Wettability prediction of such polymers as polyethylene and polytetrafluoroethylene by aqueous solutions of classical surfactants and biosurfactants

Abstract

The measurements of the contact angle (θ) of aqueous solutions of rhamnolipid (RL), n-octyl-β-d-glucopyranoside (OGP), Triton X-100 (TX-100) and sodium dodecylsulfate (SDDS) on the polyethylene (PE) surface were carried out. The θ values on PE and polytetrafluoroethylene (PTFE) were also determined theoretically by using the values of surface tension of polymers and the Lifshitz-van der Waals component of water surface tension. On the basis of θ values of surfactant solutions on PE the critical micelle concentration of RL, OGP, TX-100 and SDDS, critical surface tension of PE wetting (γC), Gibbs surface excess concentration of these surfactants at the PE-water interface, work of adhesion of surfactant solutions to PE, fraction of PE occupied by surfactant molecules and Gibbs standard free energy of surfactants adsorption at the PE-water interface were established. The γC of PE wetting from the relationship between the adhesion and surface tension of surfactant solutions and standard Gibbs free energy of adsorption from the Langmuir equation were determined. The standard Gibbs free energy of adsorption at the PE-water interface was compared to that at the water-air one. The good agreement between the measured and calculated θ values of RL, OGP, TX-100 and SDDS solutions on PTFE and PE was obtained.