Wetting and absorbency of nonionic surfactant solutions on cotton fabrics

The effects of changing aqueous solution properties by nonionic surfactants on the wetting and absorbency in cotton fabrics are reported. A range of s olution properties were produced by mixing and diluting two nonionic surfac tants, i.e., sorbitan monolaurate (Span 20) and polyoxyethylene(20) sorbita n monolaurate (Tween 20). Desizing and alkaline scouring were employed to p roduce hydrophobic and hydrophilic cotton fabrics. The molecular areas at w ater/air interface of individual surfactant molecules, derived from Gibbs a dsorption equation, are 19.4 and 60.3 Angstrom (2) for Span 20 and Tween 20 , respectively. Span 20 has lower surface tension at critical micelle conce ntration (CMC) and small molecular area, indicating it is more efficient in lowering the surface tension and effective in adsorption than Tween 20. Th e wetting properties of hydrophobic cotton fabrics are greatly improved by addition of nonionic surfactants in the aqueous systems. The cosine contact angles (theta) of aqueous liquid increased with decreasing liquid surface tension (gamma). The amount of aqueous liquid retained in the pore structur e of cotton fabric also increased with decreasing gamma until the concentra tion of surfactants approached CMC. In diluted surfactant systems, aqueous liquid retention dramatically increase near CMC, even though the increases in cos theta 's were relatively small. The existence of micelles in a nonio nic solution is important for the retention of the aqueous solution in the fabrics. The aqueous retention (W) in cotton fabrics is positively related to its wetting behavior (cos theta) and negatively related to the liquid ga mma. The critical surface tension of the unscoured cotton fabric, estimated from dilutions of Tween 20, is found to be 28.0 dyn cm(-1). (C) 2001 Elsev ier Science B.V. All rights reserved.