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  • 1
    Electronic Resource
    Electronic Resource
    Composite membranes for fuel-cell applications (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 93-100 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: One of the major obstacles to overcome for the realization of economical hydrogen-oxygen, polymer-electrolyte fuel cells is the high capital cost of the inert perfluorosulfonic acid (PSA) membranes, which provide a pathway for ionic transport between the cell electrodes. It has recently been shown that composite polymer membranes can be synthesized by depositing PSA polymers onto porous poly(tetrafluoroethyene) (PTFE) substrates. The resulting membranes are mechanically durable and quite thin relative to traditional PSA membranes; we expect the composite membranes to be of low resistance and cost. In this experimental study, we examine the composite membrane properties as a function of the membrane composition. Our results allow us to form a conceptual model to explain both the equilibrium and transport characteristics of these materials. For high PSA contents, the membrane behavior is similar to that of the PSA polymer; the water permeability, however, is reduced significantly. For intermediate PSA contents, the membranes have a high porosity and match the thickness of the PTFE substrate (≈50 μm); membranes of this composition range are potentially useful candidates for fuel cells because of their high resistance to water transport and reduced ionic resistance. Composite membranes of very low PSA content demonstrate characteristics similar to the hydrophobic PTFE substrate and are not of interest for fuel cells.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690380110
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  • 2
    Electronic Resource
    Electronic Resource
    Kinetics of sulfochlorination of cyclohexane in carbon tetrachloride induced by gamma radiation (1964)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 10 (1964), S. 930-934 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Solutions of cyclohexane, chlorine, and sulfur dioxide in carbon tetrachloride were irradiated in an oxygen-free system with gamma rays from uranium fission products contained in spent fuel elements. Reaction rates, equivalent to the rate of disappearance of free chlorine, were determined spectrophotometrically at 4,000Å. The reaction products were cyclohexanesulfonyl chloride and hydrochloric acid in nearly stoichiometric quantities. An empirical rate equation was derived, in which the rate of disappearance of chlorine was shown to be proportional to the square root of the product of the product of absorbed radiation, chlorine and cyclohexane concentrations, and independent of the concentration of sulfur dioxide. A chain mechanism was proposed, and the rate equation derived from this scheme was found to be in excellent agreement with the empirical rate equation. The reaction proceeded by a free radical mechanism, as evidenced by the strong inhibiting effect of oxygen. G numbers were of the order of 105, corresponding to an estimated chain length of 5,000, which is of the same order as the quantum yield of the photochemical sulfochlorination.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690100629
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  • 3
    Electronic Resource
    Electronic Resource
    Thermogravimetric kinetics of polymer degradation: Science or fiction? (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1309-1315 
    Details
    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: Weight changes in thermogravimetry are dependent on the volatility of the degradation products. Thus, molecular weight determinations (or related studies) must fist be undertaken to prove whether or not nonvolatile chain fragments will be removed only at high temperatures. In this case both thermal stability and kinetic studies by thermogravimetry are senseless. But even if volatile products are formed, the kinetic parameters will depend on the conversion degrees because of the kinetic chain character of the polymer degradation. Changes in reaction mechanism aggravate the situation; it is thus problematic to define in such conditions reliable kinetic parameters. Values calculated from a single TG curve are valid for specific conditions only, but of no sense from the general kinetic view.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321719
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  • 4
    Electronic Resource
    Electronic Resource
    Dielectric properties of plasticized melamine resins (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 68-72 
    Details
    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: During the last thrity years, dielectric measurements have been employed extensively to provide a better understanding of the interactions between polymer and plasticizer in various thermoplastic formulations. Recently, a series of melamine resins, plasticized to the extent that shrinkage and internal stress were modified, became available. Since there is little information in the literature concerning the dielectric properties of such thermosetting resins, a study was made of the variation of dielectric constant and loss as a function of frequency and temperature.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010206
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  • 5
    Electronic Resource
    Electronic Resource
    Press-forming of continuous-fiber-reinforced thermoplastic composites (1990)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 11 (1990), S. 114-120 
    Details
    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: Process-induced effects on thermoplastic-based composites were investigated for laminates processed under high production rate conditions. Press-formed carbon-fiber-reinforced poly(ether ether ketone) (PEEK) was used as a model system. The morphology and laminate quality were investigated on unidirectional laminates processed at cooling rates from 0.3 to 120°C/s and annealing of 177°C and 300°C. The laminate quality was examined for degree of consolidation, compaction, and fiber-matrix uniformity. Combined calorimetric and density measurements, as well as micrographic techniques, were used for examination of the laminates. The fracture toughness for the laminate was measured as a function of the position over the thickness of a 40-ply thick unidirectional laminate. This study clearly demonstrates the importance of uniform pressure distribution over the laminate to achieve a void free and homogeneous laminate.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750110207
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  • 6
    Electronic Resource
    Electronic Resource
    Solvent stress cracking and failure mechanisms in polyetherimide composites (1990)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 11 (1990), S. 240-249 
    Details
    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: Solvent stress cracking studies have been carried out in o-xylene and other solvents on polyetherimide (PEI) based materials including neat resin, woven fabric composites, and adhesively bonded systems. The results show crack growth in solvents at very low GI levels as compared with tests in air. The composite and adhesively bonded systems have sufficiently high residual thermal stresses to drive an array of intersecting matrix/adhesive cracks even without mechanical loading. The matrix/adhesive residual stress driven crack patterns in these systems are shown to retard main delamination crack growth relative to that in the neat resin, and to raise the applied threshold G1 level for main crack growth by about a factor of ten, as predicted by an approximate model.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750110407
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