Functional Finishing Of Polyamide Fiber Using Natural Flavonoids

Polyamide fiber has extensive applications,and in textile industry it is largely employed to manufacture underwear,knickers,bras,socks,stockings,leggings,and tight sportswear and casual clothes.These polyamide textiles have frequent contact with the skin when in use,and accordingly require such functions as antibacterial activity,antioxidant activity,and UV protection property.In this work,three natural flavonoids with different chemical structures,namely baicalin,quercetin,and rutin were applied to the functional finishing of knitted polyamide fabric by means of three following approaches: dip and adsorption technique;preparation of silver nanoparticles(AgNPs)using flavonoids as reducing agents,and application of the resulting AgNPs to the dip finishing of polyamide fabric;simultaneous in-situ preparation and finishing of AgNPs.The adsorption properties and mechanisms of natural flavonoids on polyamide fabric were investigated.The antibacterial,antioxidant and UV protection properties of the finished fabric were discussed,and their washing durability was also evaluated.The important results and conclusions were in the following:(a)The adsorption of baicalin on polyamide fiber was very sensitive to the pH of liquor,whereas that of quercetin and rutin was hardly affected by pH.The adsorption kinetics of three flavonoids conformed to the pseudo second-order kinetic model.Langmuir–Nernst adsorption model was found to fit the equilibrium adsorption isotherms of three flavonoids well.Among three flavonoids,quercetin exhibited the highest adsorption capability and affinity to polyamide fiber,and rutin had the lowest ones.Three flavonoids imparted the very good antibacterial and antioxidant activities to polyamide fiber;and the functions of quercetin had the best durability to washing.(b)Three flavonoids all possessed the ability to reduce silver nitrate into AgNPs in weakly alkaline conditions,and the resulting AgNPs had an average particle size of 30–40 nm.Higher pH and temperature was conducive to the preparation of AgNPs,and the resulting AgNPs exhibited smaller particle size and better distribution uniformity.When used to prepare AgNPs,three flavonoids had the reducing ability for silver ions in the following order: quercetin > rutin > baicalin.The polyamide fabric had an yellowish-brown appearance after treated with AgNPs,and the particle size of AgNPs was about 60 nm.With an increase in flavonoid and silver nitrate dosages,the silver content of the finished fabric increased and the color of the fabric became darker.The silver content of the finished fabric had the following order: quercetin > rutin > baicalin.The incorporation of AgNPs had no impact on the molecular structures and crystalline property of polyamide fiber.The finished fabric exhibited excellent and durable antibacterial activity and UV protection ability as well as good antioxidant activity.(c)The in-situ preparation of AgNPs also imparted a brown-yellowish color to polyamide fabric.The particle size of AgNPs on the surface of polyamide fiber ranged from 40 to 60 nm,and the agglomeration of AgNPs was found.The silver content of the finished fabric had the following order: quercetin > baicalin > rutin.The color depth of the finished fabric increased with an increase in the silver content of the fabric.The finished fabric also exhibited excellent and durable antibacterial activity and UV protection ability as well as good antioxidant activity.