抄録
To study the interfacial electrical properties of the nylon 6 fibers grafted with acrylic and methacrylic acid and the surface dyeability of cationic dye on these fibers, the ζ-Potential of the fibers was measured in the aqueous solution of Methylene Blue. With an increase in the concentration of the dye, the sign of the ζ-potential changed from negative to positive and the amount of the dye adsorbed on the fiber surface increased. These results suggest that electrostatic interaction and van der Waals force act between the fibers and the dye. The amount of the adsorbed dye decreased with an increase in the degree of grafing.
The free energy of adsorption (Δ_??_) of Methylene Blue on the fibers was calculated from the slope of the ζ-log Cd (Cd: the concentration of dye) curve etc. The negative value of Δ_??_ decreased with an increase in the degree of grafting. The heat of adsorption (Δ_??_) was negative and the entropy of adsorption (Δ_??_) was positive. The positive value of Δ_??_ suggests the importance of entropic interaction (the formation of hydrophobic bond) as a driving force to the adsorption of the dye on the fiber surface. The negative values of Δ_??_ of the ungrafted and the grafted nylon 6 fibers were larger than those of the ungrafted and the grafted polyester fibers, and the Δ_??_ values of the former were smaller than those of the latter documented in our recent report. Therefore, the dependence of hydrophobic bond on the ungrafted and the grafted nylon 6 fibers was smaller than that on the ungrafted and the grafted polyester fibers. It is concluded that the surface dyeability of Methylene Blue on the grafted nylon 6 fibers is lower than that on the ungrafted nylon 6 fiber, because the water-soluble polymer layer is formed at the fiber surface due to the grafted polymer chains.
