The influence of charge density and molecular weight of cationic poly (vinyl alcohol) on paper properties

摘要

The influences of the charge density and molecular weight (MW) of cationic-modified poly (vinyl alcohol) (C-PVA) on the properties of fibers and papers (hand-sheets) were systematically investigated in this work. The results showed that the final adsorption of polymers on fibers declined upon increasing the charge density of polymers. The surface of fibers was smoothed by adsorbing polymers, leading to the enhancements of light scattering coefficient of papers and the freeness of fibers. The improvement in the mechanical properties of papers was maximized by adding 2.0% (wt. on fibers) of high MW C-PVA with the charge density of 0.4 meq/g .The enhancements were associated with the increases in fiber wall and bonding strengths, probably attributed to the molecular weight, configuration, and charge affinity of polymers on the fiber surface. In fact, the polymers possessing tail-and-loop configurations on the fiber surface are claimed to bridge fibers that eventually increased fiber and paper strengths. Meanwhile, the apparent density and roughness of papers reached the maximum and the minimum in the presence of high MW polymer with the charge density of 0.4 meq/g. However, the impact of the low MW polymers on the fiber wall and bonding strengths appeared to be limited. Also, the C-PVA with higher charge density tended to lower the brightness of papers slightly.