The effect of core–shell particle morphology on adhesive properties of poly(styrene-co-butyl acrylate)

The objective of this work was to develop poly(styrene-co-butyl acrylate) emulsion based adhesives that simultaneously exhibit high cohesive and adhesive strength via structured core–shell particle design. The structure–property relationship was examined and optimized through changing the core–shell ratio, crosslinking of the core by using ethylene glycol dimethacrylate (EGDMA) crosslinker and modification of the soft shell by varying the concentration of a thiol based chain transfer agent (CTA). The prepared polymers were characterized by size-exclusion chromatography (SEC), cryogenic transmission electron microscopy (cryoTEM), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Crosslinking of the core part enables high cohesive strength of the adhesive, whilst the relatively soft shell facilitates adhesion by enabling the proper wetting of the substrate. The optimal adhesive performance in terms of tack, peel strength and shear strength was achieved when the latex particles had a crosslinked core, a shell prepared without CTA and a core–shell ratio of 1:1.5. Thus, we achieved the goal of combining sufficient energy storage and energy dissipation properties in one particle through structured particle design.