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  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 605-609 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 static delamination behavior of graphite/epoxy composite specimens subjected to mode I tensile opening (using UDCBUniform double cantilever beam. specimens), and pure mode II shear loading (using ENFEnd-notched flexural. specimens) were studied. The graphite epoxy composites for the study were made from commercially treated fibers, with and without an electropolymerized interlayer. The mode I fracture energy (GIC) was found to be significantly higher (more than 50 percent) for the coated fibers. However, this improvement was accompanied by a high reduction (more than 3 times) in the mode II fracture energy (GIIC). This effect is apparently related to poor adhesion between the interlayer and the epoxy resin, which may be corrected by use of a “top layer” of appropriate composition to form chemical bonds between the phases. The fracture toughness (KIC) of composites made with commercially treated fibers was also evaluated, using double side-notched specimens.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 1875-1891 
    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: Our limited success in toughening methylene dianiline (MDA)-cured Epon 828, using varying rubber types, led to a study of the role of the matrix viscoelasticity in the toughening process. Two rubber types, with different interfacial bonding capabilities, poly(n-butyl acrylate)/15 wt % acrylonitrile/2 wt % acrylic acid and poly(n-butylacrylate)/15 wt % acrylonitrile, were incorporated into systems containing varying amine concentrations to control crosslink density. Impact strengths of controls and rubber-modified compositions increased with excess amine concentrations up to 70%. The impact strengths for the poly(n-butyl acrylate)/15 wt % acrylonitrile/2 wt % acrylic acid rubber-modified compositions were greater than their equivalent controls, with the effect being greater at a lower crosslink density. This study confirmed that the matrix viscoelasticity is the controlling parameter in the toughening process. The degree of rubber-epoxy interfacial bonding is also an important parameter to consider, if the matrix viscoelasticity permits toughening. A modified stress response model was used to explain the toughening phenomenon.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 247-254 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diepoxides and in-chain carbonate groups react readily in the presence of quarternary ammonium salts, although reaction is not observed without this catalyst. Two moles of epoxide react with each mole of carbonate. When diepoxides and polycarbonates are reacted, a three-dimensional network of chains crosslinked with carbonate groups is produced; the crosslink density is controlled by adjusting the epoxy/carbonate ratio. Tertiary amines and alkoxides also catalyze the epoxy/carbonate reaction, but these have the undesirable attribute of promoting epoxy polymerization. The presence of oligocarbonates accelerates the epoxy-amine reaction.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989), S. 10-17 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The potential of uranium recovery from the dilute uranium ore bioleach solutions of the Elliot Lake district of Canada was examined using immobilized microbial biomass. Batch and continuous laboratory scale pilot plant experiments were carried out. The results have shown that the immobilized microbial biomass can successfully recover all of the uranium from dilute (less than 300 mg U/L) solutions. The uranium can subsequently be eluted producing a high uranium concentration eluate perhaps exceeding 5000 mg U/L. The biomass maintained its biosorption capacity of about 50 mg U/g over 12 examined successive adsorption-elution cycles with no apparent indication of failure.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 34 (1987), S. 2105-2124 
    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: Electro-copolymerization of methyl acrylate, acrylic acid, methacrylic acid, acrylamide, and methyl methacrylate with acrylonitrile onto graphite fibers has been successfully done in our laboratory. The coatings are relatively uniform and their properties, especially their modulus, can be systematically varied by controlling the monomer ratio in the eletrolyte solution. This technique is being used to introduce a ductile interlayer of contrlled composition and thickness between the composite fibers and matrix. Copolymers of methyl acrylate and acrylonitrile formed by this technique are random copolymers, with Tg′s varying from 10 to 90°C. These copolymers have fairly high molecular weight, in the range of 100,000 g/mol. Monomer reactivity ratios were determined, based upon free radical polymerization kinetics, from cyclic voltammetry. An indirect initiation mechanism is suggested. Bonding between interlayer and matrix can be improved by introducing vinyl monomers with proper functional groups, capable of reacting with the epoxy resin, at the last stage of the electropolymerization process.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 10 (1989), S. 162-172 
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Electrocopolymerization of acrylonitrile/methyl acrylate/acrylic acid, acrylonitrile/methylacrylate, and glycidyl-acrylate/acrylonitrile interlayers onto Hercules AS4 graphite fibers was used to improve simultaneously the effective interfacial shear strength, τe, and the fracture toughness of graphite-epoxy composite materials. With a single-fiber fracture test, τe for these coated fibers (embedded in a diglycidyl ether of bisphenol A - 4,4′-methylenedianiline matrix) was determined at various temperatures and under various hygrothermal treatments. At room temperature, the coated samples showed slightly improved shear strength over the uncoated sample. At elevated temperatures, a plot of τe vs. temperature for the uncoated sample showed two distinctive regions: an interface-controlled plateau region at low temperatures, and a matrix-controlled region at high (〉80°C) temperatures. Only one region, which was controlled by the matrix and the interlayer, was observed for the GA/AN coated sample. The τe values determined were slightly higher than the shear strength of the bulk matrix, possibly because of stronger matrix properties at the interface. Optical micrographs of the coated sample tested at temperatures less than 100°C showed no matrix crack perpendicular to the fiber axis, indicating that the interlayer has effectively blunted the crack tip and restricted its propagation. The effect of moisture in the sample was to reduce τe for the coated sample. Upon dehydration, the strength was partially recovered. The treatments did not affect the uncoated sample, however. The fragmentation length data were fitted well by both Gaussian and Weibull distributions.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 8 (1987), S. 46-52 
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Thin, high molecular weight copolymers have been applied to the surfaces of commercial, 8 micron diameter, graphite fibers by electropolymerization. Random copolymers were obtained, and the process appears to be consistent with the rules of standard free radical copolymerization. Coating thickness, Tg, and modulus can be systematically controlled. Very preliminary mechanical property measurements indicate a substantially improved impact strength and reduction in the interlaminar shear strength. These effects may be related to poor adhesion between the interlayer and the epoxy resin, however, which may be corrected by use of a “top layer” of appropriate composition.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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