The Swelling of Hair and a Viscose Rayon Monofil in Aqueous Solutions

Equipment for measuring the swelling of nearly round single fibers in a variety of solutions is described and has been used to make measurements on the swelling of human hair and a viscose rayon monofil. In particular, measurements have been made on the swelling of both types of fiber in various alkali halide solutions and of the hair in HCI solutions. Except for NaCl solutions, the solutions used in this work caused swelling beyond that caused by liquid water, indicating that the solutes were absorbed by the fibers. The results using LiCl and LiBr solutions are noteworthy in that considerably more swelling occurs in these solutions than in water. The increase in swelling over the water-swollen value is about 25% in the case of hair and 60% in the case of rayon. The high degrees of swelling of hair must be reached by successive replacement with increasingly concentrated solutions, direct immersion of a water-swollen hair into a concentrated solution causing deswelling. For the viscose rayon, either method causes similar swelling. The swelling changes in hair caused by altering the different variables common in an acid dye bath for wool have also been studied.