Pressure-Sensitive Adhesives Based on Nanostructured Latex Particles

Abstract

Conceivably, when a polymer with two opposite properties is required, two different monomers may chemically be combined by a simple copolymerization reaction. One of the commonest techniques is to synthesize copolymers by an emulsion polymerization. The homogeneous particles obtained by this method simply show a balance between the individual properties of the homopolymers. In contrast, two-stage emulsion polymerization affords simultaneously an improvement of both opposing properties (synergy). In order to study the influence of particle structure on adhesion properties, a series of nanostructured particles based on a copolymer of vinyl acetate and butylacrylate P(VA-co-BuA) and polybutylacrylate (PBuA) were synthesized by semicontinuous emulsion polymerization. The particle size and P(VA-co-BuA)/P(BuA) ratio were varied. The obtained dispersions were characterized by quasi-elastic light scattering. The adhesion properties (tack, peel, and shear strength) of the particles were evaluated according to industrial methods. It was found that improved values of peel and tack were obtained when a P(VA-co-BuA) rigid core was enveloped with a thin shell made of PBuA. A strong influence of the particle size and PBuA content on the adhesion properties was detected. The best performance was found at large particle sizes and thick shells.