Bleaching of hydroentangled greige cotton nonwoven fabrics without scouring

Abstract

Previous research had shown that processing greige cotton on a commercial-grade hydroentanglement (HE) system at a water pressure greater than 120 bar resulted in a low-weight hydrophilic nonwoven fabric. With that ability to make hydrophobic greige cotton easily wettable and hence absorbent without the conventional scouring phase, an investigation was conducted to determine whether a fabric made by hydroentangling greige cotton fibers at a high water pressure could be successfully bleached without the traditional scouring. The investigation involved production of greige cotton nonwoven fabrics at a low hydroentangling water pressure of 60 bar and at a high hydroentangling water pressure of 135 bar and their subsequent evaluations before and after scour only, one-stage bleach only, and two-stage scour and bleach. In the results, both the 60 bar and 135 bar fabrics bleached successfully in the two-stage bleaching process and yielded acceptable absorbency and whiteness values. However, when bleached in the single-stage bleaching process with no separate scour, the 135 bar fabric still produced the whiteness index almost equal to that obtained in the two-stage bleaching process and even equal to that of a fabric made with commercially scoured and bleached cotton fibers, but the 60 bar fabric yielded about 15% lower whiteness index value while its wettability-induced improved water absorbency still was comparable to that obtained via the two-stage bleaching. This shows that a hydroentangled greige cotton fabric produced at a high enough water pressure (hydro energy) could be bleached satisfactorily without the traditional scouring chemicals and that a fabric produced even at a lower water pressure and bleached without scouring could still be satisfactory for subsequent aqueous treatments for certain end-use applications where the whiteness may not be as critical as the absorbency.