Wash-durability, surface, and antibacterial properties of wool fabric treated with nature-derived thymol and totarol under subcritical CO2, aqueous, and ethanol media

Traditional aqueous-based antibacterial treatments used for wool fabrics are not sustainable as they produce toxic effluent and therefore it is necessary to develop a zero-effluent treatment. In this work, wool fabrics were treated with two plant-derived non-toxic antibacterial agents, thymol and totarol, under subcritical carbon dioxide (subc-CO2), and their antibacterial properties were measured. The wash-durability of the fabric treated with thymol under subc-CO2 was compared with wool fabrics treated with thymol in aqueous and ethanol media. The change in the physicochemical properties of the wool fabric treated with thymol under subc-CO2 at various concentrations was assessed by FTIR, contact angle measurement, and EDX spectroscopy. Thymol showed excellent antibacterial properties, but the wool fabric samples treated with totarol showed no antibacterial activity. The wool fabrics treated with thymol in the aqueous and ethanol media lost antibacterial activity after 5 times IWS 7A washes, but the fabric treated with thymol under subc-CO2 showed excellent antibacterial activity even after 20 times IWS 7A washes (equivalent to 80 domestic washes) indicating its high durability to wash. The thymol treatment slightly improved the hydrophobicity of the treated fabric’s surface as the contact angle at 240 s improved to 119° for the fabric treated with 5% thymol from 106° for the untreated control fabric.