Abstract
In order to discuss wetting behaviors of wool fibers, three kinds of sample having different surface layers (the greased, degreased and descaled wool fibers) were prepared and the ζ-potentials were measured under various conditions. The results were as follows;
i) In preliminary dyeing experiments, a high affinity of the greased wool fiber to the basic dye and the increase in acid dye-sorption on this fiber with the addition of nonionic surfactant were shown. Then, these are discussed on the basis of the fact that the grease adherent on wool showed a negative ζ-potential. From this discussion and the streaming potential vs. pressure loss curves, it was found that even in the case of the greased wool, air bubbles absorbed on the fiber-surface could be removed by the forced streaming of dip-solution through the fiber assembly.
ii) Although the ζ-potential of the greased wool fiber was negative over the entire pH-region examined, ζ vs. pH curves of the degreased and descaled wool fibers cut the holizontal axis. In latter cases, the isoelectric points (pKI) were 3.5 and 4.3, respectively.
iii) From pKI value of cortex layer estimated from the dyeing method and from ζ vs. pH curves for the above three samples, it is concluded that the lower pKI value obtained on the degreased wool, whose surface is surrounded by intact scales, are due to the structure and properties of the surface layer. These considerations are quite in accord with the fact that the lower critical surface tension, i.e. 30dyne/cm, as compared with the values reported by other authors, for the intact degreased wool fiber.
