Effect of bleaching treatments on wool fabrics analysed via attenuated total reflection Fourier Transform–infrared spectroscopy

Abstract

To investigate the effects of three commercial bleaching agents (hydrogen peroxide, sodium percarbonate and sodium hypochlorite) on textile products, the structural changes and chemical damage caused by these bleaching agents on wool fabrics were quantitatively characterised using attenuated total reflection Fourier Transform–infrared (ATR-FTIR) spectroscopy. A comparison of the spectral changes before and after the treatment showed that the wool fabrics treated with sodium hypochlorite and sodium percarbonate were severely and slightly damaged, respectively. By contrast, the fabrics treated with hydrogen peroxide were almost undamaged and whiter. Compared with untreated wools, or those treated with oxygen-bleaching agents (sodium percarbonate and hydrogen peroxide), the amide I band centred at 1647 cm−1 in the ATR-FTIR spectra of the wool fabrics broadened significantly after the treatment with the chlorine-bleaching agent (sodium hypochlorite). Furthermore, the amide I band broadened, and the intensity of the amide III band centred at 1235 cm−1 increased with increasing the chlorine content and yellowing in the wool fabrics. Based on these experiments, it was concluded that the structural changes and chemical damage caused by the chlorine-bleaching treatment of wool fabrics caused the oxidative cleavage of .SS. groups and the randomisation of cortex structures due to chlorination.