Traditional reactive dyeing of cotton requires alkaline conditions, which cause significant dye hydrolysis and prevent one‑bath dyeing of polyester/cotton blends with disperse dyes. In a study published in ENG. Chem. Eng., researchers at Dalian University of Technology and Donghua University report an acidic cross‑linking strategy that overcomes these limitations using silicon‑containing reactive dyes and the silane coupling agent KH550 (3‑aminopropyltriethoxysilane).
The method operates under weak acidic conditions (pH 5.0). The silane coupling agent KH550 is first hydrolyzed to form silanol groups. These silanol groups react with the hydroxyl groups of cotton fabric, while the amino groups of KH550 react with the reactive groups of the dyes. Simultaneously, self‑condensation of silanol groups occurs. This synergistic mechanism constructs a robust three‑dimensional “dye–crosslinker–fabric” covalent network.
For cotton fabric, all three silicon‑containing reactive dyes (red, blue, yellow) achieved fixation rates exceeding 91 %, with the red dye reaching 96.4 %. The dyed fabrics exhibited excellent fastness: dry rubbing fastness of 4–5, wet rubbing fastness of 3–4, and wash fastness above 4–5. DMSO extraction and harsh aqueous treatments (pH 1–13, 100 °C) confirmed covalent bonding. XPS analysis of KH550‑treated cotton showed a four‑fold increase in surface silicon content (to approximately 1.3 at %), with Si–O–C and Si–O–Si bonds confirming chemical grafting.
Mechanistic studies confirmed the three key reactions: (1) silanol groups reacting with cotton hydroxyls (ninhydrin test showed a 44.7 % decrease in KH550 concentration after cotton treatment); (2) amino groups of KH550 reacting with dye reactive groups; and (3) silanol self‑condensation (XPS of steamed DR showed a Si 2p binding energy increase from 102.00 eV to 102.30 eV, confirming Si–O–Si formation).
Crucially, the silicon‑containing reactive dyes showed good thermal stability, with only minor weight loss below 200 °C. The thermosol process (200 °C, 4 min) for disperse dyes did not damage the reactive dyes; instead, fixation rates increased slightly. KH550 also enhanced disperse dye uptake by improving wettability: the contact angle of the dye dispersion on polyester decreased from 116° to 92°, and wetting time dropped from 2.0 s to 0.2 s.
For polyester/cotton blends (65/35), one‑bath one‑step dyeing was successfully achieved by combining the silicon‑containing reactive dyes with commercially available disperse dyes. Total dye utilization exceeded 90 % for all three dye pairs, with reactive dye fixation surpassing 96 %. The dyed blends exhibited excellent levelness (ΔE < 0.05) and good fastness (dry rubbing 4–5, wash 4–5). Compared to conventional two‑bath two‑step methods, the new process reduces water consumption by 50.0 %, electricity by 49.1 %, and thermal energy by 36.8 %.
This acidic cross‑linking strategy provides an industrially viable, environmentally friendly alternative for dyeing cotton and polyester/cotton blends.

DOI
10.1007/s11705-026-2667-1