Moisture regain curve

Moisture-regain curves for cellulose acetate and triacetate fibers compared with those of kier-boiled cotton are shown in Figure 11.5 [56,57]. The curves for acetate fiber are positioned only slightly below those for cotton and actually mesh for intermediate values of relative humidity. Since moisture regain relates to the comfort factor of fabrics, the curves explain why cellulose acetate, like cotton, possesses this important characteristic. 

The moisture-regain curves for triacetate fiber are positioned below those of acetate fibers, as expected, because triacetate is more hydrophobic. However, the curves for triacetate show substantial moisture regain at high relative humidity. Therefore, triacetate fabrics also possess the comfort factor, even though they have the wash-and-wear and ease-of-care characteristics. 

FIGURE 11.5 Comparison of moisture-regain curves for cotton, cellulose acetate, and triacetate. (From Beever, D.K. and Valentine, L. J. Text. Inst., 49, T95, 1958 Kirk Othmer Encyclopedia of Chemical Technology, 2nd ed., vol. 4, John Wiley, NewYork, pp. 599-600, 1991.)... 

Because nylon-3 had a high amide concentration, a high moisture regain was expected. In Figure 7, the moisture regain curve of nylon-3 fibers is shown compared to silk. At a relative humidity of 65 %, the undrawn nylon-3 fibers have a moisture regain value of 9 %, which is quite similar to that of silk. Furthermore, the moisture regain curve was also quite similar to that of silk. 

Figure 7. Moisture regain curve of nylon-3 fibers [11].

Another important consideration is to ensure that the test is conducted with the libers in moisture ec uilibrium approached from the dry side of the hysteresis curve (see later). Alternatively, the oven-dry weight may be taken and an allowance made for the commercial moisture regain. If the yarn is sized or contains other finishes, cither an allowance can be made for these or the yarn can be scoured and desized prior to testing. 

Figure 3.9 Dye exhaustion curves for control and plasma-treated nylon 6 fibers with different moisture regains (a) acid dye and (b) dispersive dye (Zhu et al., 2007).

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