Nanocomposites based on renewable thermoplastic polyurethane and chemically modified cellulose nanocrystals with improved mechanical properties

In this study, freeze-dried cellulose nanocrystals (CNC) from eucalyptus, redispersed in dimethylformamide, is grafted with a polyurethane-based dimer to improve the interaction with the matrix, a biobased thermoplastic polyurethane (TPU). Dimer grafting onto CNC is confirmed by Fourier transform infrared spectroscopy. Wide-angle X-rays diffraction and thermogravimetry indicate that neither the CNC crystal structure nor its thermal stability are altered, but its crystalline fraction decreased due to the presence of the dimer on the CNC surface. TPU/CNC nanocomposite films are obtained by solvent casting. Nanocomposites with nanofiller content below the theoretical percolation threshold (3.9 wt %) do not present significant changes in the mechanical properties. However, nanocomposites with 5.0 wt % of treated CNC shown good elongation and a Young modulus increase of 55 and 30% when compared with the neat TPU and untreated nanocomposites of same composition, respectively. In addition to that, the CNC addition increases the film opacity. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46736.