Synergistic pretreatment with hydroxypropyl methylcellulose and N1,N6-bis(ethylene oxide-2-ylmethyl)hexane-1,6-diamine for ultra-high fixation efficiency of reactive dye inkjet printing on cotton fabrics.

Conventional polymer-based pretreatments improve inkjet printing quality by forming surface films to restrict ink droplet spreading. However, these polymers generally lack reactive groups capable of forming covalent bonds with reactive dyes, resulting in low dye fixation and significant discharge of colored wastewater. Herein, a synergistic pretreatment strategy was developed to construct a multifunctional interfacial film on cotton fabrics using hydroxypropyl methylcellulose (HPMC) and a cationic epoxy crosslinker, N1,N6-bis(ethylene oxide-2-ylmethyl)hexane-1,6-diamine (EH). The HPMC/EH assembly combined the high hydrophilicity and swelling ability of HPMC with the cationic character and high reactivity of EH. During inkjet printing, anionic dyes were rapidly captured by the film through electrostatic interactions and hydrogen bonding, effectively suppressing ink droplet diffusion and enhancing pattern resolution. During subsequent steaming, EH underwent covalent reactions with both dye molecules and cellulose hydroxyl groups, forming a crosslinked network that chemically anchored dyes within the fibers. The synergistic effects of physical confinement and chemical fixation increased the fixation rates of cyan, magenta, yellow, and black inks to 97.5%. Compared with conventional sodium alginate pretreatments, the HPMC/EH system delivered a broader color gamut and higher color depth. This work provided a sustainable pretreatment strategy for reducing wastewater discharge and advancing textile inkjet printing.