ISSN:
1435-1528
Schlagwort(e):
Key words Mixed cationic surfactants
;
Turbulent drag reduction
;
Rheology
;
Apparent extensional viscosity
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
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.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/s003970000088
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