Vigilancia Tecnológica

Flax fibers contain naturally colored substances, which need to be removed by bleaching to produce excellent flax-based textiles in the subsequent process. However, the traditional bleaching process has the disadvantages of high temperature, large water consumption and high chemical oxygen demand (COD) value. Therefore, an appealing alternative to make flax fiber more sustainable is to design an environmentally friendly bleaching process, which has the advantages of low water usage, easy operation at ambient temperature and without addition of chemicals. In this paper, the influence of ozone bleaching on the optical property of flax fibers at different parameter conditions (reaction phase, ozone concentration, bleaching time, water pickup value, initial pH value) was investigated. The physicochemical properties of fiber samples after ozone bleaching were analyzed and compared with those of traditional bleached fibers. Results showed that the lightness and whiteness index of SFT-O3-Gas-70% increased to 80.85 and 53.33, yellowness index decreased to 10.14 (ozone concentration 20%, 20 min, WPV 70%, pH 2.0), which was comparable with the SFT-TMB (80.75, 51.87 and 11.33). SEM analysis showed that the non-cellulosic components (hemicelluloses and lignin) on the fiber surface were removed after bleaching treatment. The crystallinity and thermal stability of samples after bleaching treatment increased due to the removal of non-cellulosic components. Compared with the SFT-TMB (16.07 cN/tex and 1166), the tenacity and degree of polymerization (DP) of SFT-O3-Gas-70% decreased to 11.40 cN/tex and 779, respectively. The whole ozone bleaching process is under gas phase, normal temperature and pressure conditions, which greatly reduces water consumption and COD values of bleach wastewater. This study provides some guidance on the use of ozone for bleaching lignocellulosic fibers and the selection of cellulose protectants.