Alkaline Hydrolysis of Polyester Fabric and Dyeing with Natural Colorants Extracted from Henna Leaves

Abstract

The aim of this study was to dye polyester fabric with natural colorant obtained from henna leaves. Due to the hydrophobic nature of polyester, it makes the dyeing process difficult at low temperature and also prevents dye molecules from diffusing into the fiber interior during dyeing. To solve such dyeability problems of polyester, the fabric were treated with alkali to convert the hydrophobic nature into hydrophilic. This alkaline hydrolysis of polyester improved its chemical properties and made dyeing of polyester with natural colorant can be possible. The coloration of hydrolyzed polyester was carried out with the extracted aqueous natural dye. In this study optimizations of surface treatment conditions of polyester were investigated and the effects of hydrolysis on the fabric properties were also studied. Dyeing conditions like MLR, time, temperature and pH were optimized based on their dyeing properties results. Modifications of the fiber surface were confirmed by wettability test and FTIR study. The alkaline hydrolysis of polyester showed weight loss but achieved weight loss has no significant effect on the fabric’s strength. Beside this, characterization of the dyeing properties like color strength, dyeing evenness and color fastness were carried out for lawsone (primary colorant in henna leaves) dyed polyester. It was observed from the study that as the dyeing temperature and time increases, the K/S value increases until dye exhaustion attains equilibrium and then there is decrease. Higher color strength was obtained at basic pH conditions. Color fastness to washing and rubbing result obtained showed good to excellent grades.