OPTIMIZING PROCESS CONDITIONS IN SEQUENTIAL OXIDATIVE REDUCTIVE BLEACHING OF WOOL

The properties of worsted challis fabric were examined after bleaching by conventional alkaline peroxide bleach and by variations of the Agr icultural Research Service (ARS) two-step, single-bath sequential oxid ative/reductive process. Whiteness and yellowness indices and mechanic al properties of fabrics bleached by the conventional process with 22 g/L (20 mL/L) 30% hydrogen peroxide at 50C and 60C were compared with those of fabrics bleached by the ARS process with (a) 16 g/L peroxide; or (b) 8 g/L peroxide in Step 1 followed by the addition of thiourea (70% of the weight of peroxide) in Step 2; or (c) 22 g/L peroxide in S tep 1 followed by modifying the baths to reach an effective peroxide l evel of either 16 g/L or 8 g/L before the addition of thiourea. ARS-bl eached fabrics were whiter or equal to the peroxide-bleached fabrics b leached within the same time and temperature limits. ARS-bleached chal lis retained its original strength but when compared to the peroxide-b leached challis, lost 11% specific stress, with only slight changes in elastic moduli and % strain at peak stress. Evaluation of fabric hand by the Kawabata Evaluation System (KES-F) showed an increase in the h and expression Shinayakasa, indicating greater softness, flexibility a nd smooth feeling for the ARS-bleached fabrics.