A study of energy dissipation in exfoliated polyurethane/organoclay nanocomposites.

Exfoliated polyurethane (PU)/organoclay nanocomposites were prepared by in situ polymerization of polyol/organoclay mixture, chain extender and diisocyanate. The effect of organoclay on energy dissipation in the exfoliated PU/organoclay nanocomposites during cyclic deformation at strain ratios of 50%, 100% and 200% was investigated experimentally and by molecular dynamics (MD) simulation. The addition of organoclay resulted in extra energy loss in the PU nanocomposites and greater energy dissipation in the exfoliated nanocomposites compared with intercalated ones containing the same percentage of organoclay. With the help of MD simulation, understanding of the energy dissipation arising from the addition of organoclay to the exfoliated PU nanocomposites is now clearer. The nanoplatelets exhibited reversible orientation behaviour at a low strain ratio of 50%, suggesting that the additional energy dissipation may be due to the frictional sliding at the interface between polymer chains and the surfaces of organoclay layers. However, when the sample was subjected to large strain, the orientation of nanoplatelets revealed more irreversible behaviour indicating that the extra energy dissipation is due to both the frictional sliding at the interface and the orientation of the nanoplatelets. The additional energy dissipation was also influenced by the strength of interactions between polymer chains and clay platelets: the stronger interactions, the greater the energy dissipation.