Pseudo-solid-like behavior of nanocomposite melts

Observations are reported on nanocomposite melts (low-density polyethylene and polypropylene reinforced with montmorillonite nanoclay at concentrations ranging from 0 to 10 wt.-%) in small-amplitude shear oscillatory tests. A constitutive model is derived for the linear viscoelastic response of a nanocomposite melt, which is treated as an inhomogeneous non-affine network of chains. Given a nanoclay content, the stress-strain relations involve 4 material parameters that are found by fitting the experimental data. The pseudo-solid-like response of nanocomposite melts is associated with formation of a “long-tail” in the distribution of activation energies for sliding of junctions due to jamming of stacks of clay platelets.