DIFFUSION OF DYES IN REPEATING COMPOSITES

Abstract

Concentration distributions of dyes in composite film rolls are measured in the non-steady state. The composite film roll, which is used as a model of a composite membrane, is in the form of laminations of substrates A and B alternating with each other. We shall designate it as a repeating composite.
The films used are nylon 6, PET, and cellulose diacetate. P-aminoazobenzene and 1, 4-diamino-anthraquinone are used as dyes.
The original concentration profiles in the repeating composites show very intricate shapes. Smooth profiles, however, are obtained by the plots of the concentration per repeating unit, and apparent diffusion coefficient D^c and surface dye concentration C^c_s are evaluated by means of Sekido and Matsui's method.
The D^c agreed with the over-all diffusion coefficient D_s∞ which is proposed by Ash et al.⁷⁾ considering the partition of dye between A and B. It is found that the C^c_s is the equilibrium concentration of the dye in the repeating composite.