Submitted to: International Wool Textile Research Conference Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2005
Publication Date: 9/1/2005
Citation: Cardamone, J.M., Yao, J. 2005. Activated peroxide-assisted enzymatic control of wool shrinkage. In: Proceedings of the International Wool Textile Research Conference, Coloration and Chemical Finishing. p. 36CCF, ISBN 0-9553154-0-9, 978-0-9553154-0-4. Interpretive Summary: The raised scales on wool are responsible for shrinkage and this limits consumer acceptance and market share. The demand for shrinkproof wool necessitates its being imported from countries that allow chlorination (not permitted in the United States). Alternatively, biopolished wool, made by an ARS-patented process that smoothes the outer scales of the wool fiber, provides itch-free, machine-washable wool without chlorination. The optimum conditions for the use of two enzymes used in this technology were established through various treatments involving the presence or absence of sulfur compounds conventionally used with enzymes to control shrinkage. Both enzymes proved to be effective for controlling area shrinkage to less than 3%. Results show that either enzyme can be selected for specific effects such as greater whiteness, less strength loss, and greater processing ease, though certain trade-offs apply -- one of the enzymes provides greater strength retention and greater processing ease but less whiteness. From scanning electron micrographs of the ARS-processed fibers, scale smoothing in medium-grade domestic wool was comparable to what is observed in fine-grade imported wool. For the first time comfortable, machine-washable wool can be made completely from United States domestic sources and resources.
Technical Abstract: To control the dimensional stability of wool, enzymes can modify the scalar surface structure by proteolysis of the polypeptide network so that the surface properties no longer assist in entanglement. Wool is resistant to enzyme attack. Efficient enzymatic systems generally include a reducing agent to rupture peptide linkages and cystine disulfide cross linkages by hdrolysis and oxidation. We have designed effective systems to control shrinkage by pretreating wool with a stable, activated peroxide followed by proteolysis treatment with either serine or cysteine protease. In the ARS patented process for whitening, biopolishing, and shrinkage control, wool fabrics are pretreated at 30 C for 30 minutes with a powerful, stable peroxide, peroxycarboximide, formed from dicyandiamide and alkaline hydrogen peroxide with gluconic acid stabilizer for sustained whitening. Subsequent treatment at 45 C for 40 minutes with serinase assisted by sodium sulfite or unassisted cysteinase applied at 50 C for 60 minutes biopolishes and controls the shrinkage of wool woven and knit fabrics of various fabric weights and constructions without appreciable loss in strength. The process provides bleached, Biopolished, machine-washable wool that can be worn with "itch-free" comfort.