Wettability of polymers by aqueous solution of binary surfactants mixture with regard to adhesion in polymer–solution system I—Correlation between the adsorption of surfactants mixture and contact angle

Abstract

Wettability of polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA) and nylon 6 by aqueous solutions of binary mixtures composed of cetyltrimethylammonium bromide (CTAB) with p-(1,1,3,3-tetramethylbutyl)-phenoxypolyoxyethylene glycols, Triton X-100 (TX-100) and Triton X-114 (TX-114) with regard to the tendency of their adsorption at the water–air and polymer–water interfaces was considered on the basis of the measured values of the contact angle, the dependence between the adhesion and surface tension as well as the Gibbs surface excess concentration. It was shown that the wettability of PTFE, PMMA and nylon 6 depends on the concentration and composition of the binary mixtures of surfactants in water and the best wettability occurs at the concentration of the mixtures corresponding to the critical micelle concentration of their solutions. However, at the lower concentrations the synergetic effect in the wettability of polymers by the CTAB+TX-100 and CTAB+TX-114 mixtures takes place. This effect was confirmed by the standard Gibbs free energy of adsorption of binary mixtures of surfactants at the polymer–water interface calculated on the basis of the Gu and Zhu equation. The standard Gibbs free energy of adsorption being a measure of the efficiency of a given mixture to adsorb at the polymer–water interface changes in a different way from the maximal Gibbs surface excess concentration of these mixtures calculated from the Gibbs isotherm equation which suggests that the changes of the efficiency of the adsorption process are not proportional to its effectiveness.