Green fabrication of leather solid waste/thermoplastic polyurethanes composite: Physically de-bundling effect of solid-state shear milling on collagen bundles

As a luxury and precious natural resource, leather is widely used in human life for decades, but efficient and eco-friendly solution to leather solid waste (LSW) still maintains an urgent and challenging issue that collagen bundles with chemically crosslinked structure are hard to reproduce and thus only hydrolysis and pyrolysis are accessible. Herein, we reported a facile method to physically de-bundle the crosslinked collagen fibers (CFs) and prepared LSW-based composites with excellent comprehensive properties via solid-state shear milling ((SM)-M-3) technology. It was found that the interaction between CFs in LSW was easily broken down under the three-dimensional shearing force generated by (SM)-M-3 equipment and the collagen bundles with millimeter-scale diameter could be untied into independent CFs with micro-scale diameter, which can significantly promote the utilization of CFs with over 50 wt% in thermal polyurethane elastomer (TPU). The even dispersion and exposure of hydrogen bond displayed great impact on tensile strength and elongation of the TPU/CF composite, which were similar to 14.5 MPa and 100%, respectively, as well as good thermal stability and water absorption. The S3M technology not only provides a new way to facile fabrication of CFs, but also shed light on new designing principals of leather-containing products.