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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Materials and Processing Methods Used in the Production of Polymer Composite Bipolar Plates for Fuel Cells
A method of producing bipolar plates with high electrical conductivity, adequate mechanical properties, and the ability for rapid formation of channels into the surfaces is described. Polyphenylene Sulfide (PPS) based wet-lay composite plates have in-plane conductivities of 200-300 S/cm, tensile strength of 57 MPa, and a flexural strength of 96 MPa. These values exceed industrial as well as Dept. of Energy targets or requirements and have never been reached before for composite bipolar plates. The use of wet-lay material also makes it possible to choose different components including polymer, graphite particles, and reinforcement for the core and outer layers of the plate to optimize the properties and/or reduce the cost of the plate. Using polyvinylidene fluoride (PVDF) doped with graphite as an outer skin layer has potential to reduce the processing time for generation of the channels and reduce manufacturing cost.
Structure to Property Relationships in Polycarbonate/Polydimethylsiloxane Copolymers
Block copolymers based on polycarbonate (PC) and polydimethylsiloxane (PDMS) have been known for over 40 years. These materials have achieved considerable commercial success due to a favorable combination of low temperature impact, melt processibility, weathering resistance and unique surface properties. Most commercial products are opaque due to scattering by the PDMS domains dispersed in the PC matrix. By controlling synthesis conditions, optically opaque or transparent materials may result from the same combination of base monomers and both types of materials have been prepared and characterized. Lower PDMS block lengths lead to higher levels of light transmission. Opaque materials typically have siloxane domains in the 0.1 to 10 um region while low haze products can be achieved when domains are less than 20 nm. Small siloxane domain copolymers can exhibit considerable mixing of PC into the PDMS blocks. This likely alters the effective refractive index of the PDMS phase and contributes to the low haze measured in these copolymers.
Response Surface Modeling of Formaldehyde-Free Wood Composites
A response surface model using a Box-Behnken design was constructed to statistically model the material compositions-processing conditions-mechanical property relationships of formaldehyde-free wood composite panels. Three levels of binding agent content, pressing time and press temperature were studied and regression models were developed to describe the statistical effects of the formulation and processing conditions on the mechanical properties of the panels. Linear models best fit both the flexural strength (MOR) and internal bond (IB) strength of the panels. Increasing any of the manufacturing variables resulted in greater MOR and IB strength. Flexural stiffness (MOE) was best described by a quadratic regression model. Increased MOE could be obtained through higher pressing times, binding agent concentrations and/or pressing temperatures. However, binding agent concentration had less effect on increasing the MOE at higher pressing temperatures.
Bio-Based Polyurethane Nanocomposites
Polyols derived from soybean oil are new polyurethane raw materials derived from the renewable resources, and with isocyanates they produce polyurethanes that can compete in many aspects with ones derived from the petrochemical polyols. Combined with polyisocyanurates, they produce materials of good thermal, oxidative and weather stability.The main objective of this research is to synthesize mechanically reinforced polyurethanes, and study the influence of the concentration of nanoparticles on the properties of the new material. Two different soybean oil based polyols, SOY169 and SOY201 were selected to synthesize the polyurethane nanocomposites using a diisocyanate (pure MDI) as a curing agent. The clay used at different concentrations (0%, 1%, 3%, and 5%) in the synthesis of the nanocomposite polyurethanes was organo modified Montmorillonite clay, Cloisite®10A. Methanol was chosen as solvent media in preparing the samples.Several methods were used to analyze the samples like, mechanical tests – Tensile strength, Flexural modulus, and Notched Izod Impact strength; Thermal analysis – Differential Scanning Calorimetry (DSC), Thermomechanical Analysis (TMA), and Thermogravimetric Analysis (TGA); Structural analysis – Atomic force microscopy (AFM), Fourier Transform Infrared spectra (FTIR).
Modification and Scale-Up of the New Miniature Mixer-APAM
Our previous papers show that the Alberta Polymer Asymmetric Minimixer (APAM, 2ml, see Figure 1) is very effective mixing equipment for blending polymers and nanocomposites in the small scale. There are different capacity requirement for different applications, therefore, more flexible designs of the APAM are needed. For example, to have enough material for mechanical property testing, 10ml or more may be required. The simplest way to have a larger capacity is to increase the radius of the outer cup, which will increase the minimum clearance as well. Another way is to scale up the entire mixer. These changes will definitely affect the flow and thermal fields. In this paper, Polyflow 3.10 (Fluent Inc.) is used to model the transient non-isothermal process of polystyrene in these modified mixers. Simulation results show that it takes longer time for the thermal field to develop with increasing size of the cup and the mixer. The flow fields inside these modified mixers are characterized by radial and axial veloc ity profiles. The shear rate and shear stress change due to the modification. The transient temperature value at a point increases, and the steady state temperature distribution shows the effect of viscous dissipation.
Performance of Susceptor Materials in High Frequency Magnetic Fields
Joining of thermoplastics by electromagnetic implant welding is a mature process, yet little information is found in the literature to describe the relationship between the properties of magnetic susceptor particles, the plastic matrix materials in which they are dispersed, and their interaction with high frequency electromagnetic fields.Magnetic implant welding uses susceptors that couple, due to ferromagnetic hysteresis, with high frequency electromagnetic radiation to generate controllable heat in the plastic. The relationship of coupling distance, power level, and frequency to the heating response of susceptors is studied.Conclusions are presented, based on the results of statistically designed experiments, that suggest optimal conditions for effective welding processes.
Optimization of Process Parameters of an Injection Moulded Gear Using Taguchi Methodology
This paper suggests a systematic approach to reduce defects in injection moulded components. The component taken for analysis was an injection molded gear made of Stanyl (Nylon 4, 6)-15% Carbon Filled, used in an automobile. The analysis applies Taguchi Methodology to investigate the effects of process conditions on the shrinkage and warpage characteristics of the product made from a two cavity injection mould. The effect of seven process parameters on the Shrinkage and Warpage of the component were analyzed. An L18 standard orthogonal array (seven parameters with three levels) was chosen. The samples selected at random from each experiment were measured for warpage and shrinkage. The data thus obtained were analyzed with quality control tools like ANOVA (Analysis of Variance) and Factor Plots. Based on the results from ANOVA, the parameters which have significant effect on the quality of the product were identified. The factor plots gave information regarding the optimum levels of parameters to be maintained . The optimum levels of the parameters were used for conducting confirmatory experiments, which gave products with shrinkage and warpage within acceptable limits.
Enhanced Anhydride Coupling Agents for Wood Polymer Composites
In this study, we report on next generation coupling agents based on high molecular weight, random copolymers of ethylene and anhydride functional monomers that have been specifically designed for wood-polymer applications. A standard high-pressure free radical synthesis technique was used to create a high molecular weight ethylene copolymer with a very high level of reactive functionality (greater than 3 weight percent anhydride). This anhydride-functional- ethylene copolymer has been shown to improve the flexural strength and decrease the water absorption of wood-polymer composites when incorporated at loadings as low as 0.5 weight percent in the final part.
Ultrasound Aided Extrusion Process for Preparation of Polypropylene-Clay Nanocomposites
Two methods for the fabrication of PP/clay nanocomposites using a continuous ultrasound assisted process are compared. In the first approach a two stage process was implemented. The nanocomposites were prepared using a co-rotating twin screw extruder followed by a single screw extruder equipped with an ultrasonic die attachment. In the second method a single stage process was used. The nanocomposites were compounded using a single screw extruder with mixing elements and an ultrasonic die attachment. Two regimes of feeding were realized, namely, starved and flood feeding. The gap size in the ultrasonic treatment zone was varied. Die pressure and power consumption were measured. Similarities and differences of nanocomposites obtained by these two methods are discussed based on their rheological, mechanical properties, and structural characteristics.
Shape Memory Polymer Orthodontics
Shape memory polymers (SMPs) have been intensively investigated for multiple medical applications in recent years. In our lab, we have developed several SMPs with tailored transition temperatures, excellent shape fixing and shape recovery, and variable stiffness, with values ranging from > 1 GPa (hard) to < 1 MPa (soft). Recently, we have endeavored to apply two particular SMPs, a castable shape memory polymer (CSMP) and a shape memory rubber, to orthodontic appliances. We have measured the mechanical properties, water absorption, stain resistance, and stress stability and compared the results with currently used orthodontic polymers, revealing significant advantages. Prototype appliances are presently under evaluation. In this presentation, we will introduce the progress we have achieved and propose how SMPs can offer unique functionality to orthodontic appliances.
Development of a High-Pressure Slit Rheometer
In thin - wall injection molding processes, parts thinner than 1 mm are produced using high injection pressures and velocities. Modeling has not been successful in predicting process physics during molding. We have built a high pressure slit rheometer that enables us to measure the rheological properties of polymers at elevated pressures and temperatures. Measurements were done with polystyrene, and the results showed the effect of pressure and the effect of viscous heating on the viscosity. Results from such measurements will allow us to introduce viscosity pressure effects during mold filling of Thin-Wall Injection Molding.
Viscosity of Soy Protein Plastics as Determined by Screw Extrusion Through a Capillary Die
Processing of soy protein plastics using conventional methods (injection molding, extrusion) has met with some success. At this point the lack of data on fundamental flow behavior of soy protein plastics limits future advances. Previous work by Japanese researchers showed the effects of moisture content, temperature, and strain history on the viscosity of soy protein isolate at elevated temperatures. However, no studies to date have explored the viscosity of processable formulations that contain soy protein along with the necessary additives (e.g., glycerol and corn starch). Viscosities of several soy protein formulations are evaluated using screw-extrusion through a capillary die. The viscosities are found to conform to the power-law model, but are substantially higher than those of commodity petroleum-based resins.
Using Multilayer Films to Fabricate Reactive, Submicron Patterned Surfaces
Highly layered structures are important to microfabrication and nanofabrication technologies as tools for understanding and controlling surface structures through manipulation of chemical and physical interactions. A new approach is introduced to create submicron patterned surfaces with surface chemical functionality using multilayer polymer films. Alternating layer structures of two immiscible polymers, linear low density polyethylene (LLDPE) and ethylene-co-acrylic acid copolymer (EAA), were formed by co-extrusion with subsequent compression molding. Thin sections of the multilayer molded sheets were prepared by microtoming and the highly layered microstructure was verified by SEM, TEM, and polarized optical microscopy. Regionally confined chemical functionality was confirmed by grafting a fluorescent label selectively to the alternating layers of EAA.
Surface Modification of Ethylene-Acrylic Acid Copolymer (EAA) Films Using Various Linker Layers
Two reaction systems were developed to covalently graft polyethylene glycol (PEG) chains on ethylene acrylic acid copolymer (EAA) surfaces without significant penetration of reactants. The scheme involved surface grafting of link molecular l-lysine or link layer poly(glycidyl methacrylate) (PGMA), followed by covalent bonding of PEG chains. For the PGMA method, AFM images showed that large, isolated surface domains on the micron scale existed on the EAA surface because of phase separation during dip coating and drying of the PGMA. For the l-lysine method, NHS and EDC were used to activate the carboxylic acid groups of the EAA. After activation, l-lysine was grafted onto the EAA surface, followed by PEG grafting. Each step of the surface modification was followed by ATR-FTIR spectroscopy, XPS, and AFM.
Birefringence Distribution in Gas Assisted Tubular Injection Moldings
Flame Retardancy and Rheological Behaviour of Acrylonitrile-Butadiene-Styrene Copolymer (ABS) Composites Filled with Magnesium Hydroxide Sulfate Hydrate(MHSH) Whiskers
Flame-retardant ABS composites were prepared using MHSH whisker as a flame retardant. The morphology observation indicates that the addition of zinc stearate could lead to the uniform dispersion of the whisker and improvement of flame retardancy. With increasing whisker content, flame retardancy properties of the composites is improved, the viscosity and storage moduli of the composites increase at low frequency zone. The presence of zinc stearate leads to slight increases in the storage moduli.
Effects of Molding Conditions on the Conductivity Properties of Injection Molded Bipolar Plate Used for Fuel Cell
Fuel cell is an important energy source for the 21st century. Among fuel cell components, plastics have been chosen as a candidate material for bipolar plates which needs to fulfill the conductivity requirement. In this study, polymer polyphenylene sulfide (PPS) containing 50% carbon fiber was in injection molded and its conductivity was measured by the four point probe. The carbon fiber dispersion and orientation were examined by scanning electron microscopy (SEM). It was found that at high mold temperature, high melt temperature and lower injection rate, the carbon fiber distributed more uniformly leading to higher conductivity. High holding pressure closely tangled the carbon fiber, also increases conductivity. 3D-CAE simulations were also conducted to verify fiber dispersion and orientation under different molding parameters and show reasonable consistency.
Analysis and Experimantal Verification on the Optical Performance of Injection Molded Light Guide Plates with Micro-Feature Design
This study investigates the optical performance of light guide plates with micro-feature characteristics. The light guide plates are made of injection mold PMMA. Both one- and two-sided micro-feature designed patterns were conducted. The results reveal that the micro-feature with smaller interval of dot array would lead to better luminance. It is also found that the uniformity in luminance distribution can be greatly improved if proper geometry of micro-structure dot is arranged. In addition, the luminance can be improved as the elevation of the temperatures of melt and mold, filling speed and packing pressure. The luminance may achieve highest value under proper packing pressure.
Efficiencies of Various Mold Surface Temperature Controls and Their Effects on the Qualities of Injection Molded Parts
Various mold surface temperature control methods including mold surface coating, induction heating, infrared heating and suitable combinations of surface coating with different surface heating are utilized to achieve a rapid mold surface temperature controls. Surface coating with thermally insulated materials can introduce heat hysteresis effect and the plastics melt-mold surface contact temperature may sustain high temperature for about one second leading to the elimination of weld line marks for ABS parts. For rapid mold surface heating with temperature rise ranging from between 50° and 100° or higher, induction heating seems to be the most efficient method (within 2 to 4 seconds). Infrared heating combined with surface coating although can achieve the same effect as compared with that of induction heating, however; it takes longer time (about 15 seconds). Both heating methods can definitely eliminate weld line marks, reduce residual stress and enhance the associated weld line strengths. For molding micro-featured parts, induction heating also exhibits a significant assist in melt flow within micro channels and improves the molding accuracy in the micro-features.
Prediction of the Weld-Line-Induced Strength Reduction for Injection-Molded Plastic Parts
Weld-lines look like cracks on the appearance of plastic parts. Sometimes these visible features are not accepted esthetically in many applications. However, most importantly, the local mechanical strength in the weld-line area could be significantly weaker. It could be one of the most significant problems for structural applications due to the potential failure in the weld-line areas. Hence, how to prevent the weld-lines and guarantee the good quality are the major concerns to part/mold designers. In this paper, a numerical approach is proposed to predict weld-lines and weakened mechanical strengths. Furthermore, through the data link between mold-filling simulation and structure analysis, the effects of weld-lines towards part structure are predictable.
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