Effect of TiO2 Incorporation Sequence on Color, Wearability and Photocatalytic Self-Cleaning of PET/Cotton Blend Fabrics

Abstract

Integrating dyeing with photocatalytic finishing provides a promising route to colored self-cleaning textiles. However, the TiO₂ incorporation sequence strongly influences color and functional performance. In this study, poly(ethylene terephthalate) (PET)/cotton blend fabrics were dyed with disperse and direct dyes and modified with TiO₂ or Ag/TiO₂ using tetrabutyl titanate as the precursor. Five TiO₂/Ag–TiO₂ incorporation routes were compared with a dyed-only control: TiO₂ loading after dyeing, dyeing after TiO₂ loading, TiO₂ incorporation during disperse dyeing, TiO₂ incorporation during direct dyeing, and Ag/TiO₂ loading after dyeing. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy confirmed the deposition of Ti-containing species and the formation of anatase TiO₂. The incorporation sequence produced distinct structure–color–function relationships. Dyeing after TiO₂ loading gave the highest surface Ti atomic percentage (3.30 at%) and color strength [(K/S)_max = 6.03], but subsequent dyeing likely reduced the exposure of photocatalytic sites. In contrast, post-dyeing TiO₂ or Ag/TiO₂ loading provided more accessible photocatalytic particles and enhanced pollutant degradation, although it markedly reduced visible color depth. Introducing TiO₂ during dyeing resulted in lower surface Ti abundance, indicating interference from dyes and auxiliaries during precursor hydrolysis, particle growth, and deposition. The Ag/TiO₂ post-treated fabric showed the highest methylene blue degradation rate constants of 23.82 × 10⁻² h⁻¹ under ultraviolet irradiation and 5.40 × 10⁻² h⁻¹ under visible-light irradiation. It also effectively removed Congo red and soy sauce stains. The fabrics retained good washing and rubbing fastness and largely preserved breaking force, although air permeability decreased after wet-thermal processing and particle deposition. Overall, TiO₂ loading before dyeing favored deposition and color development, whereas post-dyeing loading favored photocatalytic accessibility.