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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Computational Materials at NASA Langley Research Center
The paper provides details on the structure and implementation of the Computational Materials Program at the NASA Langley Research Center. Examples are given that illustrate the suggested approaches to predicting the behavior and influencing the design of nanostructured materials such as high-performance polymers, composites, and nanotube-reinforced polymers. Primary simulation and measurement methods applicable to multi-scale modeling are outlined. Key challenges including verification and validation of models are highlighted and discussed within the context of NASA's broad mission objectives.
Mechanical Properties of Injection Molded Glass Fiber Reinforced PC/ABS with PC Oligomer
In this study, the effect of PC-oligomer on mechanical properties and internal structure of injection molded glass-fiber reinforced PC/ABS was investigated. The mechanical properties of PC/ABS with PC-oligomer were lower and the difference became larger with increasing GF content. However, the internal structure was different from the surface to the middle layer through thickness direction. It is thought that this difference in structure and the dispersion of GF affected the mechanical properties of the composites.
Modeling of Viscoplastic Constitutive Equation for Inelastic Deformation of Polymer with Unloading
A viscoplastic constitutive equation for inelastic deformation of polymers was formulated by combining the kinematic hardening creep theory of Malinin and Khadjinsky with the nonlinear kinematic hardening rule of Armstrong and Frederick. The nonlinear kinematic hardening rule was modified in order to describe peculiar inelastic deformation of polymers during unloading in particular. Experimental results for polyethylene were simulated by the constitutive equation and the validity of the modification was verified.
Mechanical Properties of PC/ABS Ultra High-Speed Injection Moldings
Effect of the content of PC/ABS and injection speed on the mechanical properties of PC/ABS ultra high-speed injection moldings, in which ABS content was varied, was investigated. Tensile modulus of near the surface evaluated using sliced specimen showed the highest values, and flexural modulus of the specimen was higher.
Influence of Gamma Radiation Dose and Loading Rate on Fracture Toughness of Polycarbonate
Fracture toughness of a polycarbonate plate was measured as a function of gamma radiation dose and loading rate using a SENB specimen. The fracture surfaces were analyzed by SEM. The test results showed that the material presents a ductile-to-brittle transition as the radiation dose and loading rate increase.
Determination of Scratch Behaviour of Molded Plastics
Scratch behavior in several types of plastics have been investigated in order to develop scratch test method for plastics. The effects of scratching conditions such as scratch speed and normal load on scratch behavior have been discussed. The scratch behavior was classified into three modes (i.e. ploughing, wedge formation and cutting) based on the vertical scratch tip displacement and the horizontal load during the scratch process and scratched surface observation. A concept of scratch behavior evaluation is described by using mapping technique and some of the typical results are introduced.
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.
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