Elasticity of foam bubbles measured by profile analysis tensiometry
Elasticity of foam bubbles measured by profile analysis tensiometry
复制标题
DOI：
10.1016/j.colsurfa.2010.08.008
复制
发表时间：
2010-10
期刊：
影响因子：
--
通讯作者：
S. Karakashev;Roumen Tsekov;E. Manev;A. Nguyen
中科院分区：
文献类型：
--
作者：
S. Karakashev;Roumen Tsekov;E. Manev;A. Nguyen
Elastic modulus of foam bubbles, stabilized with tetraethylene glycol octyl ether (C8E4) and 1×10−5M NaCl, was determined by cyclic expansion and shrinking of foam bubbles with frequency of 0.1Hz and volumetric amplitude of 2mm3. The film tension was monitored by a commercial profile analysis tensiometer (Sinterface Technologies, GmbH). The elastic moduli of foam bubbles were obtained as a function of surfactant concentration in the range of 2×10−3–1×10−2M. The theory of Lucassen and van den Tempel [1] for the elastic modulus of a single liquid/air interface at a given frequency was employed. In the theoretical analysis the bulk diffusion coefficient of surfactant molecules was considered as a unknown model parameter which was obtained by matching the theory with the experimental data. Hence, the dependence of the bulk diffusion coefficient of C8E4molecules upon the C8E4concentration was obtained. The diffusion coefficient reached a maximum at 5×10−3M C8E4(D=8.5×10−11m2/s). In the experimental surfactant concentration range (2×10−3–1×10−2M, CMC=7.5×10−3M) the foam bubbles were relatively dry, with visible interferometric fringes corresponding to thin films stabilized by repulsion of the electrostatic disjoining pressure. Hence, the overall dynamics of periodical expansion and shrinking of the foam bubbles occurred within the thin film state.
