A green tanning method based on POSS-COONa and zirconium: Achieving cleaner leather production

In this study, a two-step green and clean tanning technology based on the polyhedral oligomeric silsesquioxane sodium carboxylate (POSS-COONa) and zirconium was studied to relieve the environmental pressure and resource strain caused by chrome tanning. Firstly, amino sesquisiloxane was prepared from γ-aminopropyl triethoxy silane by hydrolysis and condensation method, and then was substituted with sodium chloroacetate to form POSS-COONa. The POSS-COONa had crystallinity and maintained cube structure by X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Subsequently, POSS-COONa combined with zirconium sulfate was applied in tanning process of goat skin. Compared with untanning, chrome tanning, zirconium tanning crust leather, the shrinkage temperature and thickening rate of combination tanning crust leather were 90.5 °C and 118.3 %, respectively. The tensile strength, tear strength, elongation at break and softness of the combination tanning crust leather were 26.4 MPa, 96.3 N/mm, 105.5 % and 6.5 mm. The scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) showed that combination tanning crust leather collagen fibers were braided more loosely, and POSS-COONa and zirconium sulfate could be uniformly distributed in the collagen fibers. The isoelectric point of the combination tanning crust leather (∼6.7) was similar to that of chrome tanning crust leather (∼7.7). Based on the above results, POSS-COONa combined with zirconium sulfate tanning has a broad prospect in green clean production.