Bridging-induced densification strategy based on biomass-derived aldehyde tanning integrated with terminal Al(III) crosslinking towards high-performance chrome-free leather production.

Chrome-free leather manufacturing has been acknowledged as a desirable option to eliminate potential environmental and human health risks of conventional chrome tanning. This work applied a sequential bridging-induced densification strategy to produce high-performance chrome-free leather with high crosslinking density derived from the biomass-derived aldehyde (BAT) crosslinking (BAT tanning of leather), followed by terminal Al(III) crosslinking (TAC). The TAC conditions for BAT tanned leather were optimized and the results suggested that the optimized conditions were as follows: the fixation pH was 4.2, the pre-penetration time was 180 min, the fixation temperature was 40 °C, and the dosage of the aluminum tanning agent (ATA) was 0.5% (based on AlO). Under the optimized conditions, the resultant BAT-TAC crust leather exhibited favorable overall performances compared with BAT crust leather in terms of higher hydrothermal stability, mechanical strengths, more pleasant uniform color, and comparable smooth grain surface. The obtained high-performance chrome-free leather is scalable, providing an avenue for designing and rationalizing other engineering technology towards high-performance eco-leather production.