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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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.
MELT EXTRUSION - SHAPING PHARMACEUTICAL DOSAGE FORMS
Melt extrusion has been an established industrial manufacturing technology for over 50 years. Today, applications of melt extrusion for pharmaceutical production range from controlled release systems to oral bioavailability enhancement and show potential for small molecules and therapeutic peptides. The emergence of novel drug delivery systems and routes of administration have allowed for the expansion of melt extrusion applications within the pharmaceutical industry. This review presents an overview of the processing technology and also four major areas of application: bioavailability enhancement; oral controlled release; melt granulation; and the production of advanced controlled release dosage forms.
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.
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