Adsorption characteristics of cationic-modified poly (vinyl alcohol) on cellulose fibers–A qualitative analysis

Poly (vinyl alcohol) (PVA) has been widely used in papermaking and coating processes. However, its application as a strength agent is confined due to its poor affinity to adsorb on fibers. To address this problem, PVA with different molecular weights were rendered cationic via introducing quaternary ammonium groups along PVA chains. The work presented in this paper focused on the adsorption behavior of the cationic-modified PVA (C-PVA) on cellulose fibers (sulfite pulps). The results, obtained from polyelectrolyte titration, indicated that the adsorption of C-PVA with low charge densities was enhanced, regardless of polymer molecular weight (MW). However, the C-PVA with high MW had markedly lower maximum coverage than the C-PVA with low MW. Adsorption of low MW polymers achieved saturation at a relatively shorter period than high MW polymers. The influence of pH, ionic strength (or electrolyte concentration) and temperature on the adsorption of C-PVA on fibers were also investigated. Apart from the study on the adsorption using colloidal titration, the degree of substitution of cationic groups on PVA was quantified using 1H NMR.