(665h) Effect of Polyacrylamide Polymers On Floc Size and Rheological Behaviour of Papermaking Suspensions

The influence of cationic and anionic Polyacrylamides (PAM) on the floc size, and rheological behaviour of papermaking suspensions has been investigated. Cationic C496 and C492 and anionic A130LMW  PAMs were used in this study. At optimum PAM concentrations, the floc sizes were larger in the presence of the anionic PAM than the cationic PAMs due to the repulsive forces between the anionic PAM and particle surface, leading to the formation of open structure flocs of less effective density. The results also show that increasing the cationic surface charge from 10 % to 35 % reduces the floc size and increases the effective floc density.

On the other hand, the magnitude of yield stress, elastic and viscous moduli are strongly dependent upon the floc structure; with greater values being observed for the cationic PAM than for the anionic PAM flocculated papermaking suspensions. The difference in the shear sensitivity may be attributed to floc structure-related adsorption. It was found that the yield stress and viscoelastic behaviour are important factors that should be considered when selecting the type of polyelectrolyte for use in a particular solid liquid separation. This work has been very successful in establishing the link between greater particle attraction and higher yield stress, and elastic and viscous modulus.