bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of reaction injection molding of polyurethane microcellular foam
Authors: Park Hyeog , Youn Jae R. 
Published: December 2004

AbstractProcessing of microcellular foam was investigated for the feasibility of production of tough and lightweight polyurethanes. To increase the nucleation rate in a gas‐supersaturated resin, ultrasonic excitation was applied to the mixture of polyol(polyether‐based polyol) and isocyanate(diphenyl methane diisocyanate). A microcellular structure was produced by two sequential steps, i.e., supersaturationof the polyol resin with nitrogen gas at elevated pressure and ultrasonic bubble nucleation right after the impingement mixing of two components of the polyurethane system. Theoretical analyses based on nucleation theories were employed to predict the rate of nucleation in the gas‐supersaturated polyurethane. The rate of nucleatio in the resin was predicted by classical nucleation and cluster theories. In the experimental investigation, ultrasonic excitation was applied to increase the nucleation rate in the resin that had been saturated by nitrogen at a saturation pressure < 2.0 MPa.
Coefficients of dynamic friction and the mechanical melting mechanism for vinylidene chloride copolymers
Authors: Spalding Mark A. , Hyun Kun S. , Jenkins Steven R. , Kirkpatrick Donald E. 
Published: December 2004

AbstractPrevious research and this research indicate that the mechanical melting for poly(vinylidene chloride) copolymers (PVDC) is complex. Mechanical melting is defined as the melting (or devitrification) of a polymer when a significant portion of the thermal energy originates from a mechanical energy dissipative process. PVDC mechanically melted on a moving metal surface at temperatures of the test instrument that were considerably lower than the differential scanning calorimetry (DSC) onset melting temperature. PVDC formulated with low levels of high density polyethylene (HDPE), however, melted at metal temperatures near the DSC onset melting temperature. Two different mechanical melting mechanisms are proposed to explan the data, and the frictional data are discussed with respect to solids conveying in a single‐screw, plasticating extruder.
Sintering high performance semicrystalline polymeric powders
Authors: Brink A. E. , Jordens K. J. , Riffle J. S. 
Published: December 2004

AbstractPoly(ether ether ketone) (PEEK) is high performance semicrystalline thermoplastic with a glass transition temperature of 143°C. The melting point (Tm) is quoted as 334°C. Because of its high thermal transitions, PEEK, requires high temperatures for processing, at least 370–400°C. It has been determined that under the recommended processing conditions PEEK can undergo branching and eventually crosslinks. An alternative to melt processing PEEK is to apply the powder metallurgy technique of sintering. This involves cold (room temperature) compaction of the polymeric powder, followed by pressure free sintering of the resultant green body. We have reported a process for preparing submicron PEEK particles, and the focus here is on the free sintering of these particles with emphsis on the effects of particle size, sintering temperature, and compaction pressure. The data is evaluated using the two particle model developed by Frenkel as well as the crack healing theory developed by Wool.
Processing and morphology of polystyrene/ethylene‐propylene rubber reactive and nonreactive blends
Authors: Scott Christ E. , Macosko Christopher W. 
Published: December 2004

AbstractThe difference between reactive and nonreactive polymer blends in terms of processing and morphology has been investigated. The glassy phases for the blends are an oxazoline functional polystyrene (PS‐Ox) and a similar non‐functional polystyrene (PS). The rubbery phases are an ethylene‐propylene rubber (EP) and a similar ethylene‐propylene rubber (EP‐MA) with 07% grafted maleic anhydride. In the case of PS‐Ox/EP‐MA blends, the oxazoline group may react with the grafted rubber functionality at the interface between the two immiscible components during blending to form a compatibilizing agent in‐situ. The nonreactive blends systems of PS‐Ox/EP and PS/EP‐MA were used for comparison to the reactive system. The blend components are rheologically matched to simplify the interpretation of the process and morphological data. The blends were prepared in a batch mixer with roller blades. The torque required for mixing was measured during the blending process. The torque traces for the reactive blends exhibited a peak in torque, attributed to the chemical reaction at the interface. The weight fraction of gel in the blends was used to measure the extent of reaction. It correlates well with the mixing torques and rheological properties. The nonreactive PS‐Ox/EP and PS/EP‐MA blends show poor interfacial adhesion between the two phases. In contrast, the reactive PS‐Ox/EP‐MA blends show excellent during annealing is also much greater for the reactive blends. Varying the functionality concentration in the PS phase shows that the dispersed phase rubber particle size is reduced by increasing the concentration of oxazoline in the matrix. Blends with no or small amounts of functionality in the PS phase exhibit yield behavior in tension. However, a level of concentration of reactive functionality may be reached where the material becomes brittle.
The leveling of thermosetting waterborne coatings. Part III: Leveling under controlled conditions
Authors: Kojima Shunji , Moriga Toshinori , Takenouchi Ken 
Published: December 2004

AbstractExperiments on coated films of water borne, coatings (WBC) under controlled conditions (i.e., 25°C, 65% RH) were carried out to study the mechanism of leveling. Data in a companion paper imply that the development of the surface tension gradients plays an important role in promoting leveling. The stress due to surface tension gradients is found to be much greater than the stress introduced by hydrostatic pressure gradients in the film caused by surface tension and the free boundary curvature of the film. This reconfirms that the use of a co‐solvent, which evaporates faster than water, greatly accelerates the leveling of a WBC.
Study of the morphology and mechanical properties of polypropylene composites with silica or rice‐husk
Authors: Toro Patricio , Quijada Raúl , Murillo Omar , Yazdani‐Pedram Mehrdad 
Published: December 2004

AbstractThe mechanical, morphological behavior and water absorption characteristics of polypropylene (PP) and silica, or PP and rice‐husk, composites have been studied. The silica used in this study as filler was a commercial type produced from soluble glass or rice husks. The compatibilizing effect of PP grafted with monomethyl itaconate (PP‐g‐MMI) and/or with vinyltriethoxysilane (PP‐g‐VTES) as polar monomers on the mechanical properties and water absorption was also investigated. In general, a high loading of the studied fillers in the polymer matrix increases the stiffness and the water absorption capacity. This effect is more noticeable in the tensile modulus of the PP/silica composite with PP‐g‐VTES as compatibilizer. However, the increase of the rice‐husk charge as a natural filler in the PP matrix decreases the stiffness, and in the presence of PP‐g‐MMI as compatibilizer in PP/rice‐husk, the tensile modulus and water absorption of the composite were improved. The better adhesion and phase continuity in the PP/silica and PP/rice‐husk composites with different compatibilizers was confirmed by the morphological study. Copyright © 2004 Society of Chemical Industry
Plasma Deposition of Allylamine on Polymer Powders in a Fluidized Bed Reactor
Authors: Tatoulian Michaël , Brétagnol Frédéric , Arefi‐Khonsari Farzaneh , Amouroux Jacques , Bouloussa Otman , Rondelez Francis , Paul Alan John , Mitchell Robert 
Published: December 2004

AbstractSummary: Thin films of plasma‐polymerized allylamine (PPAA) have been deposited onto polyethylene powders (PE) and polystyrene (PS) beads by using a low‐pressure 13.56 MHz plasma in a fluidized bed reactor. Chemical derivatization using a set of three different blocking agents has allowed quantitative measurement of the relative percentages of primary, secondary, and tertiary amines. Under optimized conditions, it is possible to incorporate up to 110 nmol of amine groups per gram of powder and with a selectivity of 75% for primary amines. Moreover, our data clearly show that for films deposited at 10 W the selectivity for primary amines is at a maximum, but this is at the expense of resistance to washing. A power of 20 W corresponds to an optimum value since both the amount of primary amines and the degree of resistance of the coating to solvents reach maximum values.Distribution of the primary (I), secondary (II), and tertiary (III) amine groups on plasma‐polymerized allylamine films deposited on polyethylene powders.imageDistribution of the primary (I), secondary (II), and tertiary (III) amine groups on plasma‐polymerized allylamine films deposited on polyethylene powders.
FTIR Plasma Phase Analysis of Hexamethyldisiloxane Discharge in Microwave Multipolar Plasma at Different Electrical Powers
Authors: Raynaud Patrice , Despax Bernard , Segui Yvan , Caquineau Hubert 
Published: December 2004

AbstractSummary: In this paper, the gas phase composition of hexamethyldisiloxane (HMDSO) microwave plasma at 4 × 10−3 mbar and of the corresponding films were studied by FTIR spectroscopy under different power conditions. At low powers, species with a chemical structure very similar to that of HMDSO were observed in the gas phase, whereas the film essentially contained short [(CH3)2SiO]n‐like chains with a low branching rate and the end group Si(CH3)3. At higher powers, the chemical entities present in the gas phase contained several (SiO)x bonds, whereas the branching rate in the film increased with the amount of SiH, SiC and SiO bonds. The interpretation of these observations led to a proposal involving a chemical mechanism. In this mechanism, the increasing decomposition of HMDSO into by‐products, which themselves increasingly decompose as the power is raised, plays a determining role.Comparison of FTIR plasma and deposit spectra showing the relationship between the HMDSO by‐products present in the plasma phase and the different functional groups and end groups present in the deposited films.imageComparison of FTIR plasma and deposit spectra showing the relationship between the HMDSO by‐products present in the plasma phase and the different functional groups and end groups present in the deposited films.
Dynamic Particle Size Analysis with Light Scattering Technique
Authors: Tüzün Ug̃ur , Farhadpour Farhad A. 
Published: December 2004

AbstractThe commercial forward light scattering equipment, Malvern analyser was used to determine the size distribution of two crystalline powders in the micron range dispersed in aqueous suspensions. The powders used represent two different forms of a micro‐porous crystalline adsorbent, silicalite [1]. Previous work by the authors [2], has established the partially absorbing nature of the silicalite crystals at visible wavelengths of the incident light. The theoretical analysis indicates that it is possible to obtain quite accurate size distributions in the (1–10 μm) size range providing measured values of the relative refractive index and the coefficient of absorptivity of the particles are used in the calculations. The present work illustrates the consistency with which the light scattering equipment can respond to changes in the measured size distributions as a function of a number of process parameters such as the solids loading in suspension, the period of agitation, and the intensity of agitation.
Cometary Dust Sizing: Comparison between optical and in‐situ sampling techniques
Authors: Crifo Jean François 
Published: December 2004

AbstractWe try to evaluate the level of confidence that can be placed in the optical methods available for sizing cometary dust (and, at the same time, deriving all its other characteristics). We use for this purpose the new informations provided by the in‐situ sampling of Comet Halley dust. We try to determine whether data from this origin are compatible with visible and I. R. spectra of this comet acquired from the Earth, and with earlier interpretations of such spectra. We find that, as happens frequently when remote sensing and local sampling techniques data can be compared, none of these techniques can claim to be fully satisfactory. In the case of cometary dust, current estimates based on optical sizing only may be much less accurate than precedingly assumed. Improvements in the observational approaches appear needed, as well as new laboratory investigations and theoretical developments to improve the capabilities of the optical studies of cometary dust.
Particle Trajectory Effects in Phase Doppler Systems: Computations and experiments
Authors: Gréhan Gérard , Gouesbet Gérard , Naqwi Amir , Durst Franz 
Published: December 2004

AbstractThe effects of the particle trajectories on phase Doppler measurements were explored numerically using generalized Lorenz‐Mie theory. Computations were performed for a commercial phase Doppler system and various schemes for elimination of the trajectory effects were examined. It is shown that these effects cannot be completely suppressed if the ratio of the two measured phase shifts from a single receiving unit is used to validate the measurements. On the other hand, the errors due to particle trajectories can be eliminated satisfactorily by employing an additional receiving unit, which allows one to detect the asymmetry of the scattered light pattern due to displacement of the particle trajectory from the centre of the measuring volume. A preliminary experimental evaluation of this method is presented and discussed.
Laser Diffraction – Unlimited?
Authors: Witt Wolfgang , Rüthele Stephan 
Published: December 2004

AbstractWithin the past 20 years, particle size analysis with laser diffraction (LD) has been subject to rapid development, extending the size range stepwise from 1–200 μm to about 0.1–3500 μm. The limits of LD are discussed in terms of light sources, the influence of the beam diameter, special Fourier optics and a new detector design.It is shown that the size range is not only restricted by the wavelength of the laser and the transmission limits of the medium. Its extension is mainly related to improvements in the measurement of the angular intensity distribution. Influences from stability and flow dominate on the coarse side of the measuring range. On the fine side, the spatial extension of aerosols and the resulting demand for extended working distances can be covered only in a parallel laser beam. Extended Fourier optics in combination with an adapatable beam expansion technique and a detector with virtual borders between semicircular elements overcome the existing limits and extend the size range to a lower limit of about 0.05 μm and an upper limit above 10 mm.The sensititivity limit of LD is approaching that of single particle counting techniques. For medical spray and inhaler applications, a 0.1% optical concentration can be converted to particle size distributions even for time‐resolved analyses with sample intervals of a few milliseconds.The reproducibility of the sensor, with a standard deviation typically much less than 0.5%, is no longer the limiting factor. The reproducibility of the results is mainly dominated by the reproducibility of sampling, sample splitting, dispersion and the contamination of the optical path. The latter can be improved by the control of flow, especially for in‐line and inhaler applications.
Tomographic Imaging of Phase Distribution and Spatial Correlation of the fluidization dynamics in a fluidized bed
Authors: Wang Shijie , Dyakowski Tomasz , Xie Cheng‐Gang , Williams Richard A. , Beck Maurice S. 
Published: December 2004

AbstractThis paper describes the use of a capacitance tomography system for imaging gas bubbles in a fluidized bed in the vicinity of an air distributor plate. The results show how the solid concentration distribution varies as a function of time for three different flow regimes: bubbling, slugging and the transition to turbulent. Bubble shape, Length and coalesence can be observed. A method of spatial correlation to elucidate the bubble formation process is described.
Experimental Determination of the Response Envelope of fine limestone
Authors: Feise Hermann J. , Schwedes Jörg 
Published: December 2004

AbstractDesigning modern devices for bulk solids storage and handling requires an increasingly complex understanding of the handled bulk solids' mechanical behaviour. Models able to describe the behaviour of bulk solids can neither be formulated nor their parameters determined from common shear tests, since these do not contain sufficient information especially about the materials' stiffness characteristics. The paper describes the response envelope as a measure of the deformation resistance and its experimental determination from biaxial tests. It is shown that for fine limestone powder the stiffness in compression is only about 1/70 of the stiffness in expansion. The shape of the response envelope depends only on the ratio between the principal stresses at the stress state considered, whereas the size of the response envelope also depends on the stress magnitude.
Experimental Determination of Force using Gun Propellants of various grain sizes – comparison with thermodynamically calculated values
Authors: Jahnk H. 
Published: December 2004

AbstractSince force is a parameter which is shape independent it is possible, and moreover advantageous, to use ground propellants for its experimental determination. These, due to their smaller grain size, give much shorter burning times than the unground propellants, which in turn reduces the pressure losses due to heat transfer to the containment vessel, and hence to a better agreement with theoretical values.By using different grain sizes one can extrapolate to the force values at zero grain size and hence for zero burning time. These values are only on average about 2% less than the thermodynamically calculated values. Without extrapolation, as the present results show, one can expect a difference between the theoretical and experimental values of about 5%.The conventional methods of determining force using closed vessels with volumes between 200 ml and 700 ml require a relatively large amount of sample material. The use of a ground powder allows the volume of the vessel to be reduced to 25 ml. This can be important when unknown foreign propellants have to be tested since these are usually only available in small quantities.
Determination of the Lifetimes of Gun Propellants using thin‐layer chromatography
Authors: Volk F. 
Published: December 2004

AbstractA thin‐layer chromatographic method was developed in connection with the determination of the safe lifetimes of gun propellants. This method enabled the numerous stabilizer reaction products of diphenylamine and ethylcentralite, which were formed on storage, to be qualitatively analysed.Since a correlation could be established between the temperature and the decomposition or formation of certain of these reaction products, it became possible to estimate the time of onset of autocatalytic decomposition of powders and solid propellants from an analysis of the material at much earlier times.
Die Europäische Kommission zur Vereinheitlichung der Sprengstoffprüfungen (Ab 1976 geändert in: Internationale Studiengruppe zur Vereinheitlichung der Sprengstoffprüfmethoden)
Authors: Ahrens H. 
Published: December 2004

AbstractSeit 1960 ist eine auf freiwilliger Basis zusammengetretene Gruppe von Experten tätig unter dem Namen „Europäische Kommission zur Vereinheitlichung der Sprengstoffprüfungen”︁ (European Commission for the Standardization of the Tests of Explosives – Commission Européenne de Normalisation des Essais d'Explosifs).In dieser Mitteilung werden der Ursprung und die bisherige Aktivität sowie die beabsichtigte weitere Tätigkeit der Kommission kurz beschrieben.
Chemistry of Metal Benzylidene Picramates – benzylidene picramates of iron, cobalt and nickel
Authors: Srivastava R. S. , Agrawal S. P. , Bhargava H. N. 
Published: December 2004

AbstractFerrous, cobalt and nickel benzylidene picramates have been prepared by treating the corresponding aqueous sulphate and chloride solutions with sodium salt of 4′‐dimethyIaminobenzylidene‐2‐hydroxy‐ 3.5‐dinitroaniline. A metal: ligand ratio of 1:2 has been established in all these cases with the help of micro‐analysis and confirmed by spectrophotometric, colorimetric and magnetic susceptibility measurements. I.R. studies of metal benzylidene picramates show N + M coordination, where M is iron, cobalt or nickel. Explosive properties of these benzylidene picramates have also been studied and it was found that the thermal stability of these benzylidene picramates increases as the atomic radius of the metal decreases. Ferrous, cobalt and nickel benzylidene picramates increased as the atomic radius of the metal decreases.
A Rapid, Accurate Technique for Determining Densities of High Explosives
Authors: Lagus P. L. , Turner P. L. , Gaffney E. S. 
Published: December 2004

AbstractAn improved gas comparison pycnometer has been developed, based on precise differential pressure measurements coupled with a sample volume compensator. Using helium gas, volumes of solid and powdered explosives can be measured to a precision approaching one part in lo4. Coupled with a precise mass measurement, these volumes allow densities with an uncertainty of ∼± 0.002 g/ml to be inferred. Measurements performed on various explosives have allowed assessment of the purity and homogeneity of individual samples. It is also possible to infer void percentage or porosity in pressed explosive pellets.
5,6,7‐Trihydro‐5,7‐diphenyl‐thiazolo[3,2‐b]‐s‐triazin‐3 (2h)‐one as a stabilizer for the double base propellant
Authors: Soliman Adly Abdel‐Wahid 
Published: December 2004

Abstract5,6,7‐Trihydro‐5,7‐diphenyl‐thiazolo [3,2‐b]‐s‐triazin‐3(2H)‐one (C17H15N3OS) is used as a stabilizer for the double base propellant and gave good results with the stability tests. The samples were stored for 12 days at 100° C and were extracted by different suitable solvents. The column partition chromatography helped in separation of 5,6,7‐trihydro‐5,7‐(2‐nitrodiphenyl)‐thiazolo[3,2‐b]‐s‐triazin‐3(2H)‐one; 5,6,7‐trihydro‐ 5,7‐(4‐nitrodiphenyl)‐thiazolo[3,2‐b]‐s‐triazin‐3(2H)‐one; 5,6,7‐trihydro‐5,7‐(2,2′‐dinitrodiphenyl)‐thiazolo[3,2‐b]‐s‐triazin‐3(2H)‐one; 5,6,7‐trihydro‐5,7‐(4,4′‐dinitrodiphenyl)‐thiazolo[3,2‐b]‐s‐triazin‐3 (2H)‐one with their different percentages.
Versuche zur Detonationsübertragung von Wettersprengstoffen mit Ionenaustausch in natürlichem Einschluß
Authors: Scholz F. , Meerbach H. 
Published: December 2004

AbstractDie Detonationsübertragung von selektiv detonierenden Wettersprengstoffen hängt in besonderer Weise von dem Einschluß der Ladesäule ab. Obwohl es für eine standardisierte Prüfung notwendig ist, eine einheitliche Prüfapparatur zu erstellen, dürften Versuche zur Detonationsübertragung unter praktischen Einschlußbedingungen doch von erheblichem Interesse sein.Zur Tagung der Europäischen Kommission 1972 war ein kurzer Beitrag vorgelegt worden, der sich mit der Detonationsübertragung verschiedener Wettersprengstoffe mit Ionenaustausch in Bohrlöchern in der Kohle und im Karbongestein über ein Hindernis von Acetatscheiben hinweg befaßte. Diese Arbeiten wurden fortgesetzt, wobei besonders eine Kombination von Luftabstand und Hindernis aus Acetatscheiben in Betracht gezogen wurde.