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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 127-134 
    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: A new carbon fiber was prepared from the lignin (steam-exploded lignin), which was isolated from steam-exploded birch wood (Betula platyphylla). The lignin was modified to melt thermally on hydrogenolysis. The chloroform soluble and carbon disulfide insoluble fraction (HL) of the reaction products was heated at 300-350°C for 30 min, giving a molten viscous material (HHL). The HHL had a softening point of 110°C and melted at over 145°C to form viscous liquid. When HHL was subjected to a spinning test, according to a conventional fusion spinning method at a speed over 100 m/min, a fine filament could be continuously formed through a pinhole (diameter: 0.3 mm). After the filaments were heated in air at 1-2°C/min up to 210°C, by which time the filament was converted to have an infusible property, the filaments were carbonized by heating from a room temperature to 1000°C at a heating rate of 5°C/min in a stream of nitrogen. The typical properties of the lignin based carbon fiber were as follows: Fiber diameter = 7.6 ± 2.7μ Elongation = 1.63 ± 0.29% Tensile strength = 660 ± 230 MPa; Modulus of elasticity = 40.7 ± 6.3 GPa. The chemical structure of the precursor was remarkably changed from that of the original lignin, indicating the elimination of aliphatic functional groups implied originally in the starting material.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 1-11 
    ISSN: 0887-624X
    Keywords: chemical amplification ; photoresist ; poly(p-hydroxystyrene) ; photocrosslinking ; carbocationic ; radiation-sensitive ; crosslinker ; triarylsulfonium salt ; thin-film chemistry ; UV ; E-beam ; x-ray ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New resist systems based on acid-catalyzed, electrophilic aromatic substitution are described. These new resists show high sensitivity to deep UV and E-beam radiation with values approaching 2 mJ/cm2 and 2 μC/cm2, respectively. The resists are based on a three component system consisting of poly(4-hydroxystyrene), a polyfunctional, low molecular weight, latent electrophile, and a photoactive onium salt used as an acid generator. Irradiation of the resist film produces a latent image of acid dispersed in the matrix. During the postbaking step the photo-generated acid reacts with the latent polyfunctional electrophile and releases a reactive carbocationic intermediate with concomitant liberation of acetic acid. The carbocationic intermediate then reacts with neighboring phenolic moieties in a crosslinking reaction. The substitution reaction liberates a proton, making the process catalytic in nature, thus incorporating the concept of chemical amplification. These highly sensitive materials can be used as nonswelling negative multipurpose resists that function in deep-UV, x-ray or E-beam modes. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 1485-1491 
    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: A lignin-pitch for carbon fiber was prepared in a high yield from exploded lignin on phenolysis followed by heat treatment under a vacuum. The lignin-pitch had an excellent spinnability in the melt state to form a fine filament. The green fibers were easily made infusible when heated in air at a relatively high heating rate (15-60°C/h). The lignin-based carbon fiber was produced in 43.7% of yield based on a starting material. The tensile strength was more than 400 MPa, indicating that the lignin-based carbon fiber is classified into a general purpose grade. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 729-734 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Zirconia has received special attention, mainly because of its high strength and toughness. However, there is some controversy about the time-dependent deterioration of its mechanical properties. To examine the change in mechanical properties of zirconia ceramics in vivo and in vitro, tetragonal zirconia polycrystal pieces were introduced into the medullary cavity of the tibia in Japanese rabbits and animals were sacrificed after 2, 4 and 6 weeks and 6, 12, and 30 mo, respectively. Alumina ceramic and hydroxyapatite (HAP) pieces were used as controls to investigate the differences in biocompatibility. Zirconia showed a bending strength of over 1000 MPa initially, and little time-dependent change in strength was found in both in vivo environments. x-Ray analysis showed little change in the transformation rate, i.e., less than 5 mol % in vivo and in vitro over a period of 3 years. To estimate time-dependent changes in zirconia over a longer period, zirconia pieces were placed in 95°C saline solution for over 3 years and their mechanical properties examined at chosen intervals. No serious decrease of bending strength was found over the 3-year period under these conditions. It is concluded that zirconia can be used clinically because it retains a bending strength of over 700 MPa under any experimental conditions for over 3 years. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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