Study on chemical kinetics of leather degradation in conventional vegetable tanning and alkaline burial environment

Leather relics are extremely important to China’s cultural heritage; however, since the leather relics have been buried underground for a long time, affected by acids, alkalis, salts, and other factors, leather artifacts usually undergo different degree of degradation. To elucidate the degradation mechanisms of leather artifacts, cattle, yak, camel, horse, donkey, dog, and rabbit hide samples were used as research objects in this study, all the above-mentioned hide samples were processed by conventional vegetable tanning and artificially degraded by simulating alkaline burial environment. The degradation degree of leather at different stages was characterized by the change in puncture strength to study the chemical kinetic process and rate of leather degradation. The results suggest that the chemical kinetics associated with the degradation of cattle, yak, camel, horse, donkey, and rabbit leather samples were mainly second-order kinetics, which was consistent with collagen degradation, and the half-lives of their degradation were 2.5, 2.2, 2, 1.2, 2.1, and 1.2 years, respectively; however, the degradation mechanism of dog leather was dominated by a first-order reaction with a half-life of 3.4 years, owing to the differences in its structure. Therefore, it is concluded that the chemical kinetics associated with the degradation of the most of conventional vegetable tanned leathers were mainly second-order kinetics under alkaline burial environment, and the degradation rate of dog, cattle, yak, donkey, camel, rabbit, and horse leather samples accelerated gradually.