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  • Articles  (174)
  • Chemistry  (174)
  • Process Engineering, Biotechnology, Nutrition Technology  (91)
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  • 1
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: An Folien (Dicke 100 pm) aus isotaktischem Polypropylen mit verschiedenen Antioxidansgehalten (0,0% bis 0,1%) wird die thermooxidative Alterunq mit der isothermen Langzeit-Differential-Thermo-Analyse (ILDTA) bis zu Temperaturen weit unter dem Kristallitschmelzbereich verfolqt und die Messwerte mit Ergebnissen aus dem Zeitstand-Zugversuch korreliert. Dabei zeigt sich, daß aus Messunqen mit der ILDTA bereits vor Einsetzen der autokatalytischen Zersetzunq sreaktion Ruckschlüsse auf die thermische Vorqeschichte der Proben und Aussagen auf das rnit einem Abfall der mechanischen Eigenschaften verbundene Ende der thermo-oxidativen Stabilität des Polymeren getroffen werden können.Weiters bietet die ILDTA die Moglichkeit, durch den direkten Zusamenhang zwischen Oxidationszeit und Antioxidansögehalt die örtliche Stabilisatorverteilung in Platten und in Folien zu bestimmen und damit Diffusionsvorqange zu verfolgen.
    Notes: Thermo-oxidative ageing processes were investigated in films (100 μm thick) made from isotactic polypropylene with different antioxidant concentrations between 0% and 0.1% using isothermal long-term differential thermal analysis (ILDTA). The end of the oven life of polypropylene coincided with the loss of mechanical properties which was confirmed by tensile tests at temperatures far below the crystallite melting range. Already prior to the beginning of autocatalytic decomposition, ILDTA experiments permits conclusions to be drawn on the thermal history of the specimens and statements made regarding the end of thermo-oxidative stability of the polymer, which is accompanied by a deterioration in the mechanical properties.In consequence of the correlation between oxidation time and antioxidant concentration the local antioxidant concentration in sheets or films can be measured by ILDTA. Thus, investigating the diffusion of an antioxidant in polypropylene using ILDTA is possible.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 24 (1952), S. 401-402 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Es wird gezeigt, daß die im Betriebe von Spinnbadeindampfern fallweise auftretenden, schwer entfernbaren Verkrustungen der Heizrohre im wesentlichen durch die Ausscheidung von Glauberit verursacht werden. Verschiedene Einflüsse, die die Bildung des Doppelsalzes begünstigen, werden aufgeklärt.
    Additional Material: 3 Ill.
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  • 3
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Nach einführender Betrachtung des Meßproblems hinsichtlich der zu verlangenden Meßgenauigkeit und den sich ergebenden Einzelforderungen werden die Bestandteile des Staubmeßgerätes, nämlich die Waage, die Staubabscheidungskammer, das Gebläse, das Hochspannungsgerät und die zum selbsttätigen Ablauf notwendige Automatik besprochen. Ferner wird über vergleichende Versuche mit einem optischen Staubmeßgerät berichtet.
    Additional Material: 9 Ill.
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  • 4
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Die Ähnlichkeitstheorie hat den Weg gezeigt, die Gesetzmäßigkeiten des Wärmeüberganges mit Hilfe dimensionsloser Kennzahlen auszudrücken. Die Anzahl der zur eindeutigen Beschreibung eines Vorganges notwendigen Kenngrößen ist recht verschieden, sie ist z. B. besonders groß bei komplizierten Austauscherformen. Bei der Zusammenfassung der Einzelfaktoren zu Kennzahlen hat man gewisse Freiheiten, die man dazu benützen kann, die Gesetzmäßigkeiten bei der Berechnung von Wärmeaustauschern in einer möglichst zweckmäßigen Form darzustellen. An einem Beispiel wird gezeigt, daß die Rechnungen sich verhältnismäßig einfach durchführen lassen.
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 26 (1954), S. 94-96 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Die konstruktiven Voraussetzungen für Laboratoriumszentrifugen mit bisher in der Praxis nicht erreichbaren Fliehkräften werden dargelegt. Das entwickelte Gerät, das im Gegensatz zu anderen Bauarten nur eine einzige radial um die Drehachse rotierende Zelle für die Einsatzflüssigkeit besitzt, wird beschrieben. Es ermöglicht bei 84 000 U/min Normalbeschleunigungen von 584 000 g, bei 120 000 U/min und kleineren Präparatmengen von 915 000 g. Besondere Einsätze zur Erfassung des Sediments bringen bei präparativen und möglicherweise auch analytischen Arbeiten besondere Vorteile.
    Additional Material: 3 Ill.
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  • 6
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 7
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Organic radicals were produced in the tensides C16H33(OCH2CH2)21OH and C14H29(OCH2CH2)3-SO3Na in aqueous solutions using a short pulse of high energy electrons. The radicals were formed by OH attack on the (OCH2CH2)x-parts of the tensides. The decay of the 250nm absorption of the radicals was recorded at different initial radical concentrations and tenside concentrations. Several radicals could be produced in one micelle. Radicals formed in the same micelle decay within microseconds or faster. The half life time τ1 in a micelle carrying two radicals is 2,0·10-6 s for C16H33(OCH2CH2)21 OH and less than 6·10-7 s for C14H29(OCH2CH2)3SO3Na. A model for intramicellar radical-radical reactions is proposed according to which the rate is faster in tensides of high critical micelle concentration. Single radicals in micelles of C16H33(OCH2CH2)21OH can deactivate each other without leaving the micelles. This intermicellar reaction is discussed in terms of the rate of diffusion-controlled micelle-micelle encounters, an encounter time of 7·10-8s, and the above time τ1 for intramicellar reaction. The observed rate constant 2k of intermicellar reaction is 3,5·106 mol-1·l·s-1. At low tenside concentrations, the bimolecular rate constant increases since more single tenside radicals are present in solution. They react rapidly (ca. 108 mol-1·l·s-1) with radicals in micelles. Single radicals in C14H33(OCH2CH2)3-SO3Na micelles cannot directly react with each other because of the Coulombic repulsion between two anionic micelles. Reaction occurs after the exit of a tenside radical from its micelle, the rate of which depends on the micellar equilibrium Mn⇄Mn-1+M (M: tenside molecule; n: agglomeration number of micelle). A single radical in solution reacts with a single radical in a micelle with 2k = 1,0·108 mol-1·l·s-1 and with another single radical in solution with 4,0·107 mol-1·l·s-1.γ-Irradiation of both tensides in aqueous solution leads to slight increases in viscosity, followed by turbidity beyond the “gel dose” and phase separation. These effects are explained in terms of crosslinking of tenside molecules. Formation of a large network requires bridges between all participating tenside molecules (not only bridges between micelles).
    Additional Material: 11 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 577-587 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Complex mixing flows and mixing parameters are calculated to evaluate mixing quality on the basis of kinematic parameters together with a statistical analysis. The results allow for a comparative evaluation in terms of geometry and flow parameters. The evaluation is limited to two-dimensional flows with moving boundaries in periodic motion such as the flow in the cross section of a twin-cam mixer. The finite-element calculation requires a remeshing procedure for every time step with special techniques to upgrade mixing variables from one time step to the next. The relative mixing quality of single cam and co: or counterrotating cam devices are compared by evaluating segregation scale, length stretch, and efficiency. The numerical results exhibit a good correspondence with their experimental counterpart.
    Additional Material: 15 Ill.
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  • 9
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cultivation of Norcardia sp., Mycobacterium phlei, and Candida lipolytica in inorganic salt solution containing n-alkanes C10-C20 as solo carbon and energy source was investigated. Generation times of 0.5-7.0 hr were typical during the exponential growth phase. The final cell concentrations (dry weight) were usually 9-26 g/l with n-alkane mixtures ranging from n-decane through n-eicosane. A linear dependence was found between the production of cell mass and the consumption of n-alkanes. The rest concentration of n-alkanes in the cell mass is in all experiments smaller than 0.5% (w/w). Cell yields were Ysub 60-142% and for Ye 50-97% based on n-alkane utilization. In one case, with the Nocardia NBZ 23, the substrate specifity on hydrocarbons and on a n-alkane mixture C10-C20 was studied. The cell mass recovered from the fermentations contained 47.8-57.7% carbon, 5.6-9.95% nitrogen, 7.2-9.4% hydrogen, 35-62% crude protein, and 6-36% lipid. Cellular protein and lipid synthesized by an organism is influenced by the type of nitrogen source. The amino acid, glucosamine, muramic acid, 2,6-diaminopimelinic acid, and fatty acid distribution in organisms grown on n-alkanes compared with a corresponding fermentation on glucose as sole carbon source were also estimated.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 588-597 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Numerical tools for the analysis of complex 3-D mixing devices were developed. Calculations are based on the finite-element method. The flow calculation is combined with that of pathlines for a fairly large number of material points; along these pathlines, relevant kinematic variables, which are then subjected to a statistical treatment, are evaluated. These numerical techniques are applied to the analysis of a Kenics mixer. It is assumed that the geometry is periodic in the axial direction, that is, that the mixer contains an infinite number of blades; the finite-element analysis may then be completed on a single wavelength of the geometry. To test the accuracy of the three-dimensional calculation, a Kenics device was mounted in order to mix clays of different colors, and photographs of experimental cross-sections were compared with numerical results showing concentration maps. A statistical treatment was performed on some 8,000 material points crossing the entry section to evaluate mixing quality.
    Additional Material: 16 Ill.
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