Role of cationic polyacrylamide in fiber‐CaCO₃ pigment interactions

Abstract

It is believed that the action of cationic polyacrylamide as a retention aid for incorporating pigment particles into a paper is based on its ability to form a polymeric bridge between particles and pulp fiber suspended in water. When the polymer is added to a mixture of fibers and pigments, this process is complicated by the different rates of polymer adsorption on the fibers and the pigment particles, the rate of collision between them, and the charge reversal of the polymer from the hydrolysis. To elucidate under which conditions the polymer can form a bridge, the processes of polymer adsorption and pigment-fiber interaction were separated. A deposition of pigment particles onto fibers suspended in water was investigated, using both components pretreated with the polymer. The results indicated that polymer adsorbed on fiber can form a bridge with untreated pigment particles regardless of the polymer charge. On the other hand, negatively charged hydrolyzed polymer adsorbed on the pigment does not form a bridge with untreated fiber. When both the fiber and the pigment are pretreated, the bridge formation depends on their surface coverage by polymer and its charge. No deposition takes place when both components are sufficiently coated by anionic hydrolyzed polymer, which indicates electrosteric repulsion.

Effect of Shearing Forces and Flocculant Overdose on Filler Flocculation Mechanisms and Floc Properties

“…6,[28][29][30] Therefore, the monitoring of the chord length distribution has also allowed us to have an idea about the existence of repulsive electrostatic forces among particles when the flocculation process occurs. GCC Flocculation Induced by CPAM.…”

“…The flocculation of small particles did not affect the evolution of the measured number of counts when CPAM was added to the suspension because the flocculation mechanism induced by CPAM is by bridges between particles and does not require neutralization. 6,[28][29][30] Therefore, the monitoring of the chord length distribution has also allowed us to have an idea about the existence of repulsive electrostatic forces among particles when the flocculation process occurs.…”

“…The flocculation of small particles did not affect the evolution of the measured number of counts when CPAM was added to the suspension because the flocculation mechanism induced by CPAM is by bridges between particles and does not require neutralization. ,− …”

Adsorption of new hydrophobic polyacrylamide on the calcite surface

“…Since being synthesized, hydrophobic polyacrylamide (HPAM) has been gaining attention in application fields. It has been widely used in paper making, medicine, water treatment, agriculture, and especially petroleum exploitation . Theoretically, the molecular weight of HPAM is huge, and there is a large volume of hydrophilic groups on the chain of HPAM; this leads to an increase in the viscosity of the aqueous solution after it HPAM disappears quickly into water.…”

Evaluation of an Alternative Flocculation System for Manufacture of Fiber−Cement Composites

“…However, there is very limited information about flocculation mechanisms and floc behavior in the fiber cement industry. Many authors have studied the mechanism of the flocculation of different suspensions, even cement suspensions, induced by PAM, concluding that it involves bridge formation. ,,− However, the mechanism of cement flocculation induced by the PFR/PEO system has not been studied. Different mechanisms have been proposed for the flocculation of papermaking suspensions induced by this dual system.…”