抄録
A biaxial film extending apparatus has been developed to investigate the dynamic property of the liquid film originated from aqueous poly (oxyethylene)-9-octadecenyl ether (_??_=15) solution. Using this apparatus, the effects of addition of acid dyes (C. I. Acid Red 134 and C. I. Acid Green 25) on the thickness of liquid film at its rupture were investigated. The thickness was estimated from the relationship between the adopted liquid volume and the film area at its rupture by the method of double regression analysis with simplification of the film construction. The thickness of liquid films at their rupture passed through the minima in the nonionic surfactant concentration region from 1.8×10-3 to 2.8×10-3mol dm-3 (c. m. c. under dynamic condition) and generously increased beyond these concentration. At the concentration below the c. m. c., the surface movement, the so-called Plateau-Marangoni-Gibbs effect, and also the surface adsorption of the surfactant molecule effected on the thickness. At the concentration above the c. m. c., a black spot appeared in the extended liquid film because of local thinning and nonhomogeneous film thickness. The black area, of the film was observed to behave like a rigid film. This rigid region affected the transformation of the film in the dynamic condition. Further, the larger the velocity of wire movement was, the smaller the film thickness at its rupture was, and the minimum of the curve appeared more concentrated region. This suggests that the dilational viscoelasticity of the film influences the film thickness at its rupture. When the surfactant concentration was lower than the c. m. c., the addition of C. I, Acid Red 134, with large hydrophobic moiety, considerably increased the film thickness. At the concentration higher than the c. m. c., its differential thickness became small. On the other hand, the addition of C. I. Acid Green 25, with moderate hydrophobic moiety, scarcely effected on the film thickness at its rupture. Therefore, the acid dye, with large hydrophobic moiety, adsorbed on the film surface and affected the surface movement of the surfactant molecule.
