MECHANICAL PROPERTIES OF NATURAL RUBBER AND STYRENE–BUTADIENE RUBBER NANOCOMPOSITES WITH NANOFILLERS HAVING DIFFERENT DIMENSIONS AND SHAPES AT LOW FILLER LOADING

Abstract

Reinforcement of rubber by nanofillers has been a topic of great interest in recent years. This work compares the reinforcing efficiency of nanofillers with different topologies such as spherical (carbon black and silica), fibrous (silicon carbide nanofibers and carbon nanotubes), and sheetlike (nanoclays, expanded graphite, and graphene) in two different diene rubbers (natural rubber [NR] and styrene–butadiene rubber [SBR]) at low loadings. Tensile strength improved by 88% in the case of NR and 57% in the case of SBR by the addition of just 3 phr of graphene nanoplatelets with high aspect ratio and surface area. An increase in the Mooney–Rivlin constant (C1) with filler loading variation was also observed for these filler systems in NR and SBR. The analysis of the composites using a tube model showed that the confinement of rubber chains due to the presence of fillers with a high aspect ratio gave rise to a lower tube diameter. The addition of nanofillers resulted in higher hysteresis losses, confirming their ability for higher energy dissipation. A higher Payne effect was observed in the composites due to the formation of a percolating filler network, which was accompanied by a weak strain overshoot in the loss modulus. Dynamical mechanical analysis of the composites showed a significant increase in the storage modulus of the composites at both low and room temperatures. The reduction observed in the tan δ was correlated with the crosslink density of the composites.