PERFORMANCE OF CATIONIC POLYACRYLAMIDES IN PAPERMAK ING - FLOCCULATION, DRAINAGE AND RETENTION

SUMMARY Flocculation, drainage and retention were investiga ted with distilled water and industrial water. As expected, it was concluded that flocculation, drain age and retention are highly affected by the qualit y of the water and by the polymer characteristics, na mely the charge density, the number of branches and the molecular weight. Flocculation with distilled water shows that the fl oc size increases with the molecular weight and the degree of branching or/and charge density. The opposite occurs with flocs compactness. Drainage tests show that the reduction of the polym er molecular weight or of the charge density increases the drainage time. However, for polymers with a high branching degree, a reduction of the drainage time is detected. An increase from 50% to at least 75% of PCC retention was achieved by adding any of the flocculants. The flocculation results obtained with industrial w ater were similar to those of the tests carried out with distilled water, the difference being the opti mum concentration of each flocculant. As for the results with industrial water, the polymers that ex hibit the better performance are those with high molecular weight and branching. Polymers with low branching resulted in flocs not so resistant to shear and more fragile, thus affecting negatively d rainage/retention.