Abstract
Purposing for precise evaluation of water-repellency of surface active agents, authors have devised the following new simple method. A filter paper (5 × 5 cm2) for use of paper-chromatography is treated under definite conditions with aqueous solution of the surfactant to be tested, then dried and conditioned in a desiccator. A small amount of water (0.01-0.04 ml) is made flow down upon the treated paper from the graduated capillary tube (the inner diameter : 0.4-0.6 mm), inclined at 10-30 degrees and equipped perpendicular to the paper so as to lightly touch the paper with its sharpened tip (the outside diameter : 1.0-3.0 mm). By recording migration of meniscus in the capillary at every time interval, the wetting time of the paper is determined.
The results measured for several cationics and commercial water-repellent products, indicated that this method gives satisfactorily reproducible data and also could serve efficiently for examining the structural effects of hydrophobic part of a surfactant on the water-repellency.
