Direct Scouring of Greige Cotton Fabrics with Proteases

Our previous work demonstrated that proteases are effective scouring agents for boiling-water pretreated cotton fabrics. In this study, we investigate whether proteases are effective scouring agents when directly applied on raw greige cotton fabrics without the boiling water pretreatment. Direct reactions with three proteases, i.e., trypsin, chymotrypsin, and subtilisin, on greige cotton fabrics show that all three improve fabric wettability to a level similar to alkaline scouring under mild conditions (45-55°C, pH 7). The reaction conditions required to achieve optimal fabric wettability (cosθ > 0.6) are 5 g/L and 45°C for trypsin and 5 ml/L at 55°C for subtilisin. Chymotrypsin is effective under several reaction conditions, i.e., 1 g/L at 55°C, 2 g/L at 45°C, and 5 g/L at 35°C. Most reactions take 30 minutes, and room-temperature water rinses replace the post-reaction buffer rinses. Compared to protease scouring of boiling-water pretreated cotton, direct protease scouring of greige cotton fabrics requires increased concentration (subtilisin), higher temperature (subtilisin and chymotrypsin), or longer time (trypsin and chymotrypsin) to achieve similar water wettability and absorption properties. The most distinct outcome of direct protease scouring of greige cotton fabrics, in comparison to boiling-water pretreated and protease scoured and alkaline scoured cotton, are the resulting fabric characteristics, i.e., less lateral shrinkage, no change in surface friction, easier to shear, and more resilient to compression and bending.