A mixture of acetic acid (25%) and sulfuric acid (3%) stirred at 70 °C for 30
min was prepared to activate CNF. The acetylation of CNF was performed by adding
10 mL anhydride acetic and 50 mL acetic acid, and then stirring for 4 h at 100 °C. The
acetylated CNF were then added to a solution of acetone: methanol (2:1, v:v) and
chloroform to fulfill the sequential phase transition of acetylated fibers to chloroform,
which could then be adequately mixed with PLA