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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Advances in Barrier Concepts for Improved Rigid Packaging
Poly (ethylene terephthalate) (PET) has become the material of choice for soft drinks, juices, medical and pharmaceutical applications, and some foods. Over the last ten years, efforts have intensified to improve barrier properties and hot fillable capabilities of PET in order to extend its applications to include even more food and oxygen sensitive products. These advancing technologies include new high barrier resins, coatings, oxygen scavengers, multilayer structures, heat setting and blending.A brief review of the current status of the above technologies will be presented. Specifically, a thorough discussion of experimental results will include blends of PET and other polyesters as well as blends with nylon polymers. The issues related to transesterification kinetics, optical clarity and compatibilization, strain-induced crystallization, injection molding, stretch blow molding, microstructure and container physical properties will be presented and discussed.
A New Family of Barrier Nylons Based on Nanocomposites and Oxygen Scavengers
The gas barrier properties of nylon 6 could be improved significantly by a ‘passive barrier’ nanocomposite approach in which ultra-thin, nanoscale silicate platelets of high aspect ratio were incorporated via an in-situ polymerization process. The oxygen barrier properties of nylons have also been further enhanced by a novel ‘active barrier’ approach in which proprietary polymeric oxygen scavengers were melt blended into nanoscale dispersions of high oxygen scavenging efficiency. By combining the nanocomposite and oxygen scavenger technologies, a new family of barrier nylons (Aegis®) have been developed for use in multilayer packaging structures, particularly in multilayer, coinjection stretch blow molded PET bottles for extended shelf-life packaging of oxygen-sensitive foods and beverages.
Saran™ Barrier Resins – A Historical Perspective
Saran barrier resins, which are copolymers of polyvinylidene chloride (PVDC), are-well known for their use in demanding barrier packaging applications to minimize the permeation of oxygen, water vapor, and odors. Less well known is the fact that Saran resins were not originally used in barrier packaging applications. As a matter of fact, the first commercial application for Saran resins was as an acid catalyst in the production of grinding wheels. Another early application of Saran resins, which was developed in the late-1930’s, was monofilament fibers. Over the nearly 65 years of their history, Saran resins, fabrication methods and markets have changed dramatically.
Polymeric Electrolyte Membrane (PEM) Nanocomposites for Fuel Cells via Direct Polycondesation
Polymeric electrolyte membrane (PEM) based fuel cell systems for automobiles, homes, and portable power fuel cells are already important for high energy density and very good environmentally benign energy sources . Currently, film forming fluorinated sulfonic acid containing copolymers are utilized primarily at 80C or lower for cost insensitive applications, such as the NASA space program. An increase in the fuel cell utilization temperature is desired for a number of reasons, including better efficiency and to improve the tolerance to impurities in fuels derived from H2, methanol, natural gas, biomass or reformed gasoline, such as carbon monoxide. New and improved mechanisms for conductivity above the boiling point of water are needed, which operate with little or no water. We have been interested in the direct copolymerization of sulfonic acid containing monomers to afford ion conducting systems such as poly (arylene ethers), including sulfones and ketones, and naphthalene dianhydride 6 membered ring based polyimides. Both random (statistical) copolymers and block copolymers based on these two major classes of materials are being investigated [2-7]. Several of these systems are surprisingly highly compatible with important additives, e.g., heteropoly acids (HPA), such as phosphotungstic acid, and zirconium hydrogen phosphate, which have potential for allowing conductivity above 100C. Highly dispersed nanocomposites have been achieved, which are possible because of specific interactions between the inorganic additive and the host copolymer, including hydrogen bonding, and dipolar interactions between the HPA and the sulfonic acid groups and/or backbone functionality. That highly dispersed HPA systems have been achieved can be demonstrated by FE-SEM, AFM and water extraction studies, and the fact that conductivity values of >0.1 S/cm are possible at temperatures approaching 140C. Excellent adhesion of the HPA to the matrix affords transparent mechanically robust
Pilot Plants of the Future
Pilot plants have historically been used in polymers R&D for scale-up of new catalyst, product and process technology. Because of their essential role, pilot plants are likely to remain an important component of new technology development in the future. However, over the past several years, a limitation with conventional pilot plants has become apparent relating to an inability to detect problems of reactor operability, such as fouling and sheeting. Improvements are required in several areas including process instrumentation and mechanistic models of reactor fouling. These developments, along with improved structure-property correlations, will define the pilot plant of the future. Although physically similar to those of today, future pilot plants will feature significantly improved utilization for reduced R&D costs and faster and more reliable scale up of new technology.
Hydrogenation at Supercritical Single-Phase Conditions
This paper gives an overview of the supercritical single-phase hydrogenation technology. It gives the basic facts from the scientific literature and the practical consequences of these facts including some possible applications to the plastic industry.The new technology can improve the product quality to levels that were impossible with the traditional multi-phase technology.The key element in the new technology is that one adds a solvent, typically propane, which dissolves both the substrate and the hydrogen. In this way a supercritical single-phase is created and the transport resistance between gas and liquid has disappeared.
A Study for Improving the Quality of a Co-Extrusion Blow Molded Bottle
The development and production of a six-layer bottle of ethylene vinyl alcohol/polypropylene for tomato ketchup is described in this paper. The main aim of this study was the analysis of the influence of some processing parameters on the through-thickness structure of the composite. It included a first for the definition of the operating conditions leading to the required bottle structure. In a second stage, and after setting the desired bottle wall structure, the optimum welding conditions were determined. In this study, the mould temperature, the mould closing speed, and the hold time (i.e., time interval between the mould closing and the inflation) were varied according to a L9 Taguchi experiment design. The effect of the processing parameters on the morphology and properties of the pinch-off welding zone was analyzed and the best operating conditions were determined.
Analysis of Permeability and Weld Line Integrity in Multi-Layer Blow Molded Automotive Fuel Tanks
In this study, numerical simulation is used to analyze the blow molding process of an automotive fuel tank. In a first step, 3D simulations employing a shell approximation are used to investigate the deformation of a multi-layer parison as well as the thickness variation for each layer. Next, 2D simulations are used to study the details of the welding line formation. Locally, the shear flow across the parison thickness can no longer be neglected. The position of the interface between the layers is calculated using adaptive meshing to handle the very large deformations. The influence of the rheology on the position of the interface is investigated.
Evaluating Quasi-Simultaneous and Contour Welding for use with the Clearweld™ Process
The Clearweld™ process is a form of through transmission laser welding that enables welding of two clear substrates with minimal effect on the appearance. Aesthetics are especially critical in the medical and packaging industries. The Clearweld™ process can also weld colored or opaque substrates, and reduces the number of color limitations imposed in traditional through transmission laser welding.Single beam contour and quasi-simultaneous welding methods were evaluated for use with the Clearweld™ process to aid users in the selection of beam delivery methods. The welding speed, laser power, and clamping pressures were varied in order to determine the effect on weld strength, amount of collapse, residual color, and weld time. Studies were focused on PETG.
Fiber Graphics in Mold Decoration
The purpose of this paper is to introduce and review basic elements of a newly available IMD material and technology that will impact the way many molded plastic articles will look and feel in the future. Another purpose is to inform molders who now offer IMD product about a new decoration option, a new arrow for the quiver to help create new business by expanding the range of product offerings and/or functionality.This paper is not about how to do IMD, and assumes the reader is familiar with the process. This subject has been described thoroughly in previous ANTEC papers (please refer to presentations by Jeff Applegate and Jordan Rotheiser).Fiber Graphics IMD was developed to help grow this category of decorated plastic; and in the most extreme scenarios, we are seeing a general increase in consumers’ base level of expectations about how they experience the touch and appearance of everyday plastic products and how they should perform. One example of this is: if cell phones do not need to ever slip out of your shirt pocket when you bend over, then why should they?
A Role of an Uneven Temperature Distribution at the Flat Die Inlet on the Die Performance
Flat dies are used for the extrusion of a wide range of flat products. In general, the main requirement to the die design is to get products with a good mass distribution. It is known that a die can be designed well but its performance may become much worse due to uneven material properties at the die inlet. Such a behavior can be studied by a 3D simulation.The described study uses a 3D FEM analysis to investigate an effect of an uneven temperature distribution at the die inlet on the final distribution. The temperature inhomogenity is modeled in two ways. At first a temperature profile created by the heat dissipation is used. In the second case, an L-shaped spindle (valve) is used to generate the temperature irregularity. The spindle orientation was horizontal or vertical to the die axis. In all cases, the influence of the temperature inhomogenity on the final distribution at the die outlet was studied.
Heat Transfer Coefficients and Screw Temperature Profiles in Modular Twin Screw Extrusion Machines
For modular co-rotating twin screw extrusion machines, we developed models of the heat transfer coefficients as well as the screw temperature profile in a machine with both starved regions and fully filled regions. The dependence of heat transfer coefficients on screw diameter, screw rotation speed and power law index of polymer melt was investigated. The screw temperatures were calculated along the screw axis and radial directions as well as compared temperature development difference between these two directions. Calculations are made with dimension of commercial machines with varying screw diameter.
Comparison of Residence Time Distributions for Different Materials in the Same Extrusion Operation
Kinematic modeling has been shown to be important for the understanding and control of co-rotating twin screw extruders. The residence time distribution (RTD) is often used to characterize an extrusion process. Due to the nature of the polymer flow in the extruder, few have felt that the RTD would be independent of material properties for the same extruder setup. To investigate this question, four different polymers, two polyethylenes and two polypropylenes, were processed on the same 30mm Werner and Pfleiderer co-rotating twin-screw extruder (CoTSE) equipped with reflectance optical probes to compare their RTD's. Additionally, each material was tested to determine its complex viscosity, to better understand the phenomena involved.
Investigation of Melting Mechanism in a Twin Screw Extruder using a Pulse Method and On-Line Measurement
A perturbation method was introduced to investigate the melting phenomena of polystyrene (PS) and polypropylene (PP) blend in a twin-screw extruder. A sliding barrel technique was used to realize the on-line visualization of the processes and to obtain the temperature and pressure profiles along the extrusion region. The melting behavior of PS/PP (80:20) blend was studied under various ratios of the flow rate (Q) over the screw rpm (N). It was found that the melting processes of the PS/PP blend in the TSE can be divided into three sections. Most of the melting occurred in a narrow transition from the partially filled region to the fully filled region. No large deformation of solid polymer pellets was found for all the processes studied here. The relative amount of solid concentration in the flow can be obtained through this perturbation method. It was shown that the solid concentration at the beginning of the fully filled region increased as the ratio of Q/N increased.
Investigation in Power Consumption of Twin Screw Extruders in Respect of Scale-up Theory
In the field of polymer recipe development the homogenization of components is one of the most important points. For reasons of economy on the one side, and to receive a convenient machine configuration on the other, practical investigations are carried out on lab scale extruders. Subsequently the optimized process has to be transferred to an industry scale extruder during a scale-up process.On the basis of temperature and power consumption measurements at a tightly intermeshing, co-rotating twin screw extruder an approach for process transferability is discussed. By keeping the screw diameter constant the influence of throughput on the system energy balance is specified for several polymers. A theoretical approach for partly filled, geometrically similar systems is validated by means of experimental data extracted from a Coperion W&P ZSK-30. The results provide a basis to transfer operating points for co-rotating twin screw extruders.
A Perturbation Method to Characterize Melting during the Extrusion of Polymers and Blends
By means of a novel flow perturbation technique, fundamental details during the extrusion of semicrystalline and amorphous polymers, such as Polypropylene (PP), Polystyrene (PS), or PP/PS polymer blends can be analyzed with respect to the kinetics of melting and energy input. The effects of extrusion conditions such as throughput and screw speed were examined. A specialized, high-speed data acquisition system, the “Extrusion Pulse Analysis System” (EPAS) has been employed to enable on-line monitoring and data analysis based on an imposed mass disturbance to provide a real-time diagnosis of extrusion melting processes in laboratory and manufacturing applications.Using the power response profile of the mass perturbation, four key sequential stages of melting have been proposed for twin-screw extrusion of a single component or polymer blends. A “lubricated melting” mechanism is also proposed for the extrusion behaviors of PP/rubber and PS/rubber blends using an Ethylene copolymer and SBS block copolymer as the minor phase ingredient.
In Line Measurement of the Polymer Melting Behavior in Single Screw Extruders
Existing experimental techniques designed to study melting behavior of polymers inside the screw extruder suffer from limited functions or tedious procedures. Their invasive nature affect friction characteristics and heat transfer, significantly influencing the outcome of measured parameters. This paper presents an in-line, non-invasive measuring technique that can accurately capture experimental data and images from inside the extruder through a small quartz window and a rigid boroscope at short response times using a highly instrumented 45 mm single screw extruder with built-in sensors. By sensing the difference in optical properties between the melt and the solid phase, the melting behavior of high density polyethylene was visualized and measured with this non-invasive technique.
Solid Bed Melting in Single Screw Extruders - An Alternative First Order Mechanism
This paper discusses our initial attempt to model the results presented at ANTEC 2003 which demonstrated that for most of the literature data on solid bed melting careful reanalysis indicates that the solid bed consumption is dominated by melting in the thickness not the cross channel direction. A first order model for the melting is presented which focuses on the melting dynamics in the bed thickness direction. A similar analysis would be necessary for the cross channel direction but is beyond the scope of this paper due to space constraints. The model combines the concepts developed by Tadmor in his classical work with the ideas developed in this laboratory focused on the importance of using the velocities based on the screw rotating.
The Influence of Melt Rheology on the Specific Output Rate of Broad Molecular Weight Distribution Polyethylenes in Single Screw Extrusion
The extrusion (single-screw) characteristics of four broad molecular weight distribution (MWD), linear polyethylene resins are discussed with an emphasis on the output rate. Despite the high molecular weights of the subject polyethylenes, their broad MWD (Mw/Mn range: 10 to 60) does not limit the pressure and torque developed during extrusion. However, the specific output of the four polymers was quite varied. The dependence of the specific output on the melt rheology of the polymers is addressed; specifically, the shear-thinning extent of the melt in the metering section was found to influence output rate. The unique and counter-intuitive temperature-dependence of the shear-thinning character of one of the four polymers will also be addressed in relation to its extrusion characteristics. Lastly, a simple and quick method to evaluate the relative solids conveying efficiencies for various polyethylenes will be presented.
Performance Characteristics of Elongational Mixing Screws
Elongational mixing (EM) screws have recently become commercially available. Elongational flow allows more efficient mixing, particularly dispersive mixing. Elongational mixing reduces viscous dissipation relative to shear mixing. This results in lower motor load and reduced melt temperatures. This paper will present detailed operational data of a 90-mm mixing screw producing cast film and a 130-mm mixing screw with a special barrier section producing filled polyolefin film. Data produced with the elongational mixing screw is compared to a conventional mixing screw.The data indicates that elongational mixing screws allow increases in output and product quality while at the same time reducing motor load and melt temperature. The ability of elongational mixing screws to disperse gels is a particular advantage in film extrusion.
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