Effect of nanotube size on the mechanical properties of elastomeric composites

Using a mesoscale coarse-grained model and dissipative particle dynamics, the mechanical properties of a cross-linked elastomer filled with surface-functionalized carbon nanotubes are investigated under uniaxial stretching, depending on nanotube length, nanotube bulk density, and crosslink density. Importantly, the system is deformed at equilibrium, allowing the cross-linked chains to be fully relaxed. Our results suggest that for a composite with chemical couplings between polymer and fillers, there actually exist different regimes of elastomer reinforcement, manifesting themselves in the stress-strain response, which is found to be dramatically dependent on the nanotube length L and the characteristic network mesh size l: while the effect of the filler particles is relatively small at L l(-1) similar to 1, there is a sharp increase in the mechanical modulus when L l(-1) >> 1.