Salt-free dyeing of cotton fabrics modified with cationic copolymer nanospheres using an acid dye

Cationic St-BA copolymer nanospheres were prepared through batch cationic emulsion polymerization. The synthesized nanospheres were used to modify cotton fabrics. The modified fabrics were then dyed using an acid dye in the absence of salt. The results show that when the nanosphere concentration was 5 g/l the nanosphere amount on the fibers and the K/S value of dyed fabric reached the maximum value. Prolonging the modification time resulted in increasing of the K/S value until the time was 60 min. Raising the modification temperature from 10 °C to 50 °C led to increasing of the K/S value. The K/S values increased gradually with increasing the modification bath pH value from 2.3 to 9. The addition of sodium chloride in the modification bath resulted in decreasing of the K/S values. CMC pretreatment of the fabric before the nanosphere modification increased the K/S values of dyed fabrics. SEM images revealed that after modification and dyeing many nanospheres deposited on the cotton fiber surfaces and the nanospheres did not form a continuous film on the fiber surface. Therefore, the nanosphere modification and the salt-free dyeing would not obviously affect the permeability and handle of the dyed cotton fabric.