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.
Shortening the design cycle by using rapid prototyping is a standard for injection molding product creation throughout the world. Developing new products while being aware of each type of prototyping technology allows the designer to judge fit, function, esthetics, economics, and product features prior to cutting a production tool; saving money and time. The use of several prototyping processes, including stereolithography (SLA) and laser sintering (SLS) are detailed with updated information on new tolerance standards and new materials.
A fluorescent probe, covalently grafted to glass, is used to study the glass / resin interphase region near the surface. A shift in the fluorescence maximum during resin cure can be monitored when the grafted dye is immersed in epoxy. The position of the fluorescence maximum is used to detect a difference between the bulk resin and interphase. To make the technique practical as a cure sensor, the dye can be grafted to a glass fiber optic.
Flexible printed circuitry (FPC) is a patterned array of conductors supported by a flexible dielectric film made of high strength polymer material such as polyimide. The polyimide core is the premier dynamic structure membrane with an extraordinary ability to withstand continuous. Flexing for hundreds of millions of flexing cycles, fatigue performance and reliability are paramount issues in the design and manufacturing of FPC. In the composite structure, the conductive layers are more vulnerable to failure due to their lower flexibility compared to polyimide film. This paper is focused on the reliability assessment of FPC based on the high cycle fatigue resistance. Fatigue resistance of various material systems has been analyzed as a function of temperature and frequency. The fatigue characteristics of selected material systems are summarized in the form of S-N diagrams. Failure mechanism observations are discussed and complete fracture analysis is presented. In various FPC systems, it has been found that the changes take place in FPC failure mechanisms from well developed and aligned through the width cracks at low temperature to an array of multiple cracks with random sizes and locations at high temperature. Comparative analysis of various material systems based on fatigue performance is presented.
True stress - strain - temperature (TSST) diagrams are being used as a tool for characterizing thermo-mechanical behavior of polymers. TSST diagrams are developed for materials that undergo necking by consideration of a material point perspective. In the present work TSST diagrams of three polyolefin types, Polyethylene, PE, polypropylene, PP, and polybutylene, PB, are constructed and their relevance to accelerated lifetime testing discussed. It is found, in contrast to PE and PP, the changes in PB deformation behavior raises the issue of validity of lifetime predictions of PB at temperatures below 70°C based on testing at temperatures above 70°C.
Chemical degradation is one of the dominant mechanisms of aging in polymers. To prevent a premature catastrophic failure of polymers in durable applications, an understanding of the causes and kinetics of chemical degradation are required. UV accelerated oxidation has been applied in this work to study the effect of oxidative degradation on physical and mechanical properties, such as crystallinity, density, toughness and deformability of unpigmented, unstablelized Poly (ethylene-co-carbon monoxide), ECO, and Poly (1-butene), PB. The correlations between the variation of physical, mechanical properties, and reduction of molecular weight are reported. The effect of oxidative degradation on fatigue crack growth rate and build-up of residual stresses due to densification is also addressed.
To characterize the notch sensitivity for short-term (e.g. notch sensitivity under dynamic impact conditions, sensitivity to failure under rapid crack propagation conditions) and long-term (e.g. slow crack growth resistance, pipe lifetime under creep conditions) strength of thermoplastics, the ratio of the energy-to-break in tensile impact test for notched and unnotched specimens (short term notch sensitivity factor) and the similar ratio for the time-to-failure in tension creep test (long term notch sensitivity factor) are introduced. The limits of these ratios as the notch length approaches zero are called the notch sensitivity factors. The test procedure is developed and applied to determine the factors for one pipe grade polyethylene (PE) and one pipe grade polybutylene (PB). The results indicate that both materials show short term notch sensitivity, and that PB shows very high long term notch sensitivity in contrast to PE.
A comparative analysis of polyethylene (PE) and polybutylene (PB) tensile behavior at various temperatures is reported. It is noted that PB exhibits different tensile behavior below and above 70 °C (transition temperature). This is in contrast with PE that does not change its tensile behavior over the entire temperature range considered. PB also exhibits different crack growth mechanisms at 110 °C (above the transition temperature) than that at 50 and 23 °C (below the transition temperature). The fatigue lifetime for PB at 110 °C is observed to be more than ten times the fatigue lifetime at 23 °C. Thus the commonly accepted opinion that temperature is always an accelerating factor of fracture process is not applicable for PB within the above range of temperatures. It is suggested that the observed anomaly in temperature acceleration of fracture in PB is related to the reported transition of tensile behavior around 70 °C
It has long been known that polymers have a structural order intermediate between that of insulators and that of amorphous materials. We show how this intermediate type of order leads to anomalous charge conduction properties for insulating, semiconducting, and metallic polymers. Concepts such as fractal dimensionality and mesoscopic order are introduced and their unusual predictions for variation of conductivity and dielectric constant with temperature and frequency are presented. A comparison with experimental results for undoped and doped polymers is presented.
A comprehensive analysis of the heat exchanges between an instrumented Aluminum mold and various thermoforming materials were made during controlled heavy gauge production trials. Five materials Impact Polystyrene, High Density Polyethylene, PETG, ABS and Impact Polypropylene Copolymer were evaluated. Heat flux was calculated. Experimental variables were quiescent and circulated ambient air, mold and coolant temperatures.
This study demonstrated that a variety of fluoro-containing polyimides with hydroxyl groups, simply incorporated with a copolymerization of 2,2'-bis(3- amino-4-hydroxyphenyl)hexafluoropropane (BAHHF), 2,2'-bis(4-aminophenyl)hexafluoropropane (BAHF), and 2,2'-bis(1,3-dioxo-1H,3H-isobenzofuran-5-yl)hexa-fluoropropane (BIFHF), were responsible for the good solubility in organic polar solvents. These polyimides exhibited optically transparent at a wavelength of 365nm with respect to the UV-visible spectroscopic determination. Measurement of differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) indicated that these polymers, having the glass transition temperatures (Tgs) varied from 306°C to 317°C, were quite thermally stable. In addition, the inherent viscosity as well as refractive index of the polymers was studied and potential applications of photoresists in terms of photosensitivity were also discussed.
Most nanocomposite materials are initially prepared by modifying the hydrophilic clay or hydrophobic clay. Related investigations emphasize the compatibility between clay and polymer, but overlook the factor of the monomer diffusing into the interlayer to proceed with polymerization. This treatment causes most of the polymer/clay nanocomposites being only the intercalated dispersion of clay instead of exfoliated dispersion in the substrate of polymers. Therefore, this study applies the catalyst after a unique polymerization process to make the stratiform inorganic mineral materials disperse proportionally in the polymer materials and form nanocomposites. Doing so significantly enhances the mechanical properties, thermal deformation temperature, and CO2 gas barrier of polymer/clay nanocomposites.
Thermoplastic elastomers are materials that combine the processing characteristics of thermoplastics with the physical properties of conventional thermoset rubbers. The combination has been sufficiently attractive that thermoplastic elastomers have become commercially successful. This success has led to their extension as specialty compounds for applications requiring increased electrical conductivity. In order to achieve desired conductivity, carbon and metal powders are typically employed. To a lesser degree, carbon and metal fibers are also utilized. New thermoplastic elastomer compounds have been recently developed that contain intrinsically conductive polymers. The properties of these novel materials are compared to conductive thermoplastic elastomers with traditional conductive additives.
The volume resistivity threshold for maximum paint transfer efficiency via electrostatically painting was determined to be in the range of 105 to 107 ohm-cm. Thermoplastic compounds have been developed for electrostatic painting which do not meet this threshold (greater than 107 ohm-cm) and still exhibit good transfer efficiencies without a conductive primer. Further, these compounds do not contain metal or carbon-based additives. As a result, they may be pigmented to any desired color. A comparison is made between electrostatically painted carbon based substrates and color-matched substrates. New options are now available for property selection while still retaining the economic benefits of electrostatic painting.
Energy transport in deforming polymeric materials, despite its technological significance, is poorly understood from both experimental and theoretical standpoints. Simple arguments suggest that thermal conductivity is anisotropic in a deformed polymer. In this study we have developed a sensitive and non-invasive optical technique known as Forced Rayleigh Scattering to measure anisotropic thermal diffusivity in both static and dynamic (relaxing) polymers subjected to deformations. Results for a polymer melt in step-shear strain flow and a cross-linked elastomer in uniaxial extension indicate that the thermal diffusivity is enhanced in the flow (or stretch) direction compared to the equilibrium value.
The goal of this study was to determine the degree of degradation during PVC injection molding and to compare the results with a computational model. It was found that a good agreement between experimental and computational results was obtained only if the reaction was assumed to be more thermally sensitive than found in literature. The results from this study show that during injection the activation energy for degradation was 65 kcal/mol, compared to 17-30 kcal/mol found in literature for quiescent systems.
This work reports the results of CAE simulation of thin-wall injection molded part by 3D TIMON. The model used in this simulation was a speaker grille that has thin wall and many tiny openings (net) for sound through them. These openings cause unfavorable weld lines. Effects on weld lines and effects of the number and location of gates were discussed.
Rotational molding is a fast growing process with a constant demand for new materials. As a result of the recent advances in the metallocene single site catalyst systems, a new generation of polyethylenes with unique molecular structure has been developed. The present study compares the rotomolding characteristics of polyethylenes made by metallocene and conventional catalysts.
Recycled high density polyethylene (HDPE) filled with up to 70 wt% rice hulls was compounded and tested for dynamic shear properties on a parallel plate rheometer. A 60 wt% formulation was extruded through two profile dies. Extrudate tearing occurred at all throughputs. The magnitude of the tearing increased with increasing throughput and decreasing land temperature. Observations, 2-dimensional finite element and fully 3- dimensional finite volume simulation suggest the tears are most severe where the wall shear stress is relatively lower.
Although thermoplastic polyolefins (TPOs) have been considered as costwise and environmentally attractive materials, they face the difficulty in being used as potential automotive applications because of poor scratch resistance and oil resistance. The new thermoplastic vulcanizates (TPVs) composed of thermoplastic polyurethane (TPU) / polypropylene (PP) /polystyrene-block-poly(ethylene-co-propylene)- block-polystyrene copolymer (SEPS) systems have been found out to have outstanding oil resistance and scratch resistance. Now they can be used for various kinds of automotive applications such as injection molded, blow molded, extruded, calendered and further, slush molded automotive parts, particularly for automotive interior skins without any coat. The essential issue is conceivably just prolonged weathering resistance and durability. In this paper, this new TPVs are evaluated from the standpoints of weathering stability, long term heat aging and fogging as well as the mechanical and physical properties.
Thermoplastic vulcanizates (TPVs) of polypropylene (PP)/polystyrene-block-poly(ethylene-co-propylene)- block-polystyrene copolymer (SEPS) are able to become much more fascinating for automotive and architecture industry by using polystyrene-polybutylene-polystyrene copolymer (SBS) together. While SBS decreases tensile strength in these systems , it does improve compression set and oil resistance greatly and furthermore, overall balance of properties improve in proportion to the amount of peroxide as coupling agent and acrylic ester as coupling coagent. The goal of this study is to investigate the interaction between SEPS and SBS, which are dynamically crosslinked and microdispersed in PP matrix from the point of mechanical behavior and morphology.
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Brown, H. L. and Jones, D. H. 2016, May.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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