Cellulose nanofibril grades’ effect on the strength and drainability of security paper

Abstract

The aim of this study was to evaluate the effect of the grades of cellulose nanofibril (CNF) on the strength and drainage of security paper made from cotton lint mixed pulp (CLMP). Refined CNF (RE-CNF), enzymatic CNF (EN-CNF), and carboxymethylated CNF (CM-CNF) were prepared, and their characteristics were analyzed. Handsheets were made via the addition of three CNFs into CLMP furnish, and their physical properties were measured. The drainability of the CLMP in the presence of CNFs was also determined depending on the grades and the dosage of the CNFs. The CM-CNF was the most effective at enhancing tensile strength by 50%, folding endurance by 464%, and sheet density by 10% when 5% of CM-CNF was added in the CLMP furnish. Moreover, 5% of EN-CNF improved tensile strength by 30% and folding endurance by 156%, but it was less effective as a paper strength promotor than CM-CNF and RE-CNF. A dramatic drainage reduction by 34% was observed when 5% of CM-CNF was added into the CLMP furnish, and EN-CNF presented the highest drainage rate. A high dosage of CNFs deteriorated the furnish drainage and promoted the strength. Therefore, papermakers should select the proper grade and the dosage of CNF for the manufacture of high-strength security paper.