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
Multi-Component Injection Molding-Part 1: Interface and Microstructure Development
K.P. Palluch, A.I. Isayev, May 2000
The purpose of this paper is the physical modeling and numerical simulation of the interface and microstructure development during the multi-component injection molding process. A software has been developed based on the control volume finite element method to calculate the transient non-isothermal multi-phase flow of viscoelastic polymer melts and to predict the stress-induced crystallization within the semi-crystalline polymers. Based on the developed simulation software material selection and process optimization becomes possible.
Gas Barrier Behavior of Syndiotactic Polystyrene
K. Hodge, S. Nazarenko, G. Capaccio, May 2000
The effect of crystallinity on barrier properties of syndiotactic polystyrene (s-PS) was studied. The crystallinity was induced in s-PS by cold crystallization and crystallization from the melt. Two thermally induced crystalline forms ? and ? were observed in all crystallized samples as well as the presence of ?-mesomorphic phase in the samples cold crystallized at lower temperatures. The oxygen permeability and diffusion occurred at finite rates in the loose a hexagonal crystalline phase while it was negligible in better-packed ? orthorhombic phase. The permeability and diffusion of oxygen increased with an increase of the amount of a ordered phase while the solubility decreased, remaining, however, still soluble for oxygen even at 100%.
A Study of the Tensile Creep Behavior of Recycled High Density Polyethylene in Aqueous Mediums
John Raybuck, Daniel Heuer, Paul Koch, May 2000
Recycled polymers are currently being used in the design of commercial products for the maritime structure industry. Marine pilings, pier fenders, and pier support elements are just some of the products being designed with recycled polymers. Understanding the effect of submersion in salt and fresh water on the mechanical properties of the material used in these products is important. This study will examine the tensile creep behavior of recycled HDPE in ocean water, fresh water from Lake Erie, distilled water, and air. A specially designed apparatus for aqueous creep testing was utilized to obtain the data for this study.
A Comparison between Open Flame and Hot Air Heating Methods for the Rotational Moulding of Plastics
M.P. Kearns, R.J. Crawford, N. Corrigan, May 2000
In the 1940's when rotational moulding of plastics was first developed, open flames were used to heat the mould. In the 1950's there was a switch to hot air ovens as a cleaner method to heat biaxially rotating moulds. Today hot air ovens dominate the market due to the convenience that they offer the user, although it is widely recognised that they are relatively inefficient as a means of heating. This paper presents results from an experimental investigation to assess the relative merits of open flame and hot air oven rotational moulding machines. Polyethylene mouldings of varying thickness were produced on both types of machine and cycle times were compared by using ROTOLOG to record mould internal air temperatures. It is shown that significant cost savings are possible using the open flame heating method. These savings arise from both lower energy consumption and reduced cycle times.
Evidence for a Master Curve Behavior for Polypropylene (PP) Degradation and Durability
Samuel Ding, Craig L. Sandford, Michael T.K. Ling, Atul Khare, Lecon Woo, May 2000
We have studied material degradation and durability in a broad based program in selecting medical materials. In addition, the specific requirement that medical devices and packaging must have specified shelf-lives supported by real time data also prompted for quantitative evaluation. A large number of PP types and samples were studied under diverse conditions. These included high temperature oxidative stability by oxidation induction time (OIT), high oxygen pressure OIT, oven aging, aging and oxidative stability after ionizing radiation and real time ambient storage. The activation energies from the surface embrittlement processes were also found to have a striking similarity to the thermal processes. To overcome the difficulties in generating long term ( greater than 10 years) data, well characterized historic samples of up to 23 years in age were included in this study. When all data were combined, a striking feature was apparen very few data points at higher temperatures could allow a reasonable determination of the shift factor and quite accurate estimates for lower temperature durability. This methodologyt: that for PP, a self-similarity existed among all systems examined. This allows a simple vertical shift of data to construct a master curve" similar to rheological master curves. The implication being if the master curve can be constructed when supported by further studies could lead to broader applications and deeper understandings on polymer degradation"
Effect of Electron Beam Irradiation on Medical Packaging Materials
Sherwin Shang, Tahua Yang, Craing Sandford, Michael T.K. Ling, Lecon Woo, May 2000
Medical devices industry differs from other polymer applications in one major aspect: that the products frequently need to be sterilized. Recently, sterilization by ionizing radiation has become increasingly popular, due to simplicity and cost effectiveness. In particular, the beta or electron beam (E-beam) irradiation has been adopted along with the traditional gamma radiation from radioactive Cobalt or Cesium sources. Of course, the ionizing radiation that disrupts bio-macromolecular structures in bio-burdens can and also frequently do damage polymer chains. We have conducted a study on material degradation due to E-Beam irradiation and compared with treatment with gamma. Similarity of the two processes as well as significant differences will be presented.
Electrofusion Joint Strength of Polyethylene Pipes
Hiroyuki Nishimura, Fumio Inoue, Hiromichi Inoue, Hideki Tani, Yuji Higuchi, May 2000
Electrofusion (EF) joints have been widely used as easy-to-fuse and high-quality joints for joining polyethylene (PE) pipes. When we introduced EF joints 150 mm or more in diameter, an electrofusion simulation program was concurrently developed to reduce time for design and experimental work. It was verified that the simulation results calculated by using the program agreed well with the experimental results. This paper describes the features of the program and its application to EF joints developed for the casing pipes of district heating and cooling pipelines.
Simulation of Shearing and Mixing Sections
H. Potente, W. Többen, May 2000
Three-dimensional finite-element-calculations on spiral shear sections and faceted mixing sections have been applied to test the influence of geometry onto pressure-throughput and mixing performance. Well-chosen dimensionless numbers described the geometrie of the elements so a statement about the process development could be reached. Residence time and the Flow Number ? were utilized to evaluate the mixing effect and its information value.
Tooling Project Management of Injection Molding
Michael Yue, May 2000
Delivering good qualify mold on time is always a big issue for both mold maker and molder. Either of them could loss business if the tool is delayed and or in poor quality. How to avoid these? This paper starts with tooling flow chart and discusses tooling project management techniques. The problems encountered in tooling scheduling and manufacturing process are analyzed. Also, tooling qualification and cost reduction are discussed.
Single Fiber Composites: A New Methodology for Determining Interfacial Shear Strength
Gale A. Holmes, Donald L. Hunston, Walter G. McDonough, Richard C. Peterson, May 2000
One of the critical factors controlling the long-term performance and durability of composites in structural applications is the interfacial shear strength (IFSS). The single fiber composite (SFC) test has been viewed by many as the best test for determining this parameter. Although the SFC test has been extensively researched, the micro-mechanics models used to obtained IFSS values are based on simplifying assumptions that are not realized under experimental conditions. Thus, results from this test often violate the known strength of the constituent materials. Therefore, a new methodology is presented that utilizes realistic assumptions.
Degradation during Long Term Storage for Post Gamma Polypropylenes
Craig Sandford, Samuel Y. Ding, Michael T.K. Ling, Lecon Woo, May 2000
Medical devices differ from other polymer applications in one major aspect: that the product frequently needs to be sterilized. Due to simplicity and cost effectiveness, sterilization by ionizing radiation has become increasingly popular. Of course, the ionizing radiation that disrupts biological macromolecular structures (bio-burden) can and frequently does damage synthetic polymer chains. We have examined several polypropylenes (PP) subjected to long term ambient storage for up to 18 years after gamma irradiation at different doses. Many of the samples in thin film form have completely disintegrated. However, in many cases the degradation reaction was not homogeneous, with an apparent distinct skin-core structure and very different properties. These results and interpretations with an oxygen diffusion limited degradation reaction model will be presented.
Influence of Processing Conditions on Medical Material Degradation/Failures
Michael T.K. Ling, Craig Sandford, Adel Sadik, Henk Blom, Samuel Y. Ding, Lecon Woo, May 2000
In the medical packaging and devices industries, products are subjected to numerous converting and other downstream processing steps. For example, a vigorous drying step must be in place to minimize the reverse depolymerizing hydrolysis reaction before melt processing for condensation polymers. Another major downstream process for medical products is the sterilization. For medical devices, ionizing radiation has become increasingly popular. Of course the ionizing radiation which disrupts bio-macromolecular structures in bio-burdens can and frequently does damage polymer chains. In this presentation, we will report on case histories of processing modality and severity and their influence on material degradation and subsequent failures. In addition, situations where control limits can be created on manufacturing procedures can be put in place to prevent (minimize) failures due to processing degradation.
3-D Curing Simulation of Thick Thermoset Components
John Viego, Richard P. Theriault, Tim A. Osswald, May 2000
Thick components or sections such as ribs and bosses require a 3-D simulation to fully determine final properties due to the curing reaction and vitrification effects. A finite element simulation has been developed to model curing of thermoset parts, including compensation for diffusion control effects and varying boundary conditions. For diffusion control, the glass transition temperature (Tg) was related to conversion by the DiBenedetto equation. The simulation considers parts molded under realistic industrial processing conditions and has shown that non-uniform curing and thermal gradients occur during processing. These gradients depend on part geometry, cure kinetics, and processing conditions. This paper presents the models used, along with the results of the simulation applied to a sample geometry molded under various conditions.
Investigation of Rotational Moulding Characteristics and Mechanical Properties of Metallocene Polyethylene
X. Wang, R.J. Crawford, A.M. Fatnes, E. Harkin-Jones, May 2000
Metallocene grades of polyethylene offer exciting opportunities for the rotational moulding industry. However, as they have only become commercially available in the last few years, their full potential has yet to be exploited. This paper reports on the results of an experimental investigation in which processing conditions are related to the microstructure and mechanical properties of three grades of metallocene polyethylene. The materials have been characterised by dynamic parallel plate rheological tests, NMR spectra and DMTA. The results obtained from equivalent standard grades of polyethylene are used as a basis for comparison. It is shown that the metallocene materials possess many rheological and physical properties that are desirable in rotational moulding. A detailed understanding of the unique nature of these materials is necessary in order to take full advantage of their properties in rotational moulding.
An Assessment of Weld Heterogeneities in PMMA Using Birefringence
R.J. Wise, R. Thomas, May 2000
This paper concentrates on the measurement of melt orientation of polymer chains and welding residual stress using birefringence. PMMA specimens were welded using four techniques, hot plate welding, laser welding, hot gas welding and ultrasonic welding. Measurements of birefringence made in transverse sections showed that levels of polymer chain orientation and some components of residual stress could be measured. These measurements were used as a basis for the assessment of heterogeneities introduced into PMMA during welding by the four techniques.
Foaming of Thermoplastic Elastomers with Water
Abdelhadi Sahnoune, May 2000
We present results on foaming of a thermoplastic elastomer (TPE) using water as the physical blowing agent. The TPE is a blend of polypropylene and fully crosslinked EPDM rubber made by a dynamic vulcanization process. The influence of the blowing agent content, and the processing conditions on foam density, cell nucleation, and foam structure are discussed. A brief discussion about the similarities and the differences between foaming in homopolymers and in TPEs is also included.
Evaluation of Layer Spreading in Coextruded Structures via a Modular Die
Joseph Powers, Joseph Dooley, Carl Reinhardt, Gary Oliver, May 2000
Layer spreading in coextruded sheet structures remains a problem solved more often with art than with science. A modular die, i.e. a die with inserts for the entrance channel and for the manifold, was designed and evaluated for a range of entrance shapes, manifold shapes, and resins. The results from these experiments lead to an improved selection process for die designs for coextruded sheet.
Biaxial Test Method for Characterization of Fabric-Film Laminates Used in Scientific Balloons
Magdi A. Said, May 2000
Space Structures that require light-weight materials with sufficiently high strength and environmental endurance have been in increasing demand since the early 1980's. However, the biaxial behavior of these structural materials under pressurized loading, is rarely found in the literature. An experimental investigation was conducted to develop a test method and hardware to characterize the biaxial behavior of a fabric-film laminate intended for use as a structural envelope for large balloons. The material tested is a composite laminate of three layers. The three layers are: polyester-based woven fabric, 6 microns film of polyester (Mylar type A) and 6 microns film of linear low density polyethylene (LLDPE). The laminate structure provides high strength to weight ratio. In this study, a test technique has been developed to measure the biaxial response of the material to known stress ratios. The information gained from the test can be manipulated to estimate Poisson's ratio and the development of a material structural model.
A Geometry-Based Model for Determining the Filling Time in Resin Transfer Molding Process
Faezeh Soltani, Souran Manoochehri, May 2000
A geometry-based model is developed for determining the fill time in resin transfer molding process. In this model, the preforms are assumed to be thin flat with isotropic and orthotropic permeabilities. The in-plane shape of the preform is arbitrary. The location of the vents, the maximum flow length, and the time required to fill the mold are calculated applying analytical solutions. The variety of preforms and processing conditions are used to verify the model. The mold filling time calculated by the model was in good agreement with those obtained using the C-MOLD filling simulation. Saving in the computational time was the key advantage of this model.
A Rapid Method for Prediction of the Vent Locations in Resin Transfer Molding Process
Faezeh Soltani, Souran Manoochehri, May 2000
A model is developed for predicting the location of the vents in isotropic RTM molds of various geometries. The preforms may contain holes and/or impermeable inserts. The location of the vents required to avoid trapping air bubbles are determined using neural network and geometric-based solutions. The neural network was trained with data obtained from simulation and actual molding experimentation. For a number of test cases, the performance of the method is compared to the prediction of vent locations obtained using a commercial mold filling simulation. It was found that the proposed method can predict vent locations with a good accuracy as compared to the filling simulation results. Applying the neural networks reduced the amount of computational time in comparison to the simulation methods.

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