Wetting of Low-Energy Surfaces by Nonaqueous Solutions of Dimethyl-Siloxane-Containing or Fluorocarbon-Containing Surfactants

摘要

The wetting of low-energy solid surfaces by nonaqueous solutions has been investigated with solutions of copolymers of dimethylsiloxane-ethylene oxide and solutions of fluorocarbon-containing surfactants. The organic liquids studied were propylene carbonate, bis(2-ethylhexyl)sebacate, isopropylbiphenyl, and a partially chlorinated biphenyl. Surface-tension-vs-concentration isotherms were determined for the surfactants in these liquids. The solid surfaces studied were stearic acid and 11-(perfluorodecyl)undecanoic acid monolayers on stainless steel, polyethylene, and Teflon. In nearly all instances, the surfactants produced a marked improvement in the wetting of the low-energy surfaces by the organic liquids; however, they did not cause spontaneous spreading of the organic liquids on the smooth, solid surfaces, even when when the solution surface tensions were depressed below the critical surface tensions of wetting of the solids. The failure of these surfactants to cause spontaneous wetting appears to be related to (a) the adsorption of the surfactant at the organic-solid/air interface and (b) the failure of the surfactants to significantly reduce the organic-solid/organic-liquid interfacial tensions. (Author)