Developing Ecofriendly Chrome-Free Leather Processing-Based Polymer-Intercalated Layered Double Hydroxide Supramolecules

Development of eco-friendly chrome-free tanning agents is an inevitable way to realize the sustainable development of the leather manufacturing industry. A sustainable chrome-free leather processing based on polymer-layered double hydroxide (LDHs) supramolecules is reported in this work. P(MAA-IA)-LDH (P-LDH) and GEP(MAA-IA)-LDH (GEP-LDH) supramolecules are constructed by an ion exchange method using P(MAA-IA) (P) and GEP(MAA-IA) (GEP) as intercalators, strengthening the interface interaction between the supramolecules and collagen fibers by improving their dispersion in the resulting leather. Our results indicate that P and GEP enter the LDH interlayer and increase the interlayer distance of P-LDHs and GEP-LDHs from 0.783 nm of LDHs to 1.252 and 1.158 nm, respectively, resulting in an increase in the specific surface areas of P-LDHs and GEP-LDHs. Moreover, compared with LDHs, P-LDHs and GEP-LDHs can be more easily diffused into collagen fibers and uniformly bound onto collagen fiber strands and between the collagen fibrils. The hydrogen bond, ionic bond, and coordination bond formed among collagen with LDH supramolecules can stabilize the integral triple-helical conformation of collagen, giving the resulting leather enhanced thermal stability, porosity, mechanical properties, enzymatic resistance, and decreased swelling ratio. Meanwhile, the incorporation of LDH supramolecules can improve the flame retardancy and smoke suppression property of the resulting leather, and the peak heat release rate (PHRR), total heat release (THR), and smoke production rate (SPR) of GEP-LDH tanned leather decrease by 23.1, 45.1, and 55.5%, respectively, in comparison to those of the pickled pelt. The GEP-LDH tanned leather exhibits better multifunctional properties due to more uniform dispersion in collagen fibers. Moreover, the absorption rate of dyes (91.2%) and fatliquoring agents (85.7%) of GEP-LDH tanned leather is higher than that of F-90 and TWS, close to the traditional chromium tanning agents, and the GEP-LDH tanning system exhibits a better degradability in comparison with the F-90 and TWS tanning systems. This work provides insights for developing a sustainable chrome-free leather system for versatile eco-leather manufacture.