ABSTRACT
The surfaces of fibers treated with a repellent are not homogeneous but are covered with patches or islands deposited during chemical finishing. Although the critical surface tension concept has been criticized for its empirical nature, critical surface tension data have been very useful in developing water- and oil-repellent finishes. Since modern rainwear fabrics are made water repellent by chemical finishing, the main concern is to select the fabric structure best suited for finishing with repellent chemicals. The nature of the support under the repellent fabric and its compressibility are important. One of the oldest water repellents is aluminum acetate hydrolyzed on fibers to basic aluminum acetates and hydroxides of undefined structure. The poor adhesion and dusting of the repellent was a major shortcoming of the finish. The oldest and most economical way to make a fabric water repellent is to coat it with a hydrophobic substance, such as paraffin.
