STUDIES ON THE DYEING PROPERTIES OF SPANDEX FIBER AND THE STRESS RELAXATION OF WET-TREATED AND DYED FIBERS

Abstract

The chemorheological and dyeing behaviors of spandex fiber were studied.The equilibrium adsorption of acid dyes on the spandex fiber at 70°C and 90°C was investigated. The dyes used are C. I. Acid Orange 7, Blue 25 (monosulphonates) and C. I. Food Yellow 3 and Acid Blue 45 (disulphonates). The stress relaxation measurements were carried out in air at 120°C for 10 hrs. under 100% or 10% elongation on the wet-treated and dyed spandex fibers.The results obtained are as follows:(1) From the adsorption isothers (Figures 2 and 3), it is suggested that the adsorption of dye acids on the spandex fiber at 70°C is of a L+C type proposed by Giles. The adsorption isotherms at 90°C are irregular compared with that at 70°C. But the tensile strength and elongation of the fibers dyed at 90°C decrease remarkably (Table 2). The dyeing behavior at 90°C may be due to the degradation of the spandex fibers.(2) The stress relaxation data of the wet-treated and dyed spandex fibers are plotted in the forms of f(t) and f(t)/f(0) vs. log t (Figures 5 to 8). The spandex fibers dyed with disulphonated dye acids and treated with water have the almost same initial stress values (f(0)) as those of the untreated fibers. On the other hand, the fibers dyed with monosulphonated dye acids have lower initial stress values (Table 2). However, the stress relaxation curves (f(t)/f(0) vs. log t) of the untreated, wet-treated and all dyed fibers are essentially identical. The decay of the stress (Fig. 8) therefore seems to be independent of the initial concentration of network chains (n(0)). As indicated by Tobolsky and others, the fact that f(t)/f(0) is independent of n(0) suggests that cleavage takes place at the network junctures or at the neighbourhood for the untreated, wettreated and all dyed fibers. At present, it is not possible to identify the broken linkages responsible for stress decay.(3) The intermittent measurement at 120°C shows no stress decay up to 10 hrs. for both the dyed spandex fibers and the untreated ones. It is suggested from this fact that the stress relaxation in the deformed state might be attributed to the cleavage of the network junctions, which are easily reformed after the removal of stress.