn results in a decrease of the volume conductivity of the composite.
Energy Absorption and Damage Mechanisms in Rubber Modified Systems Tested in Multi-Axial Stress States
S. Ramaswamy, Alan J. Lesser, May 2002
The toughening mechanisms in three different systems namely, acrylonitrile-butadiene-styrene (ABS), methacrylate-butadiene-styrene (MBS) modified poly (vinyl chloride) (PVC) and styrene-butadiene-styrene (Kraton D) have been investigated. Samples were tested over a range of biaxial stress states followed by analysis of damage using confocal microscopy and scanning electron microscopy. In a certain range of biaxial stress states, the damage in these systems was in the form of cracks propagating perpendicular to the direction of the maximum applied tensile principal stress. The cracks appear to be arranged in more or less a periodic manner that would result in stress reduction at the crack tips. Similar patterns have also been found to occur in several other polymeric systems. Since materials themselves fashion these patterns, it is speculated that they are energetically favorable.
Enhancing Sales with Strategic Marketing Tools - Avoid Costly Errors and Sell More Products
Martin K. Pottle, May 2002
In today's lean corporate environment, businesses must focus each dollar spent on creating maximum impact and return in the marketplace. Effective allocation of funds, without costly marketing blunders, is essential to the growth of a company. This presentation will expose six of the most commonly held marketing misconceptions, and offer insight into effective marketing. Directed toward sales engineers, engineering managers, general managers and sales and marketing personnel, smart strategic marketing strategies and tactics will be discussed to give you and your company a competitive advantage.
Equations of the State of Polymer Solids and Melts
Agnieszka Habel, Gonzalo Martinez, Witold Brostow, May 2002
Pressure-volume-temperature (PVT) relationships in polymer solids are used in prediction of long-term performance from short-term tests. We use a technique such that the sample is under hydrostatic mercury pressure, so that solid and molten states are studied in one experiment (isothermal varying P stepwise or isobaric varying T stepwise). The results are represented by the Hartmann equation of state in terms of its characteristic parameters T*, P* and v*. The last one can be used to calculate the free volume by a simple subtraction. We shall try to connect the Hartmann parameters of selected polymers not only to mechanical but also to tribological properties.
Establishing a Foaming Agent Material to Aid in the Development in a New Expandable Cast
Amanda R. Lecker, John M. Avolio, May 2002
There is a need for a size compensating bone cast. When an injury occurs, and a bone is broken, the area around the injury swells. A cast is applied to the arm to prohibit movement. Over time, as swelling decreases, another cast must be sculpted to the reduced size of the arm. Through research of material properties and characteristics, a foaming material has been found that will aid in creating a one-time application cast. Some advantages of this material are: flexibility, expandability, and the ability to create pressure points, however, cost efficiency, safety, and ability to hold a constant pressure must be determined. This research charts the development of such a product.
Establishment of Valve Gate System for Sequential Injection Molding
Shia-Chung Chen, Ming-Shiu Chung, Hsin-Shu Peng, Lei-Ti Huang, May 2002
Sequential injection molding using valve-gate controlled hot runner system has attracted attentions for industrial applications in recent years. Due to the complication in operation mechanisms, commercial valve gate usually delays for about 0.3 to 0.5 seconds once the valve-opening command is given. This signal to operation delay is acceptable for conventional injection molding of large parts. However, it becomes critical for 3C thin-wall molding application where the required filling time is short. In this study, a gas-driven valve gate control system was established. Valve-gate opening monitoring system using both CCD camera and cavity pressure transducers was also constructed. All design parameters including gas-valve response characteristics, tolerance between inner piston and cylinder, gas pressure, melt temperature, etc., that would affect valve-gate opening were investigated. The delay time for vale-gate shaft movement in a non-melt environment can be reduced to about 50 mini-seconds whereas it increases to about 80 mini-seconds in a melt-filled environment.
Ethylene Polymerization with Cp2ZrCl2 Supported Catalyst
Rodrigo A. Silva, Carla C. Pombo, Anunciata Conte, Maria de Fátima V. Marques, May 2002
In this work metallocene polyethylene was obtained through catalysts comprising of Cp2ZrCl2 supported on silica/methylaluminoxane (MAO) prepared with different methods. The metallocene complex was directly immobilized on the support surface or on the support pretreated with MAO. The results showed that, at the supported catalyst preparation conditions employed in this work, the pretreatment with MAO did not enhance the activity for ethylene polymerization. Moreover the average molecular weight of the polyethylene obtained with the supported catalysts were higher than those obtained with the homogeneous precursor. Morphological control of polymer particle produced with the supported systems was also observed.
Ethylene-Propylene Copolymers Synthetized by Cp2ZrCl2/MAO Homogeneous Catalyst System
Anunciata Conte, Maria de Fátima V. Marques, May 2002
Biscyclopentadienyl zirconium dichloride and methylaluminoxane (MAO) complex catalytic solution was used in ethylene-propylene (E-P) copolymerization. Reaction temperature and time were varied in order to find the relationship among the polymerization activities, average molecular weight (Mw), polydispersity (MWD) and thermal behavior of the copolymers. The parameters evaluated influenced on the catalytic performance in such a way that E-P copolymers with different polydispersities are obtained just by changing the concentration of the comonomers dissolved in the reaction medium. Also, it was observed that, in the range studied, the increase of the reaction temperature contributed to the decrease in the catalytic activity.
An Evaluation of Heat Management in Injection Mould Tools
P.S. Allan, B.A. McCalla, Y. Mubarak, D. Mulligan, May 2002
The control and management of heat in the mould tool is vital for obtaining the optimum production processing conditions in injection moulding. Work at the Wolfson Centre, Brunel University is evaluating the conventional mould cooling methods and also a technique called Pulse Cooling Technology". A special instrumented mould tool was designed for the project and this will be described in the text. The tool has a number of features that represent some common moulding features and it also has pieces that can be subjected to standard mechanical testing procedures. Data from the moulding runs will be compared with high-pressure thermal conductivity and pVT measurements. Finally a comparison will be made between the two mould cooling methods."
Evaluation of Poly (ester-ether) Block Copolymers for Use in Automotive Fluid Handling Applications
F. Gribben, G.M. McNally, W.R. Murphy, T. McNally, May 2002
Block copolymers based on Poly (ester-ether) block structure were in part tested to SAE (Society of Automotive Engineers) J2027 as to their suitability for use in automotive fluid handling applications. Six block copolymers of varying microstructure (that is hard-soft segment ratio) were injection moulded into ASTM test specimens and immersed in five standard automotive test fluids; Aggressive Water, Fuel C, Transmission Oil, Ethylene Glycol, and Zinc Chloride solution. Deterioration in tensile strength, tensile and flexural modulus of up to 15% for the block copolymers was observed after immersion in all test fluids except Fuel C where the reduction in mechanical properties was as high as 50% when compared to the neat dry polymers. Similar but less dramatic behaviour was also seen for the elongation at break measurements. The loss in impact strength on immersion in the test fluids was small, the greatest loss was seen for the softer grades of block copolymer. The degradation of mechanical properties is correlated with the ratios of hard to soft segments in the block copolymers studied.
Evaluation of Slip Coat Materials Co-Extruded on TPVs for Automotive Weatherseal
Reza Sadeghi, Hua Cai, Chris La Tulippe, Ryszard Brzoskowski, Edwin Currie, May 2002
The sliding friction of TPV strips co-extruded with a thin layer of slip coat material was measured at different temperatures. These strips were used to predict the performance of the slip coatings in automotive weatherstrip applications. The static and kinetic coefficients of frictions were the parameters of interest, and their variation with temperature and composition. Abrasion resistance and some other physical properties were also tested. Five slip coat materials available from different suppliers were evaluated. Slip coat materials from Tokiwa and DSM gave the best balance of coefficient of friction, abrasion resistance and stiffness.
Evaluation of the Impact and Tensile Properties of Virgin and Reground Delrin 500 Exposed to Nitric Acid
Rhonda M. Rush, May 2002
Izod and tensile testing has been used as a way to evaluate toughness in crystalline thermoplastics like Delrin®. As with many other ways to evaluate polymer properties, reproducibility is sensitive to sample handling, technique, and mechanical factors, as well as the variation in the polymer samples. The Delrin® 500 specimens were evaluated as-molded and then after various treatments. The treatments included exposure to varying nitric acid concentrations through smears on the samples or through complete sample submersion in acid. Reground sample blends were subjected to nitric acid smears while strained. These specimens were held under a 0.5% constant strain with nitric acid exposure for limited time. The Property Retention Index (PRI) format was used to compare the as-molded results to the after treatment results. The PRI was 0.70 for weight loss after submersion in 4.25% nitric acid after 312 hours of exposure. The PRI for the Izod impact was reduced to 0.21 in 4.25% nitric acid after 312 hours of exposure. The PRI never fell below 0.97 for the tensile specimens molded out of regrind. The observed trend in the tensile value is not a simple linear decrease with increasing regrind weight percent.
Evaluation of the Tensile Properties of PET before and after Chemical Exposure
Rhonda M. Rush, May 2002
The polyethylene terephthalate (PET) specimens were evaluated as molded and after various treatments. The PET polymers are known to undergo hydrolysis and thought to be sensitive to exposure to acid. The molded specimens were exposed to various chemicals including hydrocarbons, oils and greases and solutions of nitric acid. Chemicals were selected because of an opportunity for them to contact PET parts during assembly or as used in our applications. The molded samples were subjected to exposure for different periods. Exposure effects were monitored using the tensile strength at break data. The comparison of tensile strengths at break was done by using the Property Retention Index (PRI) per ASTM D 5870-95. Materials included: black DuPont™ Rynite® SST 35, black and grey DuPont™ Rynite® 545, and Ticona Celstran® PET GF20-02.
Evaluationof Melting Performance of a Co-Rotating Twin-Screw Extruder
P.H.M. Elemans, P. Bleiman, J. Blanchard, May 2002
A method is proposed to evaluate the melting performance of a corotating twin-screw extruder. The method involves model experiments whereby the polymer pellets (coated with blue pigment powder) are extruded using a screw configuration that only contains the functional zone (melting zone, kneading section) placed at the down-stream end of the screw. The polymer can flow out almost unrestricted through a large die opening. The extrudate contains a mixture of unmelted pellets in a colored melt: as soon as the polymer starts to melt, it turns blue; the polymer pellets that do not melt remain opaque. The extrudate is chopped off into samples that are cooled down and cut into thin slices, from which the unmelted fraction of polymer can be determined using image analysis. The data serve as a basis for the evaluation of the melting performance of a particular screw configuration.
The Evolution of Direct Extrusion Using High Speed Twin Screw Extruders
Charlie Martin, May 2002
Historically, 95%+ of high speed twin screw extruders have been used to perform compounding, devolatilization and reactive extrusion operations with the end product being pellets, where dimensional stability is secondary to the mass transfer operations that occur in the twin screw extruder. Although high speed twin screw extruders have been used for many years to extrude products such as sheet, film, profile or fibers, it is only in the past 5 to 10 years that there has been a concerted development effort to perform direct extrusion from this device. The initial applications that utilized twin screw technology for direct extrusion, versus purchasing a pre-compounded material from a toll compounder for processing on a single screw extruder, were mandated, in desperation, for formulations that were adversely affected by the second heat and shear history inherent with the single screw extrusion step. Once the technical viability of direct extrusion was demonstrated, it became readily apparent to the marketplace that substantial cost savings were also possible using this technology. Additional benefits include the ability to adjust formulations in-line to accelerate development efforts, and to maintain a proprietary in-house manufacturing process. Some of the materials that have benefitted from direct extrusion include, but are not limited to, filled olefins, TPE/TPO/TPV’s, polyesters, PVB, woodfiber composites, adhesives, foamed polymers, nylons and degradable plastics.
Exfoliation of Polypropylene/Clay Nanocomposites under Electric Field
Kyung Hyun Ahn, Do Hoon Kim, Jun Uk Park, Jungsook Hong, Seung Jong Lee, May 2002
Polypropylene (PP) is known to form an exfoliated structure only when maleic anhydride functionalized polypropylene (MAPP) is added together. This can be easily achieved by melt processing, however, MAPP costs a lot as to prevent its commercial production.In this talk, we will present a novel approach to make exfoliated PP/clay nanocomposites without adding MAPP. PP/clay systems under large electric field do show the exfoliated structure, which is evidenced by rheometer and XRD. As applying electric field is a physical process, similar effect can be expected in other polymer systems that do not show exfoliated structure in a normal condition.
Expandable Foam from Amorphous Polyester Resin
Chung P. Park, Gerald A. Garcia, Roby G. Watson, May 2002
A resilient foam that is both expandable and moldable was prepared from an amorphous polyester resin using a mixed blowing agent of a high-solubility compound and a low-permeability compound. The high-solubility compound permits a high degree of expansion, while the low-permeability compound renders secondary expandability. The polyester foam remedies the deficiencies of existing bead products. Polystyrene beads retain blowing agents but lack resilience. Polyolefin beads are resilient but do not retain blowing agent. The polyester foam board has a low thermal conductivity as well as excellent dynamic cushioning.
Experimental and Numerical Analysis of the Flow Imbalance in a Runner System
Askwini Kumar, Aleksandra Egelja, Eric W. Grald, John P. Beaumont, May 2002
The flow of molten polymer in a multi-cavity injection mold is a complex fluid dynamics problem involving temperature- and shear-dependent viscosity and viscous heating. Recent work has shown that cavities are not filled evenly, even in a geometrically balanced runner. We investigated this phenomenon for two polymers (Nylon 6/6 and Acrylic) using the computational fluid dynamics (CFD) program FIDAP (Fluent Inc., Lebanon, NH), and compared the results with experimental measurements in a test mold. The results from the CFD model successfully capture the flow imbalance in the runner system for these polymers. The validated flow model can thus be used as a predictive tool to quickly evaluate the new runner system designs.
Experimental Evaluation of Composite-Concrete Interface Properties Using Sandwich Specimen
Katayoun Soulati, Raymond Gauvin, May 2002
The experimental test results on the composite strengthened reinforced concrete beams showed that the failure of composite-concrete interface can originate from an existing concrete tensile crack at the interface. Due to the difference in the properties of the individual materials and due to practical conditions of loading, cracking of the composite-concrete interface involves mixed-mode of fracture effects. Fracture mechanics concept was used to design special types of sandwich specimen, in which a thin layer of composite is sandwiched between two parts of concrete. It is shown that the interface toughness as well as interface failure mode depend on composite type and combination of loading conditions.


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