Abstract
The crosslinking of viscose rayon staple fibers with bis-β-isocyanatoethyl disulfide (BIED) in dimethylformamide at 80°C was studied. From the sulfur contents of the product (DTV) and its reduction product (RDTV), the crosslinking efficiency (the ratio of BIED forming crosslinks to total BIED combined in DTV) was calculated. The efficiency increased with the reaction period and was greater than that for the reaction of of cotton with BIED conducted under similar conditions. Cadoxen solubility test indicated that disulfide crosslinks in DTV were cleaved by reduction with tri-n-butyl phosphine and reformed by successive oxidation with air in buffer.
The stress strain behaviors of DTV, RDTV, and its oxidation product (ORDTV) were measured in toluene, water and 50% aqueous urea. The breaking elongation of crosslinked rayon fibers (DTV and ORDTV), in any of the solvents, decreased with increasing crosslinks. The breaking strength and the stress at 30% elongation in toluene changed little by crosslinking. The stress at 3% elongation of the rayon fibers in water and 50% aqueous urea increased remarkably by crosslinking with BIED, decreased to the level of control sample by successive reduction, and increased again by the following recrosslinking by oxidation. The breaking strength of the rayon fiber in 50% aqueous urea increased slightly by crosslinking. The reversible nature of the mechanical properties of reversibly crosslinked rayon fibers was demonstrated.
