Tara-aluminum tanning as an alternative to traditional chrome tanning: development of a pilot-scale process for high-quality bovine upper leather

In this study, an industrial-scale tanning process to replace chrome tanning in the production of high quality bovine shoe upper leathers, based on a multi-step vegetable-aluminum tannage, is presented. Tara extract was used as vegetable tanning agent in order to obtain a wet-white tanned leather; a pretannage with glutaraldeyde or syntan was introduced to improve penetration. This paper reports the best recipes developed, the properties of the leather obtained and the results of differential scanning calorimetry (DSC), thermogravimetric analysis (TG and DTG), and scanning electron microscopy (SEM) used as investigation methods to follow the tanning process steps and better understand the cross-linking mechanisms.