Effects of Chitosan, Poly-diallyldimethylammonium chloride, and Cationic Polyacrylamide on the Optical and Mechanical Properties of Paper from Chemi-mechanical Pulp

Abstract

The effects of chitosan, poly-DADMAC, and cationic polyacrylamide (cPAM) were evaluated relative to the optical and mechanical properties of paper from chemical-mechanical pulp (CMP) from Mazandaran Pulp and Paper Mill. Additives were applied at different concentrations: chitosan (0%, 1%, and 2%), poly(diallyldimethylammonium chloride) (poly-DADMAC): 0%, 0.3%, 0.5%, and 0.7%), and cPAM (0%, 0.25%, 0.5%, and 0.75%). Papers with a basis weight of 60 g/m² were prepared, and brightness, opacity, a* factor, tensile strength, breaking length, tear strength, and burst strength were evaluated. Factorial analysis of variance showed that the effects of the three additives varied depending on the property evaluated. Chitosan positively affected brightness, breaking length, and tear strength; PAM showed a particularly strong effect on breaking length and tensile strength; and poly-DADMAC contributed to improvements in brightness, tensile strength, and the a* factor. Scanning electron microscopy showed a relatively denser and more interconnected fiber network in treated papers, with fewer visibly open void spaces and greater apparent fiber contact. These morphological changes may be associated with improved inter-fiber interactions and the observed changes in paper properties. Among the tested formulations, the combination of 2% chitosan, 0.25% cPAM, and 0.7% poly-DADMAC provided favorable overall performance.