A sustainable strategy for promoting the colour strength and ultraviolet/oxidation resistance of polylactic acid fabric integrating quercetin and food-grade ester

The combination of green chemicals with biodegradable polymers is highly encouraged to enhance the sustainability of textiles and their manufacturing process. Polylactic acid (PLA) is a promising biodegradable polymer to replace petroleum-based fibres and fabrics. However, to enhance the compatibility between PLA and bio-based dyes or finishes is still a challenging issue. This study achieves a simultaneous bio-colouration/finishing on PLA using quercetin, especially focusing on the adsorption enhancement with a food-grade methyl cinnamate (MC). Results show that the exhaustion of quercetin on PLA is significantly enhanced from 26% to 64% using MC. At similar concentrations, MC enables much better colour depth (K/S) improvement on PLA than synthetic n-amyl acetate. The factorial significance follows the order: MC concentration > quercetin concentration > temperature. Under the optimal condition (0.97 g/L quercetin, 3.0 g/L MC, at 103.5 oC), a theoretical highest K/S of 6.15 can be achieved. PLA treated with quercetin/MC displays much higher b* value than that of the PLA only treated with quercetin. MC also increases colour uniformity of the PLA treated with quercetin. Quercetin/MC efficiently decreases UVB and UVA transmittance of PLA and reaches the UPF 50 + rating. Around 98% of free radicals were scavenged by 10%owf quercetin/MC treated PLA in 30 min. The marginal tensile loss (<5%) of PLA after treatment is acceptable in wet processing. In all, the strengthened colour shade and functionality of PLA using MC stemms from the adsorption enhancement, which expands the applicable area of PLA.