Wettability and adsorption of PTFE and paraffin surfaces by aqueous solutions of biquaternary ammonium salt Gemini surfactants with hydroxyl

The surface tension of five biquaternary ammonium salt Gemini surfactants with hydroxyl and the corresponding contact angles (theta) on Polytetrafluoroethylene (PTFE) and Paraffin are measured. The interfacial properties of surfactant solution in liquid-air-solid are investigated and changes in spreading coefficient (S), adhesive tension (gamma(LV)cos theta) and the work of adhesion (W-A) are discussed. The obtained results indicate that the surface tension decreases with the increase of surfactant concentration, and it tends to be stable when the concentration is more than CMC. The contact angle has the similar trend with surface tension. A linear relationship exists between the adhesional and surface tension in a range of certain concentrations, the slope is less than 1. It means that the adsorption amount of the surfactant solution at the liquid-air interface is larger than that at the PTFE-water interfaces. However, there is no linear relationship between the adhesional and surface tension for Paraffin-surfactant solution systems. The adhesional tension increases with the increase of concentration, and it keeps constant when the saturated adsorption film has been formed at both liquid-air and solid-liquid interfaces. The wettability of biquaternary ammonium salt Gemini surfactants with hydroxyl solutions on PTFE is poorer than that of Paraffin. The wettability of C-10-OH solution on PTFE surface is best, and C-14-OH solution has the best wetting effect on Paraffin. (C) 2016 Elsevier B.V. All rights reserved.