Jegon Lee

Flocculation behavior of cellulose nanofibrils under different salt conditions and its impact on network strength and dewatering ability

Flocculation of cellulose nanofibrils (CNF) was induced by charge neutralization with different types and concentrations of salt, and its effects on the network strength and dewatering ability of the CNF suspension were investigated. Aggregation of the CNF suspension was evaluated by measurement of light transmission using Turbiscan equipment. This procedure enabled us to characterize the aggregation and sedimentation behavior of nanofibrils under different salinity conditions. Aggregation and sedimentation of CNF occurred on salt addition because the degree of compression of the electrical double layer was changed by adsorption of cations onto the CNF, depending on the type and concentration of salt. The changes in network strength of the CNF suspension due to flocculation were evaluated using a conventional oscillatory rheometer. The viscosity, storage modulus, and yield stress of the CNF suspension increased with an increase in the ionic strength of the suspension. Microrheology measurements using the dynamic light scattering technique were also adopted to characterize the viscoelastic properties of the CNF suspension, revealing that CNF suspension containing a high concentration of salt showed more solid-like behavior. In addition, the aggregation degree of the CNF affected the dewatering ability of the CNF suspension. Bivalent cations were more effective for increasing the network strength and dewatering for a small amount of added salt compared with monovalent cations.

Strengthening effect of polyelectrolyte multilayers on highly filled paper

Abstract Polyelectrolyte multilayering (PEM) treatment is regarded as one of the surface modification techniques to increase paper strength. In this study, the strengthening effect of PEM treatment of highly filled paper was investigated. PEM treatment was performed on both fiber and filler with cationic starch and anionic polyacrylamide systems. Both approaches provided an improvement in the strength of filled paper. However, the strengthening effect of PEM treatment on fibers became weaker as filler content increased, whilst the PEM treatment on fillers was more effective in improving the strength of the highly filled paper. This was because PEM treatment on fillers improved bonding strength between fiber and filler as well as bonding strength between fillers. This was confirmed by the evaluation of specific debonding factor between fiber and filler, and the measurement of the breaking strength of dense film composed of fillers.

Effect of salt concentration in polyelectrolyte multilayering on properties of modified GCC and filled paper - OPEN ACCESS

This study investigated the effects of salt concentration in polyelectrolyte multilayering (PEM) treatment on the properties of ground calcium carbonate (GCC) and the mechanical strength of the filled paper with the PEM treated GCC. Polydiallyldimethyl-ammonium chloride (PDADMAC) and poly(sodium 4-styrene sulfonate) (PSS) were used as cationic and anionic polyelectrolyte, respectively, for the PEM treatment. The PEM treatment was performed in 0 0.1 M NaCl solutions. Polyelectrolyte multilayers could be formed without flocculation of the PEM treated GCC particles, which was confirmed by the zeta potential and particle size of GCC. The amount of polymer adsorbed onto GCC showed different behavior depending on salt concentration. At relatively higher salt concentration (0.1 M NaCl) in this study, more adsorption of polyelectrolytes occurred, which resulted in a thick multilayer on GCC. In addition, it provided strength improvement of the filled paper when the PEM treated GCC was used as filler. As a results, salt concentration during PEM treatment affected both of properties of the PEM treated GCC and mechanical properties of filled paper. ADDRESSES OF THE AUTHORS: Jegon Lee (ljg234@snu.ac.kr), Kyujeong Sim (sim0828@gmail.com), and Hye Jung Youn (page94@snu.ac.kr), Department of Forest Sciences, College of Agriculture and Life Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826 Corresponding author: Hye Jung Youn