Elongational Flow and Strain-induced Hardening

Okamoto et al. [48] first conducted an elongation test on PP-based nanocomposites in the molten state at constant Hencky strain rate, so using elongation flow optorheo-metry [49]. They also attempted to control the alignment of the dispersed silicate 

As in PP-based nanocomposite systems, the extended Trouton rule, 3r 0 (y t) = r E (so t), also does not hold for PLANC melts, in contrast to the melt of pure polymers. These results indicate that in the case of P LANC, the flow induced internal structural changes also occur in elongation flow [48], but the changes are quite different in shear flow. The strong rheopexy observed in the shear measurements for the PLA-based nanocomposite at very slow shear rate reflects the fact that the shear-induced structural change involved a process with an extremely long relaxation time. 

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