Effect of dye bath pH on dyeing and functional properties of wool fabric dyed with tea extract

• Tea extract is applied as a natural dye for wool fabric dyeing.
• Tea imparts excellent dyeing, UV protection and antibacterial properties to wool simultaneously.
• The properties of dyed wool are effected by the pH value of dye bath and the mechanism is analysed.

This study involved the dyeing of wool fabric with tea natural dye, and focused on the influence of dye bath pH on the color characteristics, fastness, UV protection property and antimicrobial efficacy of dyed wool. Furthermore, the possible mechanism was revealed. The results indicated that the pH value of dye bath had great effects on apparent color and color strength. When the pH value was 5.5, it exhibited the maximum Integ value. All dyed fabrics possessed good rubbing and washing fastness but presented growing hyperchromic effect under light with the decrease of pH value. Besides, tea imparted excellent UV protection ability and outstanding antibacterial activity to wool fabric. The antibacterial activity against Escherichia coli and Staphylococcus aureus decreased under acidic or alkaline dyeing conditions, especially in alkaline dye bath. This research pointed out that the conventional dyeing technology of tea natural dye could impart the color and functional performances to wool.