Effect of the chain-transfer-agent content on the emulsion polymerization process and adhesive properties of poly(n-butyl acrylate-co-acrylic acid) latexes

The preparation of a series of poly(n-butyl acrylate-co-acrylic acid) latexes with different contents of chain-transfer agent are reported, and investigations into the adhesive properties of the latexes were made. The latexes were prepared at a solid content of 50 wt % by a two-stage sequential emulsion polymerization with the monomers «-butyl acrylate (BA) and acrylic acid (AA). This process consisted of a batch seed stage (BA), which gave a particle diameter of 112 nm, which was then grown by the semicontinuous addition of monomers to a final diameter of 303 nm. Dynamic light scattering was used to monitor the particle diameters and showed that the particles grew without significant secondary nucleation occurring. The molecular parameters were characterized by gel permeation chromatography and dynamic mechanical analysis. The adhesive properties measured were loop tack force, peel strength and shear resistance according to Fédération Internationale des Fabricants et Transformateurs d'Adhésifs et Thermocollants sur Papiers et Autres Supports (FINAT) test methods. The relationship between pressure-sensitive properties and molecular parameters, such as gel content and molecular weight, was evaluated.