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  • Polymer and Materials Science  (8)
  • Chemical Engineering
  • 2020-2024
  • 1975-1979  (8)
  • 1976  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Stability of steady states in nucleic acid poly[d(A-T)] synthesis and the stirred flow reactor (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1-14 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The template directed synthesis of poly[d(A-T)] from the nucleoside triphosphates in the presence of DNA polymerase I is carried out continuously in a stirred flow reactor for the first time. The initial objective is to test the kinetic stability of the established steady states at various flow rates. Graphical analysis predicts instable steady states for certain high flow rates. As a consequence of instabilities multiple steady states and steady-state hysteresis may occur. Steady-state hysteresis has now been found experimentally. For a different enzyme fraction of low exonuclease activity we found the steady-state absorbance at 260 nm to be almost invariant with flow rate at high enzyme concentrations even if the flow rate was increased by a large factor. We call this phenomenon kinetic buffering. Relaxation of a large flow perturbation approaches the steady state in a sigmoidal fashion. Concentration oscillations at 260 nm occurred in one experiment using an enzyme fraction of low exonuclease activity after perturbing the steady state by monomer (dATP). Advantages of the stirred flow reactor method over serial transfer are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150102
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  • 2
    Electronic Resource
    Electronic Resource
    Über die kinetik des thermischen und thermooxidativen abbaus von polyäthylenterephthalat (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 121-129 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The apparent kinetic parameters of the thermal and the thermal and thermooxidative degradation of poly(ethylene terephthalate) for non-isothermal conditions were evaluated. The dependence of these parameters on the heating rate, the mean molecular weight, and the degree of conversion was also established. It is shown that the degradation in nitrogen probably occurs by a short chain mechanism, while the degradation in air is more complex. In the latter case, the exothermic character of the DTA-curves suggests that the chain degradation reaction is overlapped by oxidation processes.
    Notes: Es wurden die scheinbaren kinetischen Parameter der thermischen und thermooxidativen Abbaureaktionen von Polyäthylenterephthalat für nicht-isotherme Bedingungen bestimmt und die Abhängigkeit dieser Werte von der Aufheizgeschwindigkeit, dem mittleren Molekulargewicht und vom Umsatzgrad festgestellt. Es wurde gefunden, daß der Abbau in Stickstoff nach einem einheitlichen Kettenmechanismus mit kurzen kinetischen Ketten erfolgt, wogegen sich in Luft der Kettenabbaureaktion Oxidationsprozesse überlagern, bemerkbar an einem exothermen Ausschlag der DTA-Kurven.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021770110
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  • 3
    Electronic Resource
    Electronic Resource
    High resolution 1H-NMR study of association of polymers in solution. Poly(methyl methacrylate) and poly(vinyl chloride) (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 957-957 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021770334
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  • 4
    Electronic Resource
    Electronic Resource
    Problemlösungen durch Schichtverbundwerkstoffe in der ElektrotechnikVortrag anläßlich der Tagung „Verbandwerkstoffe“ der Deutschen Gesellschaft für Metallkunde vom 31. März bis 2. April 1976 in Konstanz (1976)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 7 (1976), S. 413-417 
    Details
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Clad Metals for Electrical Engineering. Materials with optimum properties for conducting springs can be produced by cladding a metallic sheat of high electrical conductivity between two sheats of a metal with high stiffness.Using suitable cladding components, thermo bi metals with different electrical resistance can be produced without essential variation of deflection and force. With this it is possible, to use groups of devices with uniform mechanical construction for different currents, which means a good technical as well as economic solution.High prices of noble metal based contact materials have led to the production of contact bimetals some years ago. Inspite of higher production costs these materials can be used very economically.
    Notes: Durch geeignete Anordnung hochfester und hochleitfähiger Komponenten in einem Schichtverbundwerkstoff lassen sich Werkstoffe mit optimalen Eigenschaften für stromführende Federn herstellen. Durch Verwendung geeigneter Plattierungskomponenten können Thermobimetalle mit unterschiedlichem elektrischen Widerstand ohne wesentliche Veränderung der Ausbiegung und der Kraftwirkung hergestellt werden. Somit ist es möglich, Gerätegruppen mit gleichem mechanischen Grundaufbau für verschiedene Stromstärken zu verwenden und damit technisch und wirtschaftlich günstige Problemlösungen zu erzielen.Der hohe Preis der Kontaktwerkstoffe auf Edelmetallbasis führte schon vor vielen Jahren zur Herstellung von Kontaktbimetallen. Trotz höherer Formkosten sind diese Werkstoffe in den meisten Fällen besonders wirtschaftlich einsetzbar.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19760071106
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  • 5
    Electronic Resource
    Electronic Resource
    Neue epoxidharze auf resolbasisEine gekürzte Fassung dieses Artikels wurde am 20. September 1974 vom erstgenannten Autor am XXIII. Internationalen IUPAC-Symposium über Makromoleküle in Madrid vorgetragen. (1976)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 54 (1976), S. 91-117 
    Details
    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: A process for the preparation of novel epoxy compounds on the basis of hydroxymethylphenols or resoles is described which comprises the alkylation of the phenolic intermediates in a first step in order to reduce their tendency to resinification. The hydroxymethyl compounds thus stabilized are subsequently etherified with epichlorohydrin and caustic soda in presence of a phase transfer catalyst under azeotropic removal of water. The structure of pure isomers of model compounds obtained by this process is confirmed by analytical and spectroscopic data. Typical resins made by the same process exhibit the same structural features. They are characterized in addition by gel permeation chromatography.The choice of the phenolic starting material, the amount of formaldehyde and the valency of the alkylating agent enable us to prepare a great variety of mono- and polynuclear resins having 1 to 4 epoxy groups per molecule. Their cure with 4,4′-diamino-diphenylmethane and with phthalic anhydride yields castings with good mechanical strength and heat distortions up to 150°C. Tough surface coatings with good chemical resistance are obtained by the cure with cycloaliphatic diamines.
    Notes: Ein Verfahren zur Herstellung von neuen Epoxidverbindungen auf Basis von Hydroxymethylphenolen und Resolen wird beschrieben, welches dadurch gekennzeichnet ist, daß man diese Zwischenprodukte zuerst am phenolischen Hydroxyl alkyliert, um ihre Neigung zur Verharzung zu vermindern. Die so stabilisierten Hydroxymethylverbindungen werden mit Epichlorhydrin und Natronlauge in Gegenwart eines Phasentransferkatalysators (z.B. (CH3)4N+Cl-) unter azeotroper Wasserabscheidung veräthert. Die Struktur reiner, isomereinheitlicher Modellverbindungen, die auf diese Weise hergestellt wurden, wird durch Analysen und spektroskopische Daten belegt. Ihre typischen Strukturmerkmale finden sich in den Harzen wieder, die auch durch Gelpermeationschromatographie charakterisiert werden.Die Wahl der phenolischen Verbindung, die Formaldehydmenge und die Wertigkeit des Alkylierungsmittels machen eine große Vielfalt von ein- und mehrkernigen Harzen mit 1 bis 4 Epoxidgruppen pro Molekül zugänglich. Ihre Härtung mit 4,4′-Diaminodiphenylmethan oder mit Phthalsäureanhydrid führt zu Formkörpern mit guter mechanischer Festigkeit und mit Formbeständigkeiten in der Wärme nach Martens bis zu 150°C. Mit cycloaliphatischen Diaminen werden Lackfilme mit guter Chemikalienbeständigkeit erhalten.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1976.050540108
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  • 6
    Electronic Resource
    Electronic Resource
    The thermal transition behavior of polyorganophosphazenesBased on presentation given at the Polyphosphazene Conference, AMMRC, Watertown, Massachusetts, May 1975. (1976)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 20 (1976), S. 3087-3103 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The thermal transition behavior of poly[bis(trifluoroethoxyphosphazene)] (I) and two samples of poly[bis(p-chlorophenoxyphosphazene)] (II) have been studied as representative alkoxy- and aryloxy-substituted polyorganophosphazenes. Several of the polymers of this class are reported to exhibit two first-order transitions, denoted herein as T (1) for the transition from a crystalline to mesomorphic state and Tm for the true melt. Studies of these two polymers were undertaken to gain a further understanding of this behavior. Optical microscopy on a solution-cast film of I showed that the details of spherulitic morphology persist through T(1) = 90°C and remain undisturbed through the temperature interval up to Tm = 240°C. The study of II by x-ray diffraction reveals that two sharp lines are observed above T(1) = 165°C and that orientation is not randomized upon heating to temperatures as high as 238°C. Considerable improvement in the crystalline diffraction pattern results from the thermal treatment. A detailed examination was also made by differential scanning calorimetry (DSC) of the effects of cycling through T(1), annealing in the temperature interval between T(1) and Tm and for I, the influence of controlled crystallization from the melt. The results indicate that the organization in the mesomorphic state, as influenced by thermal history, has a profound affect on the peak position, area, and sharpness of the endotherm at T(1). For I, the apparent heat of fusion at T(1) is about ten times greater than at Tm, whereas for II, no DSC peak is observed at Tm = 365°C, suggesting that the ratio of the heats of fusion at T(1) and Tm is greater than 50. However, estimated volume changes at the two transitions are nearly equal. These results are compared with those of other polymers which exhibit an intermediate state of order and with molecular liquid crystals.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1976.070201114
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  • 7
    Electronic Resource
    Electronic Resource
    High resolution 1H-NMR relaxation study of polyisobutylene in solution (1976)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1789-1800 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: From the temperature dependence of integrated intensities and from line widths in high-resolution 1H-NMR spectra, the relaxation times T1 and T2 of protons in CH2 and CH3 groups of polyisobutylene in CCl4 solution have been determined. Although the relaxation time T1 of methylene protons is determined mainly by intragroup interactions, intergroup interactions of two methyl groups from each two consecutive monomer units were found to contribute considerably to T1 of methyl protons. The Structure and mobility of polyisobutylene (PIB) molecules in solution is discussed on the basis of the relaxation time data.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1976.180141005
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  • 8
    Electronic Resource
    Electronic Resource
    Behaviour of concrete under thermal steady state and non-steady state conditions (1976)
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 1 (1976), S. 103-115 
    Details
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Stress-strain behaviour of concrete at elevated temperatures is extremely complex and is not completely understood up to now. The creep properties of concrete at temperatures up to 300°C thus need to be determined, as well as the thermal stability of concrete during repeated cycles of heating and cooling. In this report the results of recent high temperature experiments with normal concrete specimens are presented. The main objectives of the tests were to investigate the dependence of strength and elasticity on temperature and to study the creep and deformation characteristics of concrete at temperatures up to 450°C. Transient creep data, i.e. data derived under transient temperature conditions, are compared with creep data which were measured at constant elevanted temperatures. The results suggest that transient creep values and steady state creep values in some cases may be of the same magnitude.The creep measurements appear to be in good agreement with data presented by other workers. However, the scatter in all data increases significantly with increasing temperature and differences of more than 100% can be observed. When loaded concrete specimens were cooled down to ambient temperature exptraordinarily large compressive strains can be observed. The experiments indicate clearly the considerable strain capacity of normal structural concrete can be used at temperatures higher than 100°C. In areas of high stress concentrations a tures. On the other hand, with respect to the whole structure it is necessary to limit the deformations. For a constant maximum temperature this can only be done by limiting the admissible stresses. The test results permit an initial estimation of maximum permissible stress and temperature values.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fam.810010305
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