(545c) Tailored and Integrated Production of Carboxylated and Lignin Containing Cellulose Nanocrystals and Nanofibrils for Composite Applications

Here we demonstrate di-carboxylic acid hydrolysis for the integrated production of lignin containing cellulose nanocrystals (LCNC) and nanofibrils (LCNF) using two unbleached mixed hardwood chemical pulps of lignin contents of 3.9 and 17.2%. Acid hydrolysis experiments used maleic acid solution of 60 wt% concentration at 120°C for 120 min under ambient pressure. Yields of LCNC were low of less than 6% under this set of condition. The higher lignin content samples produced LCNC with greater height (diameter) of 25 nm but similar length of approximately 230 nm to that from the lower lignin content fibers (height of 20 nm). Interestingly, the higher lignin content sample resulted in LCNF with smaller height (diameter) of 7 nm but longer length of > 1 µm, or greater aspect ratio than the LCNF from the lower lignin fibers of height 10 nm and length < 1 µm. Lignin protected cellulose from esterification which resulted in LCNC and LCNF that was less carboxylated compared to those lignin-free CNC and CNF and therefore had lower charges. However, lignin is more hydrophobic and thermally stable than carbohydrates therefore LCNC and LCNF are favorable for composite applications.