Quantifying dispersion of layered nanocomposites via melt rheology

Rheol. measurements are used to compare clay nanocomposites prepd. through melt mixing using two different polypropylene matrixes. Steady state and transient nonlinear rheol. expts. are employed to sep. the contributions of flow induced orientation of the tactoids and particulate network build-up. The conditions under which the rheol. properties are dominated by the aggregate network are subsequently identified. Under these conditions, the low frequency linear viscoelastic behavior is analyzed using scaling concepts for fractal networks to det. the degree of network formation by exfoliation. Moreover, the high frequency behavior of the moduli can be used to quickly assess the dispersion quality. The results from the anal. of the linear viscoelastic data are compared to structural features extd. from electron microscopy and small angle X-ray scattering data. (c) 2007 American Institute of Physics.