Nonmonotonic Strain Rate Dependence on the Strain Hardening of Polymer Nanocomposites.

This Letter investigates the external deformation on modifying the polymer-nanoparticle (NP) and NP-NP interactions as well as their influences on the macroscopic properties of polymer nanocomposites (PNCs). Specifically, the applied uniaxial extension brings together the NPs along the transverse stretching direction and catalyzes the percolation transition from the initially well-dispersed NPs in the PNCs. The percolated NP network thus increases the strength of PNCs and leads to a strong surge in the elongation viscosity at very low strain rates, exhibiting the unexpected nonmonotonic strain rate dependence on the strain hardening. These results reveal explicitly the unconventional roles of the external deformation on modulating the relative strength of the polymer-NP and the NP-NP interactions, enabling advanced structures and properties control of PNCs.