Effects of mechanical fibrillation time by disk grinding on the properties of cellulose nanofibrils

Cellulose nanofibrils (CNF) were successfully produced from a bleach kraft eucalyptus pulp by a supermasscolloider. Effects of grinding time on structure and properties of CNF and the corresponding CNF films were investigated. Grinding time was important to increase the optical transparency of CNF suspensions. The degree of polymerization (DP) and crystallinity index (CrI) of CNF decreased linearly with the increase in CNF suspension transparency. This suggests optical transparency of a CNF suspension can be used to characterize the degree of fibrillation. Specific tensile strength and Young’s modulus of the CNF films made of CNF suspension with only 0.5 h grinding were increased approximately 30% and 200%, respectively, compared with conventional handsheets prepared by valley beating to 300 Canadian Standard Freeness (CSF). Energy input was only 1.38 kWh/kg for 0.5 h grinding. Grinding beyond 0.5 h produced negligible improvement in specific tensile and specific modulus. Opacity of CNF films decreased rapidly during the first 1.5 h of fibrillation and then plateaued.