Novel Wet-White Tanning Approach Based on Laponite Clay Nanoparticles for Reduced Formaldehyde Release and Improved Physical Performances

In this work, a novel eco-friendly wet-white tanning approach based on tetrakis(hydroxymethyl) phosphonium sulfate (THPS) and synthetic Laponite clay nanoparticles has been developed to reduce potential HCHO risk as well as to improve leather performances. Our results indicate that the hydrothermal stability enhancement of the leather and the HCHO release are closely related to the dosage of THPS and final float pH in the THPS-based wet-white tanning process. The introduction of Laponite can cause distinct increase in shrinkage temperature (Ts) of the combination tanned leather and reduced HCHO contents, implying the presence of synergistic effects between THPS and Laponite. The wet-white tanning system of 2.5% THPS combined 3% Laponite by two-bath method at final pH ∼4.5 is thus optimized, conferring the leather with a Ts above 85 °C. Laponite clay nanoplatelets can be evenly bound between collagen fibrils without altering the native D-periodic banding patterns. Moreover, the novel combination tanning not only improves yellowing resistance and lightfastness but also enhances strength properties of the wet-white leather. These findings provide a potential application of Laponite to meet growing demands for reasonable tanning materials and related technologies toward eco-friendly leather manufacture.