Utilization of fly ash acid residue as a reinforcing filler in ethylene propylene diene monomer rubber

Fly ash acid residue (FAAR), a by‐product of circulating fluidized bed fly ash extracted Al₂O₃ by acid leaching method, has been posing problems because of its disposal. The major chemical components of FAAR are amorphous SiO₂ (66.38 wt %) and unburned carbon (20 wt %). Attempts were made for its application as a reinforcing filler for ethylene propylene diene monomer (EPDM) rubber in this article. Surface modification for FAAR by silane coupling agent (Si69) was carried out. The effect of surface modification and unburned carbon existing in FAAR on the performance of FAAR was characterized by Fourier transform infrared and dispersibility test. The results indicated that surface modification could reduce the hydrophilicity of FAAR and unburned carbon also had positive effect on the dispersion of FAAR particles in kerosene. The effect of partial replacement of carbon black by FAAR on the curing behavior, mechanical properties, and morphological characteristics of EPDM rubber was also studied. It was proved that with partial replacement of carbon black by FAAR, the cure time (t₉₀) and maximum torque (M_H) of EPDM composites increased with the content of FAAR. The mechanical properties were significantly improved when 15 wt % of carbon black was replaced by FAAR. SEM micrographs confirmed that surface modification can improve the compatibility between FAAR and rubber matrix. Unburned carbon existing in FAAR was also beneficial to the interface bonding. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013