Highly crystallized and tough polylactic acid through addition of surface modified cellulose nanocrystals

To prepare a fully organic polylactic acid (PLA)-based bio-nanocomposite, cellulose nanocrystals (CNCs) were grafted by PLA through ring-opening polymerization (ROP) of L-lactide monomers onto CNCs. The grafting process was evaluated by (HNMR)-H-1 and FTIR spectroscopic methods. The effect of surface-modified CNCs (M-CNCs) was investigated on thermal, mechanical, rheological, and dynamic mechanical thermal properties of PLA. The M-CNCs were successfully dispersed in the PLA matrix. Isothermal and non-isothermal DSC studies revealed that M-CNCs caused an intensive increase in crystallization kinetics and therefore nucleation density and crystallization extent. DSC, XRD, and DMTA analyses indicated the formation of different crystal structures [alpha, alpha', beta] in PLA after addition of M-CNCs. Rheological analysis was carried out for microstructural investigation of the nanocomposites. Interestingly, after the addition of M-CNCs not only the tensile strength and modulus of the samples increased but also the toughness of PLA was considerably improved.