Co-reinforcement of paper wet strength by cellulose nanofibers and NaOH treatment

This study examined the co-reinforcing effects of cellulose nanofibers (CNFs) and NaOH treatment on the wet strength of paper sheets. CNFs were added to the pulp in varying amounts (20–100%), and the resulting dried sheets were treated with 8 wt% and 16 wt% NaOH. The wet strength of the paper sheets was analyzed and compared. When only CNFs were used, the paper sheet exhibited a wet strength of 10.3 MPa. In contrast, when NaOH treatment was combined, the maximum wet strength of the paper sheet reached 23.1 MPa (8 wt% NaOH) and 22.1 MPa (16 wt% NaOH) at 60% CNF, which were 26- and 24-fold higher than that of the paper sheet without CNFs and NaOH treatment (0.87 MPa), respectively. This result shows that combining CNFs and NaOH treatment is a promising approach for reinforcing paper wet strength.