Sustainable high-performance elastomers: integrating recycled nano WO 3 into EPDM for enhanced thermal and chemical properties

This study presents a comprehensive investigation into the development of sustainable, high-performance elastomeric composites based on ethylene propylene diene monomer (EPDM) reinforced with recycled nano-tungsten oxide (WO 3 ). The work focuses on the effect of using recycled WO 3 on enhancing the thermal stability, flame retardancy, and chemical durability of the composites. The recycled nano-filler was incorporated into the EPDM matrix at various loadings (0–20 phr). Flame retardancy was evaluated using horizontal burning tests and limiting oxygen index (LOI) measurements, in which the WO 3 content significantly reduced the burning rate from 15 mm/min to 4 mm/min and increased the LOI to 21.7 %. Thermal gravimetric analysis (TGA), conducted from room temperature to 600 °C, demonstrated a marked improvement in thermal stability, with the onset decomposition temperature shifting from 221 °C to 228 °C and a 22 % increase in char residue at 600 °C. Furthermore, chemical resistance was evaluated by immersion in xylene, nitric acid (HNO 3 ), and sodium hydroxide (NaOH). Swelling measurements in xylene indicated a robust filler-polymer interaction, reducing the solvent uptake by 3.65 %. A comparative study of Shore A hardness before and after chemical immersion revealed that WO 3 -filled EPDM maintained its structural integrity better than neat EPDM, with a minimal hardness loss (less than 10 %) after acidic and basic treatment. Optical microscopy confirmed these results, showing significantly lower surface degradation and pitting in the reinforced composites compared to the neat rubber. These findings position the recycled WO 3 /EPDM composite as a robust, eco-friendly material for industrial applications requiring high thermal and chemical resilience.