Effect of fiber drying on properties of lignin containing cellulose nanocrystals and nanofibrils produced through maleic acid hydrolysis

The effect of fiber drying on the properties of lignin containing cellulose nanocrystals (LCNC) and nanofibrils (LCNF) produced using concentrated maleic acid hydrolysis of a never dried unbleached mixed hardwood kraft pulp was evaluated. Two drying conditions, i.e., air drying and heat drying at 105 °C were employed. It was found that drying (both air and heat) enhanced acid hydrolysis to result in slightly improved LCNC yields and less entangled LCNF. This is perhaps due to the fact that drying modified the cellulose supermolecular structure to become more susceptible to acid hydrolysis and the enhanced hydrolysis severity at the fiber surface when using dried fibers. Drying substantially improved LCNC crystallinity and LCNF suspension viscoelastic behavior. The present study quantitatively elucidated the effect of pulp drying (either air or heat) on producing cellulose nanomaterials and has practical importance because commercial market pulp (heat dried) is most likely to be used commercially.