The influence of HLB (hydrophilic-lipophilic balance) and surfactant blend concentration (SBC) on flocculating performance of latex particles of acrylamide and [2-(acryloyloxy)ethyl]trimethylammonium chloride copolymers with a cationic charge density of 40%, obtained by inverse microemulsion copolymerization by using a surfactant blend of Arlacel 83 and Softanol 90 as emulsifier and Rolling M-245, a mixture of n-decane and n-tetradecane in about 40/60 weight ratio, as oil phase, has been studied for a total comonomer concentration of 32.5% (w/w). Comonomer inverse microemulsion copolymerizations were carried out in the semicontinuous mode by adding continuously an aqueous solution of sodium metabisulfite (SMB) as initiator into stirred inverse comonomer microemulsions. From 7.75 to 8.26, HLB has a strong influence on average molar mass (Mw) and flocculating performance (FP), the higher the HLB the higher the FP. A small decrease in SBC causes a dramatic increase in Mw and a decrease in FP although the influence on copolymer viscosity is small. Results are explained in terms of copolymer structuring degree and collapsed state of copolymer chains inside latex particles as well as in terms of the observed composition drift with conversion.
Influence of surfactant structural characteristics on stability of inverse microemulsions of acrylamide-based anionic flocculants (40% (w/w) sodium acrylate and 60% (w/w) acrylamide, based on total amount of comonomers) has been studied by using 17 surfactant blends consisting of two non ionic surfactants with different length of hydrophobic chains, different number of hydrophobic chains per molecule, and with and without double bonds on their hydrophobic chains. Experimental evidence shows that unsaturated emulsifiers are needed for obtaining stable inverse microemulsions of acrylamide-based anionic flocculants and that presence of double bonds on the hydrophobic tails of a surfactant is its major structural characteristic to stabilize this kind of polymeric inverse microemulsions (PIM).