Processing–Structure–Property Relationships in Flame-Retardant Recycled LLDPE Composites Filled with Semiconductor Chip Tailings

Semiconductor chip tailings (SCTs), a glass fiber-rich residue from waste integrated circuit chips, were incorporated at 50 wt % into recycled linear low-density polyethylene (rLLDPE) to develop flame-retardant composites for rigid flooring. The effects of zinc borate (ZB), magnesium hydroxide (MH), and zinc stearate (ZnSt) on the processability, flame retardancy, and mechanical performance were investigated. All SCT-filled composites showed markedly higher stiffness, with the tensile modulus increasing from 530.4 MPa for neat rLLDPE to 2951.5 MPa and yield strength increasing from 11.8 MPa to 20.7 MPa, although ductility and impact strength decreased. The ZB/MH/ZnSt-containing composites showed the best flame-retardant performance, achieving a limiting oxygen index of 28% and a char residue of 59.5%. ZnSt improved melt processability but reduced the strength and impact performance. All composites exhibited water absorption below 1.0% after 45 days, supporting their potential for further development in floor-related applications.