Influence of dye pickup on different functionalized regenerated cellulosic fibres

The present study deals with the effect of dyeing on different types of regenerated cellulosic fibres such as viscose, modal, and lyocell, and on different modifications of regenerated cellulosic fibres such as non-woven fibres, anionically modified viscose fibre, cationically modified viscose fibre, and hydrophobic viscose fibre. The water-soluble direct dye and reactive dye were used to colour these fibres. The dye pickup of these regenerated cellulosic fibres was studied by evaluating and comparing the extent of colour exhaustion in terms of K/S values measured by a spectrophotometer. The dye pickup behaviour of fibres was observed to be different in the case of reactive and direct dyes. Based on the experiments, the factors influencing on the dye pickup of regenerated cellulosic fibres were narrowed down to modified functionality of the fibre and properties such as, denier, surface area, and % crystallinity of the fibres. Furthermore, the dyed samples were examined using SEM, optical microscopes for morphology studies, XPS and nitrogen estimation analysis to understand the functionality changes on the fibres, and UV Vis spectrophotometry was carried out to understand dye bath exhaustion, and the FTIR spectra of fibre were done to analyse the functional group variation in cellulose before and after dyeing. It was observed that the increase in crystallinity of fibres lower down the dye pickup, and the functional modification with cationic, hydrophobic, or non-woven additives increases the dye pickup.