Whiteness improvement of citric acid crosslinked cotton fabrics: H2O2 bleaching under alkaline condition

• CA firstly forms aconitic acid before forming anhydrides under elevated temperature.
• H2O2 can improve the whiteness of CA–treated fabrics via Michael addition reaction.
• H2O2 bleaching of CA–treated fabrics is a more kinetically controlled reaction.
• Yellowing problem is reduced under proper pH, short bleach time and high temperature.

Polycarboxylic acids have been employed as formaldehyde-free crosslinking agents in anti-wrinkle treatment for cotton fabrics. Cotton fabrics treated by citric acid (CA) catalyzed with effective catalysts have shown satisfactory anti-wrinkle properties. Meanwhile, CA is a natural-based and environmental friendly compound. However, the yellowing of CA treated fabrics is a stumbling block for its practical application. Due to the fact that CA firstly forms aconitic acid (AA) before forming anhydrides, the cause of the yellowing, hydrogen peroxide (H2O2) bleaching was adopted to treat the CA treated fabrics in order to break the CC bond structure and reduce the yellow color but retaining the desired anti-wrinkle properties. Thermogravimetric analysis and Fourier transformed infrared spectroscopy were employed to investigate the reactions. The results revealed that the H2O2 bleaching can effectively improve the whiteness and also maintain a good anti-wrinkle performance of the CA treated fabrics under an appropriate bleaching temperature and time.