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.

Comparative study of the mesostructure of natural and synthetic polyisoprene by size exclusion chromatography-multi-angle light scattering and asymmetrical flow field flow fractionation-multi-angle light scattering.

This paper presents results from the first analyses of the mesostructure of natural rubber (NR) by asymmetrical flow field flow fractionation (AF4). The results are compared with those obtained by size exclusion chromatography (SEC) in terms of average molar masses, radius of gyration and insoluble part (or gel quantity). Comparable results were obtained for the sample not containing gel. Conversely, for samples with gel, significant differences were found due to the presence of microaggregates. Contrary to SEC, AF4 fractionation enables partial fractionation of polyisoprene chains and microaggregates in a single run without preliminary treatment. The results presented here also highlight the special structure (very compact spheres) of microaggregates in NR compared to chemical crosslinked microaggregates in synthetic polyisoprene. The advantages and drawbacks of both techniques for analysing NR samples are also discussed.