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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A Study of Blown Film Nanocomposites Consisting of Polycaprolactone and Montmorillonite Clay
Nanocomposite blown films of polycaprolactone (PCL)/montmorillonite clay were investigated to determine the influence of processing conditions on the polymer-clay interaction. PCL and clay at various loadings (2, 3 and 5%) were processed using a twin-screw extruder with various screw speeds, barrel temperatures, and feed rates. The interaction of the polymer and clay was determined by x-ray diffraction and transmission electron microscopy. Exfoliation was optimized with slower screw speeds and feed rates. The thermal and mechanical properties of the films were examined. The transition temperatures of PCL did not change significantly in the nanocomposites, but tensile strength and modulus increased as a result of increasing the feed rate or reducing the screw speed during processing.
Study of Flow Marks during Injection Molding
In this paper, alternate and synchronous dull and glossy flow marks are studied. The effect of rheology, flow front velocity, mold geometry, melt temperature, mold temperature, and mold surface coatings on flow marks was studied. For the alternate flow marks, it was found that the flow marks did not occur at high injection speeds. The generation of the flow marks is explained by entry viscoelastic instability. For the synchronous flow marks, it was found that coating these surfaces could not prevent the occurrence of the flow marks, although it could alleviate them. Slip is not the cause of the generation of the synchronous flow marks.
Study of Polypropylene/ Polyamide 6 Blends by Raman Microspectroscopy
Binary blends of polypropylene (80 and 60 weight %), polypropylene grafted with diethyl maleate and polyamide 6 were prepared in a Leistritz co-rotating twin-screw extruder at 230ºC, 90 rpm and 9 Kg/h of mass flow rate. Scanning Electron Microscopy (SEM) combined with Raman Microspectroscopy (RM) in samples previously tested in an Instron tensile equipment showed the effect as interfacial agent of the functionalized PP. In fact, when the PP-g-DEM was used an homogeneous dispersion with smallest and elongated particles was found. Tensile properties and heat distorsion temperature were also determined.
A Study of the Foaming Process of Polyethylene with High Pressure CO2 in a Modified Extrusion System
A conventional single screw extruder is used to process polymeric materials (HDPE, LDPE) in the presence of high pressure CO2. The extruder has been modified to allow for high pressures created by the injection of high-pressure CO2 into the system. The redesign includes a modified feed section that allows a given mass of polymer to interact with a metered amount of CO2 prior to the extrusion process. A variety of extrudate morphologies are obtained as a consequence of the inherent shear mixing and the presence of high-pressure CO2. Some of the relevant parameters in the foaming process of HDPE and LDPE during extrusion are analyzed and related to the processing conditions.
Study of the Parameters of Influence in the Mold that Vary the Roughness of Molded Parts
The research project to study the influence of the mold roughness in the roughness of molded parts (PA 6.6/6 reinforced with glass fibres) was the result of collaboration between the University of Vigo and the University of Minho.The design of experiments was applied to studing the behavior of the roughness of molded parts. The material with glass reinforcement was considered and the same plastic in a neat (no reinforcement added) condition. Different shapes of test molded parts were also considered.Finally a model was obtained relating the different parameters of the mold and the roughness of the molded parts.
Study of the Relationship between Crystal Size and Nano-Hardness in Ultra High Molecular Weight Polyethylene
Gamma radiation was used to induce chemical modifications in ultra high molecular weight polyethylene. UHMWPE specimens were compression molded and gamma irradiated in an inert atmosphere at dosages of 75 and 150 kGy. The surface hardness and modulus were characterized by nano-indentation. The effect of the gamma irradiation treatment on the surface properties was determined to a depth of 20,000 nm. The surface modulus and hardness exhibited a dependence on radiation dosage. The UHMWPE sample irradiated at 150 kGy exhibited the highest surface hardness and modulus. Both the modulus and hardness show a direct dependence on crystal thickness.
Study of Weld-Line Strength and Microstructure of Injection Molded Microcellular Parts
Microcellular injection molding (also known as MuCell process) can produce parts with excellent dimensional stability using lower injection pressure, shorter cycle time, and less material. This study is aimed at understanding how the process conditions affect the weld-line strength and microstructure of microcellular injection molded parts so that the advantages of the process can be fully realized. A design of experiments (DOE) was performed to produce polycarbonate tensile test samples with four systematically varied process conditions. It has been found that the weld-line strength increases with increasing melt temperature, injection speed, and shot size and is weakly dependant on the supercritical fluid level. This paper also presents the microstructure of the molded samples at various cross-sections.
Study on the Characteristic of New Type Screw Element in Co-Rotating Twin Screw Extruders
In order to meet the development towards higher speed and efficiency of co-rotating twin screw extruders, we designed and manufactured a new type screw element of co-rotating twin screw extruder, it has linked together left and right hand flights and large pitch, i.e. similar to inner mixer rotor. After carrying out flow field simulation of this element, we carried out a lot experiments to verify the calculating results. The calculating and experimental results indicate that this new screw element is possessed of better plasticating and mixing ability, lower melt temperature and lower energy consumption than the conventional screw elements and FAMME.
Studying Additive Migration in LLDPE and Pop Films Using Synchrotron-Based FTIR Microspectroscopy
The migration of additives in thick (~500 ?m) single layer and multilayer films has been characterized using FTIR microspectroscopy [1,2]. The objective of this research was to investigate additive migration and concentration profiles in single-layer and coextruded bilayer films of industrially relevant thicknesses. In particular, the investigation focused on the migration of an erucamide slip agent in 50-?m thick extruded films of linear low-density polyethylene (LLDPE) and a polyolefin plastomer (POP). Erucamide concentration profiles were successfully mapped using synchrotron-based FTIR microspectroscopy. The synchrotron radiation helped to achieve a higher spatial resolution for the thin films. A meticulous sample preparation was needed to map the thin film samples. Results with FTIR microspectroscopy showed that the additive-concentration profiles were relatively uniform across the multilayer-film thickness irrespective of the intended initial additive distribution. Results also showed that more erucamide migrated to the surface of a POP layer than an LLDPE layer.
Subinclusion Morphologies in HDPE/PS/PMMA Ternary Blends Prepared by Twin Screw Extrusion
Ternary blends of PS and PMMA in a PE matrix were prepared by twin screw extrusion to investigate the effect of viscosity ratios, sequence of addition and composition on the core/shell encapsulation phenomenon. The morphology was observed by SEM after selective extraction of either PS or PMMA. Composite droplet morphologies were observed with PS encapsulating PMMA as predicted by spreading coefficient theory. Processing and material viscosity effects are discussed. Good agreement was found between the obtained morphology and those expected from the theory of spreading coefficient.
Sulfonated Block Copolymer Ionomers for Use in Direct Methanol Fuel Cells
Optimizing the efficiency of direct methanol fuel cells (DMFCs) requires the use of polymer electrolyte membranes the exhibit high proton conductivity and are resistant to methanol crossover (1). Figure 1 shows a schematic of how methanol crossover takes place. To accomplish this, a novel class of self-assembled block copolymers have been developed and investigated. The novel polymers are comprised of tri-blocks of polystyrene-polyisobutylene-polystyrene (PS-PIB-PS). The major component of the copolymer is PIB lending low temperature flexibility to the material and good barrier properties (2). When the PS monomers are chemically modified via sulfonation, the microphase-segregated morphology provides pathways for ion conductivity through the polymer film, while preventing methanol diffusion.In this study, the proton conductivity and methanol permeability of a series of sulfonated (PS-PIB-PS) polymer membranes have been examined. The polymers were sulfonated at various levels ranging from 0 – 40 % by weight in PS and compared to Nafion 117, a polymer currently utilized in fuel cell applications. Results reveal that these membranes show improved resistance to methanol permeability while providing sufficient ion conductivity to be used in fuel cells.
Sulfonated Poly(Ether Ketone Ketone)
Proton exchange membrane (PEM ) fuel cells represent an attractive alternative to conventional power plants, especially the internal combustion engines (ICEs) used in motor vehicles. They are inherently more efficient than ICEs, which results in better fuel economy and lower fuel costs, have no moving parts, have lower CO2 emissions and do not emit common air-pollutants such as SO2, NOx and unsaturated hydrocarbons. A polymer electrolyte membrane is a crucial component of the PEM fuel cell. The membrane serves both as the electrolyte and as a separator to prevent direct physical mixing of the hydrogen at the anode and the oxygen at the cathode.
Supplier Strategy for Complying with Regulatory Requirments Relating to Transmissible Spongiform Encephalopathies
Global regulatory agencies are implementing strict guidelines associated with Transmissible Spongiform Encephlopathies (TSE). Medical manufacturers need to certify that their products are free of bovine derived products. In order to comply with these mandates, medical manufacturers must identify and address sources of their starting materials including active ingredients, excipients and reagents. Some additives utilized in the thermoplastic industry have bovine components.The following system allows a medical manufacturer to systematically search their processes and identify potential issues with meeting regulatory mandates.
Surface Activation of Crosslinked Rubbers and Ground Tyre Rubber via Monomer Grafting
Crosslinked rubbers and ground tyre rubber (S-GTR) have been treated using a surface grafting process allowing the incorporation of carboxyl and epoxy groups onto the polymer surface. The rubber were functionalised with glycidyl methacrylate (GMA) or methacrylic acid (MA) by photoinitiated grafting. The grafting degree of the rubber was determined by attenuated total reflectance Fourier-transform infrared (FTIR-ATR) spectroscopy. The grafted GTR can well be incorporated in various thermoplastics and thermosets. The surface grafting strongly enhances also the glueing ability of rubber sheets.
Surface Characterization of Hydrosilylated Polypropylene
Polypropylene (PP) containing terminal unsaturation was modified with a hydride terminated polydimethylsiloxane (PDMS) through a catalytic hydrosilylation reaction in the melt phase at various temperatures. This paper presents a comprehensive study of the surface characteristics of these hydrosilylated polypropylenes (SiPP) using the axisymmetric drop shape analysis - profile (ADSA-P) technique and atomic force microscopy (AFM). Static and dynamic contact angle experiments were carried out using ADSA-P. The results of contact angle measurements show that the lower the reaction temperature, the larger the static/advancing contact angle, the smaller the permeability coefficient, and the more hydrophobic the surface. Surface topographic and compositional features were investigated using lateral force mode of AFM. All sample surfaces were rough on a micrometer scale and two different compositional domains were found to exist on the sample surfaces. The results show that decreasing the reaction temperature increases the amount of incorporated PDMS.
Surface Cleaning of Mold Release Compounds from Metals and Non-Metallic Materials
Mold release compounds can be transferred to molded parts and interfere in downstream painting, decorating, and bonding operations. These agents also accumulate on tool surfaces necessitating periodic cleaning which disrupts productivity and can involve the use of caustics or solvents. This study reports the promising results of using short duration exposures to UV irradiation to remove mold release compounds from both metals and non-metallic materials, such as plastics and polymer composites. In this study assorted materials were intentionally contaminated with heavy amounts of industrial mold release agents. The surfaces were rapidly and efficiently cleaned following exposure to high intensity UV light as demonstrated by a significant reduction in the water contact angle. UV treatments provide an environmentally benign alternative means to remove mold release compounds from tool or molded part surfaces.
Synergistic Effects in Halogen-Free Polymer Compounds Containing Hydrated Mineral Fillers
Compared to alternative fire retardants, hydrated fillers are relatively ineffective, requiring addition levels of up to 60% by weight in order to achieve acceptable combustion resistance. This has a deleterious effect on melt viscosity and mechanical properties, commonly requiring use of surface treatments to offset these adverse effects. There would be considerable commercial benefits, therefore, if filler levels could be lowered through the combined use of synergists for hydrated fillers, without compromising fire performance.This paper reviews approaches, which have been reported or are currently being developed, for achieving more efficient fire retardant action using hydrated fillers in combination with co-agents including those formed from phosphorus, inorganic tin and boron compounds. The optimum mode of combining filler and co-additive is discussed with reference to physical admixtures and novel coated forms of hydrated filler.
Synthesis and Characterization of Styrene/Butyl Acrylate Gradient Polymers Obtained by Emulsion Polymerization
The combination of properties at particle level has been accomplished by emulsion polymerization preparing core-shell polymers, to produce stable materials of technological importance. In this work, a change in properties in a more continuous way is sought varying copolymer composition during the second stage of the emulsion polymerization process. Gradient copolymer composition of the system (styrene/butyl acrylate) was followed by IR. Stress-strain, impact and mechanodynamic properties were evaluated. The results were compared with materials of equivalent global composition, obtained in two-stage seeded emulsion polymerization. Performance difference was notorious for certain compositions, showing the gradient materials higher deformation capacity.
Temperature Effects during Capillary Rheometry Testing
A non-contact temperature monitoring technique based on fluorescence spectroscopy was used to measure the temperature of a polymer resin during capillary rheometry testing. Polyethylene and polycarbonate doped with a fluorescent dye, perylene, were used in experiments to measure resin temperature changes due to shear heating as shear rate in the capillary increased from 10 s-1 to 10000 s-1. Resin temperature at the exit orifice of a 1 mm diameter capillary die was found to increase monotonically with increasing shear rate reaching as much as 40 °C above the capillary set point temperature at the highest shear rates. The implications regarding rheometry testing are discussed.
Temperature Isolation in Blown Film Dies
Market demands that blown film processors produce multilayer film with the ability to thermoform and with improved properties such as barrier to moisture and oxygen. These properties require the use of materials with widely divergent melt temperatures. To coextrude materials of different melt temperatures, each individual material must be processed at its own ideal temperature. Temperature isolation in tested dies allows coextrusion of film consisting of materials with a melt temperature difference of up to 150°C. Based on trial results in Japan, USA and Canada this paper will demonstrate the ability to provide consistent temperature in each layer and super temperature isolation.
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