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Conference Proceedings

Effect of Montmorillonite on Formation of Polystyrene Foams Using Supecritical CO2
Will Strauss, Ajit Ranade, Nandika Anne D'Souza, Richard F. Reidy, Meaghan Paceley, May 2004

Polystyrene was in-situ polymerized with a range of montmorillonite layered silicate (MLS) concentrations, and subsequently compression molded into thin laminates. The laminates were foamed in a batch supercritical CO2 chamber at various temperatures and pressures from 60°- 85°C and 7.6-12MPa. The resulting foams were analyzed by scanning electron microscopy to determine effect of MLS on cellular morphology. Differential Scanning Calorimetry was used to determine the impact of nanocomposite microstructure on glass transition of the foamed polymer.

Effect of Talc Content on the Volume Expansion Behavior of Extruded PP Foams
Hani E. Naguib, Chul B. Park, PatrickC. Lee, Donglai Xu, N. Reichelt, May 2004

This paper elucidates the effects of cell density on the volume expansion behavior of polypropylene (PP) foams blown with butane in extrusion. The cell density was controlled by varying the talc content, and foam expansion was observed at a fixed blowing-agent content while varying the melt and die temperatures. As observed in our previous studies, the curve of the final expansion ratio of PP foam versus temperature showed a typical mountain shape for each talc content, indicating the two governing expansion mechanisms which are gas loss and stiffening of melt. As the talc content increased, the expansion curve skewed towards the lower temperature, which showed that the expanded foams of high talc content were more susceptible to gas loss. In order to analyze this change, the early-stage expansion behavior of extruded PP foams was investigated using a CCD camera. The expansion-profile images captured at the die exit show that the expansion rate of extruded foams was observed to be faster at a high talc content because of the reduced diffusion distance of gas molecules to the nearest stabilized cell. The higher growth rate promoted the formation of an initial hump in the expansion profile which is known to be detrimental to large expansion. In order to decrease the expansion rate and thereby to remove the initial hump, the temperature had to be further decreased, and consequently, the optimum temperature to maximize expansion decreased at a higher talc content. On the other hand, the increased cell density at a high talc content increased the number of cell layers in the cross section of the extruded foam, and thereby the gas loss was localized to the cells on the surface which acted favorable for the final expansion ratio to a certain degree.

Lightweight Performance of Load Bearing Plastic Components with an Integral Foam Structure
Norbert Müller, Gottfried W. Ehrenstein, May 2004

Employing a modified injection-molding technology, where the mold is opened a short stroke after injection of the polymer melt, it is possible to manufacture plastic parts with low overall density and an integral foam structure. For this processing approach, thermoplastic materials together with chemical foaming agents are used. The resulting plates are a real lightweight design with compact skin layers and a foamed core fraction. A significant gain in stiffness can be observed. The lightweight potential of the design was investigated using mechanical testing methods and the stiffness enhancement was modeled using several models for multi-layer arrangements.

High Temperature Polymeric Microspheres and Foams: Liquid Phase Models
Camilo I. Cano, R. Byron Pipes, Erik S. Weiser, May 2004

The present paper focuses on the understanding of processes and property changes during formation of precursor forms of polyimides for high temperature foam applications. This understanding is to be used in the development of models for the void formation in the liquid state. The relationship of these voids to the initiation and formation of microspheres from the solid phase polymer particles will be discussed. Three sources of inflation pressure will be examined: organic compounds within the chemical structure of the polymer, volatiles released in the imidization process and residual solvents. The influence of reaction kinetics and molecular weight development on diffusion transport and viscosity within the polymer in both the liquid and solid phases will be examined to describe a major source of rate dependence of these phenomena. Void topology within solid phase polymeric particles will be studied as a cause of the multiple microstructures realized in the foaming process.

Glass Filled Polycarbonate Ester-Polyetherimide Blends
Nazan Gunduz, Robert R. Gallucci, May 2004

Polymer blending is an attractive and convenient way to obtain new polymeric materials with flexible combination of desired properties. Polyetherimide-polycarbonate blends provide attractive heat, flow and impact balance with high strength and dimensional stability. These blends find various applications for small appliances, microwave trays and automobile lighting bezels.Glass fiber filled PEI/PCE blends have been recently developed to further improve the dimensional strength and stability of these blends. It was found that fiberglass used in these blends compatibilizes the resins giving good control of viscosity and easy compounding. These reinforced resins are suitable for variety of applications in the area of automotive, telecommunication and electronics.This paper will discuss the work has been done on the fiber glass reinforced PEI/PCE blends, the influence of level of glass loading on blend performance.

Injection Molding of Polyetherimide Using Water Cooled Molds
Mark A. Sanner, George F. Bixby, May 2004

Many injection molders when processing high temperature amorphous resins like Polyetherimide (PEI) use oil cooled molds to enhance the mold filling process and achieve the best mechanical properties attainable. The practice of molding with high mold temperatures is generally recommended by material suppliers in order to reduce molded-in stress, which can have a negative effect on final molded part performance. While it is still good molding practice to use oil cooled molds, there are many instances in which PEI can be molded into acceptable parts using water as the heat transfer fluid. Water cooled molds offer several advantages over oil and includes reducing environmental and personnel safety concerns in addition to lower capital cost and ease of operation.

Mold Release Agents for Polyetherimides
Mark A. Sanner, Robert R. Gallucci, May 2004

Thermoplastic resins with mold release agents are currently used as a means to improve the ejection of molded parts during the injection molding process. Their use can be found in many different grades and types of thermoplastics including amorphous and semicrystalline materials. However, as processing temperatures increase in excess of 300°C (572°F) for resins such as Polyetherimide (PEI), the choice and availability of releases agents are limited due to their volatility and inherent thermal instability. New mold release formulations have been developed for Polyetherimide for use in opaque and transparent applications. These formulations have reduced incidence of part sticking and improved overall material processability. Process improvements of cycle time reduction, increased productivity, and wider process windows have been reported in the molding of automotive reflectors and food service cookware.

Polyetherimide Films for High Temperature and Electronics Applications
J. Vervoort, J. Newhart, J.J. Scobbo, Jr., May 2004

Polyetherimide films are often used in applications requiring high temperature capability, good dimensional stability, and excellent mechanical and electrical performance. One example of such an application is flexible circuitry for airbag sensors. In order to extrude films to meet demanding electrical requirements, the films must be virtually defect free to avoid arcing and other electrical anomalies. To avoid these problems and enable, generation of defect-free films, there is a need for resins with excellent thermo-oxidative stability and processing that optimizes melting and residence time.

Branched Polyethylene Terephthalate Foaming Using HFC-134a: On-Line Process Monitoring
M.F. Champagne, R. Gendron, M.A. Huneault, May 2004

PET chain extension and branching was made through reactive extrusion. A terpolymer of ethylene, ethyl acrylate and glycidyl methacrylate selected for its ability to react with PET end-groups was extruded with PET. The effect of various processing parameters on the extent of reaction was monitored using a commercial on-line process control rheometer mounted on the twin-screw extruder.The reactively modified PET was foamed using 1,1,1,2-tetrafluoroethane (HFC-134a). On-line solubility measurements were made using an ultrasonic technique. The relationship between HFC-134a solubility and PET branching level was established. The opportunities to develop low density extruded PET foams were then identified.

Characterization of Epoxy Curing Using High Heating Rate DSC
Bryan Bilyeu, Witold Brostow, Maggie Keselman, Kevin P. Menard, May 2004

A limitation in the characterization of epoxy cure with DSC is the overlap between the glass transition and the curing exotherm. Since the glass transition is independent of rate, whereas the curing reaction is dependent, scanning rate can be used to shift the exotherm while not affecting the glass transition temperature. At 100°C/min, the two overlapping events are separated, whereas at 200°C/min, the curing doesn’t occur in the temperature range studied. The glass transition temperature can be measured without affecting the degree of cure, the exotherm can be shifted to separate it from the glass transition for accurate measurement of enthalpy and the complete glass transition can be measured.

Modification Mechanisms, Curing Kinetics and Properties of Polymethylphenyl Siloxane-Modified Epoxy Resins
Man Zhang, George C. Martin, May 2004

The mechanisms of chemical modification of diglycidyl ether of a bisphenol A (DGEBA) epoxy resin modified with a methoxyl-terminated polymethylphenyl siloxane oligomer were characterized by Fourier Transform Infrared Spectroscopy, Thin Layer Chromatography, and Epoxy Equivalent Weight measurements. The curing behavior, the thermal and mechanical properties of the modified epoxy resins cured with meta-phenylenediamine were investigated as a function of the weight concentration of siloxane modifier. The activation energy and frequency factors were dependent on the siloxane content. For modified epoxy resins, an enhancement in thermal stability and the flexural and the tensile strength were observed, and the overall toughness was increased by three to four fold. The glass transition temperature and the flexural moduli of cured samples showed a decrease with an increase in the siloxane content.

Dynamic Mechanical Analysis of UV-Curable Coatings While Curing
Robert W. Johnson, May 2004

A method has been developed for following the dynamic mechanical properties of a UV-curable coating while the sample is curing. The resulting data and plots can be used to measure the material’s cure speed. The precision is sufficiently high to allow small differences in cure speed between different formulations to be reliably estimated.The sample is contained in parallel plate stress rheometer in which the usual metal bottom plate has been replaced by a UV-transparent quartz plate, allowing UV light to illuminate the sample from below. A nitrogen atmosphere is established before every run.The instrument is set up to measure G’, G”, and phase angle vs. time at a frequency of 10 Hz, taking 72 data points per second. Two seconds after a run starts, the software puts out a signal for input to a relay that opens the UV shutterTwo arbitrary criteria for cure times are: 1) The time for G’ to reach 2X104 Pa; 2) The time for the phase angle to decrease to 45°. Typical cure times for fiber optic coatings range from 0.2 to 0.6 seconds

Thermal and Mechanical Properties of Epoxy/Monofunctional and Epoxy/Multifunctional POSS Nanocomposites
Shan Lu, George C. Martin, May 2004

The thermal and mechanical properties of diglycidyl ether of bisphenol-A (DGEBA) copolymerized with two types of polyhedral oligomeric silsesquioxane (POSS) nanophases, namely, monofunctional POSS-epoxide macromer (MoPOSS) and multifunctional POSS-epoxide macromer (MuPOSS) cured with polyoxypropylene diamine were investigated. The glass transition temperature, Tg, measured by DSC increased with an increasing weight fraction of the MoPOSS. For the MuPOSS series, the Tg of the composite containing 3.0 wt.% MuPOSS increased; however, the Tg’s of the composites containing equal to or greater than 5.0 wt.% MuPOSS decreased because of a reduced cross-linking density and a plasticization effect from the excess curing agent. The curing of the MoPOSS systems followed firstorder kinetics with lower activation energies and frequency factors. TGA experiments indicated that both types of the POSS provided enhancement in the thermal stabilities compared to the epoxy network. Fracture analysis showed that the POSS-incorporated epoxy network glasses had higher fracture toughness values than the neat epoxy resin.

A Mathematical Model for the Increase of G’ with Time during the Irradiation of UV Curable Coatings
Robert W. Johnson, May 2004

Another paper in this session describes a method for following the development of rheological properties of a UV-curable coating while it is being cured. An equation has been found that models the development of G’ as a function of time from that method. It is an empirical model, not one derived from theory, e.g. reaction kinetics. The model curve conforms to the data points on a plot, all the way from start to finish of curing. Standard non-linear curve fitting algorithms such as Marquardt-Levenberg and Quasi- Newton work satisfactorily. Since the G’ values cover 2 to 3 orders of magnitude, a weighted fit emphasizing lower G’ values gives better results than an unweighted fit. The model is useful for comparing and classifying cure behavior of coatings used for fiber optic waveguides.

Development of a New Class of Nonlinear Optical Polymers with High Electro-Optic Coefficients
Zhi Yuan Wang, Liqiu Men, Naiheng Song, Andrew M.R. Beaudin, Cara A.M. Weir, Jian Ping Gao, May 2004

Described is a facile synthesis of Z-?-(1-substituted-4- pyridinium)-?-cyano-4-styryldicyanomethanide chromophores and incorporation of these chromophores into a polyimide. Polymers containing only 8-10 wt % of a chromophore showed quite high electro-optic coefficients (e.g., r33 = 25 pm/V at 1550 nm) depending on the poling conditions and film quality. The chromophore polymers were thermally stable up to 230 °C in the absence of oxygen and light. The stability of the electro-optic coefficient at 85 °C was preliminarily investigated.

Improving the Luminescent and Electronic Properties of OLED Materials through Structural Modification
Ye Tao, Marie D’Iorio, Man ShingWong, Zhong Hui Li, May 2004

Organic light emitting diodes (OLEDs) technology has attracted increasing research efforts from both industry and academia in the past decade. One of the main advantages of using organic materials in light emitting devices is the tuneability of the materials. A good knowledge of the structure-property relationship in these materials is indispensable in order to take advantage of the tuneability. In this work, we will report our investigation of the luminescent and electronic properties of structurally modified oligo(phenylenevinylene)s (OPVs), and oligo(paraphenylene)s (OPPs). We are particularly interested in understanding the relationship of the electroluminescent (EL) and charge transport properties with the molecular structures and related thin film morphology. EL properties were characterized on multilayer organic light emitting devices fabricated using vacuum deposition, the charge transport properties were characterized by current-voltage and transient electroluminescent measurements. The molecular structure modification leads to significant change in emission colors, HOMO-LUMO levels, charge carrier mobilities, and device stability.

A Novel Characterization Method for Investigating the Morphology of Polymer Blends Including Polyolefin/Polyolefin Blends
Jeong-Min Kim, Minhee Lee, Seohwa Kim, Sung-yi Kang, May 2004

A new characterization method for investigating the morphology of polymer blends was proposed in this paper. This new technique involves cryo-microtoming, plasma etching in the presence of oxygen gas and SEM observation. In binary and ternary polymer blending systems, the SEM observation has been generally performed on the fracture surfaces treated or untreated with etching chemicals. It has known that the fractured surface does not always give clear interfaces between blending components, specifically in compatible polymer blends. For chemical etching, it is very difficult to find a proper solvent for the selective etching when the solubility parameters of the blending components are similar each other. However, the plasma etching technique proposed in this study gives us very clear contrast on the interface because of the different susceptibility of polymers to the oxygen plasma. Therefore, various ternary polymer blends having encapsulated morphology were successfully characterized. It should be noted that this technique was also applied for the morphological characterization of polyolefin/polyolefin blends including PP/HDPE, PP/LDPE, and LLDPE/LDPE blends.

Nylon 6 and Montmorillonite Layered Silicate (MLS) Nanocomposites
Ajit Ranade, Nandika Anne D'Souza, Bruce Gnade, Amit Dharia, May 2004

The properties of nanocomposites are dependent on the degree of dispersion of expandable smectites clays in the polymer matrix. The different states of dispersion are exfoliated, intercalated and immiscible systems. However we and others have demonstrated that within a single system, the exfoliated dispersion is far from homogeneous. Here we investigate the effect of dispersion of MLS in nylon 6 nanocomposite films. A 20% by weight master-batch of nylon-6 and MLS was prepared in a twin screw extruder followed by various individual MLS compositions (1-5%). Films of nylon nanocomposites were prepared by a film extrusion. A highly exfoliated dispersion in different films was investigated using x-ray diffraction. Little platelet aggregation observed by optical microscopy indicating that the platelets achieved uniform distribution even at the macroscopic scale. The glass transition and mechanical properties were related to the nucleation capabilities of MLS.

Improving Impact Properties of Polymer Clay Nanocomposites
Ajit Bhaskar, Nathan Tortorella, Kwabena A. Narh, Charles L. Beatty, May 2004

Polypropylene-clay (montmorillonite) nanocomposites were prepared by melt compounding. The impact properties were modified by reactively bonding oligomeric, end functionalized elastomer to the polymeric chains. For comparison purposes, another sample was prepared where end functionalized polyolefin elastomer was also reactively bonded to the polymeric chains of the nanocomposites. Based on stress-strain curves and impact testing we have found improvement in the impact properties of the nanocomposites containing the oligomeric elastomer, compared with that containing polyolefin elastomer, without sacrificing the tensile properties. This was supported using TEM, DSC and XRD.

Conducting Molecular Wires: Nanofibers and Nanotubes for Electronics Applications
Wayne E. Jones, Jr., Hong Dong, Verrad Nyame, Frederick Ochanda, May 2004

The preparation of well-defined nanomaterials represents an important new approach in the design of optical and electronic systems. In an effort to prepare novel thermally and electrically conducting materials, we have recently prepared extremely low dimensional conducting nanowires and fibers from conducting polymers (e.g. polyaniline, polypyrrole) using an electrostatic, non-mechanical “electrospinning” method. This method provides for the preparation of fibers as small as 3 nm in diameter. We have applied this technique to conducting fibers, and more recently fluorescent chemosensory polymers. Using template methods we have also used insulating Poly(L-lactide) (PLA) fibers with average diameter of 200-700 nm as core materials. These fibers were subsequently coated with thin 50-100 nm films of polyaniline or polypyrrole by in-situ polymer deposition methods. Upon relatively mild thermal treatment under inert atmosphere the PLA core fibers decompose leaving conducting tubes as demonstrated by SEM. The greatly enhanced surface to volume ratio of these materials and nanometer scale structure are predicted to yield enhanced physical properties compared with thin films prepared on traditional substrates.

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