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  • 1
    Electronic Resource
    Electronic Resource
    Numerical simulation of the post-filling stage in injection molding with a two-phase model (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 835-846 
    Details
    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: A two-phase model is presented for simulating the post-filling stage of injection molding of amorphous and semicrystalline materials. A finite-element scheme with quadratic shape function for the pressure is proposed. The melt is considered in terms of Hele-Shaw flow for a non-Newtonian fluid using a modified-Cross model with either an Arrhenius-type or WLF-type functional form to describe the viscosity under nonisothermal conditions; the compressible behavior of the polymer is assumed to obey either a double-domain Tait or single-domain Spencer Gilmore equation of state. The interfacial energy balance equation including the latent-heat effect for semicrystalline materials is coupled with the transient energy equation for the solid and melt phases in order to predict the solidified layer and temperature profile. Two well-characterized materials, namely a commercial-grade PP and PS, were used in the present work. Good agreement is obtained between the present simulation and experimental pressure traces from this study and from previous investigation in the literature. The effects of compressibility, viscosity model, and thermal properties upon the predicted pressure field are also considered.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341009
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of aggregation of p-phenylphenol on enzymatic polymer synthesis in dioxane/water mixture (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2339-2345 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The state of p-phenylphenol molecules in dioxane/water mixture, a commonly used reaction system for enzymatic polymerization of phenols and aromatic amines, was investigated by difference UV absorption spectroscopy and Fourier transform (FT) Raman spectroscopy. The aggregate of p-phenylphenols is found on the basis of the exciton peaks observed in difference UV absorption spectra. FT Raman spectroscopy demonstrates further that p-phenylphenol molecules aggregate together in “face to face” fashion. A simplified model is proposed for aggregation of p-phenylphenol molecules in dioxane/water mixture, which can elucidate the variation of the molecular weight of poly (p-phenylphenol) coupled in the reaction system. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331406
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  • 3
    Electronic Resource
    Electronic Resource
    Optimal shape design for systems governed by variational inequalities, part 3: Necessary conditions in the elliptic case (1992)
    Springer
    Journal of optimization theory and applications 74 (1992), S. 273-304 
    Details
    ISSN: 1573-2878
    Keywords: Optimal shape design ; variational inequalities ; mapping method ; optimal control for variational inequalities ; optimality conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract General optimality conditions are obtained for optimal shape design for systems governed by a class of elliptic variational inequalities. The conditions are established by making use of the necessary conditions for optimal control of systems governed by strongly monotone variational inequalities. These conditions are then applied to an electrochemical machining problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00940895
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  • 4
    Electronic Resource
    Electronic Resource
    Optimal shape design for systems governed by variational inequalities, part 1: Existence theory for the elliptic case (1991)
    Springer
    Journal of optimization theory and applications 69 (1991), S. 351-371 
    Details
    ISSN: 1573-2878
    Keywords: Optimal shape design ; variational convergence theory ; elliptic variational inequalities ; existence theorems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Some general existence results for optimal shape design problems for systems governed by elliptic variational inequalities are established by the mapping method and variational convergence theory. Then, an existence theorem is given for the optimal shape for an electrochemical machining problem, in which the cost functional is not lower semicontinuous, by extending the general results to this case. Furthermore, this problem is approximated by a set of optimal shape design problems which have more smooth cost functionals and are easier to handle computationally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00940649
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  • 5
    Electronic Resource
    Electronic Resource
    Optimal shape design for systems governed by variational inequalities, part 2: Existence theory for the evolution case (1991)
    Springer
    Journal of optimization theory and applications 69 (1991), S. 373-396 
    Details
    ISSN: 1573-2878
    Keywords: Optimal shape design ; variational convergence theory ; evolution variational inequalities ; existence theorems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Some general existence results for optimal shape design problems for systems governed by parabolic variational inequalities are established by the mapping method and variational convergence theory. Then, an existence theorem is given for the optimal shape for an electrochemical machining problem, in which the cost functional is not lower semicontinuous, by extending the general results to this case. Furthermore, this problem is approximated by a set of optimal shape design problems which have more smooth cost functionals and are easier to handle computationally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00940650
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  • 6
    Electronic Resource
    Electronic Resource
    Moisture-induced aggregation of lyophilized proteins in the solid state (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 177-184 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A critical problem in the storage and delivery of pharmaceutical proteins is their aggregation induced by moisture. A model system has been elaborated and investigated to elucidate the mechanism of this phenomenon. When 10 mg of bovine serum albumin lyophilized from an aqueous solution of pH 7.3 are wetted with just 3 μL of a buffered physiological saline solution and incubated in the solid state at 37°C, the protein progressively loses its solubility in water; e.g., after a 24 h incubation 97% of the protein becomes insoluble. This moisture-induced aggregation of albumin has been discovered to be due to an intermolecular S - S bond formation via the thiol-disulfide interchange reaction. The dependence of the extent of the solid-state aggregation on the amount and mode of addition of moisture and the atmosphere, additives, temperature, and history of the protein powder have been investigated. The moisture-induced solid-state aggregation has also been established and studied for three other lyophilized proteins: ovalbumin, glucose oxidase, and β-lactoglobulin. In all cases, the loss of solubility is caused by thiol-disulfide interchange either alone or in combination with a conformational (noncovalent) process. The aggregation can be minimized by lyophilizing the proteins from acidic aqueous solutions, by adding inorganic salts, by co-lyophilizing the proteins with water-soluble polymers, or by controlling the moisture content at optimal levels.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370210
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  • 7
    Electronic Resource
    Electronic Resource
    Instability of film coating of wires and tubes (1975)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 21 (1975), S. 775-782 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The stability problem of the free coating of wires and tubes by withdrawal is formulated and solved. The necessary condition for the stability of the film coating is given explicitly in terms of the Reynolds number, wave number, the Weber number, and implicitly in terms of the withdrawal velocity. The outcome of the competition between the destabilizing capillary pinching and the stabilizing capillary restoring force associated with the film thickness variation is shown to dictate the stability of the film. The comparisons between the present theoretical results and the known experimental results for falling films and creeping annular threads of viscous liquids are good. A possible application of the present results to some aspects of the qualitative design of a coating process is given.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690210420
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  • 8
    Electronic Resource
    Electronic Resource
    Numerical simulation and experimental investigation of injection mold filling with melt solidification (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1039-1050 
    Details
    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: A two-phase model is presented for simulating the injection mold filling process including the effect of transient melt solidification, i.e., the phase change effect. The liquid region is governed by Hele-Shaw flow for a non-Newtonian fluid using a modified Cross model to describe viscosity under non-isothermal conditions. Further, the energy equation of the solid phase is dominated by a transient condition. The interfacial energy balance equation is also proposed to predict the solidified layer thickness and temperature profile. Two well-characterized semicrystalline materials, polypropylene and polyethylene, were used in the present work. Good agreement is obtained between the predicted results and experimental observations from this study and the previous literature concerning the thickness of solid layer, the shape of, advancing melt front, and the pressure traces. In particular, the predicted pressure based upon the two-phase model is higher than that in terms of the single-phase model by about 13 percent. Finally, the semicrystalline structure of the frozen skin layer and the central core were investigated with a scanning electron microscope to verify the two-phase model.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760291510
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  • 9
    Electronic Resource
    Electronic Resource
    Unsaturated polyester diol-polyurethane composite networks (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 240 (1996), S. 163-170 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This article introduced the formation of an unsaturated polyester/diol-polyurethane hybrid polymer networks(UP/PU HPNs). The phase behavior was examined by the dynamic mechanical properties and the morphology was investigated by transmission microscope(TEM) and atomic force microscopy(AFM). The effect of phase separation on mechanical properties is briefly described as well.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052400114
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  • 10
    Electronic Resource
    Electronic Resource
    Phase separation of poly(ether sulfone imide) modified epoxy resin (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 61 (1996), S. 2423-2435 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: Poly(ether sulfone imide)s (PEI) with molecular weight Mn ∼ 104 were synthesized from 3,3′,4,4′-benzophenone tetracarboxylic dianhydride and amine terminated poly(ether sulfone) having molecular weights ranging from Mn ∼ 400 to Mn ∼ 4000. Thus, the PEIs had the same molecular weight but various imide and ether sulfone contents. The PEIs were mixed with a stoichiometric mixture of diglycidyl ether bis-phenol-A (DGEBA)/diamino diphenyl sulfone (DDS). The effect of PEI on the curing reaction of DGEBA/DDS and the morphology of the polymer blend were studied by differential scanning calorimetry (DSC) and optical microscopy. In the DGEBA/DDS/PEI blend with a fixed PEI molecular weight and PEI concentration but with various imide content, the experimental data revealed the PEI with a higher content of ether sulfone had a lower Tg and a better compatibility with solvents and epoxy resins; the curing reaction rate of DGEBA/DDS/PEI was faster for PEI with a higher imide content; the DSC data of cured DGEBA/DDS/PEI showed two Tgs, indicating phase separation between PEI and cured epoxy resins; and the data of optical microscopy showed that the compatibility of PEI with epoxy resins increased with the content of ether sulfone in PEI. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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