Influence of pH and Conductivity on Properties of Paper Made of Polyelectrolyte Multi layered Recycled Fibers

This study focuses on the modification of recycled fiber surface through polyelectrolyte multilayer (PEM) assembly of cationic and anionic starches using the layer-by layer (LbL) technique. The properties of handsheets made of those multilayered fibers under various pH values and salt concentrations of the pulp suspension were evaluated. It was found that (potential variations had a close correlation with consecutive multilayer construction, and conductivity shifts influenced (potential and strength characteristics more than varying the pH did. Mechanical properties of the handsheets, i.e., tensile index and internal bonding (Scott type), showed considerable improvement ranging from 125 to 365% depending on the pH and conductivity of the pulp suspension. Moreover, higher pH values between 7.5 and 10 and low electrolyte content around 0.001 M NaCl (140 mu S/cm conductivity) were found to be the best conditions to assemble PEMs on recycled fibers, possibly as a consequence of the increased degree of fiber and polyelectrolyte ionization and more efficient conformation of polyelectrolyte.