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  • 1
    Electronic Resource
    Electronic Resource
    Experimental results from a plate-column wet scrubber with gas-atomized sprayPaper presented at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, September 30 to October 2, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 73-79 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A pilot wet scrubber was examined experimentally. It is constructed like a plate column. Its plates are designed to set the gas into a whirling motion with tangential velocities of up to 25 m/s and to ensure a uniform distribution of the liquid throughout the gas flow. Particles suspended in the waste gas are collected by gas-atomized droplets to yield cut diameters between one and two microns. Energy consumption is lower than in the case of other scrubbers. The scrubbing mechanisms are analyzed by examining the measured pressure drops. Finally, methods of determining the collection efficiency are discussed and an empirical approach to its calculation is presented.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110111
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  • 2
    Electronic Resource
    Electronic Resource
    Relationship between residence time, fluid dynamics and efficiency in countercurrent flow equipmentPaper presented at AIChE Annual Meeting 1986, Miami Beach, Florida, USA (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 139-148 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The suitability of any item of equipment for a given thermal separation process cannot always be judged solely in the light of efficient and loading range data. In vacuum rectification, involving a large number of theoretical stages, the vapour pressure drop per transfer unit exerts a considerable effect on the energy consumption and thus largely governs the choice of column fittings. Furthermore, the pressure drop per transfer unit determines the temperature at the bottom of a rectification column and, hence, the suitability of the equipment for the separation of heat-sensitive products. It is also an important criterion for compressor requirements in absorption processes. Another factor of considerable importance in separating heat-sensitive mixtures by distillation is the time during which the product, particularly the liquid phase, is exposed to a given temperature in the column. Therefore, a standardized liquid residence time has been adopted to evaluate the systems in their entirely. This residence time depends on the hydrodynamic conditions in the column and is thus closely related to pressure drop and efficiency. Further important factors, which may decide the selection of column internals, are the specific volume and mass of the column. Based on theoretical considerations, a flow model is derived for describing the main loading range of countercurrent packed columns; the relationships between the above mentioned parameters are presented.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110119
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  • 3
    Electronic Resource
    Electronic Resource
    Absorption of SO2 by aqueous NaOH solutions in the presence of a surfactant (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 156-162 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A report is presented on the influence of liquid flow rate, NaOH concentration, column length and presence of 5 × 10-3 wt-% of the surfactant SLS on the rate of absorption of pure SO2 by aqueous NaOH solution in a sphere-and-cylinder column. The presence of sodium lauryl sulphate (SLS) prevented axial turbulence which increased mass transfer in longer columns and was almost independent of the flow rate. The enhancement factor due to the reaction between SO2 and NaOH with respect to the process of physical absorption was analyzed for the systems with excess OH- in the outflow. The results obtained in the presence of a surfactant are satisfactorily explained by film theory with a single reaction plane model. Those obtained in the absence of surfactant are best described by a two-plane model using renewal theory.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110121
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  • 4
    Electronic Resource
    Electronic Resource
    Measurement of temperature fields in mixing vessels using optical topographyPaper presented by W. Ostendorf at the “Jahrsterffen der Verfahrens- Ingenieure”, Freiburg, September 30 to October 2, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 148-155 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental investigation of stirring processes require the measurement of temperature changes and concentration profiles in all the zones of the mixing volume. The conversion of simultaneous chemical reactions during the mixing process depends on the local temperature and concentration. The time-dependent temperature and concentration fields can be recorded for the entire mixing volume with the use of optical tomography and correlated with time. This technique offers the possibility of continuous measurement of temperature and concentration changes during the mixing process throughout the measurement volume. In the described investigations, optical tomography is used to examine the transport and equalization processes during mixing in stirred vessels.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110120
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  • 5
    Electronic Resource
    Electronic Resource
    Heat transfer between particle beds and submerged surfacesPaper presented by O. Molerus at the “Jahrestreffen der Verfahrens-Ingenierue”, Freiburg, September 30 to October 2, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 126-138 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Theoretical modelling of heat transfer to particle beds comprises two sequential steps: transfer from the heating surface to contacting particles followed by transfer to the interior of the bed. Two different limiting case can be formulated for the second step: unmixed and homogeneously mixed bed. In the case, heat is transferred gradually via a repeated sequence of heat transfer in the gap between adjacent particles and conduction in the particulate material. In the second case, heat is transferred to the interior of the bed by mixing of particles which have previously attained the temperature of the heating surface. On the other hand, the mixing motion maintains a homogeneous lower temperature throughout the bed. Theory predicts a significant and easily measurable difference in the behaviour of heat transfer coefficients for the two regimes at long contact times t: unmixed beds ∝ \documentclass{article}\pagestyle{empty}\begin{document}$$ \sqrt t $$\end{document} and homogeneously mixed beds ∝ 1/t. For short times t, both regimes show the same behaviour, namely of t.From a theoretical standpoint, it makes sense to differentiate further between the behaviour patterns of unmixed beds: at long times t, instantaneous heat transfer coefficients are independent of heat transfer form the heating surface to adjacent particles. Comparison with experimental result from literature shows that the derived models, which are consistent, are suitable for describing the heat transfer from submerged surfaces to unmixed and mixed beds of particles.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110118
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  • 6
    Electronic Resource
    Electronic Resource
    The role of energy dissipation in contacting and mixing devicesPresented in memory of Professor Otto Nagel, at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, September 30 to October 2, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 276-287 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The aim of the present paper is the discussion of the relevance of power dissipation as a criterion for the understanding and prediction of transfer and mixing efficiencies in contactors and chemical reactors. After reviewing the approach of Le Goff to the energetic efficiency of exchangers, based on the deviations from Chilton-Colburn analogy, the following processes are studied: mass transfer between a flowing fluid and a reactive solid surface, transfer to a fixed object in a stirred vessel, macro- and micromixing of miscible fluids, and mass transfer in fluid-fluid contractors (especially gas-liquid reactors). It is concluded from the various examples that a direct relationship between the dissipated power and intensity of transfer or mixing can be established only under the two following conditions: local values must be considered at the point where the actual transfer and mixing occur, and not average values over the whole device, and power dissipation must be coupled to transfer or mixing and appear physically as the driving force of the process.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110137
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  • 7
    Electronic Resource
    Electronic Resource
    A new regenerable process for the recovery of SO2Dedicated to Professor Hanns Hofmann on the occasion of his 65th birthday (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 402-407 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Increasing demand for regenerable processes with SO2 recovery is to be expected. Advantages and limitations of the earlier developed citrate and adipate absorption/ steam stripping process are compared with those of the Wellman-Lord (sulphite) process. On the basis of comprehensive laboratory studies, a new process is proposed which supplements the citrate and adipate process. In this new process, the absorbent is a concentrated sodium phosphate buffer and the loaded buffer is regenerated by evaporation. The main buffer component is Na2HPO4, but NaH2PO4 is added in order to obtain a more complete stripping of SO2 during regeneration. The new process promises excellent absorption properties for SO2 with extremely low oxidation losses, regeneration with few incrustation problems and appreciable energy savings.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110152
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  • 8
    Electronic Resource
    Electronic Resource
    Masthead (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988) 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110101
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  • 9
    Electronic Resource
    Electronic Resource
    Axial pressure profile in circulating fluidized beds (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 11-17 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Design and operation of a circulating fluidized bed requires the knowledge of fluid mechanics. According to heat and mass transfer as well as chemical reactions, the effect of the set superficial gas velocity on the axial pressure profile is of particular interest. The axial pressure profile was measured for a variety of solids, as a function of the superficial gas velocity, in a cylindrical circulating fluidized bed with an inner diameter of 0.19 m and an overall height of 11.5 m. Depending on the solids content and superficial gas velocity, two or one sections can be observed in the plant where the pressure gradient is constant. A pressure profile with one pressure gradient exists only at high gas velocities, so long as the acceleration pressure drop immediately above the gas distributor is negligible. Comparison of measured pressure drops in circulating fluidized beds with those measured in vertical pneumatic conveying led to a state diagram for vertical gas-solid flows. The operation behaviour of different types of circulating fluidized bed plants can be explained with the aid of this diagram.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110103
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  • 10
    Electronic Resource
    Electronic Resource
    Engineering aspects and applications of crossflow microfiltration (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 17-25 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Crossflow microfiltration (CMF) is a pressure driven membrane process for the separation of suspended microparticles, bacteria and emulsion droplets. The fluid to be filtered flows in parallel to the membrane surface and restricts the formation of a filter cake. This contribution explains the basic process characteristics and the combination of the crossflow technique with other membrane cleaning methods (periodic backflushing, chemical cleaning). Special attention is paid to the influence of different process parameters on the flux through the membrane. The principle of plant design and different operation modes are described. Engineering aspects such as hydrodynamics, energy requirement and selection of construction materials are discussed in some detail.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110104
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  • 11
    Electronic Resource
    Electronic Resource
    Mass transfer contributions of solid particles to gas permeation in viscous laminar tube flow (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 25-31 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: While two- and multiphase flows find more and more application in chemical engineering practice, and the demand for theoretical information about mass and heat transfer processes in such systems is increasing, such data or at least experimental results which could be generalized are still lacking. The following pages are concerned with mass transfer in laminar suspension tube flows normal to the main direction of flow due to the individual motions of small, inert spherical particles. On the basis of a large number of experimental data, an interpretation is attempted of the role of nearly neutrally-buoyant particles in mass transfer enhancement, and a model for a semi-empirical description is suggested. The experimental arrangement uses the mass transfer of carbon dioxide in laminar flow of salt water during the process of gas permeation through a permeable membrane tube wall.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110105
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  • 12
    Electronic Resource
    Electronic Resource
    Interfacial areas and gas hold-ups at elevated pressures in a mechanically agitated gas-liquid reactor (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 1-10 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Interfacial areas and gas hold-ups were determined at pressures of up to 1.7 MPa in a glass vessel, 88 mm in diameter and of standard geometry. Superficial gas velocities between 0.25 and 2.0 cm/s were used and the stirring speed varied between 4 and 30 rps. The interfacial areas were determined by the chemical method, using the model reaction between CO2 and aqueous diethanolamine (DEA). Hold-ups were determined by observation of differences in height. In contrast to literature indications, the gas hold-up was found to be independent of reactor pressure. This is also true for the interfacial area.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110102
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  • 13
    Electronic Resource
    Electronic Resource
    Effect of ethane addition on propane pyrolysis (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 243-248 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pyrolysis of propane/argon mixture in the presence of trace quantities (0.1% and 0.9%) of ethane was investigated at reflected shock wave temperatures between 1200 and 2000K. Traces of ethane accelerated propane decomposition at high temperature. However, increase in the quantity of ethane added to propane/argon mixture did not result in the same increase of its accelerating influence. Ethylene, methane and acetylene were the main hydrocarbon reaction products, with small quantities of propylene and ethane detected only at lower temperatures. Below 1500K, addition of ethane slightly enhanced the yields of ethylene and methane at the expense of propylene and ethane respectively. The selectivity for acetylene increased with increasing temperature and with the decline of those for the other products. For none of the products, did the presence of ethane alter the relationship between product formation rates and temperature. The influence of ethane addition on propane pyrolysis at high temperatures was explained in terms of increased radical concentrations, especially hydrogen atoms and vinyl radicals, formed at high conversions. These accounted for the rapid acceleration of propane decomposition and the high yield of acetylene at high temperatures.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110132
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  • 14
    Electronic Resource
    Electronic Resource
    Mass transfer in centrifugal extractorsPaper presented by F. Otillinger at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, September 30 to October 2, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 312-320 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This contribution presents the methods of measuring the mass transfer in centrifugal extractors and of determining it during the individual life stages of a fluid element of the dispersed liquid, i.e. drop formation, motion, coalescence and stay in the stationary layer of the dispersed phase. The experimental mass transfer coefficients of the dispersed and continuous phases are compared with well-known theoretical models developed for extraction columns in gravitational field. Due to the fast motion and coalescence of the fluid particles at high centrifugal field intensities, mass transfer in centrifugal extractors takes place during short contact times. Nevertheless, this contribution shows that mass transfer in a centrifugal field can be calculated with selected theoretical models of the gravitational field. The investigations on mass transfer are completed by a classification of the strongly deformed fluid particles in centrifugal field into regimes of circulating and oscillating drops. In addition, data on the performance of centrifugal extractors, undergoing several exchange steps, are given.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110141
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  • 15
    Electronic Resource
    Electronic Resource
    Kinetic investigation of methacrylic acid synthesis on hetropoly-compoundsDedicated to Professor Dr. Hanns Hofmann on the ocassion of his 65th bithday (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 392-402 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of heterogeneously catalyzed methacrylic acid synthesis from isobutyric acid has been investigated. Initial catalyst screening pointed to 10-molybdo-2-vanado-phosphoric acid and its Cs-salts as the most promising catalysts. A model describing the reaction behaviour of all the different hetropoly-compounds used in this work was developed. A relationship was found between model parameters and composition of different catalysts. First insight was gained into the catalyst deactivation phenomena. Deactivation appears to be caused mainly by loss of molybdenum with simultaneous collapse of the Keggin structure.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110151
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  • 16
    Electronic Resource
    Electronic Resource
    A new appraisal of mass transfer processes in zeolites by transient methodsDedicated to Professor Dr. Hanns Hofmann on the occasion of his 65th birthday (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 432-438 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient diffusion of inert gases into Zeolon 900 H, a zeolite of the mordenite type, was studied by the chromatographic method. Experiments were performed with argon and helium either as tracer or as carrier gas. The diffusion of argon was also studied in a carrier gas containing methanol at a low temperature (75°C, no reaction) and at higher temperatures (up to 130°C) when some dehydration of methanol to dimethyl ether takes place. The adsorption isotherm of argon is linear. In the absence of methanol, its penetration into microcrystals of zeolite is equally well represented either by an effective diffusion coefficient D′μ = 7.4 × 10-8exp(-2873/T)m2s-1 or by a mass transfer coefficient at the crystallite surface keμ = 1.9 × 10-4 exp(-1324/T) ms-1. A small amount of methanol in the carrier gas considerably slows down the transfer of argon (by a factor of 40 for D′μ and 550 for keμ) showing the “blocking” effect of adsorbed methanol. In addition, transient adsorption can no longer be accounted for by a single transfer time. The size distribution of microcrystals, determined from Scanning Electron Microscope photographs leads to a Transfer Time Distribution which account well for experimental breakthrough curves without any parameter fitting. This interpretation is supported by experiments under reaction conditions where transport of argon within crystallites increases faster with temperature than in the absence of reaction due to the transformation of methanol into dimethyl ether, which is less adsorbed and thus provides lesser hindrance to argon diffusion.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110155
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  • 17
    Electronic Resource
    Electronic Resource
    Effect of chlorine on the selectivity of a fischer-tropsch catalyst composed of iron/vanadium oxidesDedicated to Professor Dr. Karl Schügerl on the occasion of his sixtieth birthday (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 32-39 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fischer-Tropsch catalysts (Fe/V oxides with ZnO and K2CO3 as promoters) were exposed to CHCl3, thereby producing surface and bulk chlorides. The effect of this exposure on activity and selectivity was studied in a continuous recycle reactor at a total pressure of 10 bar (CO/H2 in most experiments: ca 1:1) in a temperature range between 200 and 343°C. CHCl3 was introduced in amounts of up to 1 × 10-2 mol chlorine per g catalyst. The catalyst samples were characterized by internal surface area, pore-size distribution and adsorption capacities for CO, H2 and C2H4. Prior to synthesis, the catalysts were reduced by H2. Catalyst exposure to CHCl3 resulted in a decrease of activity and considerable changes in product distribution. Hydrogenation and isomerization of 1-olefins were partly suppressed; the chain length of the products was slightly increased. Deactivation of the catalysts due to chlorine addition was partly reversible during operation, while olefin formation was not significantly altered with time-on-stream. The effect of chlorine on activity and selectivity is explained by dissociation of CO as the chain initiating step and CO insertion into a carbon/metal bond as a possible chain propagation step. Since adsorption capacity for H2 decreases on the addition of chlorine, this may also contribute to lower activity and change in selectivity, compared to the unexposed catalyst.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110106
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  • 18
    Electronic Resource
    Electronic Resource
    Effect of enzyme inhibition on the performance of packed-bed biological reactor - a theoretical study (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 50-56 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The performance characteristic of a packed bed reactor has been analyzed by considering diffusional resistance of the biofilm. Model equations were solved by the method of orthogonal collocation for various classical enzyme inhibition kinetics, including partially non-competitive, partially competitive, partially uncompetitive, partially mixed and fully mixed. For all considered modes of inhibition, an increase in the inlet substrate concentration decreases the steady state conversion in the reactor. However, an increase in the Peclet number has been found to improve the conversion. The effects of various other process variables of physical importance were also investigated parametrically.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110108
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  • 19
    Electronic Resource
    Electronic Resource
    Derivation, selection, evaluation and use of asymptotes (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 63-72 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Asymptotes are known to be useful, but their potential in interpreting and correlating chemical and physical behaviour is seldom exploited fully. The derivation and selection of asymptotes for particular as well as limiting cases is described. The evaluation of the range of validity and applicability, if any, of asymptotes is also considered. Asymptotes are shown to be uniquely useful in the identification of groupings of variables which minimize parameteric variations, as upper and lower bounds, as trial functions in the method of weighted residuals, and most especially as components of correlating equations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110110
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  • 20
    Electronic Resource
    Electronic Resource
    A robust pole-placement self-tuning controller for chemical process control: Theoretical studies and simulation (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 57-62 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A single variable pole-placement self-tuning controller (PPSTC) is used to simulate examples typical of chemical processes; i.e., open-loop stable, unstable, and unstable non-minimum phase systems with unknown varying process dead time. The PPSTC is shown to be effective in each case. Set-point tracking and rejection of randomly occurring deterministic disturbances for all three types of processes are achieved. Simultaneous estimation of process parameters and process time delay is realized by using a recursive extended least squares method.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110109
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  • 21
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    The influence of stress and attrition on crystal size distributionPaper presented at the Annual Meeting of German Chemical Engineers 1986, September 17 to 19, in Strasbourg.Dedicated to Prof. Dr.-Ing. Rolf Lacmann on the occasion of his 60th birthday (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 40-49 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An important parameter influencing the crystal size distribution in mass crystallization from solution is the mechanical stress exerted on crystals in the crystallizer. This contribution presents the study of the influence of mechanical stress and attrition of the system potassium nitrate-water in an FC-crystallizer and in various draft-tube crystallizers, fitted with different types of impellers. The intensity of stress is a newly defined variable which is used to describe the level of stress in crystallizers. The reduction of crystal size by attrition is described by the linear attrition rate. The influence of impeller design and crystal hold-up on crystal size distribution and scale-up rules is discussed.
    Additional Material: 16 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270110107
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  • 22
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    Attrition and secondary nucleation in crystallizers (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 80-88 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The mean crystal size of coarse crystalline products is determined by secondary nucleation and crystal growth. Secondary unclei are mainly produced by contacts of crystals with parts of the crystallizer or with other crystals. As a consequence, attrition effects are very important. In this paper, a model is proposed in order to calculate the attrition rate of crystals, depending on the physical properties of the crystalline product, the geometry of the crystallizer and on the operating conditions such as the stirrer speed or the suspension density. The effective rate of secondary nucleation can be expressed in terms of the attrition rate by introducing effective values for number and size of attrition particles. Finally, a scale-up criterion based on this model is derived. This criterion allows to predict effective rates of secondary nucleation and mean crystal sizes if data obtained in a laboratory crystallizer are available.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110112
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  • 23
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    Theoretical and experimental study of sedimentation in vertical flow tanks (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 95-104 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Settling characteristics of four different suspensions were measured by batch settling tests (glass spheres in glycerol-water mixtures and CaCO3) and by continuous settling test in a bench-scale vertical flow tank (activated sludge and kaolin in water), including the measurement of solids concentrations inside the tank. The characteristics could be described by different correlation functions which now include all the information about the settling behaviour of ideal suspensions. Continuous settling experiments in a bench-scale vertical flow tank were carried out with the same four material systems. These results correspond with sufficient accuracy to those from the theory of limiting flux if the settling characteristics determined earlier are considered.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110114
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  • 24
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    Thermal deactivation of heterogeneous catalyst, part 1. The theta-rule - a critical review (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 113-119 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thermal deactivation can be described either by deactivation kinetics or by the isokinetic effect. The latter expression is used synonymously with the “compensation effect” and the “Theta-Rule”. An examination of the original literature shows that only the compensation effect is applicable to thermal deactivation but not the Theta-Rule. The introduction of the preparation temperature as a parameter of the compensation effect results in a “modified Theta-Rule”, which describes the experimental data and is proposed for the non-separable kinetics. The consequence of the observed deviations from the validity range of the Theta-Rule is that the activation energy cannot be used as a universal activity criterion.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110116
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  • 25
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    The stability of crude oil residues and factors affecting their decomposition during mild thermal treatment (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 89-94 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A number of topped crude oil residues were subjected to mild thermal cracking in the temperature range between 613 and 673K at N2 pressure of one atmosphere. It was found that the thermal stability of the six topped crude oils decreased in the order Brent 〈 Piper 〈 Auk 〈 Saudi Arabian 〈 Romashkinskaya 〈 Tia Juana Pesado. This was measured in terms of light end production (C1-C5 hydrocarbons). The asphaltene, sulphur and metal (nickel and vanadium) contents were also determined. The production of light ends, exemplified by methane, was found to be related to the metal asphaltene content of the crude oils, but the sulphur content exerted a moderating influence upon the extent of cracking. Hence, metal asphaltenes, probably as metal porphyrins, catalyse cracking but the presence of sulphur reduces that catalytic activity and can inhibit cracking. If cracking of long chain hydrocarbons is to be minimized, metal asphaltenes should be removed (preferably) or reduced in concentration or poisoned, in order to decrease their catalytic activity.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110113
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  • 26
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    Kinetic analysis of the oxidation of isobutyraldehyde in liquid phase (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 120-126 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of non-catalytic as well as catalytic oxidation of Isobutyraldehyde has been investigated. Reaction rate equations for the formation of the main product isobutyric acid and of the side products acetone, CO and CO2 were derived. Kinetic parameters, namely the order of reaction, preexponential factor and activation energy were estimated by non-linear regression. The influence of selectivity and activity of the different type of catalysts employed was investigated quantitatively.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110117
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  • 27
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    Thermal deactivation of heterogeneous catalysts. Part 2: The compensation effect and the Catalytic Paradox (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 228-236 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The interpretation of the term “compensation” obscures a logical contradiction, the catalytic paradox, which is caused by inconsistent validity ranges of the Arrhenius parameters, the pre-exponential factor and the activation energy. For this reason, a theory which contains the Arrhenius parameters cannot be established for the entire system (whole temperature range) on the basis of classical logic. Only the subsystems can be consistent and complete. One subsystem is the range of the topocatalytic concept which is relevant for thermal deactivation, thermal bistability and for all reactions with surface dependence of activity. The other is the range of the energetic concept which is preferred in fundamental research. In order to complete the subsystems, new consistent symbols are introduced. The change of particle size caused by thermal deactivation can result in four possible particle size effects, two of which have been discussed in the literature.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110130
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    Thermal radiation of gas/solid mixturesPaper presented by Th. Elsner at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, September 30 to October 2, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 237-243 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thermal radiation of gas/solid mixtures in high-temperature heat exchangers is of considerable importance for the design of heat exchange surfaces. Therefore, an experimental plant was constructed to measure solid particle emissivities, since there is a lack of relevant data in the existing literature. A theoretical equation was derived to describe the solid particle emissivity as a function of layer thickness, specific solid surface area, solid loading and absorption and scatter coefficients. Measurements were carried out for fluidized bed ash and quartz sand. The emissivities of these particle fractions increase with increasing layer thickness, slid loading, specific solid surface area and temperature. The description of these data by the derived model equation is very satisfactory. No dependence on wavelength was observed. The ash components do exert some influence which, for the present, cannot be described exactly.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110131
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  • 29
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    Application of modern packings in thermal separation processesPaper presented by R. Villet at ACHEMA ′85. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 213-227 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A report is presented on the performance of modern dumped and structured packings for application in the field of thermal separation processes. The evaluation of the results is based on extensive experimental investigations of rectification, absorption, and desorption systems. The following are indicated: the efficiency in terms of the number of theoretical stages per unit height or in terms of the height of transfer unit or volumetric mass transfer coefficient, the pressure drop per unit height as well as per theoretical stage or per gas phase transfer unit, and the liquid hold-up, whereby either the gas capacity factor or the liquid load was adopted as influencing parameter, and finally the maximum gas capacity factor as a function of the flow parameter. The results are presented in diagrams and tables.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110129
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  • 30
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    Volumetric mass transfer coefficient in stirred reactors (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 249-251 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It is shown that the volumetric mass transfer coefficients, presented recently by Schmitz et al. [1] for viscous solutions of carboxymethyl cellulose (CMC) in aqueous sodium sulphite, are considerably underestimated as a result of unjustified neglect of the oxygen back pressure during oxygen absorption. Schmitz et. al. [1] found a decrease in the exponent n in the relationship between the oxygen mass transfer coefficient, kla, and the power dissipated per unit volume of the liquid phase, e (kla ∝ en), and ascribed it to viscosity effects. However, no such decrease is observed, provided that the actual oxygen back pressure is taken into account.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110133
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  • 31
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    Effect of combustion air preheating on NOx emissions from gas burners in high-temperature industrial applicationsPresented by M. Flamme at the “Jahrestreffen der verfahrens-ingenieure”, strasbourg, september 17 to 19, 1986. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 104-112 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: NOx emissions from different commercial gas burners for metal heat treatment applications were measured for a research project of the Gaswärme-Institut. The burners, rated at up to 50 kW, were installed for the tests in a laboratory combustion chamber operated at temperatures of up to 1400°C. The air for combustion was preheated to maximum temperature of 600°C. Following the tests, the potentials of different NOx control techniques were investigated. Methods explored included staged combustion air injection, staged fuel injection and fuel gas injection into the flue for NOx reduction. The results showed that it is feasible to reduce the NOx content of flue gases by as much as 90%.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110115
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  • 32
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    A new fluid dynamic model for mixing of newtonian and power-law liquids in the transient regimeModified version of a paper presented at the “GVC Working Party on Mixing”, Trier, 4./5. May 1987. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 162-170 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the description of mixing processes influenced by viscosity in pseudoplastic (power-law) fluids, a definition of representative viscosity is normally used which takes into account the variable flow behaviour of the stirred material as a result of different shear stresses. In this context, the Metzner and Otto concept, which postulates that a representative shear rate is proportional to stirring speed, has become widely know, although the power calculation is inaccurate, particularly in the transient regime between the laminar and turbulent flow. A new model of fluid dynamics in the mixing vessel is presented, based on the increase of the mean flow velocity standardized with the stirrer's tip velocity in the transition regime. It provides a physical explanation for the above deviations. A suitable definition of representative viscosity substantially improves the accuracy of calculations of the stirring power in power-law fluids.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110122
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    Scale-up of bioreactors for fermentation of mammalian cell cultures with special reference to oxygen supply and microcarrier mixingPaper presentet by J. Vorlop at the “Jahrestreffen der Verfahrensingenieure”, September 17 to 19, 1986 in Strasbourg (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 171-178 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The increasing demand for products from mammalian cells has prompted the authors to develop a new type of bioreactor. Its significant features include the supply of oxygen, homogeneous distribution of microcarrier suspensions and process control. Media with high protein contents, required for mammalian cell cultures tend to generate foam. This causes the flotation of solid particles. The reactor was equipped with a system of porous hydrophobic Accurel hollow fibre membranes in order to prevent the formation of bubbles. The membrane is coiled in the form of a basket, or fixed on several carriers. If the liquid pressure is higher than that of the gas phase inside the membrane, a bubble - free oxygen supply to the culture broth can be achieved. The problem of axial mixing of microcarier suspensions was solved by the use of a spiral agitator, attached underneath the aeration system at the bottom of the reactor. The combined aeration and mixing system, which is driven by an eccentric motor, undergoes a tumbling motion. Sufficiently homogeneous suspensions are produced in this system at low membrane velocities, i.e. in presence of low shear forces.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110123
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  • 34
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    Organosolv delignification of southern pine - an alternative pulping process (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 195-199 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aqueous ethylenediamine-ethanol-anthraquinone (EDA-EtOH-AQ) pulping of Southern Yellow Pine was studied for lignin removal and pulp yield. Temperature, time and ethylenediamine concentration in the solvent solution were studied and equations for lignin content and lignin-free yield were developed. Lignin content is decreased by an increase of temperature, time or EDA concentration. Lignin-free yield of pulp decreased with an increase in temperature or time, but increased with increasing EDA concentration. Overall, the solvent is selective, that is, large quantities of lignin are removed while the retention of cellulose remains high.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110126
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    Influence of mechanical stress on the growth of Rhizopus nigricans in stirred bioreactorsPaper presented at the “Jahrestreffen der Verfahrensigenieure”, Freiburg, September 30 to October 2, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 178-187 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This investigation was undertaken in order to examine the factors affecting mechanical damage to micro-organisms in stirred bioreactors. Growth of the mould Rhizopus nigricans was studied in stirred bioreactors at different geometrical and operating parameters. Since experimental results cannot be described by conventional key parameters, a new concept has been suggested. It is based on the analogy to processes of mechanical disintegration. It is shown that the same key parameter, i.e. the ratio of power input to flow rate, can be used for a satisfactory correlation of experimental data on mechanical damage to micro-organisms, which is an important step in the recovery of intracellular products in biotechnology.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110124
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  • 36
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    Consistent scale-up procedure for the power consumption in agitated non-newtonian fluids (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 199-205 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It is shown how a consistent scale-up rule for the power consumption in agitated non-Newtonian liquids can be obtained. The new approach is based on the concept of including the real liquid in a set of liquids with similar rheological properties and of using, in a small scale laboratory system, a suitable member of that set instead of the original liquid. Considerations of similarity lead to simple unique selection rules for the actual test liquid and for the stirrer speed in the laboratory experiment as well as to a prediction of the power requirement in the real system. The theory is tested experimentally by means of different aqueous polyacrylamide solutions. The results are compared with predictions, according to Metzner and Otto as well as Rieger and Novák.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110127
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  • 37
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    Bubble column research in Japan (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 205-212 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many experimental studies on the bubble column have been reported by Japanese researchers since around 1960. They include studies of bubble behaviour, bubble size distribution, transition from the homogeneous bubbly flow regime to the heterogeneous liquid circulation regime, liquid velocity distribution, longitudinal liquid mixing, hydrodynamic modelling, the gas holdup, and the volumetric coefficient of gas-liquid mass tranfer kLa. Studies covered various modified bubble columns, such as the airlift reactor with an external or internal loop, the packed bubble column, and others. Performance of three-phase bubble columns, which deal with suspensions or emulsions, and their use as bioreactors or chemical reactors were also studied.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270110128
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    A model-based control system for a distillation columnPaper presented by F. F. Rhiel at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, September 30 to October 2, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 188-194 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A control concept which includes an adaptive multivariable control algorithm and an observer model has been put into practice in the operation of a distillation column which separates water from a solvent. The model yields predictions of solvent concentration in the waste water which forms the top product. Early detection of disturbances permits an adjustment of the process in time. This has resulted in an exceptionally smooth operation of the column, with a drastic reduction in solvent concentration fluctuations, observed with conventional control technology. Since the only measurements required are pressure, temperature and the rate of flow, this control system is largely free from disturbances. In addition to considerably reducing the burden on operating personnel, use of this control system has lowered the costs of waste water treatment, solvent losses, analysis expenditure and energy consumption.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110125
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  • 39
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    Parametric sensitivity of the ignition process to mass transfer in adiabatic tubular reactors with exothermic heterogeneous reactions (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 251-258 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The alternative effects of reaction kinetics, mass, heat and momentum transport on mass conversion by chemical reactions are examined theoretically for a reacot tube with laminar flow. The reaction enthalpy is considered. A heterogeneous reaction between several gaseous components takes place at the inner surface of this reactor tube. Strongly exothermic reactions lead to self-acceleration of the reaction, unless reaction enthalpy is removed through the tube wall. Under certain conditions, there will be a sudden change from mass transfer controlled by the reaction to that controlled by diffusion. This phenomenon is known as ignition of the reaction. The effect of ignition and its sensitivity to reaction enthalpy, thermal conductivity and diffusivity of the fluid as well as activation energy of the first order heterogeneous wall reaction are investigated by a numerical solution of the transport equations. Axial conduction of heat and mass is neglected both in the fluid and in the tube wall. Non-stoichiometric wall reactions of first order, with temperature dependent reaction rates and equilibrium constants, are considered. The results are presented in graphical form, as plots of the local mass flux at the reacting wall as functions of the dimensionless tube length.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110134
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    Chemical engineering aspects of precipitation from solutionPaper presented by A. Mersmann at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, Spetember 30 to october 2, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 264-276 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Precipitation is a rapid solidification. As a rule, it applies to substances which are sparingly soluble and is coupled with a chemical reaction or with a salting out process. The chemical engineer has to ensure that the product obtained has a constant and preferably coarse size distribution. This contribution compares the literature data on crystallization of soluble and sparingly soluble substances; it can be shown that, during precipitation processes, nuclei are formed, most probably by a primary mechanism. Analysis of the processes occurring during precipitation, such as chemical reaction, mixing and crystallization, leads to recommendations for the operation of precipitation processes.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110136
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  • 41
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    Scale-up of mechanically agitated extraction columnsPaper presented at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, September 30 to October 2, 1987 (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 259-263 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The deterioration of mass transfer efficiency of an extraction column with increasing column diameter is the result of developing residence time distributions. These effects can be described by one-dimensional dispersion model. However, it must be verified whether the requirements for its application are fulfilled in the different types of agitated extraction columns. For the columns for which the dispersion model can be applied, a relationship will be derived between the necessary increase of column height with column diameter. This is based on the equations for calculation of the dispersion coefficient of the continuous phase. If the dispersion model cannot be applied to given a type of column, an investigation will be made on the possible modifications of operation or changes in construction, in order to permit a scale-up procedures as proposed here.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110135
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    Development of design charts for fixed-bed adsorptionPaper presented by W. Otten at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, Spetember 30 to October 2, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 289-297 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model of the dynamic behaviour of non-isothermal fixed-bed adsorbers has been developed which takes into account the various mass and heat transfer resistances. Comparison of experimental and simulated results confirms that the model can predict the adsorption and desorption breakthrough curves of an adiabatically operated column, using only equilibrium data and tortuosity factors obtained from single pellet experiments. A simplified model with a reduced number of parameters was derived by investigation of the dimensionless transfer parameters under industrial conditions. It becomes evident that the main transfer mechanisms are convective heat and mass transfer in the bulk flow and diffusion within the pores of the particle. Dimensionless effluent concentration is expresses in terms of dimensionless time, a transport parameter, a non-isothermal parameter, the adsorption equilibrium and the inlet and initial concentrations and temperatures in the simplified model. For a chosen system of adsorbate and adsorbent, design charts can be developed by computer simulation, to determine graphically the breakthrough time as a function of significant process parameters, i.e. the dimensionless transfer parameter and the feed concentration.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110138
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    The significance of fly ash in wet-dry scrubbing of SO2 (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 298-305 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A bench scale flue gas desulphurization spray dry scrubbing unit was employed to study the effect of fly ash on the removal of SO2. The equipment consisted of a spray dryer with and ultrasonic nozzle for atomization and a pulse jet baghouse. The flue gas rate was 1500 lN/h (dry gas). Four fly ashes, originating from different countries were investigated. The alkalinity and reactivity of the fly ashes were determined in a pH-stat equipment. Pure fly ash removed SO2 in both the spray dryer and in the baghouse. An increase of humidity divided the fly ashes into two groups. The high calcium fly ash gave a considerably higher SO2 removal than the medium and low calcium fly ashes which showed similar SO2 removals. Fly ash did not enhance the removal of SO2 when added to a lime slurry because lime suppresses the dissolution of the alkali in the fly ashes. The pressure drop build-up in the fabric filter showed a strong dependence on material properties.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110139
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  • 44
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    Subcooled boiling heat transfer to R 12 in an annular vertical channel (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 320-327 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Detailed knowledge of the physical phenomena involved in subcooled boiling is of great importance for the design of liquid-cooled heat generating systems with high heat fluxes. Experimental heat transfer data were obtained for forced convective boiling of dichloro-difluoroethane (R 12). The flow is circulated upwards through a concentric annular vertical channel. The inner and outer diameters of the annulus are 0.016 m and 0.03 m respectively. The reduced pressures studied were 0.24 ≤ p/pcrit ≤ 0.8, inlet subcooling varied from 10 to 75 K and mass fluxes from 500 to 3000 kg/m2s, which corresponds to Re numbers from 30000 to 300000. The experiments, described in this study, demonstrate that liquid fluorocarbons show certain unusual boiling characteristics in the subcooled flow, such as hysteresis of the boiling curve. These characteristics are attributed to the properties of the fluid, mainly the Pr number and the very low surface tension. The pronounced boiling curve hysteresis can be explained by the fact that large nucleation sites may have been flooded prior to incipient boiling. A dimensionless regression formula is presented which predicts the onset of subcooled boiling as a function of reduced pressure (p/pcrit), Boiling-(Bo), Reynolds-(Re), and a modified Jacob number (Ja), over the whole range of parameters studied, with a good accuracy, including water data from literature.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110142
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  • 45
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    Mass transfer behaviour of gas-liquid jet loop reactorsPaper presented by M. Geisendörfer at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, September 30 to October 2, 1987.Dedicated to Professor Dr. Horst Langemann on the occasion of his sixtieth birthday (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 306-311 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A special type of jet loop reactor (JLR), designed for continuous operation and short residence times was investigated with regard to its mass transfer behaviour, described by the volumetric mass transfer coefficient kLa. The jet stream and superficial gas velocities are varied in two JLRs of different sizes, equipped with different nozzles. Fully desalinated water, 0.08 molar NaCI solution and solutions of different concentration of carboxymethyl cellulose (CMC) are used as the liquid phase. A steady-state physical method is employed to determine kLa: air oxygen is purged from the liquid phase by gaseous nitrogen. The measurements show that the reactor is characterized by high power density and high mass transfer performance. No limit of mass transfer capacity was observed in the chosen ranges of volumetric gas and liquid flow rates, i.e. at a given jet stream velocity, the relationship between kLa and the superficial gas velocity is nearly linear. The investigations show that the mass transfer contributed by the jet stream largely depends on liquid phase composition.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110140
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  • 46
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    Characteristics of solid suspensions in a bubble column without and with draft tubePaper presented by J. Heck at the “Jahrestreffen der Verfahrensingenieure”, Freiburg, September 30 to October 2, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 335-340 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to investigate the suspension behaviour of solid particles in bubble columns without and with draft tube, minimum gas velocities for generating and maintaining complete solid suspension were determined. Experiments were carried out in a bubble column with a diameter of 200 mm and a height of 2 500 mm. The bubble column could be equipped with a draft tube with a diameter of 120 mm and a length of 1 500 mm. The state of suspension was determined by measuring the hydrostatic pressure as a result of suspended solid particles with an inductive pressure gauge. Solid content εs, solid density ϱs, particle size dp, particle shape, particle size distribution, and solid wettability were varied. Furthermore measurements of integral gas holdup were carried out.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110144
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  • 47
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    Modelling of multiphase detonations with drop disintegration - description of thermal detonations (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 327-334 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model is presented which consists of steady-state and transient codes for the description of reacting multiphase flow fields, including hydrodynamic fragmentation of liquid drops in relative flows. An application of this model for the description of large scale melt-coolant interactions (thermal detonations) is described. A simulation of two-phase chemical detonations, especially those with hydrodynamic disintegration of liquid fuel drops in the reaction zone, is possible, in principle, within the framework of the modeling.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110143
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    Modelling of a pressure swing adsorption process for oxygen enrichment with carbon molecular sievePaper presented by E. Richter at the “Jahrestreffen der Verfahrens Ingenieure”, Freiburg, September 30 to October 2, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 341-351 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Adsorptive separation of oxygen from nitrogen and argon is carried out during the desorption steps of a pressure swing adsorption (PSA) process which uses carbon molecular sieves developed by Bergbau-Forschung GmbH. The adsorption isotherms of the three main components of air are very similar. On account of the pore size distribution of CMSN2, the diffusion coefficient of oxygen is more than eight times those of nitrogen and argon so that air separation occurs by adsorption kinetics. Experimental results for the individual steps and cyclic operation of the PSA process are presented and compared with the predictions of an isothermal plug-flow model. Adsorption rate is represented by a linear driving force equation. If the diffusion coefficients are adapted separately to every step, a good agreement is observed between the model calculations and experimental results.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110145
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  • 49
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    The importance of corrosion prevention for the safety of chemical plants (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 359-365 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: One of the most important tasks to eliminate dangers in chemical plants is the prevention of corrosion. This implies the provision of safe enclosures and reaction spaces for the substances to be processed. The present contribution deals with the procedure in the selection of materials for equipment exposed to corrosion and stresses the difficulties connected with the elimination of local corrosion. The relevance of prevention of crack forming corrosion processes is emphasized. Problems to be solved in order to obtain results from investigations, suitable for a safe application of a materials under practical conditions, are indicated.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110147
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    Modelling of activated carbon desorption by a circulated inert gasPaper presented at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, September 30 to October 2, 1987 (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 352-358 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The adsorption solvent recovery process, known as Recursorb which involves desorption and cooling steps by a circulated inert gas, is analyzed in detail on the basis of equilibrium theory. Employing the method of characteristics, the model is solved for each step of the overall process. The estimations confirm that the process performance with respect to final gas purity, activated carbon useful capacity and operation times depends on condenser and heater temperatures. Simple expressions are derived for the calculation of adsorption, desorption and cooling times.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110146
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  • 51
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    Decoking of fixed-bed catalytic reactorsDedicated to Prof. Dr. Hanns Hofmann at the ocassion of his 65th birthday (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 367-375 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model for the description of the non-steady state process of decoking of a fixed bed catalytic reactor is presented. The relevant dimensionless groups are identified and their influence on the process discussed. Appropriate relationships are given for the estimation of the maximum temperature in the bed. Methods of monitoring the process and of controlling it in the case of unknown or variable coke contents are explained.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110148
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    Model discrimination and parameter estimation in the kinetic study of methanol synthesisDedicated to Professor Dr. Hanns Hofmann on the occasion of his 65th birthday (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 375-383 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The new model discrimination method is based on the correlation coefficient test of experimental data sets for different reactions, without requiring a prior parameter estimation. The new parameter estimation method reduces by n the number of dimensions to be tested, compared to the classical method where n is the number of independent reactions in the system. This has reduced the computation time for most complex reactions to a level, comparable to that needed for single reactions. The example used is the kinetic study of methanol synthesis in which the formation rates of methanol, methane, ethanol and ethane are considered. Two adequately accurate models were obtained from an extensive range of plausible models by using the new model discrimination and parameter estimation method with a relatively small computation effort.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110149
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    Evaporation and pervaporation of a binary mixture from an inert carrier liquidDedicated to Professor Hanns Hofmann on the occasion of his 65th birthday (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 384-391 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bench-Scale experiments were carried out with the ternary mixture 2-propanol/water/glycerol. In a cylindrical vessel, the stirred and thermostated liquid was exposed to a preheated and either dry or humidified air stream. The mixture was evaporated either from a free surface or from the surface of a porous plate. On evaporating the mixture from a porous plate into a dry air stream, the less volatile component water escapes preferentially; in the case of evaporation from a free surface, water is retained in the mixture. In the former case, selectivity is liquid diffusion controlled, in the latter, the gas-side mass transfer and the thermodynamic equilibrium are the controlling mechanisms. On reducing the gas flow rate, the more volatile alcohol evaporates preferentially in both cases; the selectivity is controlled only by thermodynamic equilibrium. Humidification of the air stream with water vapour causes preferential evaporation of the alcohol at an increased rate. Furthermore, instabilities in the liquid boundary layer due to density gradients and surface tension effects may affect the selectivity of evaporation. Experimental results show that the selectivity of evaporation can be manipulated by choosing appropriate evaporation conditions. The theory, which applies the generalized Stefan-Maxwell equations to diffusion in the liquid, can describe these effects.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110150
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    Remarks upon the modelling of heterogeneous catalytic reactors - the single fluid-solid casesDedicated to Professor Hanns Hofmann on the occasion of his 65the birthday (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 425-431 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To our benefit, the modelling of fluid-solid catalyzed reaction-reactor systems has long been the keen concern of Hanns Paul Hofmann. In the light of his instruction we remark upon key aspects of modelling for the (a) fixed bed (b) fluid bed and (c) moving bed/transport line reactors. There emerges from such analyses a properly renewed awareness of the need for a more sophisticated respect for reliable physical-chemical data. As Hanns has taught us, our models are no btter than our data.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110154
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    Two-phase flow in porous mediaThe Orginal, shorter form of this paper was presented by the author, as an invited speaker, at the Second Conferance of “Chemical Reaction Engineering” of the Engineering Foundation, March 8 to 13, 1987, Santa Barbara, California.Dedicated to Professor Dr. Hanns Hofmann on the ocassion of his 65th bithday (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 407-424 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two-phase flow in porous media depends on many factors, such as displacement vs steady two-phase flow, saturation, wettability conditions, wetting fluid vs non-wetting fluid is displacing, the capillary number, interfacial tension, viscosity ratio, pressure gradient, uniformly wetted vs mixed-wet pore surface, uniform vs distributed pore throats, small vs large pores, well-connected pores vs pores connected by small throats, etc. These parameters determine how the two fluids are distributed in the pores, e.g. whether they flow in seperate channels or side-by-side in the same channels, either with both fluids being continous or only one fluid being continous and the other discontinuous. In displacement, the capillary number and the viscosity ratio determine whether the displacement front is sharp, or if there is either capillary or viscous fingering.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270110153
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  • 56
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    Less known behaviour of gas-solid reactions: The expanding core model in catalytic and non-catalytic systemsDedicated to Profeesor Dr. Hanns Hofmann on the Occasion of his 65th birthday (1988)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 11 (1988), S. 438-447 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Gas-solid reactions cover a wide spectrum of industrial products. Over the years, many conceptual models have been developed to describe the progress of a gas-solid reaction starting outside the solid particle as well as that occurring throughout the particle. But the behaviour of a reaction, initiated inside the pellet, is less known. In this paper, a brief outline is given of this relatively rare but important mode of gas-solid reaction. The causes of this relatively less known behaviour and characteristic features of five typical systems displaying it are discussed.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270110156
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  • 57
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    Bending contribution to line-broadening in polymer diffraction (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 387-394 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is proposed that bending of solution-grown polymer crystals causes the observed diffraction line-broadening in many cases. Independent estimates and observations of the severity of bending which can be sustained are used to calculate corresponding apparent crystal sizes, where the apparent crystal size is that obtained when it is assumed that broadening is caused by the small crystal size effect only. Bending broadening is found to be of sufficient magnitude to produce the observed broadening reported in the literature. Some of the steps taken so far in the development of line-broadening analysis for polymer crystals show similarities with the evolution of line-broadening analysis for graphitic carbons and a brief review of the latter is included.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160302
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  • 58
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    Synthesis and properties of a new polydiacetylene: Poly[1,6-di(N-carbazolyl)-2,4-hexadiyne] (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 431-441 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The solid-state synthesis and properties are reported for a new polydiacetylene: poly[1,6-di(N-carbazolyl)-2,4-hexadiyne]. The monomer crystals polymerize quantitatively with γ irradiation or thermal annealing. An Autocatalytic effect is observed in both γ-ray polymerization and thermal polymerization and is attributed to an increase in chain propagation length at about 5% conversion. The activation energy for thermal polymerization is about 25 kcal/mole, independent of the degree of conversion to polymer. The exceptional thermal stability of the polymer crystals allowed a thermomechanical analysis over a large temperature range, -50 to 300°C. With increasing temperature, the polymer contracts in the chain direction linearly with temperature over the entire range, yielding a thermal expansion coefficient of (-2.32 ± 0.02) × 10-5°C-1. Photoconductivity action spectra are reported for the polymer crystals. The energies for the photoconductivity onset (ca. 2.3 eV) and for the lowest energy optical transition (1.89 eV) are the lowest reported for the polydiacetylenes. The photoconduction onset is blue-shifted with respect to optical absorption - a result which is consistent with the excitonic assignment for the lowest energy optical transition in the polydiacetylenes.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160307
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    Chain rupture and tensile deformation of polymers (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 485-500 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Macromolecular chain rupture occurring during tensile deformation of semicrystalline polymers has been investigated by measuring changes in the viscosity-average molecular weight. When interpreted in terms of a random-scission scheme, the observed changes in molecular weight correspond to chain rupture concentrations β ≈ 1018/cm3 for high strength nylon and poly(ethylene terephthalate) fibers. Polypropylene fibers and isotropic samples of polyethylene, polypropylene, and nylon 6 had β ≈ 1016/cm3. The effects of stretching environment and thermal and mechanical history were noted. In all cases, the present study indicated bond rupture concentrations about 10 times larger than those obtained from electron spin resonance (ESR) experiments. The relation between viscometry, ESR, and infrared (IR) estimates of bond rupture and their relevance to mechanical properties are considered.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160311
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  • 60
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    Importance of the metal-polymer interface for the piezoelectricity of polyvinylidene fluoride (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 529-543 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The piezoelectric effect in films of polyvinylidene fluoride (PVF2) is investigated using optical and ultrasonic detection techniques. From the analysis of the vibrational resonance frequencies of a freely suspended film we conclude that the polarization induced in PVF2 is inhomogeneous across the volume of the sample. Poling the foils in a sandwich configuration or using blocking electrodes, we can clearly demonstrate that the piezoelectric effect in PVF2 originates from the positive metal electrode. Monitoring the time dependence of the piezoelectric effect during the poling process, a fast and slow component are observed. Using a blocking electrode, however, the same dynamical poling behavior is found only if the contacting metal electrode is positive. In view of these observations, which clearly demonstrate the importance of the metal-polymer interface for the strong piezoelectricity of PVF2, the existing theoretical models, based on the bulk properties of the polymer, are critically reviewed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160315
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  • 61
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    Properties of aqueous salt solutions of poly(ethylene oxide): Thermodynamic quantities based on viscosity and other measurements (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 501-511 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A previous study of poly(ethylene oxide) (PEO) in aqueous salt solutions has been extended to incorporate cloud-point measurements in potassium thiocyanate solutions (salt concentration range 3.3-3.8M where salting out occurs) and, particularly, viscosity measurements. A few osmoticpressure measurements were made and molecular weights (∼2 × 104) from gel-permeation chromatography (GPC) compared. The theta temperature for PEO in water from cloud points was found to be 369 ± 3°K. An empirical linear relation has been found for sodium and potassium salts between the finite change of theta temperatures with change in ionic strength, δθ/δI, and (v3 - v̄3), the difference between the molar van der Waals volume and the partial molar volume of the salt. Values of the Huggins constant k′ are less than 0.5 for PEO in pure water at 303.2°K, indicating a good solvent, whereas in salt solutions they vary from 0.59 to 1.14 in nontheta solvents. They and other findings are attributed to binding of salt to the polymer and to water structure breaking. Kraemer's constants k″ were also determined: k′ - k″ = 0.5 for PEO in pure water, and for aqueous salt solutions of PEO, k′ - k″ = 0.666 at 298°K. Values of K0(= M-1/2[η]θ) with M = 2 × 104 were found to very with salt type (valence) - mean values of 103 K0/dlg-1 with number of observations in brackets are 1:1, 1.19 (2); 1:2, 1.45 (3); 2:2, 1.75 (3). Unperturbed dimensions 〈r2〉01/2 vary from 11.0 to 12.6 nm from 1:1 to 2:2 salts. Values of the characteristic ratio Cn, the steric parameter σ, and the enthalpy and entropy of dilution parameters χH and χS have also been calculated.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/pol.1978.180160312
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    On the location of chain-ends in rapidly crystallized poly(ethylene terephthalate) (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 159-169 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Phenylmercurated poly(ethylene terephthalate) (PET) chain-ends are obtainable through the transesterification of PET by phenylmercury hydroxide or acetate in solution in nitrobenzene at 165 ± 10°C. The reaction results in an average of one mercury atom per chain. The phenylmercuration may be followed by infrared or x-ray fluorescence. Reaction with concentrated HCI Affords the elucidation of some structural parameters of the resultant partially crystalline tagged PET, through analyses of changes in viscosity and molecular weight, in percent crystallinity, and in the amount of mercury in the system. The chain-ends are almost completely excluded from the stem region of the PET crystal with no more than 2% remaining. The chain-ends are distributed unevenly throughout the amorphous phase. This is corroborated by sharp decreases in scattered intensity of small-angle x-ray measurements. Two models for the distribution of chain-ends in the amorphous phase are considered. The one in which the ends are pushed farthest from the crystal surface and concentrate halfway between crystallites is tentatively adopted. Analysis of the HCI hydrolysis kinetics and products leads to the following picture concerning the fold tightness and position. About one out of five folds extends significantly into the amorphous matter where it is mingled with cilia, tie molecules, and unattached molecules. Random scission throughout such an amorphous mass should lead to a preponderance of cleaved molecules whose length should be four to five times the lenght of the crystalline stem region, as is indeed observed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160114
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    Thermodynamic properties of phenol-formaldehyde resin (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 759-766 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Characterization measurements of a commercial phenol-formaldehyde resin prepared from constituents including phenol and formaldehyde in the molar ratio 1:1.33 are reported. The measurements consist of (1) the linear thermal expansion coefficient between approximately 85 and 270°K; (2) the specific heat capacity between approximately 6 and 100°K; (3) the Young's modulus at room temperature. A critical examination of the data reveals that: (1) the vibrational behavior is predominantly that of a three-dimensional assembly; (2) as far as data available from other sources permit an assessment to be made, the principle of additivity appears to be applicable to the specific heat capacity between approximately 50 and 100°K; and (3) the data lie near the limit of an empirical relationship observed between the Young's modulus and linear thermal expansion coefficient of other polymers.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160501
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  • 64
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    Study of latex film structure by radiothermoluminescence (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 427-430 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Radiothermoluminescence has been used to show that the surface of latex globules in nonvulcanized latex films contain segments which become mobile at a temperature 20°K below that observed in bulk polymer. Vulcanization in latex films takes place mainly on the surfaces of the latex globules; vulcanized latex films are microheterogeneous systems.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160306
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  • 65
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    Dynamics of a polymer attached to a surface: Bead and spring model (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 457-466 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Smoluchowski formalism is used to solve the problem of a bead of frictional resistance β attached to a surface with a spring of force constant k over which a linear shear field of strenght α flows. The power dissipation is given by βα2kT/k. k and T have their usual meanings. The result is generalized to an n-bead polymer. It is found that the power dissipation of a Rouse model polymer attached to a surface at one end is twice that of an identical polymer flowing freely in solution. If the force constant k arises from an entropy force, then, because of the effect of the surface on the number of polymer configurations, there is an additional factor of two. The same relationship is expected to also hold for the frequency-dependent power dissipation. It is argued that a net circulation exists in the beads above the surface and that the magnitude of the circulation is roughly comparable to that which exists in a polymer freely rotating in solution under a shear field of the same magnitude.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160309
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  • 66
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    Association of stereoregular poly(methyl methacrylates) in dilute solution. Proton NMR study (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 523-528 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: By measurement of integrated intensities of high-resolution proton nuclear magnetic resonance (NMR) bands, associated structures of isotactic (i) and syndiotactic (s) poly(methyl methacrylate) (PMMA) in dilute toluene-d8 and dimethylformamide-d7 solutions were detected and characterized. In 1% (w/v) solutions of highly stereoregular s-PMMA in toluene-d8 at 27°C, 76% of the monomer units are present in the form of compact aggregates. Consequences of this finding for the polymerization of methyl methacrylate in toluene in the presence of s-PMMA are discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160314
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  • 67
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    An endochronic prediction of the variability in fracture times of polymers (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 555-564 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A theory of variability in lifetimes of identical polymer specimens under identical test conditions is formulated, using the theory of fracture of amorphous crosslinked polymers developed previously by the authors. Variability in fracture times follows from the assumption that the critical number Ncr of bonds that must fail in order to cause fracture of a specimen varies from specimen to specimen. A plausible physical explanation for the variation in Ncr may well lie in the variability of the spatial distribution of weak local regions. The scale of locality may vary from molecular to grosser dimensions. The theory is applied to styrene-butadiene rubber (SBR) under creep conditions and fares well in its prediction of observed results. Most notably, it predicts that the shape of the distribution curve of the observed lifetimes remains invariant with changes in the levels of stress and temperature and that the effects of these manifest themselves through shifts of the curve on the logarithmic time axis. The theory also predicts correctly that the fracture process is accelerated if the creep test is interrupted by unloading-reloading cycles at high strain rates. This last result is shown to be a direct consequence of the concept of “the endochronic time to fracture,” previously introduced by the first author.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160317
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  • 68
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    Some effects of melt-induced orientation on drawing of polypropylene monofilamentsIssued as NRCC #16467. (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 599-612 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Morphological changes accompanying the deformation of polypropylene filaments with varying degrees of melt-induced orientation are examined using wide-angle x-ray scattering (WAXS), small-angle x-ray scattering (SAXS), and electron microscopy, and their behavior is compared both to completely unoriented film samples and to very highly oriented, hard elastic filaments. Melt-oriented filaments are shown to deform predominantly by a voiding mechanism at low temperatures (〈100°C), and destruction of the lamellas to produce fibrils occurs only after extensive drawing. The bimodal crystal texture of the filaments does not appear to greatly affect the low temperature deformation mechanism. High temperature (〉100°C) drawing produces a fibrillar structure containing elongated voids.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160403
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  • 69
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    Temperature dependence of the poisson's ratios in low-density polyethylene with parallel lamellas morphology (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 667-678 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Three of the Poisson's ratios have been measured on a low-density polyethylene (LDPE) sheet with parallel lamellas morphology over the temperature range from +20 to -60°C. The measurements were carried out using a specially constructed lateral extensometer which utilized the Hall effect to detect the very small strains involved. The Poisson's ratios show considerable temperature dependence, and at high temperature the overall deformation approximates to pure shear as previously noted. It is suggested that this relates to the onset of the c-shear relaxation.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160408
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  • 70
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    A theory for the drawing of oriented crystalline polymers (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1297-1319 
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    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The load-elongation behavior during the postneck drawing stage in the deformation of crystalline polymers is shown to be modeled quantitatively by an aligned short-fiber composite in which crystalline fibrils form the reinforcing phase in a matrix of less well-ordered material. Three modes of deformation are distinguished in the model and are shown to correspond to the observed loadelongation relations in polyethylene and polypropylene. The regions are (I) elastic-plastic crystals in an elastic matrix, (II) elastic-plastic crystals in an elastic-plastic matrix, (III) elastic crystals in an elastic-plastic matrix. A requirement of the theory is that the flow stress in the crystals is little affected by temperature whereas that in the matrix falls as the temperature rises. Expressions are given for stress in terms of the applied strain and the relevant parameters of the system: concentration of fibrils, length and diameter of fibrils, and elastic and yield properties of fibrils and matrix.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160712
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  • 71
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    Four-center photopolymerization. A heterogeneous topochemical solid-state reaction (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1365-1379 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The four-center solid-state photopolymerization of distyrylpyrazine (DSP) and of 2,6-naphthalene bis(acrylic acid-2,4-dichloro phenyl ester) (NBA-DCP) was investigated by x-ray and microscopic techniques. In both cases the polymer grows as a separate product phase topotactically well arranged with respect to the monomer matrix. In the case of polymerization of DSP the space group of the monomer (Pbca) is not maintained but the polymer phase has space group P21ca. Nucleation and growth of the polymer phase was observed by light and electron microscopy. Nucleation occurs at defect sites. The polymer grows at different rates in different crystallographic directions which were identified by electron diffraction in the case of DSP. Polymerization thus occurs in the transition region between monomer crystal and product phase and not in the bulk of the crystal so that the four-center-type photopolymerization is best described as a heterogeneous solid-state reaction.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160803
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  • 72
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    Observation of preferred (epitaxial) orientation relationships between polyethylene crystals (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 171-177 
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    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Preferred orientations have been observed for polyethylene single crystals deposited at room temperature on a clean polyethlene substrate crystal or a polyethylene substrate crystal coated with silicone oil (but not with a carbon layer). The observed angular relationships can be explained in terms of a network of interfacial dislocations, the cores of which lie in the fold regions between the crystals, and the long-range strain fields extend into the lattices of both crystals. The interfacial dislocations seem likely to result from the plugging of cilia from one crystal into another.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160115
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  • 73
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    Selective degradation of nylon 6,6. II. Application of the degradation technique to commercially drawn fibers (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 215-222 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Treatement with hydrazine was used to investigate the crystalline morophology of commercially drawn nylon 6,6 fibers. Electron microscopic investigation revealed a stacked lamellar structure for the debris of a highly oriented, rapidly drawn fiber. However, the high molecular weight range of the gel permeation chromatogram of this same oriented fiber indicated the presence of high molecular weight material. This is thought to be due to the production of rod-like, partially extended regions during drawing.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160203
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  • 74
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    Nonstationary diffusion of polystyrenes through a cellophane membrane (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 297-318 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Diffusion of five polystyrene fractions at various concentrations in toluene through cellophane membranes has been observed. The results have been used to calculate friction coefficients between solvent and solute, and between solute and membrane. The calculation requires measurement of the diffusion coefficient and the reflection coefficient of the solute, of the permeability for the solvent, of the pore volume of the membrane, and of the partition coefficient of the solute between membrane and solvent. By comparing the friction coefficient between solvent and solute in the membrane with this coefficient in free solution, the tortuosity factor and the pore diameter of the membrane can be estimated. The dependence of the friction coefficients on molecular weight M2 of the solute is determined. For large values of M2, the friction between solute and solvent is the determining factor. The friction coefficient between solute and solvent increases more strongly with M2 in the membrane than in free solution owing to an entrance effect for the permeating solute at the interface.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160210
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  • 75
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    Chain folding and cross-sectional area per chain (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 371-374 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160216
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  • 76
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    Dielectric properties of aromatic polyesters: Relaxation behavior of poly(diethylene glycol terephthalate) (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1-11 
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    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dielectric behavior of a low molecular weight fraction of poly(diethylene glycol terephthalate) has been studied over the frequency range 102 to 105 Hz for temperatures between -67 and +51°C. Two relaxations, α and β, which exhibit pseudoactivation energies of 52 and 8 kcal/mole, respectively, have been found. The α relaxation, associated with the glass transition of the polymer, is amenable to a Williams-Landel-Ferry (WLF) analysis. The dipole moment ration 〈μ2〉/Nm2 (where 〈μ2〉 is the mean square dipole moment of a chain consisting of N bonds and m2 is the average of the squares of the bond moments) has also been calculated using the dielectric data obtained for the polymer in the undiluted state. The calculations yield 〈μ2〉/Nm2 = 0.710, a value in very good agreement with that obtained from measurements in solution.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pol.1978.180160101
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  • 77
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    Ion clustering in a butadiene, styrene, 4-vinylpyridine terpolymer crosslinked by coordination with iron(III) chloride (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 569-581 
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    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A butadiene, styrene, 4-vinylpyridine terpolymer has been crosslinked by coordination of the pyridine groups with iron chloride. The distribution and structure of the iron complexes have been studied. Electron microscopy has given evidence of clustering of the iron complexes. The size distribution of these clusters has been evaluated by small-angle x-ray and neutron scattering. Mössbauer spectroscopy and magnetization measurements have shown the presence of three different kinds of iron complexes: (a) complexes with a speromagnetic structure in the clusters previously found, (b) dimers with antiferromagnetic coupling, and (c) quasi-isolated complexes with weak ferromagnetic coupling. The percentages of these different iron complexes have been measured.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/pol.1978.180160401
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  • 78
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    Dielectric properties of maleic acid-ethylene copolymer in salt-free aqueous solutions (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 641-651 
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    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dielectric behavior of maleic acid-ethylene copolymer solutions has been investigated at different polymer concentrations and two degrees of neutralization α′. It is shown that this behavior is analogous to that of ordinary polyacids. Also the experimental data can be explained in terms of the van der Touw-Mandel theory, but at low α′ a possible contribution from motion of negative charges (in turn related to bound proton fluctuations) has to be taken into account. The dielectric results suggest that the formation of intramolecular hydrogen bonds has an influence on the change of the average dimensions of the chain with increasing α′. This seems to be confirmed by viscosity data.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160406
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  • 79
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    Effect of ozone on creep of vulcanizates (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 813-820 
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    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In-service secondary creep rates of natural rubber (NR) vulcanizates at ambient temperature are known to be low. However, in tests on thin strips of NR vulcanizates in tension, secondary creep at rates of up to 120%/week were observed. From an examination of the effect of antioxidants, antiozonants, waxes, and specimen thickness it was shown that the anomalous creep was due to ozone attack on the vulcanizate, which only becomes serious in tests on thin strips in tension.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160506
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  • 80
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    Conformation of poly(isoprene-gstyrene) in dilute solution (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 851-858 
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    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A detailed description of the synthesis of a model poly(isoprene-g-styrene) is given. From light scattering measurements the real radius of gyration of the polyisoprene is backbone is found to be smaller than that of the polystyrene branches. The core-and-shell conformation of graft copolymers in dilute solution in good solvents, which was proposed for poly(styrene-g-isoprene), is supported by these results.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/pol.1978.180160510
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  • 81
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    Epitaxial crystallization of polyesters on inorganic and organic substrates (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 895-906 
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    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of low-molecular-weight linear polyesters were epitaxially crystallized from dilute solution and the melt on a variety of organic and inorganic substrates. The rod-like polyester crystals which were formed assumed general orientations in alignment with substrate geometry. This yielded monodirectional orientation of these crystals on one of the organic substrates, and bidirectional orientation on the other surfaces. Heterogeneous nucleation on the organic substrates, trioxane and naphthalene, induced the growth of much larger epitaxial crystals than have previously been observed on inorganic substrates. Those polyesters, with a high percentage of methylene units per chain repeat, crystallized in an unusual polymorphic form when in contact with the organic substrates. Polymorphic transformation to the normal form was not possible under thermal treatment or with increased crystal thickness. The expected relationship between dipolar alignment in the polymer crystal and this polymorphism was established.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/pol.1978.180160513
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  • 82
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    Effect of particle shape at finite concentration on thermal expansion of filled polymers (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 967-970 
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    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Relations are derived for the linear and volumetric thermal expansion coefficients of a filled polymer containing aligned ellipsoidal inclusions at finite concentrations. The analysis follows a procedure recently developed for elastic moduli by application of a generalized approach of Eshelby. The well-known Kerner equation is shown to be a limiting case of the present finding. From data on glass in epoxy resin, we conclude that the volumetric expansion varies only slightly with the aspect ratio of an ellipsoid; however, the longitudinal and transverse, linear, expansions show a strong dependence on the particle shape.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/pol.1978.180160603
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  • 83
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    Observations on the dielectric anisotropy of solutions of flexible polymers in flow (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 989-998 
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    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Measurements of the increase in the relative permittivity for solutions of polystyrenes, poly(p-ethoxystyrene), poly(methyl methacrylate), and poly(N-vinyl carbazole) when subjected to shear gradients are reported. The influences of such factors as shear rate, concentration, viscosity, solvent permittivity, polymer dipole moment, and polymer molecular weight on the phenomenon are described. An empirical correlation for the diverse data obtained with polystyrenes and poly(p-ethoxystyrene) has been established, but this relation does not entirely match the theoretically predicted effects. We discuss the various physical processes which may have an influence on the observed phenomenon.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/pol.1978.180160606
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  • 84
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    Exploratory analysis of the influence of substitutional impurities on the electronic properties of poly(sulfur nitride) (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1023-1029 
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    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The results of extended Huckel calculations are reported for an isolated (SN)x chain in which some of the S2N2 units of the extended one-dimensional chain are replaced by (SCH2)2 units. It is found that, inter alia, the metallic behavior of the unsubstituted parent is retained but that the conductivity is lowered to an extent governed by the nature and degree of substitution.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/pol.1978.180160609
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  • 85
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    Induced crystallization of poly(ethylene terephthalate) on small metallic nucleating particles (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1155-1168 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The induction period for the onset of crystallization was determined in poly(ethylene terephthalate) in the presence and absence of small metallic particles. Two kinds of substrates were used: single microcrystals “transplanted” from the water-soluble inorganic polymer (NaPO3)x and powders of the same metals (Au, Pt, and Ir). The nucleating activity φ of the substrates was determined on the basis of classical nucleation theory. Values of φ obtained for PET are compared with the corresponding values in the (NaPO3)x melt and with theoretical concepts.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160702
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  • 86
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    Electron density calculation for polyoxymethylene in cylindrical coordinates by a new fourier method (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1219-1225 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The electron density of the polyoxymethylene molecule was calculated in cylindrical coordinates by a newly derived Fourier method. The density due to hydrogen could be obtained in addition to that from carbon and oxygen. This method is generally applicable to a helical polymer whose unit cell contains only one molecule composed of a number of chemical repeat units in the fiber identity period.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160706
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  • 87
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    Cooperative model for the mechanical deformation of polymers (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1071-1084 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A model for the mechanical behavior of solid polymers is proposed in the form of a linear elastic network with transitions. A simplified version of the model involving a single column of two-site activated processes is found to be a mean-field system. The failings of this system as a description of yield and glass transition relaxation behavior lead to two extensions to the system: that of many available sites in each activated process, and that of a finite number of such processes in the whole system. These extensions reduce the properties of the system to those of a single activated flow process with a temperature-dependent activation energy. Agreement is found between this result and time-temperature shift measurements in the α transition region of several polymers, together with an explanation of the dependence of yield stress on temperature for one of these polymers that is physically more reasonable than the usual constant activation energy proposal.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160613
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  • 88
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    An upper limit to the glass temperature of linear polyethylene as determined by high-field carbon-13 fourier transform nuclear magnetic resonance (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1135-1138 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160618
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  • 89
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    Raman spectroscopic method for determining the crystallinity of polyethylene (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1181-1193 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Raman spectrum of partially crystalline polyethylene can be described as a superposition of three components, which originate from the orthorhombic crystalline phase, a meltlike amorphous phase, and a disordered phase of anisotropic nature, where chains are stretched but have lost their lateral order. The mass fractions involved in the three phases can be derived directly from the integral intensities of characteristic bands without an additional calibration procedure. A comparison of the results obtained for a variety of samples shows agreement with the crystallinities derived from the density, and the small-angle and wide-angle x-ray diagrams. Data indicate that the disordered anisotropic phase is located at a transition zone between crystalline and amorphous layers. Application of the method in a temperature-dependence experiment permits a detailed examination of partial melting.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160704
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  • 90
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    Effect of polymorphism on the C—H stretching region of the infrared spectrum of polyethylene (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1253-1260 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A complex fine structure in the C—H stretching region of the infrared spectrum of deformed polyethylene single crystals is reported. The deformed crystals are shown to be transformed from the orthorhombic crystal form to a monoclinic structure. The previously deduced C2/m monoclinic structure does not account for the appearance of the new bands. An alternative but similar monoclinic structure is proposed. The symmetry of this structure is consistent with the Fermi resonance interactions required for the observation of these bands.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160708
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  • 91
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    Structure of the quenched form of polypropylene (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 49-57 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: X-ray diffraction has been used to further investigate the quenched form of polypropylene. The diffractometer traces were analyzed by a mathematical peak separation procedure which assumed a combined Cauchy and Gaussian shape for the peaks. The results confirmed that the quenched form contains about 60% of amorphous polypropylene. In the remainder, the x-ray diffraction peak positions indicate that the chain helices are arranged in a square array and a cubic or tetragonal symmetry is proposed for this phase. The shape of the x-ray diffractometer peaks indicates a degree of strain in the structure. Crystallite sizes, determined from peak breadths, have been estimated as approximately 30 Å.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160105
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  • 92
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    Intrinsic viscosity of polystyrene in mixed solvents (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 105-115 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The intrinsic viscosity of a single sample of polystyrene was measured as a function of the composition of solvent in three mixed solvent pairs. The parameter Y introduced by Shultz and Flory was useful for prediction of trends, but severely overestimated the effect of solvent (1)-solvent (2) interaction on the expansion of polymer coils. The system polystyrene-cyclohexane-ethyl acetate was studied in detail for five samples of polystyrene. The analysis of the data provided strong experimental proof of a strict validity of the Mark-Houwink-Sakurada relation. The dependence of the Mark-Houwink-Sakurada exponent α on the composition of the solvent mixture was unexpectedly unsymmetrical. The unperturbed dimentions of the polystyrene chain are reduced by specific interaction of polystyrene with carbonyl groups in the solvent mixture.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160109
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  • 93
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    Properties of vinylpyrrolidone-tert-butylphenyl methacrylate copolymers in solution (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 977-987 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymers of vinylpyrrolidone-p-tert-butylphenyl methacrylate (VP-MBPh) of several compositions were prepared by polymerization in benzene at 50°C using α′α′-azobisisobutyronitrile as initiator. Three of the copolymers were fractionated. Number-average molecular weights of fractionated samples were determined by osmotic pressure in benzene or 2-propanol. Kuhn-Mark-Houwink relations were established in benzene, chloroform, and 2-propanol. From the relation between Mn and the intrinsic viscosity (η), it appears that these random copolymers behave as predicted by the theory for flexible polymers. Abnormal viscometric behavior shown by one of the copolymers in nitromethane at 29°C (the theta temperature) is discussed. The Stockmayer-Fixman semiempirical method was used for estimating unperturbed dimensions from viscosity data obtained in chloroform, a good common solvent. Values of the viscosity parameter Kθ increase with the content of p-tert-butylphenyl methacrylate. In general, experimental Kθ values are higher than those calculated for the homopolymers. Excluded-volume parameters are estimated and discussed in relation to repulsive interactions between unlike monomer units.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160605
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  • 94
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    Infinite-dilution viscoelastic properties of sodium poly(styrene sulfonate)This work was part of the research program of the Rheology Research Center, University of Wisconsin. (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1031-1040 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The storage and loss shear moduli G′ and G″ of dilute solutions of two samples of sodium poly(styrene sulfonate) with molecular weights (M) of 3.28 × 105 have been measured. The Birnboim-Schrag multiple-lumped resonator technique was used in the frequency range 100-8000 Hz, and the intrinsic moduli were obtained by extrapolation to infinite dilution. Measurements were performed over the temperature range from 1.0 to 25.0°C in aqueous solvents containing from 0 to 60% by weight glycerol and from 0.001 to 0.005M added salt. The large intrinsic viscosities indicated high extension of the polymer, and the frequency dependences of G′ and G″ were matched well by hybrid relaxation spectra combining rodlike and coil-like behavior. In a solvent containing 0.001M sodium ion and no glycerol, the end-over-end rotational relaxation times for the two molecular weights corresponded to proportionality to the 1.7 power of M. With increasing molecular weight, ionic strength, and/or glycerol concentration, the polyelectrolyte appeared to become less extended, and its behavior more nearly coil-like.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160610
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  • 95
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    Spectroscopic analysis of electrically polarized polyacrylonitrile (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 13-28 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Electrically polarized and unpolarized films of polyacrylonitrile (PAN) have been investigated by both infrared attenuated total reflection (ATR) and thermally stimulated discharge (TSD). ATR analysis of PAN films has been aimed at explaining the molecular origin of thermally stimulated currents, and consequently that of phenomena contributing to electrical polarization in this material. Preferred orientation of nitrile dipoles along the thickness direction (applied electric field direction) has been detected by ATR in both polarized and unpolarized films. It is suggested that dipolar alignment in unpolarized solvent-cast films could result from internal electric fields associated with space charges. The observed orientational anisotropy is found to disappear gradually as films (both polarized and unpolarized) are heated from ambient temperature to 100°C and rotational motion in the backbone is thermally activated. TSD currents observed in this thermal range are thus associated with randomization of molecular dipoles. TSD currents observed above 100°C are suggested to originate from drift of space charges, since both an isotropic orientation of dipoles and onset of considerable diffusion are detected by ATR in this temperature range. PAN films polarized by high-intensity electric fields (5 × 105Vcm-1, as opposed to 5 × 104Vcm-1) are found to retain orientational anisotropy above 100°C, and this is believed to be associated with a structural rearrangement induced by electrical polarization.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160102
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  • 96
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    Plane-strain fracture energy instability and mixed mode crack propagation in polycarbonate at room temperature (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 91-104 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A study of crack propagation in double cantilever beam specimens of polycarbonate has revealed a large velocity-dependent instability in the plane-strain fracture energy GIc. At a crack velocity of 10-2 in./min, GIc accords with published values obtained from tensile studies of precracked specimens. Crack propagation in doubly grooved double cantilever beam specimens is unstable at higher velocities. The GIc's during crack jumping and at crack arrest are estimated to be 0.2 and 2%, respectively, of the low crack speed value, based on the amounts of crazing produced at the various crack speeds. Evidence of plane-strain shear deformation at the low speed crack tip is presented. The GIc instability is suggested to arise from differences in the kinetics of shear failure and craze breakdown.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160108
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  • 97
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    Crystal structure of isotactic poly(4-methyl-1-pentene) (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 131-142 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystal structure of isotactic poly(4-methyl-1-pentene) was determined by x-ray analysis. The unit cell is tetragonal, P4b2, with α = 18.70 Å and c (fiber axis) = 13.68 Å; it contains four molecular chains each consisting of seven monomeric units in the fiber period. The molecular conformation is essentially a (7/2) helix, but deviates slightly from the uniform (7/2) helix. The unusual low density is discussed from the structural point of view.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160112
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  • 98
    Electronic Resource
    Electronic Resource
    Epitaxial growth of low molecular weight polypropylene from vapor phase (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 179-188 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polypropylene was evaporated on the (001) cleavage faces of alkali halide single crystals, NaCl, KCl, KBr, and KI, under a vacuum of 10-5 torr. Films evaporated on the substrate were found to be composed of low molecular weight polypropylene with a narrow molecular weight distribution. The polypropylene film evaporated on the substrate maintained at 100°C, was composed of rod-like crystals of α form, the (010) plane of which was parallel to the (001) plane of alkali halide and their long axes were oriented in the (110) direction of the substrate. When the substrate was kept above 150°C, the film included three crystalline forms, α, γ, and δ forms. Fiber-like crystals of the α form lay parallel to the (110) direction of NaCl. In the initial stage of growth, lamellar crystals were observed in the film. The lamellar (001) plane lay flat in the film and branching occurred on the (010) lateral faces. Both the γ-form and the (predominately) new δ-form crystals were observed in the same area of the film prepared at temperatures above 150°C.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160116
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  • 99
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    Stability of heterocharges in poly(methyl methacrylate) thermoelectrets. II. Effect of γ-irradiation on thermally stimulated current spectra (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 223-230 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermally stimulated currents (TSC) of γ-irradiated poly(methyl methacrylate) thermoelectrets have been investigated in the high-temperature range. The two main peaks of the TSC spectrum, appearing, respectively, at about 100 (α) and 120°C (ρ), show marked differences in stability under irradiation: while the α peak is little affected by doses up to 107 rad, the ρ peak vanishes following doses of 105 to 106 rad. On the other hand, a study of the rate of decrease of the ρ peak as a function of irradiation conditions reveals the important role of the surrounding atmosphere and the existence of a flux effect, probably related to irradiation-accelerated diffusion of gas into the polymer. All these facts confirm the respective attributions of α and ρ peaks to a dipolar volume polarization and to an ionic space charge polarization, showing that the TSC study of irradiated thermoelectrets can be a useful method for identification of polarization processes in polymers.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160204
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  • 100
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    Equilibrium melting parameters of poly(ethylene terephthalate) (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 289-296 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The equilibrium melting temperature, volume, and enthalpy and entropy changes on melting of poly(ethylene terephthalate) have been analyzed and heats of fusion have been newly measured with an automated scanning calorimeter to yield the following data: 553°K, 16.9 cm3/mole, 2.69 kJ/mole, and 48.6 J/deg/mole, respectively. A more detailed discussion of annealed samples obtained from etched starting materials shows that the density of the noncrystalline regions may be variable.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160209
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