Water repellency of cotton knitted fabrics treated with alkyl ketene dimers

Abstract Water repellency is one of the expected functions for originally hydrophilic cotton fabrics (CFs) in various applications. Aqueous dispersions of alkylketene dimers have been used as efficient sizing chemicals in practical papermaking. In the present study, we soaked CFs in weakly cationic AKD dispersions of various AKD concentrations, squeezed them, and cured/dried the AKD dispersion-containing wet CFs at 120 °C for 10 min. Scanning electron microscopy revealed flake-like AKD structures in the AKD-treated and air-dried CFs, which mostly disappeared when the AKD-related compounds (such as the original AKD, hydrolyzed AKD, and cellulose-reacted AKD molecules present in the CFs) melted and spread during curing. The contents of the AKD-related compounds in the CFs were determined by Fourier-transform infrared spectroscopy. When a dispersion with an AKD concentration of 6.7 g/L and a pH of 4.5 was used, the cured and dried CF contained ~ 0.49% AKD-related compounds. The resulting CF sample had prolonged water-absorption times (a measure of water repellency) of > 1800s, even after 30 cycles of laundry treatment. The content of AKD-related compounds was decreased markedly from 0.49 to 0.06% and 0.01% by laundry treatment once and 30 times, respectively. Quite small amounts of AKD-related compounds remained in the CF after laundry treatment, and contributed to its high water repellency. Therefore, the AKD treatment developed in the present study offers a practical and efficient means of conferring high water repellency on CFs. Graphical abstract