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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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.
Ten Essential Pictures for Understanding the Mechanical Behaviour of Plastics
Many designers of plastic products have problems in understanding the complex mechanical behaviour of plastics. Their education is often more in the field of metals, which have a relatively simple mechanical behaviour up to 200 °C. Unlike for metals temperature and time (loading rate) determine the mechanical behaviour to a large extent. Moreover the structure of the polymer is of much influence on the mechanical properties.The content of this paper is based on teaching experience with students of Industrial Design Engineering. Although polymer engineering and designing in plastics are thought in each year, many students still have problems in understanding the structure related properties, the time and temperature dependent behaviour and the deformational mechanisms. I have made an attempt to summarise the mechanical behaviour using 10 essential figures.
Ternary Blends of Phenoxy Resins with Polyamides and Polyesters
The objective of this study was to investigate the potential of phenoxy resins as compatibilizer in the blending of polyamides and polyesters. Phenoxy resins react strongly with polyesters to produce grafted copolymers, which potentially can compatibilize immiscible blends of polyamide 6 (PA6) and polybutylene terephthalate (PBT). In this study, we considered ternary blends of two phenoxy resins with PA6 and PBT as both polymers are heavily used in automotive industry. Our study revealed that blends containing 5-30% by weight of phenoxy resins, although of two-phase nature, offered higher impact strengths and tensile modulus and much better phase-stability than uncompatibilized blends.
Thermal and Mechanical Properties of Siloxane-Modified Epoxy Resins
A siloxane oligomer, polymethylphenylsiloxane with with methoxyl end groups, was used as a toughening modifier for bisphenol-A diglycidyl ether (DGEBA) epoxy resins cured with 1,3-phenylenediamine (MPDA). The resins were synthesized by reacting the epoxy with the silxane at the catalyst tetraisopropyl titanate. The influence of siloxane contents on the thermal and mechanical properties of modified epoxy resins had a rougher fracture surface and higher fracture toughness compared to unmodified epoxy resins. The fracture resistance of the siloxane-modified epoxy resins increased with an increase of the siloxane oligomer content, while the fracture resistance at crack arrest increased only slightly. The glass transition temperature of the siloxane-modified epoxy resins did not change significantly with the content of the modifiers. A toughening mechanism based on the morphological and dynamic thermal behavior of the modified epoxy resins will be proposed.
Thermal and Mechanical Studies of Recycled HDPE, PP and PET from Blow- Extruded and Blow -Injected Bottles
This work examines the melting point and crystallinity behavior applying differential scanning calorimetry; mechanical properties by tension and Charpy-impact behavior and Melt Flow Index of recycled High Density Polyethylene, Polypropylene, and Polyethylen terephthalate used in blow-extruded and blow-injected bottles from post-consumer and post-industrial scrap. Some of the DSC results indicate a small decrease of the melting point for HDPE and a lower super cooling for the materials tested. Mechanical properties suffer minor deteriorations making possible the use of these recycled polymers in some industrial applications with reduction of cost.
Dynamic Mechanical Analysis and Toughening Mechanisms of Polycarbonate and 4,4’-Dihydorxydiphenyl Copolycarbonate
In comparison to bisphenol-A polycarbonate, a copolycarbonate (based on bisphenol A and 30 mole% of 4, 4’-dihydroxydiphenyl) has a higher glass transition temperature and much better notched Izod impact strength under a variety of impact test conditions before and after annealing.The copolycarbonate’s outstanding impact strength is correlated with shear yielding, and well-defined secondary relaxations centered around –34 and –100°C in the dynamic-mechanical spectrum. The –34°C relaxation is attributed to the rotation of phenylene rings around the axis of “inter-ring” C-C bonds in the diphenylene groups, while the –100°C relaxation is attributable to the rotation of carbonate groups.
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