Study of vegetable extracts effect on wet-white leather

Although the worldwide leather production is based on chromium tannage, there is an increasing share of chrome and metal free tannages. This is mainly due to the growing demand for chrome free leathers in the automotive industry. The aim of this work was the study of vegetable extracts effect on the retannage of wet-white leather, produced by the glutaraldehyde and syntan pre-tannage process, evaluating the bath exhaustion and physical-mechanical leather properties. For that, the leather thickness was adjusted to 1.4 mm and a retanning process was applied to small leather pieces by neutralization, retanning with vegetable extracts, dyeing and fat-liquoring. It was shown that the absorption of vegetable extracts by the leather was greater and faster for the hydrolysable tannins (natural chestnut vegetable extract) than for condensed tannins (mimosa vegetable extract). Different vegetable extracts: natural chestnut, sweetened chestnut, quebracho, gambier, mimosa, tara and cashew, were applied in order to evaluate their effects on leather properties. Properties, as physical-mechanical tests for tear strength, and for ball burst test (to evaluate the grain cracking), and leather behavior regarding softness and grain firmness, were evaluated for the different leather pieces.