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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EFFECT OF GATE AND RUNNER DESIGN ON ELECTRICAL PROPERTIES OF MULTI-WALLED CARBON NANOTUBE / POLYSTYRENE NANOCOMPOSITES
In this study, we investigate injection molding of 5 wt% CNT with polystyrene polymer matrix into a mold equipped with three different cavities. Electrical conductivity testing was applied in the thickness and in-flow directions of the molded samples. The injection molding conditions of mold temperature, melt temperature, injection/holding pressure and injection velocity were varied to investigate the effect of process parameters on the electrical conductivity of each sample. Among the process parameters, the injection velocity and melt temperature showed the largest influence on alignment and, consequently, the electrical conductivity of the samples.
KINK RESISTANT TUBING SELECTION FOR MEDICAL DEVICE APPLICATIONS
There is a need for angioplasty related products to achieve lower profiles. This means that devices have the opportunity to reach more distal lesions and have potential uses in neural catheterisation. Lower profiles can be achieved by reducing the wall thickness, and thus, reducing the outer diameter of the tubing. However, this, on its own, can have major consequences on the mechanical properties and performance of the device. One of these consequences is the kinking of tubing. This paper identifies a test method that can accurately reflect the kink properties of any thermoplastic tubing using Dynamic Mechanical Testing Analysis (DMTA)
EFFECTS OF TEMPERATURE AND PRESSURE ON VISCOSITY DURING INJECTION MOLDING
The pressure effect on viscosity is often neglected during injection molding. However, the pressure shift factor is in the same order of magnitude as the temperature shift factor. In the presented work, a new dimensionless number R is presented which relates the temperature to the pressure effect on viscosity. By calculating R for the temperature and pressure profile, it can be seen that the influence of pressure is always high at the entrance of the cavity but can be neglected at high melt temperatures. It is shown that the opposing effect of viscous dissipation on viscosity has to be considered.
ANALYSIS OF DAMAGE PROGRESSION IN TEXTILE REINFORCED COMPOSITE IN TENSION (STATIC AND CYCLIC) MODE USING ACOUSTIC EMISSION
A non crimp fabric (NCF) with a stacking sequence of [0?§,+45?§,90?§,-45?§] embedded in epoxy resin matrix was analyzed. Samples for mechanical test were obtained from laminates at different orientations depending on the textile direction at 0?§, 45?§ and 90?§ in order to identify the failure mechanisms. Tension mode tests (static and cyclic) were carried out to evaluate the evolution of damage using as a main tool the acoustic emission technique that allows monitoring the mechanical behavior of the materials during the test in real time.
HIERARCHICALLY-ORDERED MATERIALS USING ORGANIC/INORGANIC HYBRID NANOFIBERS: EXPERIMENTS AND SIMULATIONS
We present experiments and simulations on development of hierarchically-structured materials using nanofibers of self assembling block copolymers blended with functional inorganic nanoparticles. Materials developed in this work show high porosity, large surface area and precise control over nanoscale-assembly, exhibiting an attractive design for application as electrode/catalyst layer in fuel cells. In particular, a novel scheme has been utilized to obtain equilibrium block copolymer self assembly in nanofibers. These self assembly structures are then used as templates to direct the location of functional nanoparticles in nanofibers. Molecular dynamics simulations have been conducted to understand the effect of material processing on assembly.
PRECISION INJECTION MOLDING OF THERMOPLASTIC REPEATING FRAMES FOR BATTERY APPLICATIONS
The battery system powering the Volt is based on a repeating frame architecture that is used to assemble hundreds of Lithium-ion cells in series to achieve the necessary balance of power and weight to efficiently move the vehicle. Each cell is placed in a frame which mates with its nearest neighbors; these repeating frames are injection molded using an engineering thermoplastic. Due to very stringent assembly requirements, each repeating frame is precision molded to hold key dimensions to very tight tolerances. This paper will discuss the precision aspects of the molding process that were employed to achieve the specified tolerances.
ALTERNATE METHOD IN POLYMER FRICTION MEASUREMENT USING TIMOSHENKO / VAN KARMAN DEVICE
The most common method currently used for measuring coefficient of friction is the pin-on-disk tribometer. Although widely employed the traditional pin-on-disk test can be both expensive and time consuming. Therefore this paper proposes an alternate method to friction measurement using the Timoshenko / Van Karman device. A test system is created using POM as the measured material. Experiment result shows that the current device design is adequate for obtaining generalized friction coefficients, and that output friction data from this system is independent of normal contact force. Further analysis with numerical simulation indicates correlation between material weight and static transition velocity.
COMPARISON OF THE MELTING BEHAVIOR OF HDPE AND PP IN SINGLE SCREW EXTRUDERS
Actual experimental techniques designed to study melting behavior of polymers inside the screw extruder suffer from lack of functionality and time consuming procedures. Their invasive nature affect friction characteristics and heat transfer, influencing the outcome of measured parameters. This paper presents a technique (Patent No. 7314363) that can capture experimental data and images from inside the extruder at short response times using a highly instrumented 45 mm extruder with built-in sensors and small quartz windows. The melting behavior of polyethylene and polypropylene were visualized and measured with this technique. A comparison of the melting behavior of both polymers was obtained.
OBSERVATION AND MODELING OF THE TENSILE BEHAVIOR OF RUBBER TOUGHENED POLYPROPYLENE
Impact modified polypropylene, which is a blend of polypropylene with an impact modifier such as ethylene propylene rubber, ethylene alpha olefin elastomers or styrenic based rubber, is commonly used for applications with impact resistant requirements. In addition to the shape, amount and size distribution of rubber particles, crazes give additional deformation after elastic deformation until the necking process. In this study, a quantitative modeling of tensile behavior of impact modified polypropylene based on a micromechanical model of crazing initiated from rubber particles is presented. An accurate prediction of the stress-strain relationship until necking is possible based on the proposed model.
MULTIVARIATE FAULT DETECTION FOR THE EXTRUSION PROCESS
Multivariate modeling methods such as Principle Components Analysis (PCA) and Projection of Latent Structures (PLS) are increasingly used for process control. A design of experiments was performed on an instrumented tubing extrusion process. Results were used to develop 14 unique PLS and PCA models. A blind validation was performed to evaluate the model sensitivity to 18 imposed process faults. Results indicate that multivariate techniques are well suited for detecting faults in the extrusion process, and that PLS models slightly outperformed PCA models. Identifying the root cause of the process fault was quite challenging and requires careful instrumentation and data analysis.
DEVELOPMENT OF POLYMER FOAMS - TRENDS AND SUSTAINABILITY
Fueled by global megatrends such as energy efficiency, the demand for enhanced heat insulation and light weight solutions is steadily increasing. Due to their unique properties, polymer foams are regarded as an ideal candidate for tackling these challenges. At a minimum of raw material consumption, cellular polymers are tailor-made, cost-efficient, sustainable solutions. Despite the already high performance of today's foams, their innovation potential is still far from being tapped. Novel materials and processes provide a pathway to superior products for existing and new applications. In this paper, BASF's approach of innovative and sustainable particle foam products will be presented.
EFFECT OF POLYMER MATERIAL AND GRADE WHEN INJECTION MOLDING MICROFEATURES ON A SINGLE PLATFORM
Injection molding offers high-rate production of microstructured polymer surfaces, but very few studies have investigated the effect of material properties on microfeature replication. In this work, three grades of three commercially-available polymers were used to investigate the effect of flow characteristics and transition temperatures on replication of microfeatures with complex geometries. The results showed no correlation between replication and melt viscosity, but suggested that solidification time and interfacial effects influenced replication even with microscale features.
UNDERSTANDING THE AFFINITY BETWEEN COMPONENTS OF WOOD-PLASTIC COMPOSITES FROM A SURFACE ENERGY PERSPECTIVE
To evaluate surface compatibility in wood-plastic composites (WPCs), the dispersion and acid-base components of surface energy of various thermoplastic resins (matrices) and several wood-based reinforcing materials were determined using inverse gas chromatography (IGC). The corresponding surface energy, work of adhesion, and work of cohesion were calculated based on the van Oss-Chaudhury-Good approach. Composite performance was analyzed by measuring tensile and flexural strengths according to ASTM standards. The results indicated that for the same type of filler, the mechanical properties of the composites increased when the ratio of the work of adhesion to the work of cohesion increased.
DETERMINATION OF FLOW PROPERTIES OF THERMOPLASTICS AT HIGH SHEAR RATES BY INSTRUMENTED INJECTION MOLD
The knowledge of real viscosity of polymer melt in the processing is one of the most important properties. During the flow in nozzle, runner system and in thin walled cavities of injection molding machines, both shear and elongation deformation processes are carrying out. An injection molding slit rheometer was designed with a series of slit and orifice dies. A shear and elongational viscosity calculation method has been developed. The temperature and pressure effect were investigated. The measured viscosity curves were compared with ones given by Gttfert and HAAKE equipments.
A POST-PROCESSING METHOD TO IMPROVE THE MECHANICAL PROPERTIES OF CARBON NANOTUBE/THERMOPLASTIC FIBERS
This research studies the effects of multi-walled carbon nanotubes (MWNT) on the mechanical properties of thermoplastic fibers. The primary materials investigated are Graphistrength C M1-20 masterbatch and polyamide 12 (Rilsan PA12 from Arkema). Fibers were melt spun with MWNT contents of 1.0 wt%, 2.0 wt% and 5.0 wt%. Tensile tests were performed with an Instron 5548 Microtester machine. Following those results, fiber samples were submitted to a post-drawing under different conditions of temperature, drawing speed and final elongation with a Br¬ckner biaxial stretching machine. Increase of at least 400% in the strength and Young's modulus of the fibers was observed.
MORPHOLOGY AND RHEOLOGICAL PROPERTIES OF POLY (BUTYLENE ADIPATE-CO-TEREPHTHALATE) AND POLY (LACTIC ACID)/CLAY COMPOSITES
This work studied Poly(butylene adipate-co-terephthalate) (PBAT) and polylactide (PLA) bends compounded with organically modified silicate layers. Compounds of 80% PBAT, 20% PLA and 3% organically modified silicate layers showed significantly improved modulus and enhanced thermomechanical performance compared to PBAT. Rheological analyses showed solid-like behavior for the melt, indicating formation of a network structure of the particles in the blend although the clay platelets were partially dispersed in PBAT matrix and a large portion of the platelets was located at the interface based on the electron microscopy analysis. Also the addition of organoclay reduced the dispersed phase domain size significantly.
HYBRIDIZATION OF THERMOPLASTIC POLY(LACTIC ACID) AND POLYOXYMETHYLENE COMPOSITES THROUGH MICRO-BRAIDING
Polymer melt blending would be difficult especially when two polymers are incompatible. Therefore, this study proposes a novel polymer blending technique by using the micro-braiding technology. Micro-braided yarns (MBY) were produced by continuously braiding resin yarns around a reinforcing jute yarn. These MBY were then wound around steel frames and compression molded to form unidirectional composites. The effect of braiding sequence on the blend homogeneity, fiber-matrix interfacial strength and mechanical performance of the composites was evaluated. It was found that hybridization technique through micro-braiding was effective in blending of the matrix resins and increased the mechanical properties.
BRAIDING PULTRUSION SYSTEM FOR CONTINUOUS FIBER REINFORCED THERMOPLASTIC COMPOSITE
In this study, thermoplastic composite beams with an L-shaped Cross-section were manufactured by the braid-trusion method. This continuous manufacturing process combines the braiding performing technique and the thermoplastic composite pultrusion process to fabricate constant cross-section products. The yarn precursor was a blend of carbon filaments and polyamide 66 filaments in a parallel hybrid arrangement. The filling is the ratio between the area of material pulled through the die and the internal area of the die. Pultrusion experiments were performed at different filling ratio by modifying the braid architecture and at different pulling speeds.
RHEOLOGICAL CHARACTERIZATION OF POLY(ETHYLENE TEREPHTHALATE) RESINS USED IN THE BOTTLING INDUSTRY
Poly(ethylene terephthalate) (PET) is extensively used as the packaging material for bottled beverages. Qualifying PET properties from different suppliers is an important way to ensure the performance of manufactured bottles. In this study, we used dynamic melt rheology to determine the zero shear viscosity and the molecular weight of the polymer. This rheological characterization aids in understanding the properties of each resin in the molten phase during processing. Finally, the performance of PET bottles made from different resins was evaluated through the top load capacity.
FURTHER UNDERSTANDING OF MECHANISM OF ANIONIC POLYMERIZATION THROUGH BULK POLYMERIZATION OF STYRENE AT HIGH TEMPERATURE
A self-designed device consisting of a tubular reactor and two precision metering pumps was used for investigating the kinetics of the anionic bulk polymerization of styrene (St) at high temperatures. The results confirmed that the inactive aggregation of n-butyllithium at a low temperature (<20§C) could be transformed into the active species and initiate the polymerization of St at a high temperature (60§C). The GPC results indicated the existence of aggregated active species containing 6 polystyryllithium molecules. The effects of polar regulator THF or temperature on the kinetics of anionic polymerization were also identified, which improves the understanding of polymerization mechanism.
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