Improving reinforcement of natural rubber by networking of activated carbon nanotubes

Reinforcement of natural rubber was achieved using carboxylated multiwalled carbon nanotubes (c-MWCNT) dispersed with sodium dodecyl sulfate. The structure of the reinforced latex films was investigated by TEM and AFM. The tensile and dynamic-mechanical tests demonstrated a strong enhancement in the Young’s modulus (∼10-fold), tensile strength (∼2-fold) and storage modulus (∼60-fold) at low-strain in the rubbery state with up to 8.3 wt% of MWCNTs, with a small reduction in elongation at break. Dielectric measurement at room temperature revealed a low percolation threshold (<1 wt%) associated with the formation of an interconnected nanotube network. Latex film formation plays a critical role in the network formation due to the segregation effect at the surface of latex beads. We observed large Payne and Mullins effects due to the mechanical behavior of the nanotube network. The disruption of the network during stretching induces both an increase of electrical resistivity and mechanical stress-softening.