Influence of peroxide modifications on the properties of cereal straw and natural rubber composites

In this study, cereal straw was alkalized and treated with benzoyl or dicumyl peroxide solution. Modified straws were adopted as cellulosic filler in natural rubber biocomposites. Morphological changes and thermal stability of fillers were investigated by scanning electron microscope, Fourier-transform infrared spectroscopy and thermogravimetric analysis technique. The influence of both treated and untreated cereal straws on the rheometric characteristics, static and dynamic mechanical properties, crosslinking density and resistance to aging of composites was examined. Modified straws showed better thermal resistance compared to raw fibers and were resistant up to about 220 °C. The results indicated that the strongest reinforcing effect was achieved using 10 phr of treated cereal straw. Deterioration of the mechanical properties of composites is observed in composites with a higher content of biofiller (20, 30 phr). It might be the result of a strong agglomeration of crumbled straw particles acting as stress cumulative elements in the vulcanizate. Dynamic mechanical analysis revealed the reduction in the tangent delta of treated composites, might be due to improvement in filler/matrix interfacial adhesion. Moreover, all of the vulcanizates proved to be resistant to thermo-oxidative degradation. Cereal straw represents an interesting alternative for commercial fillers and could be successfully applied as a low-cost biofiller, which improved several properties of elastomer composites.