Novel epoxidized natural rubber composites with geopolymers from fly ash waste.

Geopolymer (GP) based on fly ash waste from electric power generating plants has been applied in natural rubber composites as a sustainable solution to deal with this industrial solid waste. This alternative type of rubber filler can reduce hazards and environmental impacts of that waste. Novel elastomer composites based on geopolymer (GP) filled epoxidized natural rubber (ENR) were prepared with various GP loadings. Cure characteristics, mechanical, dynamic, thermal, and morphological properties of the ENR/GP composites were characterized. It was found that incorporating GP significantly affected cure characteristics of ENR compounds, decreasing scorch and cure times by accelerating the cure rate via the excessive metal oxides in GP. Furthermore, the ENR/GP composites with 15 phr GP showed the highest tensile strength due to maximal chemical linkages of hydroxyl groups and metal oxides on GP surfaces and epoxide groups in ENR. This was confirmed by a new FTIR peak for SiOH bending vibrations at the wavenumber 970 cm-1. Furthermore, the Payne effect in ENR/GP composites was assessed from the relationship of shear modulus and strain amplitude at a fixed oscillation frequency. It was found that the Payne effect, or the level of filler-filler interactions, increased with GP loading. In addition, it was also found that the glass transition temperature (Tg) of ENR/GP composites increased with GP loading. Furthermore, TGA and TSSR results suggest that the metal oxide in GP activated degradation of the rubber network at elevated temperatures.