Thickening effect of dispersions of ethyl acrylate-methacrylic acid copolymer prepared by different polymerization routes

Thickening of latices (particle diameters 105, 157 and 221 nm) by model dispersions of ethyl acrylate-methacrylic acid copolymer (15 wt.% of the acid) prepared by both non-seeded and seeded semicontinuous emulsion copolymerizations was investigated. Using viscometry and dynamic and steady shear measurements, we found that the thickening effect of the dispersions strongly depends on their particle structure and the intensity of interactions between the components in the system. In weakly interacting systems (lower latex concentrations, large latex particles) the thickening effect of the dispersions is controlled by effective volume fraction of swollen particles. This leads to a higher viscosity of systems thickened by more swollen (less crosslinked) particles obtained by the non-seeded process. On the other hand, in strongly interacting systems (high latex concentrations, small latex particles) lower deformability of more crosslinked particles prepared by the seeded process causes a higher flow resistance of the systems thickened by this dispersion.