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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Mechanical Properties of High Density Polyethylene Foams
High density closed-cell HDPE foams (450-950 kg/m3) were prepared by compression molding using 0-3 wt.% azodicarbonamide as a chemical blowing agent. The samples were then used to measure their flexural, shear, and tensile moduli. The data obtained were compared with models to determine which one represents best the overall property of these polymer foams. We found that thin skins (0-5%) have an important effect of the flexural and shear moduli of polymer foams, while they seem to have negligible effect on tensile properties.
Effects of the Die Geometry on the Expansion Ratio of Polystyrene Foams Blown with Carbon Dioxide
This paper presents the effects of the die geometry on the expansion ratio of extruded polystyrene (PS) foams blown with CO2. Three groups of interchangeable filamentary dies were used to thoroughly represent the die parameters. The experimental results reveal that a strong relationship exists between the expansion ratio of extruded PS foams and the die geometry through its effects on the pressure-drop rate, die pressure, premature cell-growth time and initial shape of extrudate.
New High Heat Polyetherimide Resins
A new polyetherimide homopolymer with a Tg of ~250°C has been produced. The resin has the melt processability of lower Tg polyetherimides but increases heat related properties by ~30°C. The performance features of this resin will be discussed along with some of its polymer blends. The new polyetherimide sulfone is miscible with existing polyetherimides allowing a range of transparent materials to be produced.
High Flow Glass Filled Polyetherimide Blends
Glass filled polyetherimide blends can offer a wider range of attractive performance features: non-halogen flame retardancy, high strength and stiffness and excellent dimensional stability. One drawback to these resins has been their relatively low flow in injection molding applications. New additive technology has been developed that can improve flow ~25-35% while retaining other important performance features. Commercial products using fiber glass and milled glass blends have been developed using this new technology.
Evaluation of Different Methods of Measurement for the Isotropic Stress Development in Curing Thermosets
We have developed two novel methods for measuring isotropic stress development in thermosetting resins during cure and subsequent thermal cycling. We use a sealed stainless steel spherical pressure vessel and thick-wall tube to impose three-dimensional isotropic constraints. The strain at the outer surface of the load cell is monitored by strain gauges. The isotropy of the stresses in tension and compression are examined for both methods.
Recent Advances in Organic Semiconductors for Optoelectronic Applications
During the last decade, semiconducting conjugated molecules and polymers have undergone a rapid development and show promise as low cost alternatives to the materials used in current technologies such as silicon and other inorganic materials. In this talk, we describe recent advances in their use for real-time holographic processing, and in organic electro-luminescent devices for displays.
Conjugated Polymers for Controlling Light
It is of interest to develop new anisotropic materials for light emission. To this end, we have aligned poly[2-methoxy-5-(2’-ethylhexyloxy)-1,4- phenylevinylene], MEH-PPV, in two different nematic liquid crystalline matrices, pentylcyanobiphenyl, 5CB, and a mixture of n-cyanobiphenyl liquid crystal, E7. Their alignment was investigated through linear dichroism measurements. Based on this work, a new family of optoelectronic devices and display technologies can be envisioned.
Study of Shark Skin and Die Swell of Calcium Filled-Polyethylene by Laser Micrometer and Scanning Electron Microscopy
Laser micrometer and scanning electron microscopy were used to study the die swell and shark skin of calcium filled polyethylene. The results were strongly correlated with the filler loading and the temperature.
Structural Characterization of Linear Low-Density Polyethylene (LLDPE) Using Thermal Analysis
The structural properties of eight linear low-density polyethylene (LLDPE) resins are investigated using thermal analysis by differential scanning calorimetry (DSC). A thermal segregation technique was used to characterize the short chain branching distribution of the resins. Although each of the eight resins has a similar density and melt index, the molecular structures are all very different, with regard to the frequency and distribution of branching.
Aromatic Hydrocarbon Content of Plastic Packaging Materials
Common food and drug plastic packaging materials of polyethylene, polystyrene, polyvinylchloride and polyethylene terephthalate have been analyzed for aromatic hydrocarbons using thermal desorption gas chromatography/ mass spectroscopy. All four types contain detectable levels of benzene, toluene, xylenes and naphthalene compounds. The source, at least in part, is believed to be gasoline vapors in the air. Polystyrene contains the highest level of aromatic hydrocarbons.
A New Toughening Method for Thermosets
A new toughening method which can be used for modifying thermosets is developed. An epoxy resin system is used for demonstration. Expandable hollow microspheres are also used for modification of the resin system. Heat treatment was conducted to produce compressive residual stress around hollow microspheres in solidified epoxy. Toughening mechanisms are discussed. A cavitation criterion in the presence of compressive residual stress is proposed.
An Approach to Couple Mold Design and On-Line Control to Manufacture Complex Composite Parts by Resin Transfer Molding
Resin Transfer Molding (RTM) has been used to manufacture advanced composite parts. In this paper, we present the design and validation of an automated RTM intelligent workstation. A new injection method, which can deliver the resin to various locations within the mold, while still allowing any individual gate to be opened or closed at any time during the filling, was designed and tested.
A 3D-Simulation Study of Barrier Properties of Nanocomposite Films
Nanocomposite polymer-clay films are inherently complex systems. Many classical and recent models study this system in two dimensions via a “brick-like” structure. However, a 2D approach may not sufficiently capture 3D effects. The results of a 3D simulation will be presented which examines the effects of various geometries on the computed diffusion coefficient will be presented. These results will then be compared to existing models.
Minimizing Voids in Pultruded Polymer Composites
A finite difference scheme was used to simulate heat transfer, curing and fluid flow during pultrusion of equal leg angle glass-fiber-reinforced vinyl ester composite profiles. Corresponding experiments were conducted using a commercial resin system cross-linked with styrene. Void formation was inferred from computed velocity and pressure profiles and measured using electron microscopy. Results showed that increasing pull speeds did not necessarily lead to increasing void content. Implications for optimizing the process of manufacturing all-composite bridge decks are discussed.
Process Simulation of Structural Long Fiber Thermoplastic (LFT) Composites with Features of Geometrical Complexity
The use of long fiber thermoplastic (LFT) composites has been increasing in the mass transit and automotive industries, as a result of the progress made in new materials and processing technologies. The present work focuses on process simulation of the extrusion-compression molding process for LFTs. Material and process parameters were varied to investigate the flow front and fiber orientation in typical structural shapes such as flat sections and ribs.
Composites Derived from Post-Consumer Nylon 6 Carpet
Over 2 million tons of post-consumer carpet is landfilled each year. This waste carpet is a potential resource for composites. Since waste carpets can be rapidly identified and sorted by face fiber, this paper focuses on the processing and properties of nylon 6 post-consumer carpet. The carpet is cleaned, shredded and extrusion pelletized. This feedstock is compounded with glass fibers and compatibilizers. Based on the properties achieved and the projected costs, applications are identified.
Fiber-Reinforcement of Composites by Reaction-Induced Phase Separation
A new class of fiber-reinforced composite materials is being designed in our laboratory by using a hybrid of thermoplastic and thermosetting polymers. The thermosetting polymers form separate phase upon reaction-induced phase separation and create morphology on the fiber surfaces. Consequently, strong fiber-polymer bonding of thermosetting composites and high fracture toughness of thermoplastic polymers are obtained from the same composite.
Assessing the Use of Lower Ordered Tensors in Numerical Predictions of Flow-Induced Fiber Orientation
Orientation tensors are widely used to describe fiber distributions in short fiber reinforced composite systems. This paper considers the effect of using lower order tensors in process simulations, and when computing mechanical properties for the composite structure from the flow calculations. Evaluations are performed by reconstructing the distribution function from successively higher order orientation tensors in a Fourier Series representation. Examples of fiber orientations in simple flow fields are provided.
Characterization of Polyetherimide and Polystyrene in Shear Flow
Filled thermoplastic polyetherimide and polystyrene samples were prepared and their morphological and melt processing properties were studied with respect to the processing conditions and filler loadings. The results should provide insights that are needed to solve complex issues encountered in the industry dealing with the recycling and processing of this important class of thermoplastic materials.
Application of Image Processing Technique in Analyzing Microstructure of Nanocomposites
An image processing program suitable for analyzing the microstructure of polymer/organic-montmorillonite (org-MMT) nanocomposites was developed based on the MATLAB software. The TEM photomicrographs of polypropylene/org-MMT were analyzed using the program. It has been revealed that the shape and size of the MMT in nanocomposites can be determined effectively and promptly by using the image processing program.
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