A Comparative Study on the Environmental Friendly Bleaching Processes of Poly(lactic acid) Substrate: Application of Ultraviolet/O3/H2O2 System

Recently, there has been an increasing interest towards the finishing of textiles (fibers, yarns, fabrics and nonwovens) using eco-friendly technology, which can achieve a wide range of functional properties and environmental benefits. This study is related to a modern eco-friendly bleaching technology that relies on Ultraviolet/O3 radiation of poly(lactic acid) fabric through simple technique. The effects of Ultraviolet/O3 radiation along with the pretreatments with distilled water, hydrogen peroxide, and hydrogen peroxide/sodium silicate solutions on the bleaching of the poly(lactic acid) fabrics were examined using UV-Visible and reflectance spectral method and the results were compared with that of virgin untreated samples. Ultraviolet/O3 bleaching routes were screened to obtain desired whiteness index (WI), tint factor (Tw), lightness/darkness (L*), redness/greenness (a*), yellowness/ blueness (b*), chroma (c*) and hue (h˚) of the bleached poly(lactic acid) fabrics. The optimal properties of the bleached poly(lactic acid) knitted fabric could be obtained at Ultraviolet/O3 irradiation for 80 min on the fabrics which pre-impregnated in a hydrogen peroxide solution with a wet pick up of 70 %, pressure of 1.1 bar and speed of 2 m/min. (Ultraviolet/O3/H2O2 bleaching system). The Ultraviolet/O3/H2O2 bleached fabric showed the best colorimetric properties (WI: 87.7, : -0.1, L*:94.227, a*:-0.106, b*:0.294, c*:0.2512, h˚: 98.6551). Moreover, the reflectance of this sample has increased significantly in the range of 400-450 nm which leads to a glossy withe shade on the fibers. The SEM images presented that after Ultraviolet/O3/H2O2 bleaching process, some fractures with nano scale size (about 130 nm) are formed on the poly(lactic acid) fabric surface. The ATR-IR spectrum of Ultraviolet/O3/H2O2 bleached poly(lactic acid) fibers displays more intense C–C–O absorption bands (1161 cm-1).