Characterization of fire-retardant composites from waste materials: balancing properties and performance

The effectiveness of wastepaper (wP) reinforced with waste polyethylene (wPE) and cow horn ash (CHA) as a fire-retardant additive (FRA) was studied for fire-retardant composites (FRCs) application. The research investigates the effects of varying CHA content (0 wt.% to 50 wt.%) on the developed composites. The analysis involved determining the physical, mechanical, flammability, and thermal properties, also, the surface morphologies and function groups were assessed to evaluate the microstructure and chemical interactions. Modifying the wP/wPE matrix with CHA enhanced fire resistance and mechanical properties. The FRC containing 30 wt.% CHA (FRC-30) exhibited the best overall performance, with a density of 2.89 g/cm³, hardness of 623.29, water absorption of 3.13%, tensile stress modulus of 6.55 MPa and 802.37 MPa, and flexural strength and modulus of 8.04 MPa and 445.81 MPa, respectively. Its fire-retardant properties also exhibited the lowest burning rate (1.86 × 10⁻³ g/s), a reduced heat release (41.20 kJ), a superior ignition time of 83.96 s, and a reduced fire spread (122 mm/s). FRC-30 also demonstrated excellent thermal properties of thermal diffusivity of 73.63 m²/s and low thermal conductivity of 8.87 × 10⁻² W/m.K. The hydroxyl and phosphate groups in CHA, identified through FTIR, enhanced the interfacial bonding, and dispersion within the wPE matrix, as observed via SEM. This resulted in improved mechanical performance and fire resistance. The study concluded that FRC-30 offers an ideal combination of fire retardancy, mechanical strength, and thermal stability. This makes it a potential candidate for use in construction, insulation, and other engineering fields where enhanced fire safety is crucial.