SPE Library
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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Conference Proceedings
Using Aesthetic Additives in Engineering Thermal Plastics for in Mold Automotive Applications
Engineering Thermal Plastic (ETP) Suppliers continually look for ways to add value to their products lines enabling them to create more market share. One more recent added value strategy for ETP suppliers has been in aesthetic product portfolios. Colored pigments, dyes, non-dispersing pigments and aluminum flake are added to the supplier’s base resins. Thus creating a portfolio of molded in visual effects for the supplier to offer to their customers.The offering of aesthetic portfolios provides automotive Designers, Marketers, and Engineers with many benefits such as creating Vehicle Brand Differentiation, Cost Out opportunities along with Mass Customization of an application. Other potential benefits can be achieved with molded in effects by eliminating paint and the environmental issues associated with a paint process line. These benefits do not come without some challenges. The addition of these additives can cause property shifts in base resin. Also the use of aluminum flake will create flow line issues.Automotive applications for molded in visual effects typically are styling elements seen on the exterior of a vehicle such as a front grille or in the interior on a console bezel. The interior and exterior application come with their own set of material and performance requirements, which need to met by the supplier’s materials. A careful investigation must be made by the material supplier to matrix the application requirement and the customer chosen molded in visual effect. Part design for molded in effects must also be taken into account for a successful application. Design guidelines differ for aluminum flake additives verse translucent or clear material effects. Finally, consideration of guidelines for processing of the part must be reviewed in order to produce a class “A” surface.A case study of an in production molded in visual effect application will be presented. Nissan Quest Roof rack ends.
Universal Polyamide Overmold Thermoplastic Elastomer
Overmolding of Thermoplastic Elastomers (TPEs) has come of age (1). Fromthe traditional usage of TPEs in rubber replacement, emerging consumer market trends have driven the overmolding (OM) concept to commercial reality. Overmold eliminates the need for adhesives and primers to bond TPEs to rigid polymer substrates.Polyamide (often referred to as “Nylon”) substrate overmolded with TPE, a hard/soft combination, is often selected for high performance applications, such as power tools. Obtaining consistent bonding of TPE on polyamide substrates is well regarded to be difficult. This paper covers the various issues with respect to overmolding onto polyamide. A new generation of polyamide OM TPE products have been developed and this paper discuses the attributes of the new thermoplastic elastomer.
Biaxial Testing for the Modeling of the Thermoforming Processes
Modeling techniques for thermoforming have become increasingly important in optimizing products and processes. Model accuracy is strongly dependent on the integrity of experimental data used to fit model parameters. For this reason, a custom-built biaxial forming machine capable of strain rate up to 32s-1 was constructed in order to obtain experimental data at conditions similar to those in thermoforming processes. The biaxial deformation behaviors of a wide range of thermoplastic materials such as PET, PS, PP, and LDPE have been analyzed in three different stretching modes (simultaneous equal biaxial, constant width, and sequential stretching). The results are presented in the paper.
Measurement of Shear Viscosity and Solubility of Polystyrene Melts Containing Various Blowing Agents
The paper presents measured data on shear viscosity and solubility of HCFC-142b and HFC- 134a/Ethanol blowing agent laden polystyrene melts at different temperatures. This study establishes the baseline for more novel and innovative blowing agent systems to replace HFC-142b. The shear viscosity was measured using a Helical Barrel Rheometer. Apparent solubility was determined by observing the onset of gas bubble presence or absence in a specially designed optical cell with sapphire windows using a microscope-CCD cameramonitor/ recorder system. The paper presents a selection of viscosity and solubility data and, where possible, compares them with measurements carried out by others. The dynamic methods of measuring solubility and viscosity of gas laden polymer melts used in this study are closer to the polymer foam manufacturing practice.
Gas-Assisted Low Temperature Bonding of Polymeric Micro/Nanostructures
Polymer-based biomedical micro/nanodevices containing environmentally sensitive biomolecules are attracting increased interest. A critical requirement is the ability to assemble these devices at low temperatures in order to minimize denaturization. Studies of polymer thin films revealed that the properties at the polymer surface differed from those in the bulk. It was found that glass transition temperatures (Tg) at the polymer-air surface was substantially lower than the bulk Tg and increased toward the bulk value with depth from the surface. Subcritical CO2 could enhance the chain mobility and greatly depress Tg near the surface. Benefiting from this, we successfully demonstrated low temperature bonding of polymeric micro/nanostructures. The original micro/nanostructures are perfectly preserved after bonding.
High Performance Styrenic Thermoplastic Vulcanizates (STPVs) for Long Term Application
Styrenic Thermoplastic Vulcanizates (STPVs) were developed for long-term high temperature aging applications. These STPVs consist of polypropylene as the continuous phase and a modified Hydrogenated Styrenic Block Copolymer (mHSBC) as the dispersed phase. Property comparisons between STPVs and conventional TPVs (CTPVs) were reported in a prior monograph. These new STPVs show an improvement in solvent resistance by 20 % after 500 hours of immersion in IRM 903 oil at 125°C. The elastic recovery is 50 % better than CTPVs. The property retention for tensile characteristics is approximately 10% higher after aging for 1440 hours at 125°C when compared to CTPVs. These observed property improvements for STPVs relative to conventional TPVs are possibly explained by the unique morphology of the resulting compound. These performance characteristics make Uniprene XL™ suitable for high temperature and chemical environment applications. This new TPV technology is expected to bridge the gap between polypropylene/EPDM TPVs and more costly engineering TPVs.
Simulations of Layer-By-Layer Assembly of Polyelectrolyte Multilayers
Layer-by-layer processing of polyelectrolyte multilayers is a polymer processing technique that enables molecular-level control over the formation of precision coatings. Despite present widespread use, a fundamental understanding of the process remains elusive prompting us to employ molecular dynamics simulations of the process. Multilayer build-up was achieved through sequential adsorption of charged polymers in a layer-bylayer fashion from dilute solutions, the strong electrostatic attraction between oppositely charged polyelectrolytes driving multilayer growth. We find that a charge reversal after each deposition step is critical for steady multiplayer growth and a linear increase in polymer mass adsorbed after several deposition steps. Also, substantial intermixing between chains adsorbed during different deposition steps is observed. These results will be summarized, along with a perspective for the future, in our interactive presentation.
Microstructured Polyacrylamide-Cochitosan/ Xanthan Hydrogels
The synthesis of microstructured polyacrylamide-cochitosan and polyacrylamida-co-chitosan/xanthan hydrogels with large swelling capacity and improved mechanical properties were studied. Crosslinked polyacrylamide particles of nanosize scale are made by inverse microemulsion polymerization. These particles are then dried and redispersed in an aqueous solution of acrylamide and polymerized in the presence of a crosslinking agent and chitosan solution with or without the presence of xanthan polysaccharide solution. The swelling capacity of these hydrogels are studied and compared with the results obtained with conventional polyacrylamide hydrogels.
Morphological and Mechanical Properties of Epoxy Foam Reinforced Composites
Carbon fiber-reinforced plastics (CFRP) are widely used in a variety of industries such as sports and aerospace. In this work, the effects of presence of foam interlayer in carbon fiber-reinforced laminates on morphological and mechanical properties of the composites were investigated. Carbon fiber-reinforced plastics with epoxy foams were prepared at various processing conditions. The optical microscopy and the scanning electron microscopy (SEM) micrographs showed that the porous composites of pore size of less that 100nm were obtained. The presence of foam in the laminates resulted in composites with a better mechanical strength than the pore-free composites.
Effect of Process Parameters on Viscoelastic Properties and Hoop Stress in Micro Injection Molded Parts
Measuring the properties of micromolded parts has always been a challenge, but modified testing procedures may solve this problem. Tensile properties using a modified shear punch test and dynamic mechanical properties with modified torsion test fixture. The measured tensile strength increased significantly with packing pressure and melt temperature whereas mold temperature and injection velocities had little effect of these properties. Moreover, the strength of the micromolded parts was also greater than the values reported for standard tensile tests, thereby suggesting that skin effects influence the mechanical properties of thin-wall parts. The torsional properties of a micromold part, however, were similar to those for standard test specimens and increased with injection velocity and packing pressure.
Effect of Processing and Aspect Ratio on the Percolation Threshold of Exfoliated Graphite-Polypropylene Nanocomposites
Polypropylene based nanocomposites reinforced with exfoliated graphite nano-platelets (~10nm thickness, ~1mm diameter, < 5$/lb, Young’s Modulus ~1060Gpa) were fabricated using melt mixing. Initially, the nanoplatelets are mechanically dispersed into the polymer melt i.e., a twin-screw extruder, and then the composites are made using injection and compression molding. The effects that processing, aspect ratio and dispersion of graphite in the polymer matrix have on the electrical conductivity and percolation threshold of the nanocomposites are explored.
Co-Extrusion of Films for Medical and Other Packaging Applications
In this study the co-extrusion and use of a cyclicalpha olefin and metallocene polyethylene for medical and packaging applications was investigated. The combination of these materials are cost competitive and provides the opportunities for an environmentally friendly disposal and possible recycling. A film with alternating polyethylene, cyclic- alpha olefin, and polyethylene layers was coextruded with the use of three extruders leading into a multi-layer feedblock. The film was tested for oxygen and water permeability, tensile properties, falling dart impact strength, and tear strength. An economic analysis of the fabrication of the film for the use in medical and packaging applications was also constructed. The study demonstrated that the co-extrusion of a cyclo-olefin and metallocene polyethylene provides an opportunity for environmental means of disposal and a means of fabrication.
Comparison of Predicted and Experimental Filling of Micromolded Parts
Differences in simulation results for micromolded and macromolded parts are significant. Variations in the predicted results arise due to the governing equations used for flow analysis. Micromolded parts produced from two materials and using a range of processing conditions were compared with results of filling simulations. Critical results were the fill pressures, weld line strength and relative shear stresses developed in the parts. Fill pressures were obtained from the machine and optical birefringence was used to compare actual with predicted shear stress. These were then compared with the theoretical and experimental results. Differences were accounted for in terms of governing equations and assumptions used in the analysis.
The Solubility of CO2 in Polypropylene: Comparison of Various EOS Models
In order to get reliable solubility data, the swollen volume due to the dissolved gas is required. The swollen volume is typically estimated by an equation of state (EOS). In this paper three different EOSs, i.e., Simha- Somcynsky (SS) EOS, Sanchez-Lacombe (SL) EOS, and Perturbed-Chain SAFT (PC-SAFT) EOS, were applied in the polymer/gas mixture system. The apparent solubility was obtained using a magnetic suspension balance (MSB). The approaches based on the SS, SL and PC-SAFT EOS were proposed to predict the swelling behavior of polymer/gas mixtures for the purpose of correlation on the apparent solubility. Finally, the solubility of CO2 in PP melt was determined based on the three EOSs.
Effects of Particle Modification on the Fatigue Damage Progress in Polynanomeric Matrix Composite Laminates
The effects of the incorporation of layered clay, alumina, and titanium dioxide on the tension-tension fatigue damage progress in composite laminates were investigated by characterization of microcrack growth. The modification of the matrix systems of these composites, defined as polynanomeric matrix composites, was shown to significantly affect the fatigue damage progress. It was found that 5phr clay modification significantly improved the fatigue damage properties of the composite laminates. The mechanics of this effect were revealed by Scanning Electron Microscopy (SEM) observations in sub-micron and nano scales.
Rheological Studies of Polymers under High Pressure Carbon Dioxide
The viscosities of carbon dioxide-impregnated polymers in the literature are currently limited to high shear rates using capillary or extrusion rheometers. This paper uses a rotational rheometer to report data on the zero-shear viscosity of carbon dioxide-saturated polymers. The viscosity drop of a polybutene oil is one and half orders of magnitude at 35°C and 6 MPa, while the zero-shear viscosity of poly(dimethylsiloxane) (PDMS) drops half of an order of magnitude at 30°C and 3 MPa. Efforts are ongoing to measure the CO2- plasticized viscosity of polystyrene melt.
Load-Deflection Characteristics of Plated Thermoplastics
The theoretical and experimental load-deflection behaviors of plated and non-plated polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) samples were compared. In the first part of the study, the experimental 3-point bending load-deflection behavior of the non-plated PC/ABS samples was determined and was compared to calculated theoretical predictions. In the second part of the study, the equivalent width method was used to predict the theoretical load-deflection behavior of the plated PC/ABS samples. These predictions were compared to the experimental three point load-deflection curves. The study demonstrated that the plating did have an extremely significant effect on the actual load-deflection behavior of the PC/ABS samples and that the equivalent width technique did predict the change in stiffness, but tended to over predict stiffness. Additional tests are being conducted to determine the creep behavior of the PC/ABS and plated PC/ABS samples.
Integrity Management of Plastic Pipelines
The area of integrity management of pipelines is one of growing interest. In many pipeline applications, the aging infrastructure is posing a challenge for pipeline owners and operators. Particularly in applications involving potentially hazardous materials this is an issue that needs to be approached proactively. The Natural Gas Distribution industry is one falling into this category and new Pipeline Integrity Management Regulations are currently being considered by the federal Department of Transportation. Separate from the pending regulations, Gas Utilities are also proactively examining the integrity of plastic pipeline systems. This paper reviews the changing approach and pending legislation for managing the integrity of plastic distribution system materials. A general approach to examining the functional integrity of plastic piping systems is presented. A specific case study examining the integrity of an exhumed-from-service (natural gas distribution) plastic piping material is presented along with comparisons of projected pipeline functional integrity versus actual field service performance. It is concluded that, although the specific form of pending regulations for pipeline integrity management (PIM) is not known, some effective tools and techniques for assessing pipeline functional integrity, a subset of the overall PIM approach, are currently available.
Effect of Particle Size on the Efficiency of a Moisture Scavenging Additive
The effect of fibers and fillers is well understood in the plastics industry, where additive particle size has been shown to affect a variety of part properties. However, the result of integrating moisture scavenging additives within plastic materials is relatively unknown. This experiment will examine how particle size affects the efficiency of a moisture scavenging additive in a variety of different carrier materials. Numerous mechanical properties such as tensile strength, impact strength, viscosity, hardness, and specific gravity, among others, will be tested to evaluate the results of this analysis.
Pultrusion and Mechanical Characterization of GFRP Composite Sandwich Panels
This paper presents mechanical properties under static loads of 3.5 inch thick composite sandwich panels which were manufactured through pultrusion process. The objective of the present work is to demonstrate an automated pultrusion process for producing composite sandwich panels which results in optimal mechanical performance while minimizing unit weight and production cost. To achieve the above objective, the composite sandwich panels were designed, pultruded, tested and evaluated for their mechanical performance enhancement in relation to panels manufactured from VARTM process. Preliminary results have demonstrated that pultruded panels present significant advantages over VARTM panels, including 36% increase in tensile strength and stiffness, 87- 97% increase in bending stiffness at panel level, 8 -20% reduction in area weight, and est. 46% reduction in material and production costs.
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