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  • Chemistry  (6)
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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: Isotactic polypropylen films were highly stretched and annealed during 20 s under stretching tension at temperatures up to 206°C at maximum. The melting behaviour of these films was investigated by using a differential scanning calorimeter (DSC  -  1 B). Two melting peaks at about 165 and 174°C respectively, were observed. The heat of fusion of the former peak predominates, if the film temperature during annealing exceeds 190°C. Its position is independent of the stretching ratio. This melting peak is assigned to crystalline domains, which show a long identity period of 140 to 160 Å and corresponds to an amorphous orientation factor of 0 to -0.2. The higher melting peak appears during stretching. This peak is assigned to crystalline domains, which show a long identity period longer than 200 Å and corresponds to an amorphous orientation factor of 0.4 to 0.5. This fraction refers obviously to the paracrystalline building blocks of the microfibrils, which are transformed at a film temperature higher than 190°C to a greater part into smaller lamellaforming paracrystallites. The transformation of the fibrillar into a lamellar texture was visualised by transmission electronmicroscopy.
    Notes: Isotaktische Polypropylen-Folien wurden hoch verstreckt und unter Streckspannung bei Temperaturen bis maximal 206°C während 20 s getempert. Das Schmelzverhalten dieser Folien wurde mittels DSC verfolgt. Es wurden zwei Schmelzpeaks registriert, die bei ca. 165°C und 174°C auftreten. Die Schmelzenthalpie des erstgenannten Peaks überwiegt, wenn die Folientemperatur beim Tempern auf über 190°C angehoben wird. Seine Lage ist unabhängig vom Streckverhältnis. Dieser Schmelzpeak konnte einer kristallinen Phase mit einer Langperiode von 140 bis 160 Å bei nichtorientierten, zwischenkristallinen Bereichen zugeordnet werden. Der 2. Schmelzpeak entsteht beim Verstrecken. Seine Temperatur steigt mit zunehmendem Streckverhältnis an. Er wurde auf eine kristalline Phase mit einer Langperiode von über 200 Å bei einer mittleren amorphen Orientierungsfunktion der zwischenkristallinen Regionen von 0,4-0,5 zurückgeführt. Bei dieser Fraktion handelt es sich offenbar um die parakristallinen Bausteine der Mikrofibrillen, welche sich bei Folientemperaturen von über 190°C zum größeren Teil in kleinere Lamellen-bildende Parakristalle umwandeln. Der übergang der Fibrillen- in eine Lamellentextur wurde elektronenmikroskopisch sichtbar gemacht.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 175-184 
    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: Die innere Oberfläche und das Hohlraumsystem von verschiedenartigen Celluloseregeneratfasern werden mit Röntgenkleinwinkelstreuung untersucht. Dabei wird gefunden, daß alle Fasern ein Hohlraumsystem von 0,01 bis 0,1% (Volumenanteil 10-4-10-3) aufweisen. Es zeigt sich jedoch, daß die Größe des Hohlraumsystems für die mechanischen Eigenschaften wenig Bedeutung hat. Es ist vielmehr die Gestalt der Hohlräume und ihre Orientierung, die hier wesentlich sind. Es wird gefunden, daß langgestreckte Hohlräume, vermutlich orientiert, für gute mechanische Eigenschaften verantwortlich sind. Damit können auch verbesserte textile Eigenschaften von Lyocellfasern des NMMO-Typs erklärt werden.
    Notes: Both the inner surface and the void system of different cellulose regenerate fibers are investigated with X-ray small angle scattering. Thereby it turns out that all fibers have a void system of 0.01 to 0.1% (volume fraction 10-4-10-3). However, the amount of the void system has little influence on the mechanical properties. Rather, it is the shape of the voids and their orientation which proves essential. It is found that elongated voids, probably well oriented, are responsible for superior mechanical properties. This explains also improved textile properties of lyocell fibers of the NMMO type.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
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  • 3
    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: The size of the crystalline regions of regenerated cellulosic fibers was determined by means of transmission electron microscopy, small angle X-ray scattering, and wide angle X-ray diffraction. All three methods lead in satisfying conformity to the following dimensions: length: 120-140 Å, width: 80-100 Å, thickness: 30-40 Å. The broad plane of the platelet shaped crystallites is situated parallel to the 101-lattice plane, the small edge plane has an orientation parallel to the 101-lattice plane. The -crystallites form strands, which have a length of 1500-5500 Å. They are partly bundled up to clusters with a diameter of 300-600 Å, partly separated by less dense spacings. The distance between the crystalline regions amounts to 20-40 Å in longitudinal and cross direction.
    Notes: Die Dimensionen der kristallinen Bereiche von Regeneratcellulosefasern wurden mittels Transmissionselektronenmikroskopie, Röntgenkleinwinkelstreuung und Röntgenweitwinkeldiffraktion bestimmt. In befriedigender Übereinstimmung wurden nach allen drei Methoden folgende Abmessungen gefunden: Länge: 120-140 Å, Breite: 80-100 Å, Dicke: 30-40 Å. Die breite Ebene der blättchenförmigen Kristallite verläuft parallel zur 101-Netzebene, die schmale Kantenebene parallel zur 101-Netzebene. Die Kristallite bilden Ketten mit einer Länge von 1500 bis 5500 Å, die teilweise zu Clustern mit einem Durchmesser von 300 bis 600 Å gebündelt sind, teilweise durch Zonen geringerer Dichte voneinander getrennt sind. Die Abstände zwischen den kristallinen Bereichen betragen in Längs- und Querrichtung 20 bis 40 Å.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 94 (1961), S. 348-352 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1.2-Cyclohexyliden-D-xylofuranose läßt sich mit Sauerstoff am Platin-Kohle-Katalysator zu 1.2-Cyclohexyliden-D-xyluronsäure oxydieren, deren Spaltung D-Xyluronsäure liefert. Benzyl-β-D-ribofuranosid liefert an Adams-Katalysator mit Sauerstoff Benzyl-β-D-riburonid, welches nach Spaltung D-Riburonsäure ergibt.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 6 (1995), S. 55-64 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study deals with a three-point flexure test for the metal-ceramic bond involving geometrically simple specimens (alloy strips partly coated with ceramic) that can be fabricated with reasonable expenditure and sufficient reproducibility. The calculation of the stress distribution in such specimens with the aid of the finite-element method (FEM) is presented. The aim of this numerical analysis is: to investigate the stress distribution in a ceramometallic specimen with dimensions that, in a large number of experiments, have proven to lead to debonding at one end of the ceramic veneer instead of a crack in the middle of the veneer; and to assign a bond strength to the measured critical bending force that takes into account the influence of the Young's modulus of the alloy as well as a possible deviation of the thickness of the metal substrate from the standard value. Bond strength values of a variety of metal-ceramic combinations are demonstrated. These experimental results demonstrate the reproducibility of the test method as well as its sensitivity to diverse parameters. The presented method is proposed as an alternative to another flexure bond test nominated for international standard. In this test ceramometallic strips are bent over a rod to a 90° angle of the specimen ends, subsequently flattened, and the fracture surface visually inspected for adherence of the ceramic to the alloy substrate along the predominant part of the middle third of the specimen. It is clear that such a test can at most deliver qualitative results. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 60 (1988), S. 519-525 
    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
    Notes: Logistics in the manufacture of chemical products. This survery covers the fields of location analysis, organization of operational material flow, and materials management, all of which are interlocked with each other. Logistics problems with location analysis lie in the area of infrastructure, procurement, and distribution. The organization of the operational material flow has to be based on a closed concept, taking simultanously into consideration interests of production techniques and of logistics. Special attention has to be paid to the reciprocal effect of plant and storage capacity. With complex production structures simulation models should be used, including a statistical model of the market demands, systematic variation of material flows, and grouping of technical equipment. Target is a minimization of total cost. For market oriented operation of complex productions, integrated materials management systems have to be employed. The systems supply a transparent material flow starting from the market demands via the control of production up to the procurement of raw materials.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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