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  • Chemical Engineering  (1,427)
  • Atomic, Molecular and Optical Physics  (214)
  • Wiley-Blackwell  (1,641)
  • National Academy of Sciences
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 37-41 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experiments are reported in which the drag of single liquid droplets settling in a tall column of another lighter immiscible liquid are measured. The experimental data for the eight pairs of liquids that were tested covered a range of droplet Reynolds numbers from 10-3 to 104. Two regimes of droplet settling were encountered. In the first regime, the droplets remained spherical, and the drag agreed very well with established solid sphere drag models. In the second regime, the droplets became deformed and oscillated; the drag was found to depart suddenly from predictions of spherical models and to increase with increasing Reynolds number. Empirical models for the point of departure from spherical drag and the coefficient of drag in the unstable regime are derived.
    Additional Material: 4 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 383-388 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bifurcation problems with slowly varying control parameters are of interest in several research areas, including catalyst deactivation, combustion, and lasers and other nonlinear optical devices. Significant theoretical work has been devoted to the study of these dynamic phenomena, but very little directly relevant experimental information is currently available. Results are presented here from an experimental study of the dynamic behavior of a catalytic reaction system due to a deliberately slowly varied control parameter. Attention is focused on the dynamics due to slow passage through simple limit and Hopf points.
    Additional Material: 10 Ill.
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  • 3
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Identification and characterization of coupled diffusional and electrochemical kinetics effects was achieved under potentiostatic anodic dissolution conditions. A one-dimensional artificial pit geometry with sample wire electrodes embedded in an inert support exposed to NaCl solutions was used to study the dissolution of stainless steel and highnickel Alloy 600. Multiple steady states for both materials were determined at conditions where the diffusional transport rates balanced the electrochemical rate of dissolution at the surface of the wire electrode. A theoretical transport model was developed to quantitatively explain the observed multiple steady state phenomena.
    Additional Material: 12 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1261-1271 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This study clarifies and quantifies factors which increase the ductility of a low-molecular-weight propylene homopolymer having an intrinsic viscosity of 0.89 dl/g. The tensile behavior of homopolymer/ethylene-propylene rubber (EPR) blends was studied from the viewpoint of the associated molecular structure of EPR and its compatibility with the homopolymer. When EPR is “dissolved” in a homopolymer, the glass transition temperature (Tg) of the amorphous phase of a homopolymer was found to shift to a lower temperature, with homopolymer/EPR compatibility being subsequently evaluated using this shift, i.e., Δtg. Results show two conditions are required to improve the ductility of the low-molecular weight propylene homopolymer: ΔTg must be ≥ 3°C and ≥ 30 wt% EPR must be blended with the homopolymer.
    Additional Material: 18 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 482-487 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper examines the important dimensionless numbers that control emulsion polymerization in a tubular reactor. It was found that the activation energy of polymerization was of major importance, while the role of monomer diffusion was not very significant. By selecting certain combinations of the dimensionless numbers, changes occurring during scaleup from a small tubular diameter to a larger diameter can be approximated.
    Additional Material: 7 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 25 (1985), S. 245-249 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Copoly(carbonate imides) with varying amounts of carbonate in the backbone were prepared by reacting 4,4′-diaminodiphenyl carbonate and 4,4′-diaminodiphenyl ether with benzophenonetetracarboxylic acid dianhydride in dimethylacetamide at room temperature. Homopolymers of the two diamines as well as of 3,4′- and 3,3′-diaminodiphenyl carbonate were prepared in a similar procedure and their properties compared with those of the copolymers.
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 338-345 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dynamic dielectric analysis (DDA) has been used to study curing polymer systems and thermoplastics. Measurements have been made over a frequency range of six decades. This wide range of frequencies increases the amount of information which can be obtained. The data is analyzed in terms of the frequency dependence of the complex permittivity ε*, specific conductivity σ(ohm-1 cm-1), and the relaxation time τ, parameters which are characteristic of the cure state of the material and independent of the size of the sample. Dynamic dielectric measurements have been used to monitor polymer processing in UDEL-P1700, LARC-160, polyphenyl quinoxaline (PPQ), and Epon 828 cured with Agent U. Dynamic dielectric measurements have been correlated with viscosity for the polysulfone thermoplastic UDEL-P1700 and with viscosity and ultrasonic measurements on the DGEBA type epoxy Epon 828 cured with Agent U. The experimental results suggest that when ionic processes dominate the dielectric response, the intensive property σ is a good monitor of the resin's viscosity. The results show that the dielectric relaxation time τ can be used to monitor the state of the system and the extent and rate of the reaction. Solvent evolution can also be easily observed.
    Additional Material: 16 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 15 (1975), S. 401-405 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This note presents a coordinate frame representation for the conservation laws governing fluid motion in a helical configuration as suggested by a single-screw extruder with deep flights and by the Kenics Static Mixer. This example demonstrates the care necessary in dealing with nonorthogonal coordinate systems. The conservation equations are also presented in terms of the proper physical components, as well as the physical components of the rate of deformation tensor. The paper closes with a brief statement of the boundary conditions for flow in a static mixer.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 612-619 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The influence of tie-layer Melt Flow Index on the lap-shear strength of ultrasonic welds in oriented polypropylene (OPP) has been evaluated. The tie-layer Melt Flow Index was varied from 0.03 dg/min to 2600 dg/min; the highest lap-shear strength properties were obtained using tie-layers that had melt flow index values between 30 and 100 dg/min. When using low Melt Flow Index tie-layers, hot spot formation and concomitant changes in fusion zone and heat-affected-zone dimensions produced stress concentrations that promoted failure in oriented polypropylene material away from the bondline region. When very high Melt Flow Index (2600 dg/min) tie-layers were used, the mode of failure during lap-shear testing was a mix of cohesive, in oriented polypropylene, and adhesive failure. The molecular weight of material at the bondline was not markedly affected by the thermal cycle produced during ultrasonic welding. Only the flash ejected when using low Melt Flow Index tie-layers exhibited any evidence of degradation; it is suggested that the ejected flash may have been degraded because of a combination of thermal, cavitation, and thermo-oxidative processes.
    Additional Material: 10 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 600-611 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Ultrasonic welding of oriented polypropylene (OPP) using tie-layer materials has been examined. The thermal cycle at the joint interface was evaluated using a high speed data acquisition system, and concurrent changes in horn displacement (penetration) and the output power were monitored. The model explaining process operation involves four phases, i.e., I-where heating occurs because of the stresses generated in asperities on the contacting surfaces; II-where the whole tie-layer reaches the melting point; III-where the polymer melt is subjected to intense heating from viscous dissipation and is squeezed out; and IV-where the joint cools after welding. In the early stages of ultrasonic welding the heat generated at asperities on the contacting surfaces leads to melting of the tie-layer/oriented polypropylene interface within 50 ms. The tie-layer heats up because of a combination of viscoelastic dissipation and heat conduction from the oriented polypropylene/tie-layer interface, and the rate of temperature rise at the midline of the tie-layer is in the range 200°/s to 400°/s. The reduction in thickness of the test specimens (penetration) is negligible up to the time when the tie-layer melts completely, and then changes rapidly when the melted polymer at the joint interface is squeezed out. The influence of machine parameters (amplitude and contact pressure) and of tie-layer Melt Flow Index is also examined. The total time required for completion of the welding process decreases when the amplitude and applied pressure are increased. The use of low Melt Flow Index tie-layers produces peak temperature as high as 600° at the bondline, and little material is ejected during the ultrasonic welding operation.
    Additional Material: 19 Ill.
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