From waste to 3D printing material: upcycling leather shavings in thermoplastic polyurethane and determining the filament fabrication threshold

This study explores the potential of upcycling wet-white leather shavings as a filler in thermoplastic polyurethane (TPU) composites for fused filament fabrication (FFF). Leather waste was chemically analyzed to ensure compliance with environmental and safety regulations before being incorporated into TPU at varying concentrations (10 wt% to 40 wt%). Morphological, thermal, rheological, and mechanical characterizations were performed to assess the feasibility of composites for filament production and 3D printing. Results indicated that composites containing up to 30 wt% leather waste maintained good printability, with a speed of 50 mm/s at 220–225 °C identified as optimal printing parameters. Higher filler concentrations (40 wt%) caused severe embrittlement due to material breakage during spool preparation for printing and during filament handling in the FFF feeding system, rendering the material unusable. Despite these limitations, the material demonstrated a promising potential for sustainable additive manufacturing applications in fashion, automotive interiors, and design, offering an eco-friendly alternative for repurposing industrial leather waste.