Polyacrylamides cationic

Hydrolysis of cationic polyacrylamides prepared from copolymeri2ation of acrylamide and cationic ester monomer can occur under very mild conditions. A substantial loss in cationicity can cause a significant loss in performance in many apphcations. Copolymers [69418-26-4] of acrylamide and acryloxyethyltrimethylammonium chloride [44992-01 -0] CgH gN02(Cl), for instance, lose cationicity rapidly at alkaline pH (37). 

Salts, eg, alum or calcium chloride [10043-52-4] and cationic polyacrylamides are effective retention aids in bleached and unbleached kraft pulp. 

A number of cationic muds have been developed and used. These ate formulated around quaternary amines or positively charged polymers (108,109). The polymer in some iastances may be a cationic polyacrylamide. Poly(dimethylarnine-fi9-epichloiohydrin) is another material that has been used successfiiUy for drilling shale formations (110,111). Some of these additives may requite a salt such as sodium or potassium chloride for best results. 

Poly(acrylamide-diallylethylamine-HCl) (cationic polyacrylamide pAM-HCl) was prepared by gamma radiation-initiated copolymerization of acrylamide with di-allylethylamine-HCI in aqueous solution at the optimum composition for copolymerization of acrylamide with diallylamine derivatives [61]. 

Anionic polyacrylamide (pAM-AANa) Cationic polyacrylamide (pAM-DAEA- HCl) Amphoteric polyacrylamide (pAM-AANa- DAEA-HCl) ... 

Flocculants cause colloidal clay particles to coagulate thus promoting separation from the drilling fluid which has been circulated down the wellbore and returned to the surface. The treated fluid may then be pumped back down the well bore. Sodium chloride, hydrated lime, gypsum, sodium tetraphosphate, polyacrylamide, poly(acrylamide-co-acrylic acid), cationic polyacrylamides, and poly(ethylene oxide) have been used commercially. 

Cationic polyacrylamide may be used in the initial treatment stages to promote rapid polymer adsorption (201). Adjustment of the pH may allow deeper penetration of the fluids in an aluminate crosslinking system prior to gelation (202). A process involving injection of alternate slugs of stoichiometrically equivalent amounts of partially hydrolyzed polyacrylamide and Al O ) has been evaluated in the laboratory permeability of sana packs were reduced by more than 96% (203). Mixtures of Al(IIl) and Zr(IV) have also been evaluated as partially hydrolyzed polyacrylamide crosslinkers (204). 

Figure 6.7 A typical cationic polyacrylamide used in paper making.

Figure 6.13 The effect of charge density (degree of substitution of cationic groups) of a cationic polyacrylamide on the microelecirophoretic mobility of microcrystalline cellulose (figures in brackets are negative).

Figure 6.16 Reconformation of adsorbed cationic polyacrylamide (MW 4 x 106) on cellulose fibres as shown by the kinetics of adsorption and adsorption stoichiometry (measured by counter ion release).

Solberg D, Wagberg L (2003) Adsorption and flocculation behaviour of cationic polyacrylamide and colloidal silica. Colloids Surf A Physicochem Eng Aspects 219 161... 

Figure 5.39. Theoretical (a) and experimental (b) amount adsorbed as a function of the salt concentration for polyelectrolytes of varying charge density a, as Indicated. The theoretical figure was calculated for 0-6 and a surface charge density

Figure S.40. Charge due to adsorbed polyelectrolyte per unit of surface charge (Sa s) as a function of the total (added) amount of polyelectrolyte charge per unit surface charge (9 ). for cationic polyacrylamides of different molecular weights (expressed in K 3 kg/mole) (a) and of different polymer charge densities (b) adsorbed from salt-free solutions on anionic polyst3TFene latex. Redrawn from ref.

Flocculation of alumina suspensions obtained by the sequential addition of polystyrene sulfonate (M j, = 4600) and cationic polyacrylamide (M, = 4,000,000) at pH 4.5 is compared in Figure 7.33 with that obtained using single polymers. While the anionic polystyrene sulfonate had only a minor effect, cationic polyacrylamide did not produce any flocculation. However, when used together, both polymers adsorb completely. This coadsorption is attributed to the interaction of complexes between cationic polyacrylamide and the polystyrene sulfonate at the solid-liquid interface. The mechanism of the superior flocculation obtained with the dual polymer system is illustrated schematically in Figure 7.34. The anionic polystyrene sulfonate adsorbs on alumina surface and acts as an anionic anchor for the adsorption of the long-chain cationic polymer, which ultimately provides interparticle bridging and excellent flocculation. 

The effect of cationic polyacrylamide adsorption on the stability of aqueous cellulose suspension has been electro-optically studied by Khlebtsov et al. [19,20], The variations in transmitted light modulation in low-frequency (3-45 Hz) square-pulsed a.c. fields have been found to correlate well with the adsorption isotherm. The influence of sodium carboxymethylcellulose adsorption on the electro-optical behavior of negatively charged Si02 (ani-sometric aggregates, consisting of monodisperse spherical particles) has also been studied, and an increase of the particle induced dipole moment and its time of relaxation has been found [21,22],... 

GV Bulidorova, VA Myagchenkov. Kinetic peculiarities of kaolin sedimentation in the presence of anionic and cationic polyacrylamide flocculants. Coll J 57(6) 736—740, 1995. 

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