Rheological properties of cellulose nanocrystals engineered polylactic acid nanocomposites

Ecofriendly materials such as polylactic acid (PLA) and cellulose nanocrystals (CNCs) are widely sought as potential substitute for petrochemical-based plastics. Uniform dispersion of cellulose nanocrystals in polymer matrices has inhibited their wide-spread application. In this study the influence of masterbatch preparation techniques on molecular structure, melt strength, rheological and dynamic mechanical properties of nano composite were systematically analyzed. Film casting and spin-coating methods were used to prepare masterbatches. Nanocomposites were obtained by masterbatch dilution via melt compounding followed by injection molding process. The higher molecular weight and lower molecular number were observed in spin-coated samples in comparison with film cast nanocomposites. The spin-coated nanocomposites exhibited higher storage modulus than film cast samples in the glassy state. However, tan S curves exhibited higher peak value in spin coated nanocomposites, which were in good agreement with higher dispersity index of spin-coated samples. The complex viscosity of PLA and nanocomposites exhibited non-Newtonian behavior at a low shear rate, followed by shear thinning phenomenon. The spin-coated nanocomposites demonstrated higher complex viscosity than film cast samples, which was attributed to higher molecular weight in spin-coated samples. The shear-thinning tendency in spin-coated samples was higher than film cast nanocomposites.