β-Cyclodextrin-Based Chrome-Free Tanning Agent Results in the Sustainable and Cleaner Production of Eco-Leather

This study aimed to pioneer the development of an innovative, eco-friendly, and chrome-free tanning agent, with a focus on promoting sustainable practices in ecological leather production. Two novel biomass-derived tanning agents, namely, β-TCD and β-GCD, were synthesized through a one-pot grafting process involving environmentally friendly epoxy monomers: triglycidyl isocyanurate (TGIC) and glycerol triglycidyl ether (GTE). Characterization through various analytical methods, including FTIR, 1H NMR, XPS, GPC, SEM, and TGA, confirmed the successful grafting of TGIC and GTE onto β-cyclodextrin (β-CD) backbones. The resulting β-TCD and β-GCD exhibited notable epoxide values of 0.349 and 0.388 mol/100 g, respectively, along with a broader molecular weight distribution of intermediates. These newly developed tanning agents, β-TCD and β-GCD, were then applied in depickling goatskin tanning experiments. Results indicated that the crust leather tanned with β-TCD and β-GCD displayed favorable thermal stability, with shrinkage temperatures reaching 84 and 82 °C, respectively. Moreover, the thickening rates of the leather exceeded 40%. The crust leathers tanned with β-TCD, and β-GCD demonstrated excellent physical and mechanical properties, as well as notable resistance to yellowing compared to conventional commercial chrome-free tanning agents like TWS and F-90. Overall, this research emphasizes the efficacy of natural cyclodextrin materials as potent and environmentally friendly alternatives to chromium-based tanning agents, showcasing their significant potential in advancing sustainable and cleaner practices in leather production.