(70c) Effect of Lignin on Nanofibrillated Cellulose Production

Nanofibrillated celluloses (NFCs) have shown many potential applications due to their biodegradability, high surface-to-volume ratios and high mechanical properties. The NFCs can be produced through the mechanical defibrillation of cellulosic fibers with or without a chemical or enzymatic pretreatment. However, the NFCs trend to form cellulose bundles through the inter-fibrillar hydrogen bonding. Moreover, the mechanical defibrillation can cause the thermolytic scissions of the glycosidic bonds of cellulose and concomitantly create cellulose radicals. The formed cellulose radicals can react each other and result in the undesirable recombination of the NFCs. As a result, the NFCs yields are typically low.

Lignin is a free radical scavenger, and therefore can stabilize the cellulose radicals through forming the very stable phenoxy radicals. On the other hand, lignin is hydrophobic, and thus can interrupt and reduce the inter-fibrillar hydrogen bonding once it attached to the NFCs surface. So, lignin could potentially counteract the recombination reactions between the highly reactive cellulose radicals and prevent the formation of cellulose bundles. Herein, this study investigated the effects of lignin on the NFCs production. The results clearly showed that lignin greatly facilitated the mechanical defibrillation of cellulosic fibers and thus improved the NFCs yields. And lignin also reduced the diameters of the NFCs.