Colour and surface functional properties of wool fabrics coated with gallnut, feijoa skin, and mango seed kernel tannin-stabilised Ag nanoparticles

In the textile industry, textile materials are dyed and multi-functionalised by multi-step treatments that considerably increase the environmental impacts by increasing water, and energy usage along with increasing the generation of volume of effluent. In this work, Ag nanoparticles (Ag NPs) were in-situ formed and stabilised with gallnut, feijoa fruit skin, and mango seed kernel-derived tannins, and wool fabrics were coated simultaneously with these Ag NPs in the same bath. The Ag NP treatment produced dark to light olive-brown shades on wool fabrics. The treatment conditions for the treatment with Ag NPs were optimised to achieve the best results. The colour intensity, UV radiation absorption, antibacterial activity, surface electrical resistance, and durability of the treatment to washing were assessed by various methods. The gallnut-derived tannin (GNT)-stabilised Ag NP-coated wool fabrics showed overall the best results including excellent antibacterial activity against various types of bacteria. The treatment was durable to at least 20 cycles of IWS 7A washes (equivalent to 80 domestic washes). For the 0.5% Ag NPs on the weight of fibre (owf) dosage, the UV light transmission through the trisodium citrate-stabilised Ag NP-coated fabric at 365 and 311 nm was 6.37 and 0.95% respectively, which reduced to 1.63 and 0.20% for the fabric coated with GNT-stabilised Ag NPs providing excellent protection against UV radiation. The surface resistivity of wool fabric reduced from 1.1×1012 Ohm/cm for the untreated fabric to 1.1×109 Ohm/cm for the fabric coated with 2.0% owf GNT-stabilised Ag NPs. The stabilisation of Ag NPs with GNT prolonged the wash-durability by reducing the leaching of Ag NPs from the treated fabric. The developed method could be a sustainable alternative to traditional multi-stage treatments conducted in the textile industry with toxic synthetic dyes and finishing agents for the colouration and multifunctionalisation of wool fabrics.