The use of natural dyes has increased in the last few decades due to the eco-friendly approach of dyeing. There are still some limitations that are associated with natural dyes, such as dyeing efficiency, reproducibility of shades, process complexity, availability etc. The main problem associated with the dyeing property of natural dyes is “low exhaustion”. In this study, natural dyestuff from Curcuma longa L. was extracted and polyethylene terephthalate fabric was dyed with it in the same bath by employing the supercritical carbon dioxide method. The method was developed to improve the dye-ability of natural dyes and reduce the process time and effluent. Curcuminoid dye exhaustion on PET fabric showed almost 80% by using supercritical carbon dioxide dyeing methods, and the highest colour strength (K/S = 12) was obtained. Coloured polyethylene terephthalate fabric treated with supercritical carbon dioxide showed deeper shades (L* = 72.92) and better fastness properties as compared with high temperature exhaust dyeing methods.

Abstract

The application of cross-linking resin is an effective method for improving and controlling dimensional sta¬bility, such as the shrinkage of viscose single jersey knits. However, such treatment often leads to a significant deterioration in the bursting strength of treated fabrics. In this regard, resin treatment using a softening agent can be an additional potential solution for retaining the bursting strength of treated fabrics. Resin treatment is one kind of chemical finishing process that inhibits cellulosic textile fibre swelling during wetting, provides fibre resistance to deformation and prevents shrinkage. The key objective of this study was to model the effect of resin-finishing process variables for predicting the shrinkage control and bursting strength of viscose single jersey knitted fabrics. The MATLAB (Version 8.2.0.701) fuzzy expert system was used to model the optimum resin and softener concentrations, as well as the best curing time for the prediction of maximum shrinkage control with a minimum loss in fabric bursting strength. The optimal process variables were found to be a resin concentration of 75 g/l, a softener concentration of 45 g/l and a curing time of 225 seconds. The fuzzy expert model developed in this study was validated using experimental data. It was found that the model has the ability and accuracy to predict fabric shrinkage and bursting strength effectively in the non-linear field.

In this study, we analysed different resin finishing agents on cotton fabric dyed with reactive dye. Different tests were carried out on the resin treated fabric, such as the wrinkle recovery, tensile strength, dimensional stability, stiffness, abrasion resistance and colour strength (K/S) of the dyed fabrics. Melamine formaldehyde resin treated fabric gave a higher crease recovery angle, better smoothness and higher bending length because of higher crosslinking with cellulose. The colour strength decreased after applying the resin finish, and fastness properties were unaffected by the resin treatments.

This study aims to assess the environmental impact of different chemical classes of reactive dyes and their treatment. To attain this outcome, four different types of reactive dyes (Procion Blue PX-3R (Monochlorotriazine), Levafix Blue CA (Bi-functional heterogeneous), Remazol Brilliant Blue R (Vinylsulphone) and Remazol Brilliant Blue RR (Bi-functional homogeneous) on the cotton fabric were analyzed. The potential cytotoxic effect of different reactive dyes was evaluated using the growth inhibition test according to AATCC 22662 by exposing the culture over 72 hours at 21 °C. The dyeing operation was performed in a labrotex sample dyeing machine, and a data color spectrophotometer was administered to analyze the strength percentage of dyes in post-dye liquor. Among the reactive dyes, Levafix Blue CA exhibited better effluent characteristics compared to others, lowering the threat to the environment. The dyed wastewater was directly disposed of and treated in a pilot plant containing lime and ferrous sulfate as coagulant and polyacrylamide as polyelectrolyte, which resulted in a significant reduction of BOD5 (64.97-74.67%), COD (61.03-70.28%), TDS (55.02-61.97%) and TSS (47.07-50.19%) with improved pH and DO values. This investigation reflects the specific selection of a reactive dye leading to a lower environmental impact of a dyeing process coupled with wastewater treatment processes.