Comparison of LbL Nanotechnology and Refining on the Properties of Pulp and Paper Made from Recycled Fibers

In this study, in order to constitute polyelectrolyte multilayers (PEM) using Layer-by-Layer nanotechnology, recycled fibers were subsequently treated with cationic starch (CS) and anionic starch (AS) multi-layers each layer conducted at neutral pH for 10 minutes. Also, to compare with mechanical of refining, the pulp was refined for 25 minutes to the freeness of about 291 mL.CSF using Valley beater, and finally, handsheets (60 g/m2) were made from both types of refined and unrefined pulps and its characteristics were evaluated. The results showed that with PEM forming the charge inversion of fiber surface took place in higher value of zeta potential compare to the refining, led to increase the electrostatic absorption of particles like cationic starch. In consistent with above result, with beating of OCC pulp to the freeness of 291 mL.CSF with paper density of 0.545 g/cm3, tensile index and bending resistance were measured 37.92 N.m/g and 12.2 mN respectively. However, in CS/AS multilayer systems paper strength has dramatically increased without significant increase of density. In CS/AS multilayer system at 7th layer, density 0.445 g/cm3, tensile index, 33.51 N.m/g and bending resistance, 21.4 mN were measured. Adding 0.001M NaCl (conductivity, 140μS/cm) to the CS/AS multilayer system these values were measured 0.472 g/cm3, 36.65 N.m/g and 25.6 mN, respectively. Therefore, these results indicated that CS/AS PEMs systems are comparable and competitive with beating or refining from strength improvement point of view.