Synthesis of an amphiphilic amphoteric peptide-based polymer for organic chrome-free ecological tanning

The development of an ecological chrome-free tanning system is a research hotspot and is of great significance to green and sustainable leather production. However, most of the chemicals used in the system exhibit poor compatibility, which means the overall performance of chrome-free tanned leather is not comparable with that of chrome tanned leather. Moreover, the chemicals tend to exhibit poor biodegradability and cause pollution, which, of course, belies the original aim of green chrome-free tanning. With this in mind, amphoteric peptide-based fatliquor (APF) was prepared by introducing a flexible long chain into collagen polypeptide and compounding it with castor oil. The resulting amphiphilic amphoteric peptide-based structure of the APF ensured it had good compatibility with chrome-free tanning systems. In terms of the properties of the chrome-free tanned leather, the softness = 7.88 ± 0.21 mm, air permeability = (2.19 ± 0.04) × 103 mL·(cm−2·h−1), the burst height = 13.32 ± 2.22 mm, and tear strength = 17.77 ± 4.22 N/mm, with its overall performance, were comparable with that of chrome tanned leather. Furthermore, the absorption of the fatliquor and the dye increased to 89.68% ± 0.99% and 92.82% ± 0.93%, respectively, while the APF demonstrated excellent environmental friendliness, meaning the hazardous chemicals used in the leather fabrication process and discharged into the environment would be significantly reduced. This work is of great significance in terms of improving organic chrome-free ecological tanning systems and further promoting cleaner production within the leather industry.