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Viscoelastic Behavior of Synthesized Liquid Soaps and Surface Activity Properties of Surfactants
Author(s) -
Bratovcic Amra,
Nazdrajic Sanela
Publication year - 2020
Publication title -
journal of surfactants and detergents
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.349
H-Index - 48
eISSN - 1558-9293
pISSN - 1097-3958
DOI - 10.1002/jsde.12444
Subject(s) - chemistry , pulmonary surfactant , critical micelle concentration , surface tension , viscoelasticity , viscosity , thermodynamics of micellization , adsorption , rheology , ionic liquid , ionic strength , shear rate , activation energy , shear thinning , micelle , chromatography , analytical chemistry (journal) , thermodynamics , organic chemistry , aqueous solution , catalysis , biochemistry , physics
In the present work, a rheological study of liquid soaps prepared from different mixture of surfactants as a function of surfactant type and concentration was performed. The curves of shear stress vs. shear rate and viscosity vs. shear rate were recorded at constant temperature, 294 ± 0.1 K. The surface activity properties were also studied. The results of the study showed that values of surface tension, γ, were in the range 31–40 mN m −1 and the critical micelle concentration (CMC), was of the order 10 −4 mol L −1 . The calculated maximum surface excess, Γ max , varied from 2.40 to 3.66 μmol m −2 , while minimum area per molecule, A min , varied from 41.1 (for amphoterics) to 81.4 Å 2 (for nonionic surfactants). The standard free energy of micellization,∆ G m 0 −29.8 and −29.3 kJ mol −1 for anionic and amphoteric surfactants, respectively, were while values for nonionic surfactants varied between −31.8 and − 30.3 kJ mol −1 . The free energy of adsorption,∆ G ads 0 was the lowest for amphoteric surfactants (−37.9 kJ mol −1 ), followed by anionics (−40.4 kJ mol −1 ) and nonionics (−43.34 to −46.84 kJ mol −1 ), indicating that micellization process is spontaneous in the examined medium. The synthetized liquid soaps show pseudoplastic behavior and they achieved pipe flow. The results of this research indicate that flow behavior was affected significantly by the ionic charge of the surfactant and the ionic strength of the formulation, suggesting that the flow behavior could be changed by manipulating the choice of the surfactant and salinity. The pH value of all liquid soaps examined were weakly acidic, in the range of 5.0–6.4.