Construction of fully biomass-based regenerated leather crust via dry-process and its mechanical and hygienic properties

The traditional dry process for producing regenerated leather relies heavily on synthetic polymers, which results in poor flex resistance, inadequate hygienic properties, and reduced environmental sustainability. To address these issues, a fully biomass-based composite regenerated leather crust was developed. In this approach, chrome-tanned leather shavings (CLS) were used as the primary matrix, natural high-hollowness kapok fibers (KF) were introduced as a long-range bridging phase, and modified starch (MS) served as a green binder. A multi-level structured KF/CLS@MS composite was subsequently prepared via hot-pressing molding. The results demonstrate that gelatinized MS constructs an extensive hydrogen bond network, achieving tight interfacial bonding among the heterogeneous fibers. At a KF content of 2.0% and an MS content of 13.3%, the composite exhibits optimal comprehensive performance: the tensile strength reaches 2.59 MPa, and the flex resistance exceeds 80,000 cycles. Mechanism analysis reveals that the flexible KF creates a “long-range bridging and flexible energy dissipation” effect, significantly enhancing the dynamic fatigue resistance. Furthermore, the unique hollow structure of KF provides the material with excellent air permeability (439 mL/(cm²·h)), water vapor permeability (1118 g/(m²·24 h)), and thermal insulation (thermal conductivity of 0.13 W/(m·K)). This study offers an innovative approach for the high-value utilization of leather solid waste and the development of green, functional regenerated leather products.