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 mode l dispersions of ethyl acrylate-methacrylic acid copolymer (15 wt.% of the acid) prepared by both non-seeded and seeded semicontinuous emuls ion copolymerizations was investigated. Using viscometry and dynamic a nd steady shear measurements, we found that the thickening effect of t he dispersions strongly depends on their particle structure and the in tensity of interactions between the components in the system. In weakl y interacting systems (lower latex concentrations, large latex particl es) the thickening effect of the dispersions is controlled by effectiv e volume fraction of swollen particles. This leads to a higher viscosi ty of systems thickened by more swollen (less crosslinked) particles o btained by the non-seeded process. On the other hand,in strongly inter acting systems (high later; concentrations, small latex particles) low er deformability of more crosslinked particles prepared by the seeded process causes a higher flow resistance of the systems thickened by th is dispersion.