The Effect of pH and Detergents on the Felting of Shrink-Resistant Wool

Abstract

The rate of felting of an untreated wool fabric increases with decreasing pH of the felting solution over the pH range 2-10. The felting rate is increased at all pH values by the addition of nonionic detergent to the solution. The felting, relative to untreated wool, of wool made shrink-resistant with perman ganate/salt, acid chlorine, permonosulfuric acid followed by sulfite, permanganate hypo chlorite, peracetic acid/hypochlorite, hypochlorite at pH 8, or gaseous chlorine increases with decreasing pH of the felting solution. The magnitude of this effect can he reduced by treatment with higher concentrations of reagents. After treatment with reagents of the concentrations used industrially, no change in felting rates with pH can be de tected at pH values above 5. The actual rate of felting of wool treated with reagents of these concentrations is low and is not significantly affected by the addition of soap or nonionic detergents to the solutions. The felting, relative to untreated wool, of wool treated with ethanolic thioglycolate, aqueous hisulfite (on extracted wool). hydrogen peroxide folluwed hy bisulfite, ethanolic sodium hydroxide, or sodium hydroxide saturated salt does not vary with pH in the absence of detergent. Felting is increased by the addition of detergent to the solutions. In detergent solutions, the relative felting of wool treated with ethanolic thioglycolate, aqueous bisulfite (on extracted wool), or hydrogen peroxide bisulfite does not change with pH. hut the relative felting of wool treated with sodium hydroxide in ethanol or saturated salt solution reaches a maximum at pH 7-9. Frictional properties of fibers treated with some of the reagents have been measured (by the capstan method using a keratin rod at different pH values in the presence and absence of detergent. Felting behavior does not appear to be explained by these fric tional properties alone. Some other property, or properties, of treated wool, which vary differently with pH than do similar properties of untreated wool, must play a part in felting.