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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Nanocomposites of Polyamide 6/Metallocene Polyethylene/Grafted SEBS with Montmorillonite
Nanocomposites of montmorillonite (MMt) and ternary blends of Polyamide 6/Metallocene Polyethylene/SEBS grafted with diethyl maleate (PA6/mcPE/SEBS-g-DEM) and maleic anhydride (PA6/mcPE/SEBS-g-MA) were prepared in an internal mixer (Rheomix) in order to improve the toughness of the nanocomposite counterpart prepared with PA6 and MMt. The PA6/MMt nanocomposite was the matrix or continuous phase whereas the mcPE was the dispersed phase and the grafted SEBSs were the compatibilizer agents. Tensile properties were measured and transmission and scanning electron microscopy were used to characterize the nanoclay and phase dispersion, respectively. The results showed that the incorporation of the metallocene polyethylene produced a decrease in the embrittlement of the nanocomposite unfolding a higher rupture strain. The use of SEBS-g-MA instead of SEBS-g-DEM is a better alternative from the mechanical behavior point of view. TEM micrographs showed that tactoid, intercalated and exfoliated structures were obtained.
Analysis of Heat Transfer in Combined Socket and Butt through Transmission Infrared Welding of Plastic Pipes
Combined socket and butt through transmission infrared (TTIr) welding of plastic pipes involves radiant heating of an absorbing element that is placed at the weld interface with air cooling of the exterior of the socket. For successful welds it is important to minimize deformation of the socket while providing sufficient heat input to form the butt weld. Therefore, modeling of heat flow is important. To better understand the heat flow that occurs, infrared radiation transmission measurements were performed for couplings of different thickness. Thermocouples were also used to measure the temperature history in the pipe. The experimental results were then compared to analytical models as well as complex finite element models of the heat flow. Good agreement was found between the experimental results and the theoretical models. These models can be used as a tool to analyze and optimize the heating and temperature in the weld zone under different welding conditions.
Interfacial Effects in Replication of Nano-Scale Features
While injection molding provides the ability to produce nano-scale features at high rate high volume, the interfacial effects between the polymers melt and the tooling become more critical than with macro-scale parts. Parts molded from four amorphous materials, a cyclic polyolefin, polystyrene, polycarbonate, and polymethylmethacrylate, were characterized for part replication using atomic force microscopy. Part replication (i.e, depth ratio and feature definition) were correlated with the measurements of contact angle which then can be quantitatively converted to the wetting and surface tension. Suggestions are made for improving the replication of nano-scale features.
Three Dimensional Fiber Orientation in Vibration Welded Joints of Glass Fiber Reinforced Polyamide-6
A technique to obtain fiber orientation distribution was developed for the vibration-welded joints of polyamide-6 with 30% glass fiber. The heat affected zone (HAZ) of fiber reinforced polyamide-6 was successfully revealed by polishing and etching the HAZ. Under the polarized microscope in reflected light, detailed microstructure domains including bulk crystal zone and HAZ were observed. To obtain quantitative measurement of three dimensional fiber orientation distribution, orientation tensors were calculated from elliptical fiber cross section images. The fibers in HAZ were highly oriented toward the squeeze flow direction compared to the bulk phase. Thicker HAZ does not guarantee more random fiber orientation by average but higher fiber population more randomly oriented. High weld pressure at low amplitude promotes fiber reorientation in the tensile direction and thus weld strength.
Thermal Stress Analysis of Plastic Processing Tools
To transform the plastic materials into final products, plastic processing tools have to go through heating and cooling cycles. The dramatic temperature change develops thermal stress, often to a level where the tools start to crack. In this paper, we first reviewed the fundamentals of the thermal stress and strain. Then two case studies were presented to demonstrate the importance of considering the thermal stress in tool design. The CAE simulation proved that both cast skin tool and injection molding tool cracked due to high thermal stress. To reduce the thermal stress, the cast skin tool was required to allow freer expansion and contraction through using less constrained clamps, while the injection molding tool had to beef up the tool design at the weak spot.
Study of the Properties of Polypropylene/Cassava Starch Composites
The purpose of this work was to study the effect of incorporating cassava starch, in proportions of 10, 15 and 20 wt%, into Polypropylene (PP). All composites were mixed in a co-rotating twin-screw extruder. Blends were characterized using the DSC, TGA and Capillary Rheometry techniques. Tensile properties were also evaluated. Results obtained indicate that the crystallinity degree remains unchanged when the filler is incorporated. However, when the compatibilizer (Polybond 3150) is added, the crystallinity degree decreases independently of its percentage in the composite. All blends showed a pseudoplastic behavior and a rise in melt viscosity when the filler content was increased. Regarding the mechanical properties, an increase in Young’s Modulus and a decrease in elongation at break were obtained when cassava starch content was increased. The addition of Polybond produced a significant increase in the Young’s Modulus values.
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.
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