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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Evaluation of Scratch Resistance of Polymers
In this paper, the equivocal issue of scratch resistance of polymers is treated. Through experimental effort using a custom-built scratch test device, scratch hardness and scratch visibility are found to be the key considerations in quantifying the scratch resistance of a polymer. However, scratch hardness and scratch visibility are not necessarily interrelated. Care has to be taken to evaluate scratch resistance of polymers. Approaches for improving scratch resistance of polymers will also be discussed.
Structural Formation of Amorphous Poly(ethylene Terephthalate) during Uniaxial Deformation above and below Glass Temperature
The structural formation of PET under uniaxial stretching above and below Tg using in-situ WAXD and SAXS by synchrotron radiations was studied. Some new insights into the strain-induced mesomorphic transition were obtained. These structural developments are closely related to the mechanical responses, which have not been observed previously.
Use of Thermography in Craze Growth and Plastic Zone Studies of Polycarbonate
The occurrence of a plastic deformation zone ahead of the crack tip in fracture of thin films and sheets of polycarbonate has been reported by several authors. This presentation will report the use of a high-speed thermographic imaging technique for studying the temperature rise at the crack tip as well as the shape and temperature distribution of the plastic zone in polycarbonate sheets. The technique was used to monitor craze and crack growth in compact tension tests. New trends in the growth of the plastic zone and the crack propagation mechanism were observed.
The Craze/Yield Ratio as a Measure of Polymer Toughness
The ratio of a polymer's craze strength to its yield strength is an excellent measure of toughness. It can be used to quantitatively compare materials and to predict how the ductile-brittle transition will change as a function of a variety of environmental and material variables.
Compaction and Dilatation Effects during the Plastic Deformation of Glassy Polymers
Samples of poly(methyl methacrylate) - PMMA for short - were subjected to uniaxial tensile tests at 80 °C under conditions at which large plastic strains are obtained. The intrinsic stress-strain behavior of the material and the strain induced volume changes were simultaneously determined by means of a novel video-controlled system. It was observed that PMMA experiences a complex volume variation involving compaction and dilatation stages. These effects are correlated with orientation and crazing mechanisms.
Effect of Deformational Behavior of Cell Structure on Mechanical Properties of Polyurethane Foam under Compressive Loading
We have investigated the mechanical properties of polyurethane foam with several foaming state. Moreover, image processing system was being developed to measure the cell shape and the area in the foam. We observed deformation of the cell structure under compressive loading. Effect of cell structure on mechanical properties was examined.
In-Situ Characterization of Cavitation during the Deformation of Semi-Crystalline Polymers
A novel testing technique is presented for the quantitative measurement of cavitation in polyethylene and talc-filled polypropylene, subjected to uniaxial tension. Both materials exhibit extensive dilatation in the plastic stage. In the case of neat polyethylene, the kinetics of cavitation is correlated with SEM observation of crazing within the stretched spherulitic microstructure. For talc-filled polypropylene, extensive cavitation makes him suitable for shock absorption.
Reduction of Stress-Whitening in Polypropylene Extrusion Blow Molded Bottles
Reduction in stress-whitening of polypropylene is critical for success in the clear packaging market. Other factors desired include stiffness and toughness. A fundamental study of stress-whitening, and key factors (resin and processing) is presented. A lab scale test method for quantifying stress whitening, validation of the method with extrusion blow molding (EBM), and the observed stress-whitening mechanisms are discussed.
Novel Polypropylene Materials for Biaxially Oriented Film
A resin for BOPP (biaxially oriented polypropylene) film requires good stretchability in addition to general desirable properties of film. Although a HCPP (high crystalline polypropylene) or a nucleated polypropylene offers higher stiffness, its processability on a tenter line is significantly limited. This study introduces a novel HCPP resin that could improve processability while maintaining enhanced stiffness or toughness.
Cutting and Tear Resistance of PET Films
Comparisons between cutting and tear resistance of polyethylene terephthalate film are shown in relation to film properties and loading condition. Tear resistance is characterized by the essential work of fracture method in mode I as a function of test speed and temperature. Cutting resistance is characterized using non-standard test methodologies. Interrelationships between the two tests as well as the possibility of correlation to commercial slitting processes are discussed.
How Much Do We Really Understand about Crystallization in Polymers?
Our understanding of crystallization in polymers is based on crystallization behavior at a series of isothermal crystallization temperatures. Studies of the crystallization of nylon 66 and PET using embedded microthermocouples and rapid cooling show that a constant linear growth rate occurs as the temperature drops. This behavior shows that crystallization is controlled by a temperature gradient at the growth face, and not by the measured temperature.
Morphology, Crystallization Kinetics and Dynamic Mechanical Analysis of Phosphate Glass-Polyamide 12 Hybrid Materials
This study focuses on a fundamental study of morphology, crystallization kinetics, and dynamic mechanical properties of a novel phosphate glass- polyamide 12 hybrid system with up to 50% by volume of a low Tg phosphate glass (Pglass). The hybrid properties were enhanced with increasing amounts of Pglass. The crystallization kinetics was found to be consistent with the Avrami equation. Morphological investigations revealed a thermodynamically stable structure that could be tuned to targeted specifications.
Crystallinity, Orientation and Mechanical Property Development in Melt Spinning Poly(ethylene-co-octene) Filaments
The structure development in melt spinning of poly(ethylene-co-octene) with different octene contents has been studied. The filaments are characterized by WAXD, birefringence and DSC. Crystal structures of four copolymers are determined. The Herman-Stein crystalline orientation factors are then calculated. The uniaxial mechanical properties are also measured.
The Effect of Shear and Pressure on the Crystallization of Polymers
Among crystallizible polymers changes in state can be brought about by the action of shear and pressure. Yet, we most often characterize the crystallization staticially. All polymer conversions processes subject the polymer to high shear, stresses and pressure. These can have very significant effects on the mechanical properties of the materials. This work has shown that almost every effect we observe from static crystallization studies is reversed in studies where the material was subjected to shear and pressure.
Diverse Morphologies and Dynamic Mechanical Behavior in Metallocene Polyethylene Copolymers
Dynamic mechanical relaxation experiments were performed on a series of ethylene/1-octene copolymers with diverse morphologies from impinged spherulite to totally amorphous structure. The continuously changing dynamic mechanical relaxation behavior is related to structure parameters, such as crystal structure, crystallinity and lamellar thickness, acquired from DSC, WAXD, and SAXS experiments.
Polymer Blends as Proton-Exchange Membrane Materials for Fuel Cells
Blends of sulfonated poly(ether ketone ketone) (SPEKK) and poly(ether imide) (PEI) are being considered as proton-exchange membranes (PEMs) to achieve high conductivities while maintaining the mechanical stability required for use in fuel cells. Proton conductivity comparable to Nafion™ has been obtained. Variables such as the SPEKK sulfonation level, the blend composition and the membrane casting procedure affect the blend microstructure and the fuel cell performance.
Effect of the Viscosity Ratio on the Particle Coalescence in PS/HDPE Blends under Extensional Flow
The effect of viscosity ratio and concentration on particle coalescence in PS/HDPE blends was studied. Three different PS and HDPE were used in order to modify the viscosity ratio (p). The blends were prepared by extrusion at 200°C. A morphological study in postextrusion zone is presented where the draw-down ratio (DR) is varied. The evolution of particle to fibers is interpreted in terms of coalescence particles where the viscosity ratio plays an important role.
Modeling of Cell Structure in Polyurethane Foam
We suggested that the cell structure of polyurethane foam could be approximated to be oval by the use of Finite Element Method. Three kinds of parameters for cell modeling were employed, which are ratio of radius, the area, and thickness of cell wall.
Enhancement of Adhesion between High Density Polyethylene and Poly (Ethylene Terephthalate) Films
Blends of high density polyethylene (HDPE) and ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) prepared in a twin-screw extruder, were used to improve the adhesion between HDPE and poly(ethylene terephthalate), PET films.The results of T-peel tests showed that the adhesion strength between the films increased with increasing bonding temperature, pressing time and elastomer concentration. The adhesion characteristics of multilayer films were studied in terms of morphological and spectroscopic analyses.
Comparing Models for the Glass Transition Temperatures of Compatible Polymer Mixtures
Various proposed equations relating glass transition temperature to composition are compared for:. Relative success in fitting unsymmetrical temperature-composition diagrams,. Number (and ease of establishing) required constants, and, Ability to be cast explicitly in either temperature or composition. A novel exponential form satisfies these criteria very well. It is contrasted with another author's equally successful but mechanically awkward form which is based on thermodynamic considerations
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