Polyelectrolyte complexes of Xylan and Chitosan. Application to improve the mechanical properties of recycled paper furnish

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

Medellín

Congreso; VIII Congreso Iberoamericano de Investigación en Celulosa y Papel 2014; 2014

RIADICYP, PROVALOR CYTED, UNIVERSIDAD PONTIFICIA BOLIVARIANA

Natural polyelectrolyte complexes (PECs) of chitosan (Ch) and xylan (Xyl) were prepared, characterized, and evaluated for improving the papermaking properties of high quality recycled unbleached softwood kraft pulps. The charge densities of Ch and Xyl solutions were determined by polyelectrolyte titration method at different ionic strengths and pH 6.0. Then, complexes were prepared considering a) two ionic strengths (0.01N and 0.1N NaCl) and b) the order of addition of polyelectrolytes. Results show that the shapes of the turbidity curves as a function of the mass ratios of polyelectrolytes depend on the order of addition. By streaming current measurements, the mass ratio corresponding to charge neutralization was determined for the four complexes studied. Taken into account these results, cationic complexes (containing 70% free cationic charges) were obtained by adding the Xyl on Ch solution, and anionic complexes (containing 70% free anionic charges) by adding the Ch on Xyl solution. The charge densities of these complexes were determined by polyelectrolyte titration method and the colloidal stability by using a Turbiscan optical analyser. It was found that the complexes were stable even after 7 days. The retention of PECs on pulp was studied in a Britt Dynamic Drainage Jar system and it was found that the amount retained was low, but the increase in ionic strength, increased the amount of PEC retained. Finally, the addition of cationic complexes or anionic complexes on pulp increased 53% and 48% the tensile strength, and 74% and 49% the compressive strength, respectively.