A study on the effect of bulk water content and drying temperature on the colour of dyed cotton fabrics

In the present study, the effect of various levels of bulk and free water content and its distribution on the colour of cotton fabrics dyed with direct dyes and their combinations were analysed. Twill and plain structures with two different parameters of fabric construction were chosen. The dyed samples were adjusted to different levels of wet pick-up, with water ranging from 50% to 125% on the bone dry weight of the fabric (odwf) to achieve various levels of bulk water content. Further, the residual moisture content of the samples was adjusted to 40–10% odwf by means of hot air drying at different temperatures to obtain different levels of free water content and its distribution. For the assessment of colour and its comparison, the parameters ΣK/S and values were used. In order to bring out the true effect of moisture distribution and fabric structure, normalisation of dye uptake in the fabric based on weight and area were considered, respectively. The plain structures show a higher increase in colour than the twill structures when the bulk water content increases. At the same time, the fabric structures do not play a significant role, with increase in colour attributable to change in drying temperature. The findings reveal that the bulk water content, drying temperature and fabric geometry affects the colour of the fabric significantly.