A study of the diffusion behaviour of reactive dyes in cellulose fibres using confocal Raman microscopy

Abstract

Confocal Raman microscopy was used as a non‐destructive tool for in situ investigation of the diffusion of CI Reactive Blue 194 in viscose fibres. Dyed fibres were analysed by Raman depth imaging along the radius at different dyeing times (30, 60, 90, 120, 150, 180, 240, 300, 600, 900, 1200, 1500, 1800, 2100 and 2400 seconds) and temperatures (30, 40, 50, 60, 70 and 80°C). The dye concentration in the fibre was expressed by normalising the characteristic peak of dyes at 1577 cm−1 to eliminate the interference of the fibre. The Raman depth mapping images showed that dye molecules gradually diffused to the interior of the fibre with an increase in dyeing time, remaining ring‐shaped in the state of diffusion. In addition, the diffusion rate increased with increases in the dyeing temperature. This was understandable because dye molecules with a higher kinetic energy move faster. It was also found that the external structure of fibres played a significant role in the diffusion behaviour of CI Reactive Blue 194 during the initial stage of dyeing. The concentration gradient distribution of CI Reactive Blue 194 in the fibre was reflected by Raman depth mapping. The study demonstrates the potential of confocal Raman microscopy for monitoring the dynamic diffusion of dye molecules in fibres.

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