Nano Fly Ash - The Future Work Horse For The Rubber Industry

Fly ash, a waste from the thermal power plants is a resource material for many other industries particularly for the rubber industries. Fresh fly ash having particle size in the range from 60 to 350 microns was converted into nano fly ash of particle size varying from 60 to 150 nanometers by the top down mechano-chemical activation process and was used as a novel reinforcing filler in styrene butadiene rubber.  Nano- fly ash (NFA)-Styrene Butadiene Rubber (SBR) composites     at varying doses of NFA from 1 to 60 phr was evaluated for their physico-mechanical properties, crosslink density and degree of dispersion. A comparison was made with SBR composites derived fresh fly ash (FFA), HAF black and precipitated silica as fillers at equivalent levels. It is interesting to observe that in case of FFA and NFA containing composites, the optimum cure time was found to be independent of the dose of FFA and NFA, whereas for carbon black filled composites the optimum cure time decreased and with silica filled composites it increased with increase in the dose of the filler. Ultimate tensile strength exhibits a sharp rise from 1.98 MPa for gum SBR to 20.53 for 60 phr NFA filled SBR composite. Hardness, tear strength, heat buildup and rebound resilience of SBR- NFA composites are comparable with those of HAF black filled and precipitated silica filled SBR composites at equivalent dosages.  The chemical crosslink density of NFA filled SBR composites are found to be higher than that for FFA and silica filled SBR composites but marginally lower than that for HAF black filled SBR composite. The rubber-filler interaction parameter calculated by using Kraus equation is found to be 0.384 for NFA filled SBR composites which is higher than that for silica filled SBR composites (0.328) and much higher than that for FFA filled SBR composites (0.042), whereas it is marginally lower than that for HAF black filled SBR composites (0.416). The bound rubber content increases with increase in the NFA dosage in the composites and reach a value very close to that of HAF filled SBR composites, which is much higher than that of precipitated silica filled SBR composites. Dispersion studies under the TEM revealed a uniform dipersion of NFA   in the SBR matrix with very little agglomeration; as observed in case of HAF black in SBR matrix.