1993 年 27 巻 2 号 p. 152-158
The adsorption of Octadecyltrimemmonuim chloride (C18 TAC)/Sodium-N-lauroyl-N-metyl-β-alanine (NaLMA) mixed system on keratin powder which was used as substitute for human hair was studied. The adsorption isotherm of C18 TAC showed irreversible adsorption, resulting in the decrease of the kinetic frictional coefficient compared to other cationic surfactants (C10TAC, C12TAC, C14TAC, C16TAC). The adsorption istherm of NaLMA was of the Langmuirtype, but those of C18TAC/MaLMA mixed system showed irreversible adsorption owing to strong interaction with keratin powder. The amount of adsorption was maximum at molar ratio 7/3 of C18TAC/NaLMA. At the same ratio, the kinetic frictional coefficient and denaturation rate showed minimum values. That the behavior of C18TAC/NaLMA mixed system is similar to nonionic surfactant aqueous solution and that the monomer concentrations of C18TAC having the strong interaction decrease by formation of ionic pair between C18TAC and MaLMA may suffice as explanation for the above results.