Controlling Shrinkage in Wool Fabrics: Effective Hydrogen Peroxide Systems

Abstract

Alkaline hydrogen peroxide (H2O2) systems, including dicyandiamide, gluconic acid, and Triton X surfactant, used alone or followed by enzyme treatments, are investigated for their effectiveness in imparting shrinkage resistance to wool fabrics. Fractional factorial analysis shows that H2O 2 is the most important factor and enzyme the second contributing factor in shrinkage control. An effective H2O2, nonenzymatic system with Triton X-114 limits structural changes to surface smoothing of the fibers and yields a relative area shrinkage of 2.95%. Another effective H2O2 system, using the same pretreatment but followed by an enzymatic treatment with additives—polyacrylamide to restrict enzyme activity to the fiber surface and sodium sulfite to reduce disulfide linkages—yields 1.16% area shrinkage. The most important factor in shrinkage control is replacing the hydro phobicity of the wool's surface with an anionic charge through the formation of cysteic acid. This leads to the release of 18-methyleicosanoic (18-MEA) acid from the fiber surface and underlying cell membrane complex attached to the surface scales of wool through thioester linkages. TLC, FTIR, and EI-MS are used to prove the presence of fatty acids and 18-MEA in spent baths and in extracts of the treated fabrics. Imparting hydrophilicity to wool by conferring an anionic charge suggests new possibilities for wool reactivity.