bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanisms of mixing in single and co‐rotating twin screw extruders
Authors: Lawal Adeniyi , Kalyon Dilhan M. 
Published: May 2005

AbstractPrevious experimental studies have revealed that the mixing efficiencies of widely used continuous processors such as the single and twin screw extruders depend on the types of screw elements, which are utilized. It is generally recognized that the basic single screw extruder and the fully‐fighted sections of the fully‐intermeshing co‐rotating twin screw extruders are not efficient mixers, in contrast to the specialized mixing elements such as the kneading discs used in co‐rotating twin screw extruders. However, no simulation techniques were available to characterize quantitatively and rigorously the mixing efficiencies of continuous processors. In this study, we have solved the three‐dimensional equations of conservation of mass and momentum, and utilized various tools of dynamics to analyze the mixing occurring in single and co‐rotating twin screw extruders. It is shown that simulation methods can indeed capture the relative differences in the mixing mechanisms of continuous processors like the single and twin screw extruders. The ability to distinguish quantitatively between the distributive mixing capabilities of various continuous processors should facilitate numerical testing of new continuous mixer designs, optimization of operating conditions and geometries of existing mixers and the material‐specific design of new mixers.
A non‐Markovian model of desorption
Authors: Stastna J. , De Kee D. , Harrison B. 
Published: May 2005

AbstractThe desorption kinetics of small hydrocarbon molecules in a low‐density polyethylene (LDPE) film has been simulated via the continuous time random walk approach. A scaling relation between the amount of penetrant remaining in the film during the final stage of the process and the time has been obtained. A constant scaling exponent was obtained for various hydrocarbon penetrants in LDPE. The mutual relation between phenomenological and statistical models has been exploited.
Viscoelastic properties of acrylonitrile‐butadiene‐styrene (ABS) polymers in the molten state
Authors: Bertin Marie‐Pierre , Marin Gérard , Montfort Jean‐Pierre 
Published: May 2005

AbstractThe viscoelastic behavior of acrylonitrile‐butadiene‐styrene (ABS) terpolymers is studied in the molten state. First, the behavior of the styrene‐acrylonitrile (SAN) matrix is determined. Then, the effect of the degree of grafting on ABS rheological properties is emphasized. A critical degree of grafting (DGc), corresponding to a minimum of the viscoelastic functions in the low frequency region, is determined. It defines a critical thickness of the grafted layer, and is related to the conformation of the grafted chains at the surface of the rubber particle. The DGc affects the morphology of the ABS and also affects the appearance of a secondary plateau at low frequencies. The effects of the rubber particles, of the grafted chains, and of the morphology on the appearance of the secondary plateau at low frequencies are clearly dissociated.
Graft polymerization of monomers onto cellulose and lignocelluloses by chemically induced initiator
Authors: Mansour O. Y. , Nagaty A. , Beshay A. D. , Nosseir M. H. 
Published: May 2005

AbstractThe presence of a low percentage of lignin retards and inhibits the graft polymerization reaction of some vinyl monomers on lignocellulosic substrates. The retardation or inhibition effects of lignin in situ are discussed.
Piezoelectric polymer films. II. Piezoelectric and pyroelectric evaluation
Authors: Liepins R. , Timmons M. L. , Morosoff N. 
Published: May 2005

AbstractThe concept of piezoelectric and pyroelectric effects in amorphous polymers is presented, with experimental results, details on sample preparation, and activity evaluation. Most evaluations were performed on 25–30 mol% tributyltin methacrylate/methyl methacrylate copolymers, which possessed good piezoelectric activity, antifouling properties, and paint‐formulation characteristics. Solvent‐induced orientation effects that lead to piezoelectric activity in amorphous, unpoled, polymers are also described.
Phenylated polyimides via bifunctional monomers
Authors: Feld William A. , Serico Lucia , Genez Beverly G. , Friar Linda L. 
Published: May 2005

AbstractThe synthesis of two phenylated bifunctional monomers, dimethyl 4‐(4‐(p‐aminophenoxy)phenyl)‐3,5,6‐triphenylphthalate and dimethyl 4‐(4‐(4‐(p‐aminophenoxy)phenoxy)phenyl)‐3,5,6‐triphenylphthlate, was accomplished. Polymerization in solution or by a bulk polymerization procedure yielded a series of low molecular weight phenylated polyimides. The polymers were soluble in chlorinated hydrocarbons and exhibited thermal stabilities comparable to other polyimide systems.
Esters of alternating copolymers of maleic or 2,3‐dimethylmaleic anhydride with alkyl vinyl ethers
Authors: Xi Fu , Bassett Walter , Vogl Otto 
Published: May 2005

AbstractMaleic anhydride or 2,3‐dimethylmaleic anhydride was copolymerized with a number of alkyl vinyl ethers, with AIBN as the initiator. The comonomers were always alternating and were obtained in yields ranging from 15 to 99%. The acid anhydride group in both series of copolymers was converted to the corresponding methyl esters in a two‐step reaction. The structure of these polymers was established by elemental analysis and by infrared, 1H‐and 13C‐NMR spectroscopy. Addtional characterization of these copolymers were carried out by viscosity measurements, differential scanning calorimetry for the determination of glass transition temperatures, and thermal degradation for the determination of the thermal stability of the copolymers.
Chemical modification of poly(vinyl chloride): A conclusive study of the influence of tacticity
Authors: Millán J. , Martinez G. , Mijangos C. 
Published: May 2005

AbstractThree samples, A, B and C, of poly(vinyl chloride) (PVC) were prepared at 90, 60, and 0°C, respectively, to give them different isotactic content measured by 13C‐NMR spectroscopy. A kinetic study of the nucleophilic substitution with sodium thiophenate, carried out for the three samples, showed that even at temperatures as high as 60°C a fraction of the units remain unreactive and that the extent of this fraction depends on the syndiotactic content of the polymer. This was also supported by a comparison of the behavior of samples B and C in substitution experiments at 5 and 60°C. In contrast the substitution experiments at −30°C demonstrated that, as suggested, a small fraction of extremely reactive units exists in PVC, the content of which is higher as the isotactic content of the polymer increases. In this connection, and even though a slight contribution of some defect structures cannot be ruled out, a 13C‐NMR analysis of sample B after modification at 40°C to various degrees demonstrates that the reactivity of the isotactic triads is high in relation to the heterotactic. On the basis of the results obtained and the possible conformations in PVC the substitution mechanism is related to the occurrence of isotactic TT conformations. The results, as discussed in terms of the various ways in which isotactic TT conformations appear open new prospects in the field of PVC chemical modification and stabilization mechanisms.
Oligomerization of vinyl monomers 20. Carbon‐13 NMR of oligomers of 2‐vinylpyridine. Studies of labelled end groups
Authors: Huang S. Strong , Hogen‐Esch Thieo E. 
Published: May 2005

AbstractOligomers of 2‐vinylpyridine initiated with Li, Na, K, and Rb salts of 13C‐labeled or‐unlabeled 2‐ethylpyridine and terminated with 13C‐labeled or ‐unlabeled methyl iodide were separated by liquid chromatography and analyzed by 13C‐NMR of the initial or terminal CH3 group. The stereochemistry of the three dyads which flank the initial or terminal methyl group could be determined and this allowed us to evaluate the stereochemistry of both methylation and vinyl addition. The methylation of the Li and Na salts of the oligomer anions is highly (> 95%) stereoselective and independent of chain length, whereas the stereoselectivity of the K and Rb salts is substantially less. These data indicate that the Li and Na oligomer and polymer anions exist in a chelated form in which the metal ion is complexed with the penultimate 2‐pyridine group, the other counterions being chelated to a lesser extent. The stereochemistry of monomer addition was found to be less stereoselective than that of methylation for the Li and Na salts. In addition, the apparent meso‐stereoselectivity of monomer addition of the Na, K, and Rb systems was greater than that of the Li ion. For the latter system, in particular, the mechanism appeared to be Markoff‐like and consistent with different reactivities of anions flanked by a distinct dyad or triad stereochemistry. These data appear to be consistent with the intramolecular coordination that tends to hold the third asymmetric center close to the propagating carbanion.
Polyaromatic ether–ketones and ether–keto–sulfones having various hydrophilic groups
Authors: Ogawa Takeshi , Marvel C. S. 
Published: May 2005

AbstractPolyaromatic ether–ketones and polyaromatic ether–keto–sulfones were sulfonated by suspending the polymer powders in dichloroethane containing liquid sulfur tiroxide and trialkyl phosphate at room temperature. It was found that more than one sulfonic group can be introduced per each repeating unit of the polymers without degradation. The sulfonated polymers were soluble in various organic solvents, and solubility and mechanical properties depended on the initial molecular weight of polymers as well as the degrees of sulfonation. Strong films can be cast from their dimethylformamide solutions.
Peculiar temperature dependence on the binding of methyl orange and its homologs by 2‐hydroxyethyl methacrylate‐N‐vinyl‐2‐pyrrolidone copolymers
Authors: Kozuka Hiroshi , Takagishi Toru , Hamano Hiromitsu , Kuroki Nobuhiko 
Published: May 2005

Abstract2‐Hydroxyethyl methacrylate (HEMA)‐N‐vinyl‐2‐pyrrolidone (VPy) copolymers of various compositions have been prepared. The copolymers obtained were examined for their ability to bind a homologous series of methyl orange derivatives, methyl orange, ethyl orange, propyl orange, and butyl orange, at 5, 15, 25, and 35°C, respectively, in an aqueous solution. The first binding constants and the thermodynamic parameters that accompanied the binding were evaluated. The binding ability of the copolymer for the small cosolute was enhanced with an increase of the HEMA content in the copolymer. Moreover, a bell‐shaped curve appeared in the binding of butyl orange by the copolymers having higher HEMA residues when the first binding constant was plotted as a function of temperature, whereas no such phenomenon was detected for the copolymers with less HEMA content or for the less hydrophobic dye, methyl orange, ethyl orange, or propyl orange. This peculiar temperature dependence of the first binding constant shows that the enthalpy of the binding varies from a positive (unfavorable) value below ca. 15°C to a negative (favorable) one above this temperature. This behavior can be accounted for in terms of more hydrophobic effects involved in the binding process.
Modern Methods of On‐Line Size Analysis for Particulate Process Streams
Authors: Hobbel Erik F. , Davies Reg , Rennie Foster W. , Allen Terence , Butler Larry E. , Waters Edward R. , Smith James T. , Sylvester Robert W. 
Published: May 2005

AbstractTwo techniques for on‐line particle size measurement are evaluated on the reproducibility of their volume distribution determinations. A forward scattering laser light devise is interfaced with a dilutor to examine the potential of this technique for high concentration streams. The forward scattering instruments are capable of outputting extremely reproducible distributions and here we show that when the dilutor is well designed, the on‐line instrument can have similar performance. We compare this with a scanning back scatter instrument which is directly inserted in highly concentrated slurries. We present the methods used to improve the robustness of the conversion of the output of the back scatter instrument to volume distributions. The output of the back scatter instrument is inherently less stable but with the proper methods one can obtain reproducibilities of the order of 2 to 6 percent.
New Developments in Aerosol Characterization from the Physical Point of View
Authors: Schmidt‐Ott Andreas 
Published: May 2005

AbstractThere are a limited number of phenomena occuring with aerosol particles that depend only on physical quantities. Examples of new developments in aerosol particle characterization in situ that make use of such phenomena are briefly reviewed. They concern electrophoretic size classification, inertial size analysis and shape characterization of agglomerates. In addition to deriving basic descriptors, measurements of composite quantities can be performed and developed into sensors. Examples of sensors responding to relevant complex aerosol quantities are explained.
Characterizing the Structure of Fumed Pigments using the concepts of fractal geometry
Authors: Kaye Brian H. 
Published: May 2005

AbstractMany commercially important pigments such as titanium dioxide and carbonblack are produced as fumes from a combustion process. The fuming process generates open structured agglomerates conforming to a morphology predicated by physical considerations. For this reason widely different chemical pigments often manifest common physical structure. This structure can be characterized using the concepts of fractal geometry. In this communication the potential usefulness and physical significance of descriptive parameters of the agglomerate structure of fumed pigments based on the concepts of fractal geometry are explored. Similar structures present in high energy ceramic powders are discussed and the potential importance of fractal dimension parameters for the prediction of the physical behaviour of powders is outlined.
On the Droplet Deposition and Mist Supercooling in a turbulent channel flow
Authors: Yang Z. H. , Lee S. L. 
Published: May 2005

AbstractA combined experimental and theoretical study of the droplet deposition and mist supercooling in a turbulent channel flow has been performed. The measurement of droplet deposition on the unheated and heated channel wall was carried out using a particle‐sizing two‐dimensional reference‐mode laser‐Doppler anemomentry technique in a 41 mm × 41 mm vertical square channel at Re = 1.0 × 104 − 6.05 × 104. The dimensionless deposition coefficient kd/uZ. H. Yang Prof. S. L. Lee Department of Mechanical Engineering, State University of New York at Stony Brook, Stony Brook, NY 11794 (USA)
is analyzed theoretically based on a new unified theoretical approach for the entire transverse flow region from the turbulent core to the quasi‐laminar region next to the boundary wall. The proposed analytical model shows satisfactory agreement with the results of present experimental measurement. In the mist supercooling, the heated surface is cooled by the evaporation on the outside surface of an extra thin continuous liquid film which is maintained by the continuous deposition of extremely small droplets of an optimal size determined by a selection process on the droplets transverse migration due to the dynamic interaction between the phases in a parallel turbulent mist flow. The heat transfer enhancement coefficient depends on droplet deposition rate, droplet size, concentration and the Reynolds number.
A Study of Particle Factors Affecting Dust Explosions
Authors: van der Wel Peter , Lemkowitz Saul , Scarlett Brian , van Wingerden Kees 
Published: May 2005

AbstractSome parameters which affect the explosibility of dusts have been investigated. Important parameters are particle size, dust concentration, pore size and chemical composition. The dust explosion index measurements illustrate the importance of pore size and particle size. The reaction mechanism occurring is also important. Particles which burn at the solid surface and form gaseous products tend to react completely whereas other materials show a limited transport of the reactants.
An Estimate of Some Statistical Properties of Extinction signals in dilute and concentrated suspensions of monosized spherical particles
Authors: Riebel Ulrich 
Published: May 2005

AbstractA statistical analysis is made for the extinction of radiations in suspensions, whereby the whole range of possible particle concentrations is covered. The extinction signals are characterized by their average value and by a characteristic length of fluctuation. For simplicity, the considerations are restricted to geometric ray propagation in dispersions of perfectly absorbent, monosized spherical particles. An extinction equation is derived, which reduces to Lambert‐Beer's law in the limit of low particle concentrations. For higher concentrations, significant deviations from Lamberg‐Beer's law due to steric particle‐particle interactions are predicted. The characteristic length of the fluctuations is a function of particle diameter and transmission and has a broad minimum with medium transmissions, allowing for maximum resolution with measurements in this range.
Simultaneous In Situ Measurements of Size and Velocity of burning droplets
Authors: Anders Klaus , Roth Norbert , Frohn Arnold 
Published: May 2005

AbstractAn optical instrument for simultaneous on‐line measurements of the droplet size and droplet velocity of periodically generated droplets is described. This instrument is suitable for studying basic phenomena such as the evaporation or combustion of small droplets and the mutual interaction of neighbouring droplets. For the study of evaporation and combustion rates it is important to have precisely defined initial and boundary conditions. A vibrating‐orifice generator is used to produce monodisperse droplet streams which are characterized by their highly coherent structure. The droplets all have the same size, the same spacing and the same initial velocity. These characteristic parameters of the droplet stream can be adjusted over a wide range as required for the specific experiment. The droplet size is measured with a sizing method of very high accuracy, which evaluates the intensity distribution of the light scattered by the droplets. The droplet diameter ranges from 10 to 150 μm. The droplet velocity is measured by a particle image displacement velocimeter and is compared with conventional LDV measurements. The results of the two methods agree very well. Typical droplet velocities lie in the range from 10 to 20 m/s. Some exemplary experimental results are presented for burning droplet streams, which show the influence of a finite spacing between the droplets on the burning rate.
Anomalous Diffraction Effects in the Sizing of solid particles in liquids
Authors: Brown Dennis J. , Alexander Keith , Cao Jing 
Published: May 2005

AbstractA study has been made of anomalous diffraction effects in the sizing of solid particles in liquids using a Malvern laser diffraction sizer. The particles were N.B.S. standard reference material 1004 glass spheres. The five liquids used were chosen to give a range of refractive index (R.I.) above and below that of the glass; the ratio of solid R.I. to liquid R.I. (m) ranged from 0.92 to 1.15. Measurements were made of the change in the light energy distribution pattern as the value of | m − 1 | was in creased or reduced towards zero. At high values of | m − 1 | the measured light energy distribution pattern was predicted adequately by the Fraunhofer diffraction approximation to Mie theory and the Fraunhofer computer software could be used to derive particle size distribution from the light energy pattern. For values of | m − 1 | near to zero, the Fraunhofer approach was in error but the anomalous diffraction approximation and software proved adequate for the back‐calculation of size distribution from energy pattern.
Sedimentation of Nonspherical Particles
Authors: Bernhardt Claus 
Published: May 2005

AbstractThe motion of real oblate particles of different cross‐section can be described with sufficient accuracy by equation valid for spheroids. The proof was effected by means of velocity measurements.The application of theoretical considerations to sedimentation analysis allows it to be used to calculate apparent distributions occurring in the sedimentation of monodisperse particles of uniform shape at any orientation relative to the direction of sedimentation. The transfer to polydisperse systems involves several difficulties, which can be avoided in part by suitable approximations. In the case of a particle system with a polydisperse distribution of a main axis, but a constant particle shape, it is possible to calculate the resulting apparent distributions and their deviations from those distributions obtained when applying the volume equivalent particle diameter.
A Comparative Study on Different Scattering Techniques and data evaluation methods for sizing of colloidal systems using light scattering
Authors: Glatter Otto , Sieberer Johann , Schnablegger Heimo 
Published: May 2005

AbstractQuasi‐elastic light scattering, elastic light scattering and Fraunhofer diffraction can be used for optical particle sizing. Simulated data were used to compare the different scattering techniques in terms of resolution and range of applicability. Elastic scattering techniques have a ten times higher resolution but cover a smaller size range than quasi‐elastic light scattering. The most important inversion techniques for data evaluation for such experiments were also compared. Regularization techniques with positivity constraints and interpolating cubic B‐splines proved to be superior to truncated singular value decomposition and maximum entropy methods.
Thermal Reactivity of Double‐Base Rocket Propellants
Authors: Pai Verneker V. R. , Kishore K. , Subhas C. B. V. 
Published: May 2005

AbstractThermal decomposition studies on double‐base propellants have been carried out in air and vacuum using differential scanning calorimetric, thermogravimetric and mass spectrometric techniques. Low temperature (90 °C–170 °C) decomposition seems to involve diffusion controlled process, the mechanism in air and vacuum being different. High temperature (170 °–205 °C) decomposition involves bond breakage.
Reproducibility of Planewave Transit Times in three explosives during initiation: Comparison to wedge experiments
Authors: Dick J. J. , Engelke R. 
Published: May 2005

AbstractPlanewave transit times were measured in three explosives: PBX‐9404, pressed TNT, and PBX‐9502. Four nominally identical disks were used on each shot to measure the reproducibility of the transit time. Standard deviations in transit times were 1%–2% if most of the wave trajectory was in the initiation phase. The standard deviation in transit times is larger than the measurement precision; this indicates a distribution in the response to the input pressure wave. Comparison was made to results of previous wedge initiation experiments. We conclude that most of the scatter in run distances to detonation found in wedge experiments is not inherent in the initiation process or the explosive quality. The scatter may be due to the imprecision of the free‐surface velocity measurement coupled with the power‐law character of the relation between run distance to detonation and input pressure.