Performance analysis of recycled PET composites reinforced with waste slate dust: physicomechanical and wear properties

In this study, thermoplastic composites were developed from recycled poly(ethylene terephthalate) (rPET) reinforced with waste slate dust (WSD). The composites were processed through twin-screw extrusion followed by injection molding with varying WSD contents (0–20 wt%). The fabricated composites were systematically characterized for their physical, mechanical, sliding wear and morphological properties. The composites exhibited a monotonic increase in Young's modulus from 2.14 to 3.00 GPa and flexural modulus from 2.11 to 3.20 GPa. Flexural strength increased modestly from 72.5 to 76.8 MPa, while the tensile strength remained largely unaffected (38.07 MPa for neat rPET versus 37.27 MPa at 20 wt% WSD). In contrast, the elongation at break was reduced by ca 36% at 5 wt% and ca 80% at 20 wt%, and impact strength dropped from 19.6 to 10.0 kJ m-2. Surface hardness increased slightly (76.1 to 78.0), while wear performance improved significantly, with the specific wear rate decreasing by more than 60% at 20 wt% WSD. These findings show the potential of repurposing slate waste as a functional filler for rPET-based composites, thus providing the dual benefit of performance enhancement and circular material utilization.