Lignin-coated cellulose nanocrystals as promising nucleating agent for poly(lactic acid)

We report the effect of lignin-coated cellulose nanocrystals (L-CNCs) on the crystallization behavior of poly(lactic acid) (PLA). PLA/L-CNC nanocomposites were prepared by melt mixing, and the crystallization behavior of PLA was investigated using differential scanning calorimetry. Isothermal crystallization data were analyzed using Avrami and Lauritzen-Hoffman secondary nucleation theory, while the equilibrium melting temperature was determined using the nonlinear Hoffman-Weeks method. The lignin-coated cellulose nanocrystals acted as a nucleating agent and significantly increased the rate of crystallization and degree of crystallinity of PLA in PLA/L-CNC nanocomposites. The Avrami exponent, n, increased in the presence of L-CNCs, displaying a conversion from lamellar morphology to two-dimensional crystal growth. PLA/L-CNC nanocomposites also gave lower values of the nucleation parameters, K-g and sigma(e), due to a reduction in the activation energy for nucleation.