Adsorption of natural polyelectrolyte complexes for improving of paper strength

MARÍA V. GALVÁN; PAULINA MOCCHIUTTI; GERARDO D. ROSSI; MIGUEL A. ZANUTTINI

Santa Fe

Congreso; 14º Congreso Internacional de Metalurgia y Materiales 2014; 2014

SAM_CONAMET

The aim of this work is to characterize PECs formed from two natural polyelectrolytes: xylan (Xyl) and chitosan (Ch) and evaluate the effects of their addition on a recycled pulp from kraft liner paper. PECs were prepared at pH 6.0 and were considered: a) two ionic strengths (0.01N and 0.1N NaCl) and b) different order of addition of polyelectrolytes. The cationic complexes (CatPECs) were formed by adding the xylan on chitosan solution, and the anionic complexes (AnPECs) by adding the chitosan on xylan solution. During the PEC formation, the mass ratio of polyelectrolytes corresponding to charge neutralization was determined by streaming current technique. The shapes of the turbidity curves as a function of the mass ratio of polyelectrolytes were dependent on the order of addition, and at low ionic strength (NaCl 0.01N), the turbidity values were higher. For the characterization of cationic and anionic PECs containing 70% free chitosan and xylan charges, respectively, their charge densities were determined by colloidal titration method, and their stabilities using a Turbiscan optical analyzer. Results showed that these complexes were stable even after seven days. Also, PECs were added to cellulosic pulp in a Britt Dynamic Drainage Jar, and their retentions were calculated from the concentration of the complexes in the filtrates using the phenol-sulphuric acid method. When the ionic strength was increased, the amount of PEC retention was higher. Finally, the addition of CatPECs on pulp or AnPECs on previously chitosan treated pulp increased 53% and 48% the dry tensile strength, and 74% and 49% the compressive strength, respectively.