bluuebunny/crossref_metadata_2025_split huggingface dataset:
Arrhenius parameters for the hydrogen abstraction from ammonia by CF3 radicals
Authors: Pasteris L. , Staricco E. H. 
Published: December 2004

AbstractThe reaction of CF3 radicals with NH3 has been studied over a wide temperature range 298–673 K, using the photolysis and the thermal decomposition of CF3I as the free radical source.It was found that the reaction could not be explained in terms of a simple mechanism
equation image
in the whole temperature range because a marked pressure dependence on the rate of products formation and the presence of a dark reaction complicate the system at low temperatures. Thus, Arrhenius parameters for reaction (1) have been calculated relative to the CF3 recombination from data in the range 523–673 K where pure hydrogen transfer occurs. The rate constant expression is given by

where kH/k is in units of cm3/2/mol1/2 s1/2 and θ = 2.303 RT/kJ/mol.
Das Rhenium und seine heutigen Anwendungen in der Technik
Authors: Noddack Walter , Noddack Ida 
Published: December 2004

AbstractDas Rhenium wurde vor 26 Jahren entdeckt. Es dürfte das seltenste aller stabilen Metalle sein. Nur in wenigen Hüttenprodukten und Erzen ist es soweit angereichert, daß seine Darstellung lohnt. Die physikalischen und chemischen Eigenschaften des Elementes, das den Platinmetallen nahesteht, ließen voraussehen, daß es sich für zahlreiche technische Anwendungen eignen würde. Das geschmolzene Re‐Metall besitzt eine große Härte, seine Legierungen sind ebenfalls hart und ohne Sprödigkeit, meist auch korrosionsbeständig. Diese technisch wertvollen Eigenschaften haben in vielen Fällen bereits praktische Verwertung gefunden. In den Thermoketten mit Platin‐metallen besitzt Rhenium singuläre Eigenschaften. Von besonderem Interesse sind die katalytischen Eigenschaften des Rheniums.
Korrosions‐ und Hitzebeständigkeit von Kohlenstoffstahl und von Sonderstahl nach chemisch‐technischer Oberflächenbehandlung
Authors: Köhler Walther 
Published: December 2004

AbstractKritischer Überblick über das einschlägige neuere, sowjetrussische Schrifttum. Im einzelnen werden behandelt: Schichtbildung, Schichtaufbau, Korrosions‐ und Hitzebeständigkeit von Kohlenstoffstahl und Sonderstahl nach Zementieren, Nitrieren, Cyanieren, Alitieren, Chromieren, Silizieren, Sherardisieren, Beryllieren, Molybdänisieren, Wolframieren und Vanadisieren.
Spannungskorrosionsartige Erscheinungen an mechanisch beanspruchtem Stahl durch diffundierenden Wasserstoff
Authors: Class I. 
Published: December 2004

AbstractDie Abhandlung beschreibt das Auftreten von Rissen mit vorwiegen transkristallinem Charakter an unlegierten und legierten Vergütungsstählen im Kondensationsteil von Hochdruckanlagen, sowie Versuche zur Erzielung gleichartiger Erscheinungen im Laboratorium. Die Ursache der Risse wird darin gesehen, daß der durch einen schwachen Korrosionsvorgang an der Stahloberfläche entstehende Wasserstoff durch die Gegenwart von spezifisch wirkenden Substanzen, und zwar insbesondere von Schwefelwasserstoff, in atomarer Form in das Metall eindringt und dor durch Rekombination an ausgezeichneten Stellen hohe Drücke entwickelt. Auf entsprechende Erscheinungen in der Erdölindustrie wird unter Erwähnung der umfangreichen Forschungstätigkeit auf diesem Gebiet in US hingewiesen.Es werden die Faktoren beleuchtet, welche die Entstehung der Risse und den Rißverlauf beeinflussen, wobei auch die Bedeutung der Zähigkeit des Werkstoffes erwähnt wird. Betriebliche Kontroll‐ und Schutzmaßnahmen werden beschrieben.Da die Grenzen des Begriffs der Spannungskorrosion, deren Wesensmerkmale die geschilderten Erscheinungen tragen, beim heutigen Stand der Erkenntnisse noch nicht scharf abgesteckt sind, wird vorgeschlagen, diese hier — etwa unter der Bezeichnung kathodische Spannungskorrosion — einzuordnen.
Strukturmechanische Grundlagen der Werkstoffermüdung
Authors: Macherauch E. , Mayr P. 
Published: December 2004

AbstractDer gegenwärtige Stand der Ermüdungsforschung ist durch eine Fülle sowohl grundlagen‐ als auch anwendungsorientierter Einzelarbeiten gekennzeichnet. Trotzdem erscheint es zur Zeit nicht möglich, eine geschlossene Theorie des Ermüdungsverhaltens metallischer Werkstoffe in nächster Zukunft zu entwickeln. Die vorliegende Arbeit soll einen Überblick geben über die hinreichend gesicherten Erkenntnisse auf dem Gebiet der Metallermüdung. Die Forschungstätigkeit der letzten zwei Jahrzehnte führte zur Entwicklung einiger Ordnungskriterien für die vielfältigen experimentellen Ergebnisse sowie zu einigen quantitativen Abschätzungsverfahren. Für die einzelnen Ermüdungsstadien, den Anfangsbereich, den Rißbildungsbereich, die Rißausbreitung und den Restbruch werden einige wichtige Ergebnisse vorgestellt und diskutiert. Plastische Verformung ist die Voraussetzung für das Auftreten eines Ermüdungsbruchs bei metallischen Werkstoffen. Sie führt in der anrißfreien Phase der Ermüdung zu einer Veränderung der mechanischen Eigenschaften des Werkstoffs sowie zur Bildung besonderer Oberflächenverformungsstrukturen, die bevorzugt Ausgangspunkte für Ermüdungsrisse sind. Auch die Rißausbreitungsphase ist durch das Auftreten von plastischen Deformationen charakterisiert und erfordert eine hinreichend große Zugspannungskomponente. Strukturabhängige Werkstoffkenngrößen wirken sich insbesondere in der anrißfreien Phase des Ermüdungsvorgangs aus.
Der Einfluß von Festigkeit und Druckeigenspannungen auf die Wechselfestigkeit von Stählen bei höheren Temperaturen
Authors: Bahre K. 
Published: December 2004

AbstractDas Wechselfestigkeitsverhalten krz Stähle ist bei Raumtemperatur durch zwei Endzustände gekennzeichnet, die sich unterhalb zweier verschiedener Grenzwechselspannungen stationär einstellen: Unterhalb der einen können beliebig viele Lastwechsel ohne Anrißbildung, unterhalb der anderen ohne Rißfortschritt ertragen werden. Bei glatten Bauteilen bestimmt die erstere die Dauerfestigkeit und nimmt vor allem mit der Werkstoffhärte zu. Bei gekerbten Proben dagegen wird die Dauerhaltbarkeit durch die zum Rißfortschritt erforderliche Mindestwechselspannung bestimmt, die durch Druckeigenspannungen erheblich heraufgesetzt werden kann. – Bei höheren Temperaturen entstehen keine stabilen Endzustände mehr und es gibt keine Wechselamplituden, die nicht sowohl zum Anriß als auch zum Rißfortschritt bis zum Bruch führen. Beide Einflußgrößen Werkstoffestigkeit und Druckeigenspannungen sind abhängig von der Beanspruchungstemperatur, ihr Temperaturverlauf kann mit den Verfestigungsmechanismen nach Snoek und nach Cottrell bzw. aus dem unterschiedlichen Eigenspannungsabbau infolge temperaturveränderlicher Streckgrenzen erklärt werden.
Warmzug‐ und Zug‐Kriechversuche an reaktionsgesintertem Siliziumnitrid
Authors: Gebhard W. 
Published: December 2004

AbstractEs wird die Konstruktion einer Zugprüfeinrichtung zur Durchführung von Zug‐ und Zug‐Kriechversuchen an keramischen Werkstoffen von Raumtemperatur bis 1500 °C an Luft beschrieben. Besondere Bedeutung wird der Vermeidung überlagerter Biegebeanspruchung und deren Verminderung beigemessen. Ergebnisse der Zugfestigkeit von isostatisch gepreßtem RB‐SN verschiedener Dichte in Abhängigkeit von der Prüftemperatur werden mitgeteilt und das Kriechverhalten bei 1200 °C, 1250 °C und 1400 °C an Luft im Zug‐ und Biegeversuch verglichen.
Rheology of fiber‐ or flake‐filled plastics
Authors: Utracki L. A. , Fisa B. 
Published: December 2004

AbstractThermoplastics and thermoset materials filled with inexpensive, mainly inorganic, particulates are an important class of engineering plastics. Here, the short fiber and flake fillers play a major role. In this paper, the melt rheology and processability of these resins is reviewed, and the flow behavior of mica‐filled polyethylene is discussed in greater details.
Hot‐rolling and forging of mica‐filled polyolefins
Authors: Lee I. , Turner S. , Woodhams R. T. 
Published: December 2004

AbstractAs in the case of fibers, the mechanical properties of plastic composites containing mica flakes are extremely sensitive to flake orientation in the direction of an applied stress, so that even a small angular displacement can cause major reductions in the strength, modulus, and fracture toughness. In order to encourage parallel alignment of mica flakes in a thermoplastic composite, two methods of flow orientation were examined. In the first series, rectangular billets of mica‐filled, high‐density polyethylene were hot‐pressed in order to cause longitudinal melt flow in a narrow channel. A parallel series of experiments was also carried out with mica‐filled polypropylene in which the composite was extruded and calendered into a thin, continuous strip. In both processing techniques, the resulting extensional flow produced large increases in the tensile and flexural properties. The performance of the mica‐filled poly‐propylene was limited by its tendency to fibrillate during rolling. Drop‐impact measurements recorded a four‐fold increase in fracture toughness. The increased tensile and flexural properties were attributed to both the greater degree of parallel alignment of the mica flakes and the increased molecular orientation in the direction of flow. Such flow orientation methods appear necessary if the full benefit of mica‐flake reinforcement is to be achieved.
Experimental measurement of temperature profiles of molten flowing polymers in a heat exchanger
Authors: Forsyth T. H. , Murphy N. F. 
Published: December 2004

AbstractMolten polymer was pumped through an isothermal‐wall heat exchanger and the temperature at four radial positions was measured with a hypodermic thermocouple. Temperature profiles were obtained for heating, cooling, and isothermal flow of polyethylene, polystyrene and polypropylene at Graetz numbers from 1.7 to 9.2. The results show large viscous heating effects, particularly for cooling.
Photopolymerization studies: I. Polymers from new photoredox catalyst system
Authors: Rust J. B. , Miller L. J. , Margerum J. D. 
Published: December 2004

AbstractA new photoredox catalyst is described wherein a phenothiazine dye in its excited state oxidizes a catalyst to a free radical. This free radical efficiently initiates the polymerization of metal acrylates giving rise to polymers which are insoluble in the monomer‐containing medium. The polymers precipitate as insoluble colloidal particles. Optical transmission measurements are used to follow the polymerization and to calculate the number and size of the polymer particles. The effect of various factors such as the nature of the catalyst and the photooxidant, the pH and the temperature of the medium on photopolymerization are described. It is indicated that this new system may be useful for rapid photographic imaging and display applications.
The melting of a polymer on a hot surface
Authors: Stammers E. , Beek W. J. 
Published: December 2004

AbstractPolymer pellets are frequently melted on a melting grid. The melting capacity of the gird depends on the force with which the bed of pellets is pressed against the grid bars and on the difference between the temperature of the grid bars and the melt temperature. In this investigation, this dependence has been examined, theortically as well as experimentally, for the case where the pellets melt on the top of the grid. Agreement with the theory was found.
Rheological behavior of poly(vinyl chloride) mixture. II. Elastic behavior
Authors: Sieglaff C. L. , Vinson C. G. 
Published: December 2004

AbstractThis study was undertaken in order to understand the effect of low molecular weight additives on the visco‐elastic properties of polymers and, in particular, Diamond Shamrock Corporation's PVC‐40 resin. The viscous response has been reported in Part I of this series (11). This report describes the elastic properties of these mixtures.A new theoretical analysis of elastic response has been formulated. The direct calculation of stored elastic energy from capillary rheometer measurements is now possible.The conclusion drawn from both the viscous and elastic response study is that a change in viscosity is not a necessary nor sufficient condition for improved processability. Increased flow is obtained by lowering the viscous losses, but the melt fracture phenomena may be unchanged. In order to completely characterize the compound, both viscous and elastic response must be measured.
The effect of temperature on the delayed yield and failure of “plasticized” epoxy resin
Authors: Ishai O. 
Published: December 2004

AbstractEpoxy‐Versamid specimens were loaded in tension up to failure at different constant strain‐rates and temperatures. Results revealed three modes of behavior prevailing at different temperature‐strain‐rate regions and associated with brittle, ductile and rubbery failure modes. The ductile region was found to be confined within a narrow band on the temperature‐strain‐rate plane, and is characterized by a yield plateau in the stress‐strain curve and by linear dependence of yield stress on log strain rate and temperature. Yield strain seems to be almost unaffected by strain‐rate, but decreases slightly with temperature rise.Analysis indicated that experimental data within the ductile region are consistent with Eyring's formulation for non‐Newtonian viscoplastic flows. It leads to the evaluation of the “apparent activation energy” and activation volume for the two epoxy systems tested.Comparison with previous work indicates that the above parameters as well as yield stress and elastic modulus tend to increase with the decrease of the Versamid content in the resin.
Some physical organic chemistry of aging processes
Authors: Mayo F. R. , Irwin K. C. 
Published: December 2004

AbstractWork at Stanford Research Institute on the deterioration of polymers is based on the assumption that aging in the light is the most serious problem and that it has at least three components that must be separated if we are to understand the overall process. We have started by measuring the production of free radicals on the polymer when pairs of t‐butoxy radicals are generated from thermal decomposition of di‐t‐butylperoxy oxalate (DBPO) in bulk atactic polypropylene at temperatures approximating service conditions, 35–50°C. Our preliminary experiments have brought out experimental difficulties and have raised more theoretical questions than they have answered. Nevertheless, they show that the efficiency of production of polymer radicals is low and sensitive to the mobilities of the polymer chains. They also suggest that two kinetically different oxidation processes, with different dependencies on rates of initiation and with different susceptibilities to inhibitors, are proceeding simultaneously. The implications of these findings for results of some previous work and for design of improved accelerated tests is considered.
An izod specimen for the simulation of conditions of plastics use
Authors: Vinson C. G. 
Published: December 2004

AbstractThe stress concentration and effective flexure stiffness of an ASTM V‐notch Izod specimen is excessive for most cases of plastics use. A more typical stiffness is that of a thin plate in two dimensional bending. Such can be approached with a larger radius and deeper V‐notch. Instead of a V‐notch, however, a double edge notch with the same radius and thickness at the root is recommended. The special advantage of the double edge notch is that the notch at the back edge reduces the energy loss due to the clamp.
Oxidation of ether linked thermoplastics
Authors: Kelleher P. G. , Gesner B. D. 
Published: December 2004

AbstractStudies have been made of the heat and light induced oxidation of ether linked commercial thermoplastics using a variety of analytical methods. Our studies on polyoxymethylene, polyphenylene oxide, and its blends with polystyrene are discussed here. Comparisons of heat and light stability are made with thermoplastics previously reported.Heat aging of polyoxymethylene causes a decrease in elongation and weight as well as volatile product formation and changes in the infrared spectrum indicative of chain scission. Exposure to ultraviolet light accelerates the oxidative reaction. Polyoxymethylene copolymer is more thermally stable but both polymers are rapidly degraded during light aging.Investigation of the heat and light induced oxidation of polyphenylene oxide shows that oxidation, in either case, leads to a crosslinking reaction resulting in embrittlement of the polymer. The process is difficult to retard. However, oxygen uptake results indicate that blends of polyphenylene oxide and polystyrene can be suitably stabilized against thermal oxidation. Preliminary results indicate that oxidation of these blends proceeds by a chain scission mechanism.
Temperature profiles for polymer melts in tube flow. Part II. Conduction and shear heating corrections
Authors: Kim H. T. , Collins E. A. 
Published: December 2004

AbstractA temperature probe system to measure radial temperature profile of polymer flowing in a rod die and a method to systematically correct the conduction and the frictional shear effects were developed. Experimental data obtained on a 1‐1/2‐inch extruder using a blow molding compound show that both conduction and frictional shear heating effects are significant in melt temperature measurement and that the radial temperature profiles of the melt in the rod die are influenced by the RPM of the screw and the die‐wall temperature.The reliability of the temperature data obtained was compared with the solution obtained from the equations of motion and energy. A good agreement between the predicted versus experimental temperature profile exists. For this polymer system, the relationship between local Nusselt number and the velocity parameter could be adequately described with the theory of Van LeeuWen.
The mechanical properties of textile materials as influenced by complexity and rate of testing
Authors: Figucia Frank , Weiner Louis , Laible Roy 
Published: December 2004

AbstractFibrous structures of high complexity, as introduced by ply and twist, have been subjected to high and low speed tensile tests. The ratio of strength at high speed to low speed is always greater than one, but decreases with increasing complexity of fibrous structure. The ratio of elongation to break at high speed to that at low speed is always less than one and also decreases with increasing structure complexity. The ability to absorb energy markedly increases with increasing complexity of geometry at low strain rates, characteristic of an Instron. The reasons for this additional energy absorption are discussed. Tests at high rates of strain point out the inability of many complex textile structures to translate their superior energy absorption characteristics to high strain rates. The results obtained and the principles demonstrated are applied to the development of improved materials for use in aerial delivery and ballistic applications.
Factors influencing the thermal oxidation of polyethylene
Authors: Hawkins W. L. , Chan M. G. , Link G. L. 
Published: December 2004

AbstractThe thermal stability of polyethylene containing conventional antioxidants is adversely affected by contact with copper, by certain pigments, and by the addition of a few percent of polypropylene as a processing aid. Polyethylene inhibited with 0.1% of phenolic antioxidants has approximately the same oxidative stability when in contact with a copper surface as the unprotected polymer. A mechanism is suggested to account for the loss of stability in the presence of copper. Pigments vary in the extent to which they adversely affect the oxidative stability of polyethylene. Since several factors may combine to decrease the stability of protected polyethylene compositions, as determined by accelerated tests, it is essential that their contribution under service conditions be determined. The predicted life at temperatures encountered in service is determined by extrapolating accelerated test data to that constant temperature which is calculated to cause the same degree of degradation as would occur during the daily and seasonal temperature cycles encountered in use.
Prospective photosensitization of photopolymerization systems
Authors: Bulloff Jack J. 
Published: December 2004

AbstractThe current art for image‐wise photopolymerization is reviewed and the prospective future developments are briefly assessed. Photomechanics, photoengraving, gravure, lithography, chromophores, dye sensitization, cyanine photopolymerization, bathochromy, and phototanning are covered. Primary photoprocesses, their sensitization by cyanines, Oster photopolymerization, photovinyls, diazo and diazido‐sensitized systems, and secondary photoprocesses are discussed. A bibliography is provided.
Electrical dissipation factor: Guide to molding quality graphite/resin composites
Authors: Pike R. A. , Douglas F. C. , Wisner G. R. 
Published: December 2004

AbstractDetermination of the change in electrical dissipation factor and capacitance of epoxy/graphite and polyimide/graphite composites during compression molding provides a reproducible means of obtaining low void content composites by permitting accurate application of low pressure at the resin gel point. Of the two parameters, change in dissipation factor was found to be the more sensitive to molecular changes in the resin matrix as well as to variations in solvent content, particularly with the polyimide systems. The simple laboratory equipment required to carry out these electrical measurements is described.
Weathering of fibre reinforced plastics. Progress of dbonding detected in model systems by using fibres as light pipes
Authors: Field S. Y. , Ashbee K. H. G. 
Published: December 2004

AbstractThe progress of interfacial debonding caused by the diffusion of boiling water to glass fibre/polyester resin interfaces has been followed by shining a He‐Ne laser beam along fibres and recording the changes in intensity of the emergent beam. Compared with measurements of electical conductivity arising from the presence of diffused water at the interface, it is concluded that the laser beam method provides more certain evidence of debonding.The glass/resin interface has also been investigated in partially cured composites and in filled composites, during exposure to boiling water.
Melting rates of crystalline polymers under shear conditions
Authors: Sundstrom D. W. , Young Chi‐Chang 
Published: December 2004

AbstractThe melting of solids under shear conditions is an important operation in the processing of most thermoplastics. In this study, solid blocks of high density polyethylene were melted on a hot, moving surface over a range of surface temperatures and velocities. The conservation equations for mass, momentum, and energy were applied to the molten layer and then simplified by an order of magnitude analysis. A general model that included all significant terms gave rates of melting that agreed closely with the measured rates. A simpler model that was analogous to present extruder models predicted melting rates that were ten to twenty‐five percent lower than the experimental values. Models for polymers with low to moderate crystallinity should be modified to account for physical removal of amorphous material by shear forces.
Melt characterization of ultra high molecular weight polyethylene using squeeze flow
Authors: Shaw M. T. 
Published: December 2004

AbstractA method for determining the melt viscosity and molecular weight of ultra high molecular weight polyethylene (UHMWPE) is described. The method, based on squeeze flow, was used to characterize seventeen UHM W‐PE samples varying in molecular weight from 0.6 × 106 to 5.1 × 106 and in viscosity from 2.9 × 106 to 3.4 × 109 poise. A correlation between melt viscosity and molecular weight was demonstrated, but the reliability of a molecular weight determination decreased somewhat as molecular weight increased. As a predictor of melt processability, the method provides the speed and simplicity heretofore lacking in UHMW‐PE characterization by solution viscosity while retaining high reproducibility.