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  • Chemical Engineering  (340)
  • FLUID MECHANICS AND HEAT TRANSFER
  • GEOPHYSICS
  • Wiley-Blackwell  (340)
  • 1980-1984  (340)
  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 39-46 
    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: Thermoplastic interpenetrating polymer networks, IPN's, are defined as combinations of two physically crosslinked polymers. A styrene-b-ethylene-co-butylene-b-styrene (SEBS) triblock elastomer was combined with an ionomer prepared from a random copolymer of styrene, methacrylic acid, and isoprene (90/10/1 by volume), and subsequently neutralized. Two subclasses of the thermoplastic IPN's were identified. A sequential polymerization method yielded the chemically blended thermoplastic IPN's (CBT IPN's). Melt blending of the separately synthesized polymers produced the mechanically blended thermoplastic IPN's (MBT IPN's). Stress-strain and Rheovibron characterization revealed that the CBT IPN's exhibited greater tensile strength and higher elongation at break, but lower moduli than the MBT IPN materials of the same overall composition. Analysis of moduli data with the theories of Takayanagi, Davies, Budiansky, and Kerner disclosed more equal dual phase continuity for the MBT IPN's than the CBT IPN's at each composition. The low modulus of the more rubbery CBT IPN compositions was attributed to a decrease in the effective chain end-to-end distance between crosslinks in the elastomeric (EB) center block, brought about by the synthetic method.
    Additional Material: 4 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 86-92 
    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: An experimental investigation into the performance in general and the melting behavior in particular of a single screw extruder running with a low density polyethylene power has been carried out and the results compared with those for a granular feedstock of low density polyethylene having similar melt properties. It was found that the tendency was for the output rate, pressure generated and specific power consumption to be lower for the powders, and that the removal of barrel heating near the feed hopper increased these parameters. Two melting mechanisms were observed in powder extrusion; one being the classic “Maddock” type, and the other such that the solid bed and melt pool were in reversed positions relative to the Maddock case. There was a trend for this latter mechanism to operate with low screw speeds, shallow channels and full heating. Melt initiation occurred nearer the feed end and melting was completed much more quickly with powders. An explanation of the mechanisms is proposed which is based on the observation of early melt initiation, and the industrial practices of feed zone cooling and increasing feed pressure generation to improve the performance of extruders running with powders are seen to be consistent with this proposition.
    Additional Material: 7 Ill.
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  • 3
    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: In this paper we describe the operation of a rheometer that is capable of measuring the viscoelastic response of a polymer melt in a biaxial or planar extensional flow field under circumstances wherein the deformation history can be varied in an arbitrary manner. The principal feature of this rheometer is the use of a closed loop feedback system to control the inflation of a flat, molten polymer sheet clamped around its periphery. The feedback system is especially designed so that either stress or strain can be used as the reference point, thus permitting the deformation history to be varied arbitrarily. Illustrative data are presented on the viscoelastic response of a molten acrylonitrile-butadiene-styrene copolymer subjected to a planar extensional flow for the following deformation histories: constant stress, constant strain, constant strain rate, oscillatory stress and oscillatory strain.
    Additional Material: 7 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 329-344 
    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 new method of optimizing the fiber drawing process involving the feed roll, the heated elements and the take-up roll is presented. In this method, the process is described in terms of the filament temperature and filament extension in the drawing zone. This is in contrast to the conventional approach in which the machine control variables such as the heated element temperature, fiber feed velocity and the total draw ratio were used to describe the process. It is shown that the drawing process seldom proceeds by a simple yielding mechanism and that a one-step drawing process usually involves a yield draw followed by a post-yield stretching. Using the drawing of nylon 6 fibers as an example, it is shown that the most critical factors related to achieving the highest fiber strength in drawing from a given precursor are the yarn temperature and yarn extension at yielding and during the post-yield drawing.
    Additional Material: 17 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 127-134 
    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 technique of Thermo Stimulated Creep (TSC) has been applied to the study of anelastic properties of polyethylene, polypropylene, their copolymers and blends. In the temperature range -200 to 100°C, complex TSC peaks were observed in all samples, namely around 0°C, about the same temperature as for the homopolypolymer polypropylene. By applying “fractional stresses”, with a convenient choice or the loading program, these peaks have been experimentally resolved. Two components can be distinguished: 1. The “low temperature” component is characterized by mechanical retardation times following a compensation law. It has been attributed to microbrownian motions of polypropylene sequences liberated at the glass transition of the “true” amorphous regions. 2. The “high temperature” component which is influenced by thermal treatment has been assigned to microbrownian motions of polypropylene sequences liberated at the glass transition of the “constrained” amorphous regions. In block polymers, an additional TSC peak is observed around -50°C: it has been associated with the glass transition of ethylene-propylene-rubber (EPR) interphase. The coupling of this interphase with polyethylene and polypropylene phases is insured by diffusion of some ethylene and propylene sequences in-EPR. At about -140°C, a TSC peak associated with the low temperature component of the glass transition of polyethylene can be distinguished in all the materials studied.
    Additional Material: 7 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1173-1180 
    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 tensile fatigue behavior of unnotched injection molded polysulfone specimens has been investigated. The effects of orientation and residual stress were studied by comparing asmolded specimens with annealed or annealed and quenched specimens with a known residual stress pattern. The treatments are shown to have differing effects at high stresses, where failure is by shear yielding and necking, and at intermediate stresses, where failure is by fatigue crack propagation. The geometries of fatigue cracks are described for each case. An attempt is made to separate the effects of crack and craze initiation from crack propagation, and cyclic loading from cumulative time under load.
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 27 (1981), S. 226-234 
    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 effect of varying pore structures on the kinetics of fluid-solid reactions is investigated through the random pore model developed in prior papers (Bhatia and Perlmutter, 1980, 1981). By considering several idealized pore-size distributions it is shown that a solid having a uniform pore size is intrinsically less reactive than one possessing a pore-size distribution. For solids with bimodal pore size distributions optimal structures are shown to exist for which the reactivity is a maximum.Numerical solutions were obtained to the model equations for various values of the parameters characterizing the pore structure, the diffusion, and the chemical kinetics. The results show that the conversion-time behavior and the expected ultimate conversion can be very sensitive to variations in surface area and porosity for reactions accompanied by an increase in volume of the solid phase.These findings are in agreement with experimental literature on the SO2-lime reaction (Ulerich et al., 1978; Borgwardt and Harvey, 1972; Potter, 1969; Falkenberry and Slack, 1968) and the model is shown to fit the data of Borgwardt (1970), and of Hartman and Coughlin (1974, 1976). It is seen that this reaction is diffusion controlled under the conditions of Hartman and Coughlin, in consonance with their own finding using the grain model, and a prior Pigford and Sliger (1973) interpretation. The temperature behavior of the diffusion coefficient in the product layer suggests the participation of an activated process, possibly a solid state diffusion step.
    Additional Material: 11 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 27 (1981), S. 975-984 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Filtration of carbon black particles from tetralin through a bed of sand with simultaneous measurement of bed streaming potential shows that the charge on the filter and its neutralization by depositing colloidal particles plays an important role in filter performance. Filter capacities up to the point of charge neutralization, calculated from knowledge of the colloid and filter zeta potentials using a semitheoretical model for variation of filter surface charge characteristics, are found to be in good agreement with experimental values.
    Additional Material: 11 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 29 (1983), S. 625-631 
    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 mixed oxide system of copper and tin and the active single oxide, Cu2O, were compared for reducibility of the copper ion, relative number and type of active sites, and reaction kinetics. The enhanced selectivity of the mixed oxides may result from the formation of highly selective sites at the expense of less selective sites. The reducibility of the copper ion in the mixture is influenced by the oxidation state of the tin ion. The reactant and product reaction orders are the same for both catalysts but the mixed oxides are more sensitive to inhibition by water. The catalyst composition affects the energetics of the reaction over the copper-tin oxide catalysts.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 26 (1980), S. 928-934 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model is derived for solids mixing and material transport in a continucus flow rotary dryer or reactor. Detailed analysis of the particle motions in the turnover process provides an opportunity to apply well-known reactor models to several subregions and to relate the overall results to different design geometries and operating conditions. The essential parameters of the model are the number of stages, the volume fractions of mixed flow and plug flow in each stage, the recycle ratio and the bypass ratio.
    Additional Material: 7 Ill.
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