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 Material Properties on the Mechanical and Thermal Performance of Metallocene Catalysed LLDPEs
A range of metallocene and Ziegler-Natta catalysed LLDPEs were prepared by injection moulding to determine the effects of density, molecular weight, MFI and polydispersity on their mechanical performance. Tensile results showed that hexene based mLLPDEs exhibited higher elongation to break while Young’s modulus of the materials was found to be more influenced by density. Impact results demonstrated that metallocene LLDPEs have superior impact strength at room temperature over conventional LLDPEs. Further analysis using differential scanning calorimetry and dynamic mechanical thermal analysis was performed to study the influence of the metallocene catalyst and co-monomer type on the properties of the materials.
Propylene-1-Hexene Copolymer Obtained with Ph2C(Flu,Cp)ZrCl2 Homogeneous and Heterogeneous System
This work deals with metallocene homogeneous and heterogeneous catalysts (Ph2C(Flu,Cp)ZrCl2 and Ph2C(Flu,Cp)ZrCl2/HM) to obtain syndiotactic polypropylene and propylene-1-hexene copolymers. The effects of polymerization temperature, comonomer concentration and different reaction solvents were studied.S-PP of 138/152°C melting temperature was obtained with these catalysts. Both homogeneous and heterogeneous systems showed the comonomer effect. By changing the solvent from toluene to hexane a decrease in activity and an increase in polymer melting temperature and crystallinity were observed.
Characteristics and Properties of Metallocenic Syndiotactic Polypropylene
This work investigates the characteristics and properties of syndiotactic polypropylene produced by Ph2C(Flu)(Cp)ZrCl2/MAO metallocene catalyst system. The obtained s-PP presented melt temperature around 120°C, being more amorphous as the polymerization temperature increased. From the data obtained through HAAKE mixture chambers we could carry out the rheological characterization of the polymer, which presented a non-Newtonian pseudoplastic behavior, as expected. The polymer also had a good mechanical performance compared to conventional i-PP.
Copolymerization of Ethylene and 1-Hexene by Homogeneous and Supported Metallocene Catalysts
In this work, the performance of the homogeneous catalyst system based on Ph2C(Flu,Cp)ZrCl2 was evaluated on ethylene copolymerization and 1-hexene. The influence of the support material was studied using acid mordenite HM zeolite and the characteristics of the produced polymers were also investigated. A study was performed to compare the influence of polymerization solvents as toluene, hexane and hexane/TIBA. An increase in activity was observed in relation to the comonomer addition for homogeneous and supported systems.
Effect of Maleated Polypropylene on the Melt Compounding of Polypropylene/Clay Nanocomposites
Polypropylene/clay nanocomposites modified with different levels of maleic anhydride grafted polypropylene (PPgMA) compatibilizers were compounded on a twin-screw extruder. The effect of PPgMA compatibilizers, including PB3150, PB3200, PB3000, and E43, were studied. The structure was investigated with X-Ray diffraction (XRD) and transmission electron microscopy (TEM). The relative complex viscosity curves also revealed a systematic trend with the extent of exfoliation and showed promise for quantifying the hybrid structure of the nanocomposites. Mechanical properties and thermal stability were determined by dynamical mechanical analysis (DMA) and thermogravimetric analysis (TGA), respectively. An optimum level of compatibilizers was found to yield the greatest improvement of composite properties. Though PPgMA with low molecular weight and high MA content could lead to good clay dispersion, it resulted in less improvement in both mechanical and thermal properties of PP/clay nanocomposites.
Different Clamping System for Plastic Molds
The desire to decrease unproductive time of injection moulding machines explains why the clamping systems are becoming increasingly more powerful.After significant studies, three families of clamping system supports are currently recognised : mechanical, hydraulic and magnetic supports. The choice of the appropriate production system remains to be made by taking into account the return on investment.Whereas the sales of the mechanical and hydraulic systems remain stable, the magnetic systems represent a remarkable evolution. In spite of its price, which is relatively high, the industrialists recommend this system because of its remarkable. However the prices, which remains a real barrier to its expansion, are falling thanks to an increase in sales.
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.
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