Reusing finished leather waste to produce pigmented thermoplastic polyurethane composite

Footwear industries generate leather waste during the operation. Some of these wastes contain chromium, which may bring environmental concerns. This study aimed to reuse finished leather waste, the major part of these hazardous wastes, via producing a composite with thermoplastic polyurethane (TPU) for shoe soles. Finished leather waste containing black dyes and pigments was used to color the TPU. The finished leather waste was fragmented, milled, micronized and blended with TPU in a ratio of 10%, 15%, and 20% w/w to produce composite materials. The composite materials were evaluated by morphological and thermal characterizations, physical–mechanical analysis, and environmental tests (leaching and solubilization), which presented that the physical–mechanical and thermal properties were within the standard of shoe soles, and the composites can be classified as non-hazardous. The composites enabled a new way of coloring polymeric matrices and reusing leather waste. Graphical abstract