Lubrication of synthetic fibers with surfactants — a complex surface-chemical process at the phase boundary solid/liquid

Abstract

The lubrication of fibers by surfactants is a surface-chemical process including several simultaneous events like wetting, spreading, and adsorption, which have to take place within the very short time of a few milliseconds.

Some theoretical aspects are given and the difficulties of their transfer to the real system of polymeric fibers with their bent, irregular, and inhomogeneous surfaces are discussed. Results are given for the adsorption of ionic surfactants: In solutions containing more than 1·10⁻³ mol/l of surfactant, multilayers are created on the surface. Presence of nonionics increases the adsorption of cationic surfactants.

The investigation of wetting speed furnished only small differences at the same molar concentration of different surfactants. Wetting speed increases significantly with increasing concentration. It does not depend on surface tension of the solution.

As a special case of wetting, we considered heterocoalecence: spreading of oil droplets in surfactant solutions on solid surfaces as a model for lubrication by oil-in-water emulsions. A transition concentration C _T of surfactant has been proved depending on the nature of surfactant and the solid. This concentration is the limit between spreading and nospreading of the oil droplets indicating the suitability as detergent or as a part of lubricating oil-in-water emulsion.