A STUDY OF THE INTERACTIONS BETWEEN CATIONIC POLYMERS AND COLLOIDAL SILICIC-ACID

The kinetics of the interaction between small colloidal silicic acid ( CSA) particles and cationic polymers have been studied with a stopped- flow technique. The cationic polymers used were cationic polyacrylamid e (CPAM) and cationic amylopectin (CAP). The CSA particles were slight ly aggregated. The size of the primary particles was 5.5 nm and the pa rticles used were, consequently, somewhat larger. The components studi ed are used in papermaking as retention and dewatering aids. The kinet ic processes were followed by turbidity measurements, and the paramete rs obtained from the experiments were the changes in initial rate of t urbidity and the total turbidity. The dependence of these parameters o n electrolyte content and the structure of the CSA particles was studi ed. A comparison between the flocculation behaviour of CAP and CPAM wa s made. Also, the effect of the aggregation state of the CSA on the fl occulation behaviour was studied. We found differences between CAP and CPAM which could be referred to their structural differences. CAP is a very branched and, therefore, a rather compact molecule, whereas CPA M is a linear and extended polymer. (C) 1998 Elsevier Science B.V.