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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INVESTIGATION OF PROCESSING AND RHEOLOGICAL PARAMETERS EFFECT ON FILM BLOWING PROCESS STABILITY BY USING VARIATIONAL PRINCIPLES
In this study, a numerical stability analysis of the film blowing process is performed considering non- isothermal processing conditions, non-Newtonian behavior of the polymer and physically limiting criteria (maximum tensile and/or hoop stress) in order to investigate the complex relationship between processing conditions (internal bubble pressure, heat transfer coefficient, mass flow rate, cooling air temperature, melt/die temperature), material parameters (extensional viscosity, rupture stress, Newtonian viscosity, flow activation energy, power law index) and film blowing stability.
STRENGTHENING THE MESSAGE OF SUSTAINABLE PLASTICS PACKAGING
Recyclable, recycled-content, or bio-based plastics packaging will require more than just the right technologies and materials for sustained growth. Sustainable packaging acceptance and use will also require increasing the number of informed, enthusiastic retailers and packaging consumers interested in being “greener.” In short, their positive attitudes must be turned into buying and recycling behaviors. This paper focuses on one way in which packaging producers are drawing consumers’ attention to the recycled-content, recyclability, or bio-basis of new plastic packaging. Simple messages on the packaging itself not only can clarify green claims about the packaging, but can also serve as calls for consumer action. This paper considers the effectiveness of various messages and, referencing the U.S. Federal “Green Guides,” considers the ways in which a clear, honest sustainability claim can be communicated to both informed and skeptical audiences.
SERVO-DRIVEN ULTRASONIC WELDING OF BIOCOMPOSITES
Due to increasing desire to incorporate biocomposites into numerous applications, there is high demand for welding methods that produce consistent, high-strength joints. A servo-driven ultrasonic welding system for joining bio-derived polylactic acid (PLA) and polypropylene (PP) biocomposites was evaluated. The primary objective was to evaluate material weldability and not, at this stage, to necessarily optimize the weld process. An injection-moldable grade of PLA plastic was included in this study due to its high popularity. Wheat straw-filled PP biocomposite-welded samples were compared to non-filled PP and glass-filled PP samples.
ANALYSIS OF TERNARY NON-COVALENT FILLER/MATRIX/ UV STABILIZER INTERACTIONS IN CARBON NANOFIBER/ PMMA COMPOSITES VIA TIME-RESOLVED FLUORESCENCE EMISSION SPECTROSCOPY
Non-covalent interactions between the carbon nanofibers (CNFs), oxidized carbon nanofibers (ox-CNFs), poly(methyl methacrylate) (PMMA) chains, and benzotriazole-containing UV stabilizers were analyzed using time resolved fluorescence emission spectroscopy and fluorescence lifetime imaging microscopy. The results indicated that PMMA chains form hydrogen bonds both with ox-CNF fibers and the UV stabilizer molecules. It was also determined that UV stabilizers strongly interact with CNF particles via ?-? interactions. The extent of ?-? and hydrogen bonding interactions was determined to be lower between ox-CNF particles and UV stabilizers due to less perfect graphitic structure of the former.
CORROSION INHIBITION OF FLAKY ALUMINIUM BY SOL-GEL COATINGS OF MTES AND TEOS
For the purpose of corrosion inhibition of aluminium pigments in corrosive media, encapsulated flaky aluminium powders were prepared through the procedure of sol-gel with tetraethoxysilane(TEOS) and methyltriethoxysilicane?MTES?as precursors. The influences of the precursor, ammonia, deionized water dosages, reaction temperature and time were investigated. Under the optimum condition, the efficiency of corrosion inhibition achieved 97.2% in acid media of pH 1. The analysis with Fourier transformation infrared spectroscopy(FTIR), scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS) showed that both TEOS and MTES hydrolyzed and condensed at the same time to be able to form a dense netlike sol- gel layer on the surface of aluminium pigments. The corrosion resistance of aluminum pigments encapsulated by hybrid coating film of TEOS and MTES was compared with that of aluminum pigments only by TEOS or by MTES. The hybrid coating film formed from TEOS and MTES showed more excellent corrosion resistance, due to its compactness and surface methyl groups which have excellent hydrophobic capability.
POLYMERIC HEAT DELIVERY SYSTEM
Polymers are generally known for their excellent insulative properties. The addition of carbonaceous fillers within a polymer matrix can impart electrical and thermal properties making them good conductors. The resulting composites can be used in various applications including heaters/heating elements, for which resistive metals have been the materials of choice. The advantages of using such composites include cost reduction, chemical resistance, lighter weight, and flexibility to easily design and fabricate complex three- dimensional shapes via injection molding. For this work, various conductive thermoplastic composites were investigated as heating elements utilizing the mechanisms of Joule heating. First, composites and test specimens were prepared via melt extrusion and injection molding respectively. Thereafter, electrical and thermal properties were characterized using techniques developed in house. Results from experiments indicated significant advantages in using semi-crystalline polymers as matrices due to the superior electrical properties at equivalent filler loading. It was also determined that heating rate and maximum/plateau temperature were mainly a function of specimen resistance (formulation parameter) and voltage. Additionally, it was demonstrated that it is possible to develop polymeric heaters with operating temperatures up to 200°C. Moreover, these composites have self-regulating thermal characteristics different than the positive temperature coefficient mechanisms seen in olefin-based polymeric heaters.
EXPERIMENTS WITH CONVENTIONAL AND HIGH TEMPERATURE HOT PLATE WELDING OF THERMOPLASTICS USING DISPLACEMENT AND PRESSURE CONTROL
During hot plate welding, the final forging phase can be controlled by either pressure or displacement. When using pressure control, the parts are placed under constant pressure thereby simultaneously squeezing and cooling the melt until the interface solidifies. In displacement control, the parts are pressed together until mechanical stops are reached and the weld cools further under no pressure. In this work, we studied contact hot plate welding of high HDPE and ABS using low and high temperature hot plate with both pressure and displacement control. For HDPE, the weld strength was high regardless of the hot plate temperature or control method. For ABS high temperature hot plate welding produced stronger joints for both control methods.
ENVIRONMENTAL AGING OF COATED FABRICS COMPOSITES
The purpose of this work was to perform a comparative analysis of various candidate nitrile coated fabric materials supplied by potential vendors to be used as fuel storage tanks and compare the results to the currently fielded polyurethane storage tanks. Our strategy is to utilize advanced environmental ageing methods to simulate extended weathering conditions. Our results demonstrate that the nitrile coated fabrics performed well in our evaluation. Their breaking strengths are about equal to the currently fielded urethanes and they performed comparably when subjected to environmental ageing conditions.
COMPUTER SIMULATION OF RUBBER EXTRUSION IN THE CAPILLARY DIE USING VISCOELASTIC MODELS
Rubber compounds have high viscoelastic property. The viscoelastic behaviors shown in die extrusion are an extrudate swell and circulation flow at the entrance of die. Application of viscoelastic models to a capillary extrusion has been investigated in this study. Experiment and simulation have been performed using fluidity tester and commercial CFD code, Polyflow respectively. Die swells of rubber compounds through a capillary die have been predicted using various viscoelastic models, such as PTT, Giesekus, and POMPOM models. Simulation results of die swell were compared with the experiment. Pressure drops, velocity distributions and circulation flows at the corner of reservoir have been analyzed through computer simulations.
MECHANICAL PROPERTIES OF SULFONATED BLOCK COPOLYMERS
Dynamic mechanical analysis (DMA), and FT-IR was used to examine a series of highly sulfonated poly(styrene- isobutylene-styrene) (SIBS) block copolymers. Sulfonation levels of 53%, 64% and 97% were studied. These block copolymers were subsequently neutralized with three inorganic counter-ions, Mg2+, Ca2+ and Ba2+. The substitution of inorganic counter-ions maintained the glass transition temperature of the membrane at -60°C regardless of cation exchanged and increased the modulus of the rubbery plateau indicative of a crosslinking complex formation. New relaxations were observed above Tg for the highly sulfonated counter-ion substituted samples attributed to the Tg of the functionalized styrene segments. FT-IR results show a shifting of the IR bands attributed to the sulfonate groups when counter-ions are added, indicating the formation chemical crosslinks.
RHEOLOGICAL PROPERTIES AND FOAMING BEHAVIOR OF COAGENT-MODIFIED POLYPROPYLENE
Reactive modification of linear PP by radical mediated grafting in the melt state is investigated as a means of increasing its melt strength, thus resulting in improved foam processing characteristics. A tri-functional coagent, triallyl trimesate (TAM) is used to introduce long chain branching to the linear PP homopolymer. Rheological characterization is conducted to relate the rheological properties to the modified PP chain architecture. The foaming behaviour of the linear and branched PPs is investigated using a batch foaming apparatus with N2 as a blowing agent.
NUMERICAL VERIFICATION OF RHEOLOGICAL CHARACTERIZATION OF POLYSTYRENE DURING MICROCELLULAR INJECTION MOLDING
The purpose of this study is to investigate the rheological behavior of Polystyrene melt with dissolved SCF of nitrogen during Microcellular Injection Molding process applied with Gas Counter Pressure (GCP) technology; also, rheological behavior is compared with independent theoretical simulation using moldex3D. A slit cavity is designed to measure the pressure drop of polystyrene mixed with 0.4wt% supercritical nitrogen fluid under different mould temperatures (185°C, 195°C, and 205°C), injection speeds (5, 10, and 15 mm/s) as well as counter pressures (0, 150, 300 bars). It was found that the melt viscosity is reduced by up to 30% when GCP is increased from 50 to 150 bar as compared to conventional injection molding. The simulation results of pressure history well agrees with the experiments and provide a theoretical point of view on process design.
ANTIMONY TRIOXIDE-FREE FLAME RETARDANT SYSTEMS FOR POLYMERIC MATERIALS
Flame retardants in polymers play a significant role in protecting lives and reducing damage in the event of a fire. Typically brominated flame retardants (BFR) require a synergist such as antimony trioxide (ATO) that enables lower loadings of the BFR in polymer formulations. However for compliance to certain voluntary environmental standards, it is desirable to replace ATO partially or completely in polymer formulations. This work describes the replacement of ATO in formulations containing a newly developed flame retardant, Emerald 1000 (FR1). In high impact polystyrene (HIPS), FR1 is shown to exhibit good flame retardancy when combined with a char forming polymer like polyphenylene ether (PPE). Similarly in polycarbonate (PC)/acrylonitrile butadiene styrene (ABS) systems, FR1 shows good flame retardancy, without the need for ATO synergist. More importantly FR1 does not negatively impact the mechanical properties of the system.
HIGH-SHEAR-RATE RHEOLOGY OF POLYSTYRENE MELTS
This work presents a systematic analysis on the capillary rheology of polystyrene melts under high shear rates ranging from 103 to 106 s-1. The precise Bagley correction was achieved by means of the enhanced exit pressure technique. The end pressure drop was found to predominate over the Bagley-corrected capillary pressure drop in the high shear rate range. Furthermore, the dissipation heating, pressure dependence, and compressibility effects were quantitatively evaluated. Results implied that the apparent nonlinearity of the Bagley-corrected capillary pressure drop versus apparent shear rate profile, which occurred at the shear rates of above 105 s-1, mainly resulted from the dissipation heating. In the shear rate ranges investigated, the corrected rheological behavior could be adequately described by the power law.
MONITORING OF THERMAL HOMOGENEITY IN SINGLE SCREW EXTRUSION USING INFRARED TEMPERATURE SENSORS
The ability of infrared temperature sensors to provide information relating to the thermal homogeneity and melting performance of single screw extruders has been investigated. Infrared sensors were located in the barrel of a single screw extruder close to the end of the screw and in an instrumented die adaptor. Results were compared to those obtained from a thermocouple grid sensor located at the entrance to the extruder die. Two grades of high density polyethylene were used in experiments with three extruder screw geometries at a range of screw speeds. When located in the die adaptor, the infrared sensor detected temperature fluctuations related to melting instabilities but these were smaller in magnitude than the actual fluctuations detected by the thermocouple grid sensor due to the limited penetration depth of the infrared sensor. When located in the extruder barrel the infrared sensor provided a bulk measurement of melt temperature across the depth of the screw channel in the metering section which correlated more closely with that measured using the thermocouple grid.
COMPUTER SIMULATION OF FLOW BALANCE IN THE DIE OF SLOT COATER: PART 1: LAND GEOMETRY
Coating operations such as spin coating, curtain coating, role coating, slide coating, slot coating, and etc. are dated from long time ago and still considered very important processing. Slot coating is considered very important specially for the manufacturing of liquid crystal display parts. Photo resistant is coated on the glass and is sent to next process to make TFT board. Coating quality such as uniformity of coating thickness can be divided into two categories, which are machine direction quality and transverse direction quality. Machine direction quality is related to die lip design and operation conditions whereas the transverse direction quality is related to flow uniformity inside of the die. The flow uniformity is governed by flow balance in the die. The most important design factors for the inside die geometry are manifold and land. Through this study the flow balance according to the land design has been examined by computer simulation. The parameters for land design are length and shape. Exit velocity at the outlet of die is different from land designs. The best land design has been investigated in this study.
SUPERCRITICAL FLUID DOSAGE CONTROL USING ARTIFICIAL NEURAL NETWORK (ANN) FOR MICROCELLULAR INJECTION MOLDING
Supercritical fluid (SCF) dosage is one of the most important parameters for microcellular injection molding. Highly accurate and repeatable SCF dosage is required to ensure high part quality and consistency. In this study, an artificial neural network (ANN) based SCF dosage control strategy was proposed to predict and compensate for the possible variations in the coming SCF dosing stage to achieve a more repeatable SCF dosage. The result shows that this control strategy can be successfully implemented, and that it leads to significant improvements in dosage consistency and part quality.
COMPATIBLIZED POLYPHENYLENE SULFIDE/LIQUID CRYSTAL POLYMER ALLOY FOR ELECTRICAL&ELECTRONIC APPLICATIONS
The combination of polyphenylene sulfide (PPS) and liquid crystal polymer (LCP) in polymer blend is a potential way of creating new polymer properties. However, the two polymers are incompatible, and typical physical blends do not realize synergistic performance. Herein we report a compatiblized PPS/LCP alloy. Morphology and thermal analysis confirm the improved compatibility of PPS and LCP. As a result, mechanical properties of the compatiblized PPS/LCP alloy are improved. In particular, the notched Izod impact improves by 45% and weld line strength improves by 37% compared to PPS/LCP physical blend. The surface quality as measured by surface gloss of the compatiblized alloy is also improved significantly. In addition, the compatiblized PPS/LCP alloy is halogen free according to IEC 61249-2-21 standard and meets V-0 flammability of the UL-94 standard. Such compatiblized PPS/LCP alloy is an ideal material for electronics applications such as connectors and printer parts.
ULTRA-HIGH THERMALLY TREATED LLDPE NANOCOMPOSITES: TRANSPORT PROPERTIES AND ELECTROMAGNETIC SHIELDING
The electromagnetic shielding effectiveness (EM SE) and the electrical properties of ultra-high thermally treated carbon nanotubes/nanofibers in LLDPE matrix were evaluated. EM SE displayed dependence on electrical resistivity and electrical permittivity. Nanocomposites at 60wt% nanomodifier content showed EM SE values as high as 67 dB at 1.5GHz. The primary shielding mechanism in these nanocomposites was absorption. Therefore, such nanomaterials have potential use in electromagnetic compatibility applications.
PROGRESS ON SIMULATING LONG-GLASS FIBER ORIENTATION IN COMPLEX MOLDING GEOMETRIES
The mechanical properties of fiber reinforced materials are highly dependent on fiber orientation generated within the composite during molding operations. Rheologically obtained parameters for fiber suspensions are applied to current models to predict fiber orientation in complex geometries independent of experimental considerations. This method provides an a priori pathway to determine fiber orientation based solely on rheological testing of the suspension and independent of the mold geometry. Furthermore, predictions for fiber orientation are carried out using the traditional rigid fiber Folgar-Tucker model as well as the semi-flexible Bead-Rod model which allows for the inclusion of fiber bending to be taken into account often witnessed in long-glass fiber (LGF) systems. Computations for fiber orientation are performed for center-gated disks and predictions with the two above models are compared to experimental data.
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