Original scientific paper

Steady-State Relaxation Times for Surfactant Films at the Water/ Air Interface

Dj. Dragčević ; Laboratory of Electrochemistry and Surface Phenomena, Center for Marine Research, »Ruder Boskovic« Institute, Zagreb, Croatia, Yugoslavia
V. Pravdić ; Laboratory of Electrochemistry and Surface Phenomena, Center for Marine Research, »Ruder Boskovic« Institute, Zagreb, Croatia, Yugoslavia

Abstract

Relaxation times were measured for the surface tension
relaxation of spread and soluble surface films at the water/air
interface. Measurements were done in a modified Langmuir trough
with a Wilhelmy Pt sensor attached to an electrobalance using
surface sweeping rates between 6.4 and 57.6 Hz-1•
The relaxation times were determined in the stationary state
from the phase angle between the perturbation function (surface
sweeping) and the response function (dynamic surface tension). The
calculated values for the relaxation times of oleic acid films were
between 0.25 and 1.25 s, and were inversely proportional to both
the rate of sweeping and to the concentration of molecules in the
surface film. For the soluble surfactant, sodium dodecylsulfate, the
relaxation times were reaching a minimum value of 0.2 s, at a bulk
concentration between 9.1 and 18.3 ~t mol dm-3•

Keywords

Hrčak ID:

194610

URI

https://hrcak.srce.hr/194610

Publication date:

5.5.1980.

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