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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Optimization of Nucleating Product Forms to Achieve Handling Ease and Robustness at Maximum Dispersion Efficiency in Polypropylene
Nucleating agents are very beneficial additives in polypropylene because by promoting crystallization they improve molding productivity, enhance thermal properties, achieve simultaneously high impact and strength and provide improved clarity for special applications. Uniform dispersion of the nucleating particles throughout the polymer matrix is critical in achieving the desired performance. Additives fed as powders are intuitively thought to provide the best dispersion, but suffer from handling difficulties, including loss of the additives in the feeding / transport system. Designing a non dusting blend (NDB) form that can feed as a pellet but at the same time will disperse uniformly in polypropylene during extrusion is a challenging task. In this paper we report several NDB forms that achieve dispersion equivalent to the powdered blends and compare with systems where such dispersion could not be achieved. The influence of appropriate co-additives, as well as selection of the optimum NDB manufacturing process are discussed. Crystallization temperature and haze measurements were used to quantify the quality and extent of the dispersion.
Structure and Property Relationship of TLCP/PEN/PET Ternary Blend Fibers
Thermotropic liquid crystalline polymer (TLCP) / poly(ethylene 2,6-naphthalate) (PEN) / poly(ethylene terephthalate) (PET) ternary blends were prepared by melt blending, and were melt spun to fibers to improve fiber performance and processability. The mechanical properties of ternary blend fibers could be significantly improved by annealing. This result was attributed to the development of more ordered crystal structures and the formation of more perfect crystallites. Multiple melting behaviors observed in the annealed ternary blend fibers depended on annealing temperature and time, which were caused by the different lamellae thickness distribution.
Mechanical and Physical Properties of PEN/Silica Nano-Composites
Silica nano-particle filled PEN composites were melt-blended to improve mechanical and physical properties, and processability. Tensile modulus and strength were improved adding silica nano-particles to the PEN. The melt viscosity of the nano-composites during the process was decreased by adding small amount of the fumed silica, and hence the processability of those was improved. Dispersity and compatibility of silica nanoparticle filled PEN composites will be investigated near future. Non-isothermal crystallization kinetics and spherulite growth rate were analyzed by Ozawa equation and image analysis, and the calculated Avrami exponents revealed three dimensional growth of crystallite, and the crystallization rate constants were increased with increasing silica contents. Fumed silica may act as a nucleating agent in the PEN matrix, and the same results were obtained by calculating nucleating activity.
Morphological, Thermal and Mechanical Properties of Epoxy Based Nanocomposites
Diglycidyl ether of bisphenol-A (DGEBA) based epoxy resin was reinforced by natural and organically modified montmorillonites, namely Cloisite Na+ and Cloisite 30 B. The process involved mechanical and ultrasonic mixing of the epoxy resin with clay particles and diffusion of the resin into the space between the silicate layers. SEM analysis indicated that as the clay loading increased, the particle size of the clay agglomerates increased. X-ray analysis showed that in nanocomposites with 3-weight % Cloisite 30B, the d-spacing increased from 1.83 nm to 3.82 nm. Adding 0.5 weight % organically modified clay improved the impact strength of the neat epoxy resin by 137.1 %.
Polycarbonate/Ferrite Nanocomposites: Processing and Properties
Nanocomposites using Polycarbonate and Ni- Zn based ferrite nanoparticles were prepared using a reactive twin-screw extruder. They were found to be quite transparent and were characterized using tensile testing, XRD, DSC and TEM. Their mechanical behavior was found to be more brittle than pure polycarbonate. Also, the viscosity of the nanocomposite was significantly lower than the original polymer. This was explained on the basis of the nature of the material used to coat the nanoparticles, and the melt processing conditions employed for preparing the nanocomposites. It was also found that if the nanoparticles were not coated, they agglomerated and hence, the nanocomposites were no longer transparent.
Three-Dimensional Simulations of the Inkjet Printing Process for PLED Display
Because the inkjet deposition process reduces manufacturing costs and process steps when compared with the traditional etching and/or lithography, it seems to be an attractive alternative in the PLED display manufacturing processes. However, some microflow issues in the deposition process should be carefully treated to ensure the manufacturing quality of the PLED display. The droplets dispensing from the inkjet head, which generally contains an array of nozzles, have a volume in several picoliters, while each nozzle responds very quickly and jets the droplets into cavities on substrates with micrometer size. The nature of droplet impingement depends on the material properties, the initial state of droplet, the impact parameters and the surface characteristics. The commonly chosen non-dimensional numbers to describe this process are the Weber number, the Reynolds number, the Ohnesorge number, and the Bond number. This paper discusses the influence of droplet initial velocity on microflow characteristics in the deposition process via a numerical approach. The numerical investigations show that for the studied droplet and cavity size, an acceptable velocity range has been found to ensure the deposition quality, while this result agrees well with existing industrial experiences. The numerical simulation seems to be an efficient and reliable way to evaluate the inkjet deposition process.
The Effect of ? -Rays on PES/PA6 Blends
In this work, the effect of ? -rays irradiation and post-irradiation storage time onto different PEs, PA6 and their blends was studied by means of ESR spectroscopy, FTIR and DSC. These techniques can provide relevant information concerning the reaction mechanism of the polymers structural modifications that take place during their irradiation. The experimental results suggest that allyl, alkyl and polyenyl radicals are generated in the materials after the irradiation process. The dynamics dominating the process kinetics are crosslinking, chain scission and a coexistence of both, depending on the sample composition. The storage time produces a change in the kinetics dynamic.
Determination of the Pressure Coefficient of Polymer Melts from Shear Flow
A modified capillary rheometer was used to measure strain rate-temperature-pressure dependencies of shear viscosity for injection molding grades of polymers. The modification consisted in the addition of a second chamber and a restricting needle valve below the main die, and its purpose was to determine the effect of pressure on the shear viscosity of different polymer melts. The modified White-Metzner model was employed to simultaneously fit the measured viscosity data and determine the pressure and temperature coefficients, ? and ?. It has been found that not only the temperature but also the pressure factor significantly influences viscosity, and both of them are useful for the description of a polymer behaviour.
Testing the Effects of Hold Pressure on Hold Time in Various Materials and through Various Gates
The holding phase of the injection molding process can be critical to producing quality parts. This paper studies the relationship between hold pressure and hold time with a variety of gate types and materials. The materials will be broken into groups such as semicrystalline, amorphous, and filled materials. In addition, parts will be created with a variety of different sized and shaped gates. From this, it is believed that a pattern will be recognized with regards to the setting of hold pressure on the necessary hold time. This pattern is intended to give processors a theory with which to base their thought process when optimizing injection molding machines.
The Affects of Shear Induced Imbalance on the Concentricity of Injection Molded Gears
A number of studies in recent years have shown that shear induced melt variations developed in the runner result in cavity to cavity filling imbalances in molds with eight or more cavities. This study looks at the affects of the shear induced melt variation when molding high precision parts in molds with as few as two cavities. In particular is the case of gears which require high concentricity. The shear induced melt variations developed in the runner continue into the cavity creating irregular filling and non-concentric part shapes.This study evaluates a two cavity, three plate, cold runner, center gated gear mold. Gears are molded from a variety of different engineering resins, and the effects of the shear induced melt variation are evaluated.
Electrospinning: Preparation of Continuous Nanofibers
Electrospinning is an approach to fiber production, which relies on electrostatic forces to produce fibers with diameters in the range of 10nm to a few microns. Nonwoven nanofiber webs of Polyacrylonitrile (PAN) were prepared from solution with Dimethylformamide, with the purpose of preparing carbon nanofibers for the reinforcement of composites. Reproducible fibers with diameters between 0.38-1.5?m (FESEM) were prepared from 10-15wt% solutions electrospun between 8-16kV. The velocity of a 10wt% solution electrospun at 16kV was determined to be between 140-160m/s, from the collected mass. Partially aligned and oriented PAN nanofibers have been prepared using a high speed, rotating take-up wheel.
Modified Three Stage Injection Molding Study
The primary use of a three-stage injection molding process is to produce a process that is more stable. However, a disadvantage can be encountered when the gate end of the part is packed out more than the last portions of the part to fill. A comparison will be made between a three stage and a two-stage cycle that is to be set up on a single cavity mold. Here, an attempt to modify the three-stage process to look like a two-stage process will be made. The injection pressure profile will be changed by adjusting the pack velocity, so that there will be no pressure spike and a constant slope during packing. Once this is completed, disks will be compared and rules to accomplish this will be created.
Reactive Compatibilization as a Route to High Performance Engineering Plastics
Engineering thermoplastics provide a platform for generating light-weight structural materials with customized performance. Such formulations often involve blending with other polymers to gain additional toughness, stiffness or resistance to heat, chemicals, etc. Reactive compatibilization of these blends has proven to be a preferred way of improving the interfacial strength at the boundaries between the two polymers and for controlling and stabilizing the morphology of the blend. This presentation will review the state-of-the-art of this technique including the relative benefits and problems of the available chemical strategies and examples of the applications of various approaches. The physics of morphology generation will be reviewed along with examples of how morphology affects performance. The relevance of recent theories of reactions at polymerpolymer interfaces and model experiments to industrial practice will be analyzed.
Extruded STYROFOAM* and ETHAFOAM* Products; Historical Perspectives
STYROFOAM and ETHAFOAM are well-recognized trademarks of extruded polystyrene and polyethylene foam products that have been produced and marketed by The Dow Chemical Company for over 50 years. When Dr. Che Kao invited us to participate in this symposium he suggested that we review the early Dow research and development work which we believe provided the foundation for the long term success of Dow's extruded thermoplastics foam business. A number of books and review articles describe the science, and technology of thermoplastic foams processes and properties in detail. The philosopher George Santayana is famous for his quote: “If you do not know history you may be condemned to repeat past experiences, good or bad”. Frequently the only qualification for historical accuracy may be the statement; “I should know because I was there at the time” and this is the case for the elder co-author of this paper. He witnessed the first experiment by O. R. McIntire in the Dow Physical Research Laboratory that accidentally produced a small piece of polystyrene foam. We are still concerned with accurate recall of the origins of many ideas and contributions of numerous individuals to the successes (or failures) of innovations of DOW foam products. It is so easy to forget a key decision or minimize the importance of a key idea.
Advances in Barrier Concepts for Improved Rigid Packaging
Poly (ethylene terephthalate) (PET) has become the material of choice for soft drinks, juices, medical and pharmaceutical applications, and some foods. Over the last ten years, efforts have intensified to improve barrier properties and hot fillable capabilities of PET in order to extend its applications to include even more food and oxygen sensitive products. These advancing technologies include new high barrier resins, coatings, oxygen scavengers, multilayer structures, heat setting and blending.A brief review of the current status of the above technologies will be presented. Specifically, a thorough discussion of experimental results will include blends of PET and other polyesters as well as blends with nylon polymers. The issues related to transesterification kinetics, optical clarity and compatibilization, strain-induced crystallization, injection molding, stretch blow molding, microstructure and container physical properties will be presented and discussed.
A New Family of Barrier Nylons Based on Nanocomposites and Oxygen Scavengers
The gas barrier properties of nylon 6 could be improved significantly by a ‘passive barrier’ nanocomposite approach in which ultra-thin, nanoscale silicate platelets of high aspect ratio were incorporated via an in-situ polymerization process. The oxygen barrier properties of nylons have also been further enhanced by a novel ‘active barrier’ approach in which proprietary polymeric oxygen scavengers were melt blended into nanoscale dispersions of high oxygen scavenging efficiency. By combining the nanocomposite and oxygen scavenger technologies, a new family of barrier nylons (Aegis®) have been developed for use in multilayer packaging structures, particularly in multilayer, coinjection stretch blow molded PET bottles for extended shelf-life packaging of oxygen-sensitive foods and beverages.
Saran™ Barrier Resins – A Historical Perspective
Saran barrier resins, which are copolymers of polyvinylidene chloride (PVDC), are-well known for their use in demanding barrier packaging applications to minimize the permeation of oxygen, water vapor, and odors. Less well known is the fact that Saran resins were not originally used in barrier packaging applications. As a matter of fact, the first commercial application for Saran resins was as an acid catalyst in the production of grinding wheels. Another early application of Saran resins, which was developed in the late-1930’s, was monofilament fibers. Over the nearly 65 years of their history, Saran resins, fabrication methods and markets have changed dramatically.
Polymeric Electrolyte Membrane (PEM) Nanocomposites for Fuel Cells via Direct Polycondesation
Polymeric electrolyte membrane (PEM) based fuel cell systems for automobiles, homes, and portable power fuel cells are already important for high energy density and very good environmentally benign energy sources . Currently, film forming fluorinated sulfonic acid containing copolymers are utilized primarily at 80C or lower for cost insensitive applications, such as the NASA space program. An increase in the fuel cell utilization temperature is desired for a number of reasons, including better efficiency and to improve the tolerance to impurities in fuels derived from H2, methanol, natural gas, biomass or reformed gasoline, such as carbon monoxide. New and improved mechanisms for conductivity above the boiling point of water are needed, which operate with little or no water. We have been interested in the direct copolymerization of sulfonic acid containing monomers to afford ion conducting systems such as poly (arylene ethers), including sulfones and ketones, and naphthalene dianhydride 6 membered ring based polyimides. Both random (statistical) copolymers and block copolymers based on these two major classes of materials are being investigated [2-7]. Several of these systems are surprisingly highly compatible with important additives, e.g., heteropoly acids (HPA), such as phosphotungstic acid, and zirconium hydrogen phosphate, which have potential for allowing conductivity above 100C. Highly dispersed nanocomposites have been achieved, which are possible because of specific interactions between the inorganic additive and the host copolymer, including hydrogen bonding, and dipolar interactions between the HPA and the sulfonic acid groups and/or backbone functionality. That highly dispersed HPA systems have been achieved can be demonstrated by FE-SEM, AFM and water extraction studies, and the fact that conductivity values of >0.1 S/cm are possible at temperatures approaching 140C. Excellent adhesion of the HPA to the matrix affords transparent mechanically robust
Pilot Plants of the Future
Pilot plants have historically been used in polymers R&D for scale-up of new catalyst, product and process technology. Because of their essential role, pilot plants are likely to remain an important component of new technology development in the future. However, over the past several years, a limitation with conventional pilot plants has become apparent relating to an inability to detect problems of reactor operability, such as fouling and sheeting. Improvements are required in several areas including process instrumentation and mechanistic models of reactor fouling. These developments, along with improved structure-property correlations, will define the pilot plant of the future. Although physically similar to those of today, future pilot plants will feature significantly improved utilization for reduced R&D costs and faster and more reliable scale up of new technology.
Hydrogenation at Supercritical Single-Phase Conditions
This paper gives an overview of the supercritical single-phase hydrogenation technology. It gives the basic facts from the scientific literature and the practical consequences of these facts including some possible applications to the plastic industry.The new technology can improve the product quality to levels that were impossible with the traditional multi-phase technology.The key element in the new technology is that one adds a solvent, typically propane, which dissolves both the substrate and the hydrogen. In this way a supercritical single-phase is created and the transport resistance between gas and liquid has disappeared.
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