Shear rheology of polylactide (PLA)–cellulose nanocrystal (CNC) nanocomposites
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A simple method for the preparation of polymer-cellulose nanocrystal (CNC) nanocomposite is shown to yield good dispersion of CNCs within a polylactide (PLA) matrix, which consequently resulted in the lowest rheological percolation threshold reported so far for polymer-CNC systems. The rheological behavior of the nanocomposites was determined in dynamic, transient, and steady-shear flow fields in the molten state. The complex viscosity and storage modulus of the nanocomposites increased markedly with CNC content, particularly at low frequencies; the samples were highly shear thinning and exhibited a transition from liquid- to solid-like behavior as the CNC concentration increased. Larger values for steady-state viscosity, yield stress, shear stress, and first normal stress difference were reported for the more concentrated nanocomposites. Also, pronounced overshoots in the transient start-up viscosity of the nanocomposites were observed. These results could be ascribed to the formation of an interconnected CNC network within the PLA matrix.
KeywordsNanocomposites Cellulose nanocrystals (CNCs) Polylactide Rheological properties Dispersion
The authors acknowledge the financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC). The authors are also grateful to FPInnovations for providing the CNCs.
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