Adsorption of polyelectrolyte complexes onto recycled unbleached fibers. Effects of ionic strength

MOCCHIUTTI, PAULINA; GALVÁN, MARÍA V.; PERESÍN, MARÍA S.; ZANUTTINI M.A.

Hesinki

Congreso; 50th Anniversary, Nordic Polymer Days, 2013; 2013

Society for Wood and Polymer Chemistry in Finland; University of Helsinki; Aalto University

In order to expand the possibilities of using recycled unbleached cellulose fibers in paper production, the effect of the addition of polyelectrolyte complexes (PECs) on such fibers was studied. PECs were prepared by using poly(allylamine hydrochloride) (PAH) and polyacrylic acid (PAA), and PAH and O-acetyl-4-O-methylglucuronoxylan (Xyl) extracted from beechwood. The latter is a natural, abundant and renewable polyelectrolyte that holds a high potential to improve paper strength. Initially, polyelectrolyte charge densities at different ionic strengths (0.001 N, 0.01 N and 0.1 N NaCl) and neutral pH were determined using the polyelectrolyte titration method (1,2). Cationic PECs were formed by adding, at a controlled rate, the anionic polyelectrolyte solution (PAA or Xyl) to the cationic polyelectrolyte solution (PAH). From turbidity curves (turbidity as a function of anionic-to-cationic polyelectrolyte mass ratio (3)) or taking into account the charge densities of the polyelectrolytes, dosages of PAA or Xyl needed in order to obtain cationic PECs containing 50% of PAH free positive charges were selected. Polyelectrolyte titration method was utilized to determine the charge densities of the obtained PECs while colloidal stabilities were determined using Turbiscan optical analyser. Figure 1 shows that both cationic PECs are stable after 48 hours. Furthermore, stirring of the solution reverses the effects of sedimentation in the case of PAH/Xyl complex. Adsorption isotherm of the cationic complexes of PAH/PAA and PAH/Xyl at different ionic strengths and neutral pH were built by using the polyelectrolyte adsorption method (4). It was found that the use of PECs, instead of simple polyelectrolytes, allows reaching high amounts of cationic additive adsorbed, especially at high ionic strength. Additionally, in order to understand further the adsorption phenomena, adsorption studies of PECs on model cellulosic surfaces were monitored using quartz crystal microbalance with dissipation (QCM-D). Paper properties such as tensile strength, and compressive strength, showed significant increases upon PECs adsorption.