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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Ultra High Shear Rates and Their Effect on the Physical Properties of an Injection Molded Part
The objective of this experiment was to determine how ultra high shear rates affected the physical properties of polycarbonate and polypropylene. To accomplish this, three different runner inserts will be utilized. The three inserts vary the time that the plastic is sheared, and the plastic's shear rate. Parts were then molded using the three different inserts. Finally, tensile data was collected to determine the effects of ultra high shear rates and shear times on injection molded parts. The data was not what was expected. The higher shear rates increased the ultimate elongation and the modulus due to cross-linking in the plastic as it cooled.
Ultrasonic Characterization Performed during Chemical Foaming of Cross-Linked Polyolefins
Injection molding of cross-linked low density foams made from poly(ethylene-co-octene) resins results from simultaneous reactions occurring during the process. The ultrasonic quasi-static technique (no flow) can mimic adequately the conditions prevailing during the molding process (pressure, temperature, time). In this work, compounds prepared from resins with different MFIs are investigated, exhibiting the influence of the degree of cross-linking on the CBA decomposition, as well as the effect of viscosity on the degassing conditions. Experiments demonstrate the complexity of CBA decomposition and of gas molecules diffusion in the polymer matrix.
Ultrasonic Riveting and Hot-Air-Sticking of Fibre-Reinforced Thermoplastics
Mechanical fastening, e.g. screwing or riveting, or thermal joining techniques like ultrasonic riveting or hot-air-sticking, are used to join thermoplastic composites and metallic structures.This paper compares the experimental results of ultrasonic riveting and hot-air sticking of fiber-reinforced polypropylene (PP-GM30, PP-LGF40) and polyamide6 (PA6-GF30) with steel. The influence of glass fiber volume fraction on process stability and on the tensile strength of the joint are evaluated from micrographs and X-ray photographs. The influence of the thermoplastic matrix material and the glass fiber length on the wear of the sonotrode during ultrasonic riveting is investigated based on SEM-micrographs and surface roughness measurements.
An Ultrasonic Spectroscopic Evaluation of the Ring Opening Metathesis Polymerization of Dicyclopentadiene
Characterization of reaction kinetics and degree of polymerization can be difficult in some polymer systems. In this work, an in-situ ultrasonic spectroscopy technique is used to study the ring-opening metathesis polymerization (ROMP) of dicyclopentadiene (DCPD) by bis(tricyclohexylphosphine)benzylidene ruthenium (IV) dichloride (1). Pulse echo ultrasonic spectroscopy employing a 20 MHz transducer is used to measure reaction kinetics of the polymerizing media. By designing a reaction cell with a flexible PET window, the change in both density and velocity can be simultaneously monitored. The technique is evaluated by comparison to FTIR analysis of a model system.
Ultrasonic Tests to Monitor Cure of Dicyclopentadiene (DCPD) for Use in Reactive Rotational Moulding
Ultrasound can be used to measure viscosity by analysis of signal velocity and attenuation. This work looks at exploiting change in signal properties to monitor viscosity during cure in reactive rotational moulding (RRM). Results from off-line tests on dicyclopentadiene DCPD show a rise in ultrasonic velocity, and a decrease in relative attenuation during cure, associated with mechanical property changes owing to increased cross-linking. Variations in velocity and attenuation can be used to predict important stages in polymer development. This technique is non-intrusive; a single transducer is mounted on the mould exterior. Pulse-echo measurements are made, allowing additional estimation of part thickness.
Ultrasonic Weld Shear Strength of Mineral Filled and Glass Fiber Reinforced Polypropylene Blends
A study was conducted to determine the effects of inorganic fillers and reinforcements type and concentrations on the joint strength of ultrasonically welded polypropylene. An ultrasonic welding test specimen was designed with the goal of producing shear failure at the welded joint during tensile testing. Twelve formulations of neat, mineral filled, and glass reinforced polypropylene, each at different additive concentration levels, were prepared, injection molded, ultrasonically welded, and tested. The formulations were also evaluated for inherent bulk material shear strength. It was found that the ultrasonically welded joint shear strength reached a maximum at an additive concentration of approximately 30% by weight for all three additive types studied. It was also found that the mineral filled formulations had ultrasonically welded joint shear strengths that were approximately equal to or slightly more than the estimated shear strength of the bulk material, while the glass reinforced formulations had ultrasonically welded joint shear strengths approximately 50% less than that of the bulk material.
Undercutting Mold Performance: Ejection Wear
During mold design, most consideration given to wear in the ejector system is focused on metal-to-metal interfaces. Specifically, attention is paid to the wear between the pins, sleeves, blades, and the bores through which they pass. This research focused on wear that occurred on the metal core during ejection of glass filled plastic parts. This phenomenon has been largely undocumented, and was, in some cases, found to be aggressive. Certain tool steels and copper alloys with hard coatings were shown to be significantly more resistant to this type of wear than others. In addition, product geometry appeared to play a role in the wear process.
Upgrading Recycled Waste Stream Polyethylene by Modification with Nanoscale Clay Hybrids
Recycled polyethylene (RPE) - clay hybrids (RPECHs) were prepared by melt mixing of RPE with modified montmorillonite clay using maleic anhydride grafted polyethylene oligomer (PE-MA) as a compatibilizer. Electron microscopy and X-ray diffractometry revealed that dispersion of hydrophilic clay in the highly hydrophobic polyethylene matrix increased with increasing PE-MA content. The highly dispersed RPECH nanocomposites provide substantially enhanced mechanical properties over neat RPE. The results of experimental parametric studies are reported and applied to new value-added applications for this inexpensive and plentiful polymer resource.
Use of Fitments on Stand-Up Pouches for Liquids
Over the past ten years, there has not only been a growth but also an evolution in the use of cap fitments on flexible packages around the world.In Japan and South America, and to a lesser extent in Europe, the stand-up pouch for liquids, both with, and without, fitment has been used for a number of years as a primary package. In the U S, there has been limited use, and primarily as a “refill” package for a rigid container.A lot of fitment applications started out as pre-made pouches that where then filled on fill/seal equipment. That is currently still true in the limited applications in the US. However, for a number of years, form-fill seal equipment has been used extensively in other countries. This paper will focus on the form-fill-seal application.
The Use of FTIR/ATR to Investigate the Migration of Polyisobutylene in Polyethylene for Cling Film Applications
A range of LLDPE films with polyisobutylene (PIB) content from 2%-8% was manufactured using a Killion cast film extrusion system. The films were aged at 25, 35 and 45°C for up 28 days, to enable tack (cling) development. FTIR/ATR analysis was used to investigate the surface migration of PIB. The results were confirmed by mechanical tack (cling) analysis and these showed increased migration rates with increasing PIB concentration, ageing and storage temperature.A second series of films with 8% PIB content were manufactured from a range of LLDPE's. FTIR/ATR, DSC and mechanical tack analysis were used to investigate the relationship between polymer properties and migration rates. The study established that crystallinity was the most influential factor governing PIB migration and this could be related to polymer density. Co-monomer type was found not to be a factor influencing migration of PIB.
The Use of FTIR-ATR to Investigate the Migration of Automotive Fuel Components in High Barrier Materials used in Fuel Line Applications
A Perkin Elmer Fourier Transform Infra-Red (FTIR) spectrometer with a variable temperature Attenuated Total Reflectance (ATR) attachment was used to investigate the migration of fuel components in a series of fluoropolymer, polyester and polyamide based films at various temperatures. Diffusion of the fuel components in these films was investigated by monitoring the changes in peak height of the infrared spectrum at particular wavenumbers, specific to the individual fuel components. The results show that fuel component migration increases significantly with progressive increase in temperature. The results also show that the diffusion rates increase significantly at temperatures above the glass transition temperature (Tg) of the particular polymer. The diffusion results are similar to those obtained using other techniques such as gravimetric and dynamic permeation techniques, which involve a much more prolonged analysis regime.
The Use of Polymer Processing Additives to Improve Melt Processing of m-LLDPE Extrusion
There is a large body of work showing that the addition of polymer processing additives (PPAs) results in an improvement in the processing performance of polymers. Some of the processing improvements that have been observed include a reduction in melt fracture, pressure, die build-up, and gels along with an increased processing window and improved surface finishes. Previous papers have shown the addition of a PPA has reduced many types of gels that result from cross-linking, oxidization, and unmelted material. This paper will investigate the reduction of unmelt gels seen with the addition of PPA to a polyolefin plastomer (POP) and will infer the mechanism of how the coating of the PPA on the extrusion barrel reduces the unmelt gels. In addition to the mechanism this paper will evaluate the different methods of adding the PPA to the extrusion system.
The Use of Three-Dimensional Computation Fluid Dynamics in the Design of Profile Dies
Efficient fully three-dimensional, non-Newtonian flow algorithms have been available for several years to aid in the design of flat extrusion dies . However, there are few tools available, which can be used in a practical way by an engineer tasked with designing a complex profile die in a reasonable period of time. This paper demonstrates through an actual example how the efficient use of 3-D CFD algorithms and automatic finite element mesh generators can be used to eliminate much of the cut and try" from profile die design. The effect of die swell on the profile shape downstream of the die exit is also examined."
The Use of Zinc-Neutralized Ethylene-Methacrylic Acid Copolymer Ionomers as Blend Compatibilizers for Nylon 6 and Low-Density Polyethylene
The effect of composition on the morphologies and properties of uncompatibilized and compatibilized blends of nylon 6 and LDPE were studied over a wide range of weight fractions. The mechanical properties of the uncompatibilized blends had reduced tensile and impact strength after mixing, which was almost certainly due to poor interfacial adhesion between the two polymers. It was found that the addition of a zinc-neutralized poly(ethylene-co- methacrylic acid) ionomer as a compatibilizer can improve mechanical properties. Micrographs showed that the ionomer caused a reduction of the dispersed phase size, especially when nylon 6 is the dispersed phase of the blend.
Using a 2(cubed) Full Factorial Plan to Analyze the Effect that the Reaction Temperature, Al/Zr Ratio, and Pre-Contact Time Has on Propylene Polymerization Employing a Metallocene Catalyst
The influence of the reaction temperature (T), the Al/Zr ratio (Al/Zr) and the pre-contact time (t) on propylene polymerization using Et(Ind)2ZrCl2 (rac-( ethylenebis(indenil))zirconium dichloride) as the catalyst, and hexane as the solvent, was evaluated using a 23 full factorial plan. All the evaluated properties were mainly affected by the reaction temperature. The catalytic activity and the xylene solubles increased when T increased. Both the melting and the crystallization temperatures, the crystallinity, and the molecular weight decreased when T was raised.
Using Blow Molding Simulation Software as a Troubleshooting Tool
Currently, after a new blow molded part is designed, the molds are built then modified until a desirable part is produced. This results in higher mold costs and longer time to market. From the industry standpoint, blow molding simulation software could lower mold costs by predicting potential problems before a mold was built. Potentially, companies could test molding scenarios to determine the feasibility of the design without ever cutting steel. A considerable savings in labor and scrap costs could result. The focus of this research was to determine how effective blow molding simulation software would be when used as a troubleshooting tool.
Using Neural Networks to Predict Injection Molded iPP Shrinkage
Shrinkage occurs in all polymers and it is extremely dependent on processing conditions, like holding pressure, holding time, injection speed, mold temperature and melt temperature.The utilization of shrinkage data allows designers to predict the final part dimensions accurately. Numerical prediction of the part shrinkage can be made using simulation packages availables commercially. However, a part shrinkage involves non-linear material behavior and its estimation involves significant simplifications. The neural networks can model highly non-linear systems and predict a part shrinkage effectively.In this study, a neural network architecture was developed to predict the shrinkage of an iPP injection molded part at several process conditions defined through the design of experiments.
Using Recycled Concrete as a Filler in Polyethylene Resins
Adding concrete fillers to base plastic materials can increase mechanical properties such as tensile strength, flexural strength, and hardness. This can be done through the addition of fillers to a virgin and recycled plastic material. By increasing these properties, plastics can be used in applications where they were not previously used.The effects of compounding concrete filler with polyethylene were studied. Two different percentages of the concrete fillers were added to test different properties against a NEAT (nothing extra added to it) sample of both recycled and virgin polyethylene.
Variation of Electrical Properties with Exfoliation Condition in Nanocomposites
Dielectric measurements were made on clay filled nylon and polyethylene-ethyl vinyl acetate (PE-EVA) copolymer nanocomposites during processing by extrusion. Nylon without clay had a small dielectric dispersion while PE-EVA did not. The addition of Na treated clay to the PE-EVA copolymer increased the dielectric constant (relative permittivity) above that of the PE-EVA copolymer but did not increase the conductivity or cause any dispersion. In both PE-EVA and nylon, addition of akyl ammonium chemically treated clays gave substantial increases in dielectric dispersion that are associated with the intercalated or exfoliated state. X-ray diffraction measurements were made on the composites.
Various Plug Assist Materials and Their Effect on the Thermoforming Characteristics of Polymeric Sheet
Plug assist thermoforming is an art which thermoformers have developed through many years of experience. As the industry becomes more competitive and expands into increasingly difficult products, modeling of the process holds the potential to dramatically shorten development time, increase process and materials efficiencies and lead to new market opportunities.This report presents the results of investigating the force-deformation characteristics of a HDPE polymer sheet when formed with different plug assist materials with the aim towards developing modeling parameters. The variables investigated were plug material, plug temperature, plug speed, plug shape, plug surface roughness and polymer sheet thickness and temperature.
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