This study presents a high-efficient and cost-effective ultrasound-assisted strategy for one-bath one-step scouring and bleaching of cotton/spandex fabric using sodium percarbonate (SPC) and tetraacetylenediamine (TAED) couple. SPC plays both roles of pH regulator and H2O2 donor to initiate the peracetic acid (PAA) release from TAED. The significance and interaction effects of operating parameters (TAED concentration, temperature and time) on the WI (Whiteness Index) of fabrics were investigated through a central composite design. The bleaching mechanism was studied by exploring the relationship between WI and PAA and hydroxyl radical (HO·) concentrations. The mechanical and dyeing performances of treated fabrics were also evaluated. Results show that temperature exerted a significant impact on WI followed by TAED concentration and time. The PAA concentration decreased and HO· concentration increased upon the temperature rise. Both PAA and HO· were significant to upgrade WI and ultrasound was effective in enhancing their bleaching efficiency. The fabric treated only with 15 mmol/L TAED and 10 mmol/L SPC at 40 °C for 40 min under ultrasound could achieve a WI of 68.6 (43% higher than greige fabric), which was almost equivalent to that of the fabric treated at 60 °C without ultrasound. This verifies the contribution of ultrasound technology in reducing bleaching temperature for energy-saving purpose. Moreover, the treated fabric displayed less than 5% tensile strength loss, having a marginal impact on the apparel performance. The wettability of fabric was greatly improved leading to a good dyeing performance. Encouraging results demonstrate the high efficiency of the ultrasound-assisted pre-treatment process of cotton/spandex fabric, which contributes to the sustainable production of textiles.
Keywords: Activated peroxide; Cotton/spandex; High efficiency; Low temperature; Ultrasonic bleaching.
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