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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EPOXY/CARBON NANOTUBE COMPOSITES FOR WIND TURBINE BLADES
Epoxy based composites containing multi-walled carbon nanotubes (MWCNTs) have been successfully prepared. The effects of the addition of eight different block copolymers on the dispersion stability of MWCNTs have been systematically analyzed. The suspension of CNTs in different components of the epoxy, i.e epoxy resin and hardener, have been evaluated by preparing suspensions using a tip sonicator and different amounts of block copolymers relative to the concentration of CNTs. The stability of MWCNTs in various media was investigated by using a centrifugation technique. Dispersing agents suitable for the acquisition of long-term stable dispersions of MWCNTs have been identified.
FOAMING BEHAVIORS OF POLYPROPYLENE BLOWN WITH CARBON DIOXIDE UNDER EXTENSIONAL STRESS BELOW TM
Previously, it had been demonstrated that extensional stresses has strong effects in cell nucleation and growth within plastic foaming processes. In particular, our previous work investigated the foaming behavior of polystyrene, an amorphous polymer, under extensional stress via in situ observation of the foaming processes. On the other hand, the effects of extensional stress on semi-crystalline polymers are still not well-understood. This study aims to fill this gap by investigating the foaming behaviors of three different types of polypropylene (PP): linear PP, branched PP, and a PP-PE copolymer, via in situ observation.
UNDERSTANDING EFFECTS OF INTERFACIAL CONTACT AND AGGLOMERATION OF FILLERS ON TENSILE MODULUS OF POLYMER NANOCOMPOSITES
Analytical methods have been widely used to predict mechanical properties of polymer composites. The theories assume perfect filler-matrix interfacial contact and homogenous dispersion of individual fillers into the matrix, which however is not what is observed experimentally especially in nanocomposites. The reason is that in nano-size reinforced polymers the dominant effects of interfacial interaction and presence of fillersƒ?? agglomeration have to be considered. This study investigates the effects of these two factors on the tensile modulus of nanocomposites by combining experimental observations and micromechanical models.
MODELING THE EFFECT OF FILLER-MATRIX CONTACT AND FILLERSƒ?? AGGLOMERATION ON EFFECTIVE MODULUS OF POLYMER NANOCOMPOSITES
This study focuses on understanding the deviation between experimentally obtained and numerically predicted tensile modulus of carbon nanotube /polypropylene (CNT/PP) composites. The tensile modulus is measured according to ASTM D638 testing method. Characteristics such as presence and size of CNT agglomerates, voids at the CNT-PP interface and width and modulus of the CNT-PP contact area are studied using atomic force microscope (AFM) and scanning electron microscope (SEM). Finite element analysis is performed to determine the effective Youngƒ??s modulus considering i) ideal case (no CNT agglomeration, perfect CNT-PP contact) and ii) non-ideal case where the experimentally observed characteristics are accounted for.
KINETICS OF THERMAL DEGRADATION OF POLY(VINYL CHLORIDE) BY COLOR
Thermogravimetric (TGA) monitoring of poly(vinyl chloride) PVC degradation kinetics by loss of HCl is complicated by plasticizer evaporation, unlike monitoring by color change due to conjugated polyenes formation. Thermal degradation of PVC films plasticized with diethylhexyl phthalate and tri-isooctyl trimelitate was monitored by color change, by optical density at 350nm, and by TGA at 160C to200C. Plasticizer-free PVC powder degradation kinetics was obtained by TGA at temperatures from 160C to 220C. Apparent activation energies of plasticizer-free PVC powder degradation was 152kJ/mol (by TGA); for plasticized PVC-ranged from 165kJ/mol to 180kJ/mol (color change) and 147kJ/mol (by optical density at 350nm).
A NEW HIGH STRENGTH POM COPOLYMER
POM or polyoxymethylene is an engineering resin used for the past 50 years primarily in injection molding. Parts thusly formed typically replace metal. POM's usefulness is derived from its strength, stiffness, toughness, creep resistance and natural lubricity. Both POM copolymer and homopolymer producers compete in this market space. POM homopolymer grades exhibit a small but significant advantage in mechanical properties, while the copolymer grades exhibit advantages in thermal stability and chemical resistance. This paper presents a new POM copolymer grade with mechanical properties essentially equivalent to homopolymer while maintaining the thermal stability and chemical resistance of POM copolymers.
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.
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