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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Design and Pressure Rating of PE Fittings; Stress Concentrations, Slow Crack Growth and the Use of Regression Coefficients in Material Choice
The various test methodologies for approving fitting designs will be reviewed and their applicability to predicting the expected lifetime of a pipe/fitting assembly will be discussed. The differences between ASTM and ISO methodologies in determining design coefficients and factors of safety will be reviewed before discussing the primary long-term mode of fitting failure that is Slow Crack Growth (SCG) from the area of highest stress concentration. This area of highest stress concentration is usually situated at the edge of the fusion joint, be it a conventional socket, sidewall or electrofusion joint. These stress concentrations can be accurately predicted by non-linear Finite Element Analysis. The stress values determined by this method can be used in conjunction with ISO 9080 Stress Rupture Curves for the fitting material to predict fitting lifetime. This predictive approach will be discussed
Fabrication of Nanocomposites Using Twin Screw Extrusion
Nanocomposites, with superior material properties, have promising potential applications in almost every field. The present work aims at developing a reproducible and continuous fabrication process to obtain the nanocomposites of aluminum nanoparticles that are uniformly dispersed in a polymer matrix and carbon nanotubes (CNTs) that are uni-directionally oriented in a polymer matrix. Due to its mixing potential, extrusion through a 28 mm Werner and Pfleiderer Twin Screw Extruder (TSE) was chosen to fabricate the nanocomposites. The aim of this research effort is to understand the nanoscale mixing characteristics of TSE using aluminum nanoparticles and CNTs, and to obtain the alignment of CNTs via extrusion through microchannels. Experimentally obtained residence time distributions of the mixing process were used to relate the mixing within the TSE to the microstructure of the extrudate. The microstructure of the nanocomposites has been characterized with scanning electron microscopy.
Mean Plus – The Absolute Correction of Instrumentally Generated Spectrometer Values
We developed a software program that corrects known, systematic spectrophotometric errors seen in commercial spectrophotometers today. This enables users of spectrophotometers to correlate color values from around the world so that they will be nearly identical. This includes instruments manufactured by different manufacturers, and instruments manufactured by the same manufacturer. The program works on six different modalities; including bi-directional geometries; that is, 45°/0°; hemispherical, either d/0° or d/8° geometries; or multi-angle geometries. Multiangle geometries are used to characterize and assess gonioapparent inks and coatings. It is not necessary that both instruments be of the same geometry.We summarize the performance of the software in the following statement: For modern instruments that are close in performance; that is less than 1 DE*ab one can expect that the errors will be reduced to an average of less than 0.10 DE*ab unit across 14 BCRA tiles. This agreement or correlation between two instruments can be relative; that is one instrument to another, or absolute; that is, correlating one or more instruments to a reference international standardization laboratory.ISOi and CGATS.5ii recommend methods to improve inter-instrument agreement. The software uses traceable artifact standards to do the training. Implementing this program allows conformance to in-house certification programs, ISO requirements, and CGATS. This is of particular importance to those who utilize ICC profiling.The Mean Plus program is designed to be readily incorporated into your existing software. There are multiple implementation methodologies available. For instance; it can be incorporated into your existing software through a DLL, Dynamic Linked Library. It can be used externally in post processing modes with an MS Excel spreadsheet, or it is available in a full-featured, customizable, quality control package. This program operates transparently to the user. Included with th
Numerical Simulation of a Multiple Valve Flow Control System during Injection Molding Processes
Process control is an important factor for improving the performance and consistency of thermoplastic parts manufactured by injection molding processes. A critical process parameter for manufacturing of high quality plastic parts is cavity pressure. This paper presents a continuation of a numerical based study of flow control utilized during multi-cavity injection molding processes. The capabilities of the current system design are limited by multiple valve interactions. Obviously, the valves are coupled with one injection source. Valve interaction may produce undesirable effects on pressure distribution in multiple cavities and should be studied further. With much attention addressed to multi-cavity family molding, the extension to multiple valve systems of 4, 6, and 8… would be beneficial and an interesting study. Understanding the flow modeling details through a single valve system is essential, thereby reducing the computational work involved with a multiple valve system.
Human Osteoblast Development on Polycaprolactone and Polycaprolactone/Hydroxyapatite Composite Scaffolds for Tissue Engineering
The study investigated the growth and adhesion of normal human osteoblasts (NHOst) to two different biodegradable systems. These materials included polycaprolactone (PCL) and polycaprolactone/ hydroxyapatite (PCL/HA) composite.We studied the attachment of osteoblasts to two-dimensional films of these materials. We specifically looked at the potential of these two biodegradable systems to promote bone tissue growth. The materials were cast into two-dimensional films. They were evaluated for functionality, growth and adhesion at designated intervals using microscopy and bone-specific alkaline phosphatase (BAP) and osteocalcin (OC) immunoassays.The cells on the composite scaffold produced more BAP than the cells alone or on the PCL scaffold. However, the cells on both types of scaffolds showed lower levels of OC than the cells alone.
Thermal and Rheological Evaluation of Pharmaceutical Excipients for Hot Melt Extrusion
Hot melt extrusion (HME) technology is becoming more broadly practiced in the Pharmaceutical industry. It offers many advantages over alternative pharmaceutical processing technologies such as wet granulation, solution casting, etc. A thorough understanding of the thermal and rheological properties of the polymeric excipients used is an important consideration during the selection of the excipient and processing conditions. The purpose of this paper is to report an experimental study that characterizes the thermal and rheological properties of hydroxypropyl cellulose (HPMC), ethylcellulose (EC), and polyethylene oxide (PEO). Thermal characterization was performed via DSC and TGA to identify transition (Tg/Tm) and degradation temperatures. Rheological performance was characterized by torque rheometry on a batch mixer and on a slit-die rheometer supplied by a single-screw extruder.
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.
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