The absorption of direct dyes by crosslinked cellulose. II. Rate of dyeing and diffusivity

Authors

  • E. Chianakwalam Ibe,

    1. Fibers and Polymers Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
    Current affiliation:
    1. The Nigerian National Oil Corporation, P. M.B. 12650, Lagos, Nigeria
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  • Emery I. Valko

    1. Fibers and Polymers Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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    • Deceased June 20, 1975.


  • This paper is based on the thesis of E. Chianakwalam Ibe submitted in May 1970 to the Massachusetts Institute of Technology in partial fulfillment of the requirements for the degree of Doctor of Science.

Abstract

The effect of crosslinking in the dry state on the rate of dyeing of cellophane with two direct dyes, Chrysophenine G and Chlorazol Sky Blue FF, has been studied. Dimethylolethyleneurea and bis(hydroxyethyl) sulfone were the crosslinking agents. It was found that the rate of dyeing was reduced at high degree of crosslinking by more than 90%, whereas the amount of dye absorbed at equilibrium was reduced by only 40%. It was concluded that the major factor in the practical undyeability of the crosslinked cellulose fibers in commerce is the reduction of the rate of dyeing rather than that of the absorption at final equilibrium. The average diffusivities of the dyes in the cellulose film were calculated from the rate data. The diffusion coefficients as functions of the dye concentration in the films were estimated from the diffusivity values. The two models of swollen cellulose, the pore model and the gel model, were applied to explain the effect of crosslinking on the diffusion coefficients. The pore model offers a satisfactory explanation by assuming that crosslinking reduces the average pore diameter and therefore increases the drag and also the tortuosity. The gel model offers an equally satisfactory explanation by assuming that crosslinking reduces the free volume by increasing the rigidity and concentration of the cellulose chains in the cellulose gel.

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