Dyeing of polyacrylonitrile fibers: I. Rates of diffusion with malachite green and diffusion model

Diffusion of the cationic (basic) dye, Malachite Green, into polyacrylonitrile fibers is shown to take place from a saturated surface layer even with relatively low solution concentrations. This makes possible a simple determination of the integral diffusion coefficient from one sorption‐time curve. In place of the commonly accepted model of dye diffusion, in which the fiber elements play a passive role, it is proposed that the motion in the polymer molecules constituting the fiber is the main factor governing the diffusion process at normal dyeing temperatures. In support, data are shown on the temperature dependence of the diffusion coefficient and its relation to fiber composition and mechanical behavior.