Study on the effect of organic phosphonic compounds on disulfide bonds in wool

In this study a new type of organic phosphonic compound named LKS-610, a kind of reducing agent, was used to cleave disulfide bonds in wool fibers. Research into the extraction of keratin from wool and processing into useful textile materials is a hot topic in the field of textiles. Wool fibers are rich in disulfide bonds which are the main chemical cross-linkage to maintain the fiber's secondary structure. If the disulfide bonds between molecular chains can be sufficiently disrupted, it will facilitate to obtain the keratin solution suitable for the regenerated materials preparation. The reaction mechanism and effect were analyzed through scanning electron microscopic test (SEM), X-ray photoelectron spectroscopy test (XPS) and amino acid content test. After a period of processing time, the valence state of sulfur element on fiber surface changed significantly; this result shows that the disulfide bonds reacted with LKS-610 reagent and generated thiol groups. Amino acid analysis demonstrated that for wool fibers treated for 60 min at 80℃, the quality percentage of cystine in wool was reduced from 10.09% to 1.05%, the majority of disulfide bonds had been cleaved. In this case, fiber scales were almost completely stripped and the cortical layer was not significantly damaged but became prone to swelling. This indicated that LKS-610 reagent could disrupt the disulfide bonds in the wool thoroughly and efficiently, and reduce these bonds to thiol groups. Wool fibers pretreated by LKS-610 reagent can be dissolved readily to prepare keratin solution; this keratin solution with high dissolution ratio and large molecular weight can be used in research into modification and preparation of regenerated protein materials.