STUDIES IN DURABLE-PRESS FINISHING OF COTTON (DMDHEU, PAD-BATH PH, RESIDUES)

Durable-press (DP) finishes, when used in presence of catalysts, impart crease-resistant and smooth-drying properties to cotton fabrics. Various aspects related to these DP finishes and the DP finishing process are investigated. These studies are carried out using mainly dimethyloldihydroxyethyleneurea (the most commonly used DP finish) and include the investigation of (i) high performance liquid chromatography (HPLC) as an analytical tool for quantitative analysis of commercial finishes, (ii) storage stability of DP finishes on fabrics when applied from pad-baths of varying pH values, (iii) rate studies of the reaction between cellulose and a DP finish and (iv) the influence of (a) the reagent residues generated from finishes during finishing and (b) the catalysts on formaldehyde release from finished fabrics. The findings from these studies are summarized as follows: HPLC is a useful analytical tool for quantitating the components of commercial DMDHEU-based finishes. However, the data obtained from the use of this technique did not correlate well either with the data from the use of other techniques or the performance data from finished fabrics. Pad-bath pH and reactivity of the DP finish are important factors influencing the storage stability of DP finishes on fabrics, DMDHEU, a less reactive finish, is stable under acidic conditions (pH 3-6), whereas, DMEU, a more reactive finish, is not stable at any pH. Thus, DMDHEU can be used in post-cure finishing operation when applied from slightly acidic pad-baths. HPLC is a useful analytical tool for studying the rate of reaction of DP finishes with cellulose. The rate constants for DMDHEU-cellulose reaction in presence of magnessium chloride at three temperatures were determined by following the concentration of DMDHEU on fabric using HPLC. With the help of an Arrhenius plot from these data, the rate constant at any given temperature can be predicted. Reagent residues generated on fabric during the finishing process contribute to the formaldehyde release from fabrics finished with a monofunctional model compound, N-methylolpyrrolidone. When the studies were extended to DMDHEU, this conclusion could not be established definitely since the exact nature of some of the residues could not be determined. In case of both the finishes, it was found that the nature and the amount of catalysts used in the finishing process have a significant influence on the extent of formaldehyde release from the finished fabrics