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  • 1
    ISSN: 1435-1528
    Keywords: Key words Mixed cationic surfactants ; Turbulent drag reduction ; Rheology ; Apparent extensional viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Experimental studies of the effects of mixtures of cationic surfactants on their drag reduction and rheological behaviors are reported. Cationic alkyl trimethyl quaternary ammonium surfactants with alkyl chain lengths of C12 and C22 were mixed at different molar ratios (total surfactant concentrations were kept at 5 mM with 12.5 mM sodium salicylate (NaSal) as counterion). Drag reduction tests showed that by adding 10% (mol) of C12, the effective drag reduction range expanded to 4–120 °C, compared with 80–130 °C with only the C22 surfactant. Thus mixing cationic surfactants with different alkyl chain lengths is an effective way of tuning the drag reduction temperature range. Cryo-TEM micrographs revealed thread-like micellar networks for surfactant solutions in the drag reducing temperature range, while vesicles were the dominant microstructures at non-drag reducing temperatures. High extensional viscosity was the main rheological feature for all solutions except 50% C12 (mol) solution, which also does not show strong viscoelasticity. It is not clear why this low extensional viscosity solution with relatively weak viscoelasticity is a good drag reducer.
    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 28 (1990), S. 3185-3219 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present results of molecular orbital thory calculations of the interactions of acrylic polymers with aluminum, with a view toward understanding the nature of chemical bonding at the corresponding polymer-metal interfaces. The reported results are for the interactions of polymer model compounds with metal atoms (as opposed to our ongoing studies with metal surfaces). As such, the results relate to experimental studies where small dosages of metal atoms are evaporated onto polymer surfaces in pristine high vacuum environments. Our studies have been conducted within the theoretical framework of Hartree-Fock molecular orbital theory. We find that aluminum atoms interact primarily with the carbonyl group of acrylic polymers. The reaction proceeds by the metal atoms interacting with both the carbon and the oxygen atoms of the carbonyl functionality. This weakens the C=O bond. Finally, the carbonyl bond loses double bond character, and strong AL - O bonds are formed. Our results are compared to experimental data, and the implications of the detailed nature of bonding for adhesion applications are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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