Reducing the usage of D5 solvent in whitening polyester fabric with raw fluorescent brightener OB-1 in water medium

Purpose This study successfully achieved the whitening of polyester (PET) fibres using OB-1 particles in an aqueous bath supplemented with a D5 solvent. Design/methodology/approach The impact of various factors, including treating temperature, raw OB-1 usage, D5 concentration and treating duration, on the whitening performance was meticulously examined. Findings The peak whiteness achieved was 124.33 at a treating temperature of 130 °C, with an OB-1 concentration of 0.0325% o.m.f., 18% D5 (v/v) in water and a treating duration of 50 min, matching the results of whitening treatments in D5 solvent with minor water content. Additionally, the study confirmed through X-ray diffraction and Fourier transform infrared spectroscopy analyses that no discernible new chemical groups formed in the PET fibres during the whitening process. After the whitening, an observed accumulation of surface particles is likely due to the aggregation of OB-1 molecules. Originality/value This study has successfully achieved the whitening of PET fibres using OB-1 particles in an aqueous bath enhanced with a concentration of the D5 solvent. The key advantages of this research lie in the elimination of the milling process and other auxiliary steps, as well as a reduction in D5 solvent consumption, which is beneficial for solvent recycling and pollution mitigation, while avoiding potential fibre damage. This innovative method aims to establish a cleaner and more sustainable whitening process for PET fabrics, aligning with both the performance criteria of the textile industry and the growing demand for environmentally responsible practices.