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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FLOW EFFECTS ON REPLICATION OF INJECTION MOLDED MICROCHANNELS
Injection molding is an attractive method of manufacturing of microfeature-enabled devices, but the effect of tooling design has yet to be fully explored. This work investigated the effects of flow direction on the replication quality of complex angled microchannels. The channel designs utilized two different angles and three line widths. The design and orientation of the microfeatures significantly affected the ability to fully replicate feature depth, but not the feature definition. Design and orientation, however, did not have as large an effect on replication quality as feature aspect ratio.
FRACTOGRAPHIC CHARACTERIZATION OF PIPE AND TUBING FAILURES
Plastic piping systems are an important commercial product used in a wide variety of applications. Because of the diversity of applications and wide range of material used to produce pipes, many different types of failures can result in service. Evaluating these failures through a systematic analysis program allows an assessment of how and why the pipes failed. An essential portion of the failure analysis process is the fractographic examination, which provides information about the crack origin location, and the crack initiation and extension modes. The focus of this investigation was to characterize the surfaces of intentionally cracked laboratory samples.
FRACTURE BEHAVIOR AND OPTICAL PROPERTIES OF MELT COMPOUNDED SEMI-TRANSPARENT POLYCARBONATE (PC)/ALUMINA NANOCOMPOSITES
Two different molecular weight SMA copolymers were employed to pre-treat and coat Al2O3 nanoparticles to facilitate dispersion in a PC matrix. Melt compounding was done using a K-mixer. The low MW SMA polymer coating produced better dispersion of nanoparticles in the PC nanocomposites, resulting in fairly high light transmittance even through 2 mm thick specimens. The addition of 1 wt% well-dispersed nanoparticles improved the impact strength during brittle fracture of the PC/alumina nanocomposites through the formation of multi-level microcrazes induced by the nanoparticles. However, further increasing the alumina nanoparticle content altered the energy dissipation behavior, resulting in less effective reinforcement.
AN ENGINEERING MODEL FOR INTERPRETING RCP TEST RESULTS FROM PLASTIC PIPE
Both of the standard methods used to test plastic pipe for resistance to rapid crack propagation (RCP) evolved primarily from experience with polyethylene pipe for gas distribution. Advocates of other pipe materials (e.g. polyamide) have questioned the applicability of these methods and of the supposedly material-independent correlation factor which correlates their results. Discussion is hampered by the complexity of gas-driven RCP and the unavailability of an accepted mathematical or computational model. Using a straightforward new engineering model, we present new results on the influence of backfill, of residual stress and of water pressurisation.
FIBER MOTION IN FOUNTAIN FLOW AND ITS RELATION TO FIBER FREE REGIONS AT THE SURFACE OF INJECTION MOLDED PARTS
Mold filling of short fiber reinforced plastics play a significant role on part quality. In injection molding the fountain flow dominates the mold filling process. In this work, a mechanistic fiber model is presented, which is coupled with a simulation of the fountain flow region using the Radial Basis Function technique. The results show how the fountain flow influences the fiber content in the outer surface of an injection molded part. Therefore it plays a major role on the final fiber position and on the fiber free region or skin at the surface of a part.
CHARACTERIZATION OF SINTERED POLYLACTIDE (PLA) SCAFFOLDS FOR BONE TISSUE ENGINEERING
This study represents preliminary work on characterizing powder-sintered porous polylactide (PLA) scaffolds intended for use in bone tissue engineering. PLA powder and sintered material were characterized by DSC and GPC. The morphology and mechanical properties of cylindrical scaffolds were determined by SEM and compression testing. Scaffolds of two average particles sizes were fabricated using six different processing conditions. Values of the apparent elastic modulus ranged from 25.9 ?ñ 3.08 MPa to 97.3 ?ñ 11.5 MPa, with the maximum occurring in samples sintered for 15 minutes at 170 C. The observed modulus correlates well with the stiffness of human cancellous bone.
IMPROVING THE ENERGY EFFICIENCY OF A BARREL HEATER - COOLER DESIGN FOR HIGH TEMPERATURE SINGLE SCREW EXTRUSION APPLICATIONS
The energy efficiencies of two different types of extruder barrel heater- cooler configurations for a single screw extruder were compared. A conventional air cooled, electrical heated system commonly used in many extrusion applications today was compared to a new energy efficient heater-cooler designed to reduce both radiant and convective heat losses. Each heater-cooler design was examined over a large operating range that simulated the performance of a single screw extrusion process. The new design was found to be significantly more energy efficient compared to the conventional design.
OBSERVATIONS OF LIQUID-LIQUID ENCAPSULATION IN COEXTRUSION OFINELASTIC NEWTONIAN FLUIDS
Experiments with two inelastic Newtonian fluids flowing side-by-side in a transparent channel were conducted. Irrespective of the difference in the viscosity, no core-annular encapsulation was observed for bi-layer flows of glycerol and silicone oil. In two of the experiments with bi-layer flow of motor oil and silicone oil, motor oil encapsulated the silicone oil, even when the viscosity of motor oil was higher than the viscosity of the silicone oil. It is concluded that other fluid properties besides viscosity, such as wettability of the fluid, may play an important role in reaching the core-annular encapsulation often observed in bi-layer flows.
MECHANICAL PROPERTIES AND DEGRADATION OF COMMERICAL BIODEGRADABLE PLASTIC BAGS
The properties of six biodegradable commercial plastic bags, including BioBag, Flushdoggy, Green Genius, Oxobiodegradable, Rascodog, and World Centric, were examined. Most of the bags exhibited mechanical properties similar to traditional bags. One bag that had extensively higher properties was the Flushdoggy bag, which is based on PVA. All the bags generally start to degrade thermally at around 400C. Exposure to UV light did not have much of an effect on tensile properties. UV radiation, moisture, and weathering all had little effect on thermal degradation. Oxo-biodegrable and Flushdoggy became especially brittle after accelerated aging, although Flushdoggy still exhibited strong tensile properties.
OUTDOOR WEATHERING MUST VERIFY ACCELERATED TESTING
Outdoor exposure racks and accelerated chambers are the primary methods for testing materials for weathering durability. Because of the time constraints placed on product development, emphasis has been placed on accelerated laboratory testing to provide data on long term outdoor durability. Because state of the art weathering chambers cannot reproduce all the complexities of outdoor weathering, over-reliance on accelerated testing can lead to the wrong conclusions. This paper discusses the problems inherent in accelerated testing and shows techniques and processes that allow the user to determine acceleration and correlation factors and ensure that accelerated testing is giving the right results.
BIO-COMPOSITES OF SESBANIA HERBACEA PLANT FIBERS/POLYVINYL ALCOHOL (PVA): EFFECT OF CHEMICAL RETTING
The natural cellulose fibers used in this study with properties suitable for polymer composite application were obtained from sesbania herbacea plant stem by chemical retting method. The objective of this work is to study the effect of retting method on morphology and mechanical properties of the sesbania fibers and its composites with polyvinyl alcohol (PVA). The retting was done by using different concentrations of sodium hydroxide (NaOH) solutions. Scanning electron microscopy was used to study the morphology and thermo mechanical testing was done to study the effect of NaOH treatment on the properties of fibers and its composites with PVA.
SOLID-STATE FOAMING OF CELLULOSE NANOFIBER REINFORCED POLYLACTIC ACID BIOCOMPOSITES
This study investigates the effect of fiber content on the foaming behavior of cellulose nanofibers reinforced polylactic acid (PLA) biocomposites. The composites were prepared by a film casting and hot pressing method and then foamed via the batch foaming process with CO2. The morphology, average cell size, volume expansion ratio and cell density of the samples with different cellulose content were compared. The results suggested that cellulose nanofibers, (1) acted as nucleating agents and (2) suppressed the cell coalescence during the foaming process. The cell morphology is related to the fiber content.
MULTI COMPONENT INJECTION MOLDING FOR REPLICATING METALLIC MICRO STRUCTURES
The two component injection molding of electrically conductive carbon black-filled and insulating polymer can be used to replicate metallic microstructures in a sufficient way. This special process chain called MSG process uses the quasi-infinite conductivity gradient of such two-component templates to start controlled electroplating from the base plate only. Therefore first an electrically conductive base plate is generated by injection molding of electrically conductive carbon black-filled polymers. In a second injection molding step insulating polymers circumfluent microstructures and thereby produce micro-cavities onto these plates. These micro-cavities are filled with metal in the following electroplating step.
EFFECT OF THE ENVIRONMENTAL pH ON THE CORROSION BIOINHIBITIVE PROPERTIES OF MODIFIED CASSAVA STARCHES
The effect of the environmental pH on the properties of modified cassava starches as corrosion inhibitors of carbon steel, was evaluated. Two species were tested: activated (AS) and carboxymethylated starch (CMS). The species were studied using electrochemical measurements in tap water under neutral and alkaline conditions. It was found that protection provided by these biopolymers is dependent on the acidity of the system. Their efficiency is related to the formation of a chelate between macromolecules and ferrous cations. When lowering the pH, the active groups tend to be protonated, hindering the protection afforded for these biopolymers.
PRODUCING MICROLAYER BLOW MOLDED STRUCTURES USING LAYER MULTIPLICATION AND UNIQUE DIE HEAD TECHNOLOGY
Many polymers are extruded in the blow molding process to produce monolayer and multilayer molded articles. Various types of dies are used today in the blow molding process. Each of these types of dies can be used effectively for many polymers in structures containing up to approximately 6 layers. This paper will discuss technology in which layer multiplication techniques are combined with unique die geometries to produce microlayer blow molded structures with significantly greater numbers of layers.
STUDY OF THERMAL DEGRADATION OF PVC PLASTICIZED FORMULATIONS COSTABILIZED WITH d-SORBITOL AND TRIPHENYL PHOSPHITE
PVC is generally degraded during processing, producing several undesirable effects. In this work, mixtures of calcium and/or zinc stearates and epoxidized soybean oil are used as stabilizers. In addition, to improve overall stability, D-sorbitol or triphenyl phosphite were added as costabilizers. The formulation composition was systematically varied considering the following parameters: a) presence of epoxidized soybean oil, b)CaSt2/ZnSt2 ratio and, c) presence and type of costabilizer. Thermal stability was followed during isothermal heating by determining: a) the accumulation rate of some conjugated polyenes and, b) the changes in the tensile properties.
NEW WOOD FIBER BIOCOMPOSITES BASED ON POLYLACTIDE AND POLYLACTIDE / THERMOPLASTIC STARCH BLENDS
This paper aims at developing natural fiber biocomposites based on biopolymers reinforced with wood fibers obtained from a thermomechanical refining process. Polylactide and polylactide/thermoplastic starch blends were used as matrices. Two PLAs were considered with the purpose to investigate the effect of wood fibers on the crystallinity, and therefore, on mechanical properties of composites. Two grades of thermoplastic starch, different in plasticizer content and nature, were used. TPS content in the PLA/TPS blends was 50%. Moreover, two wood fiber types were selected, a hardwood and a softwood, to state the effect of the fiber type on the biocomposite properties.
REVERSE TEMPERATURE PROFILE RHEOLOGY STUDY OF PHB COPOLYMER WITHIN AN INJECTION MOLDING MACHINE
Rheology measurements are normally conducted using a capillary rheometer. It utilizes a flat temperature profile and is significantly different from actual recommended processing condition. This work studied the rheological behavior of PHB Copolymer within an injection molding machine. Viscosity measurements were made using an in-line capillary rheometer nozzle on a molding machine at shear rates ranging from 100 s-1 to 20000 s-1. The results showed that the viscosity of the material reduces significantly when compared to conventional capillary rheometer. These changes can be attributed to processing conditions such as reverse temperature profile, residence time and shear due to screw plasticization.
RECYCLED POLYMERS FOR SUSTAINABLE SOLUTION IN INFRASTRUCTURE
Use of recycled thermoplastic polymer composites for manufacturing and evaluation of structural products as a sustainable solution is discussed in this paper. Durability (aging) evaluations of those polymers have also been carried out to predict their service life. Specifically, ABS polymers were reinforced with 4%, 7% and 12% fiber volume fractions of bi-directional glass fabric (fabric density: 407 gm/sq. mtr. or 12 oz per sq. yard) and were evaluated. Research results indicate the significant potential of recycled polymer composites for different applications with the use of continuous glass fabrics.
HIGH GAIN LEXAN DIFFUSER FILM FOR LCD DISPLAYS
Driven by increasing demand for advanced optical films for LCD displays, a new generation of micro-lensed diffuser films is introduced. Engineered film topography provides light turning functionality for optimum redirecting of source light, through the LCD panel, towards the viewer. Factors affecting film's ability to redirect light are discussed. A new generation of monolithic Lexan display films having higher luminance gains, is introduced. Performance gains in actual LCD displays are demonstrated, and film making process is reviewed. Up to 10% luminance improvement over standard micro-lensed films was realized, while retaining inherent strength and dimensional stability attributes of monolithic polycarbonate films.
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