The influence of capillarity on the location of liquid soils on textile fabrics

Abstract

A survey is made of published work on the location of oily soil on textile fabrics. There is evidence that such soil tends to build up at certain preferred sites in the fabric, such as between parallel fibres in the yarn. A theoretical explanation is developed which correlates these observations. Because the shape of a droplet of oil of given volume depends upon the local geometry and contact angle at the site where it is located, different sites are associated with different Laplace internal pressures in the drop. It is shown that differences in these internal pressures between sites can bring about a thermodynamically favored movement of the droplet towards sites where the Laplace excess pressure is least. On this basis, a heirarchy of sites can be constructed and this is found to parallel the observed favor of sites for oily soil in fabrics.