Tuning adhesion/cohesion properties of water-borne pressure-sensitive adhesives through rigid core–soft shell structured particles design: effect of amino resins cross-linkers type

In the present research work, a pressure-sensitive adhesive (PSA) with hard core-soft shell structured latex particles was synthesized through semi-continuous emulsion polymerization of butyl acrylate (BA) and acrylic acid (AA). Urea formaldehyde (UF) and melamine formaldehyde (MF) were used to cross-link the core materials and the effects of type and weight percentage of the cross-linker were evaluated on the chemical, morphological, thermal, and adhesion properties of the resulting latexes. Chemical analysis verified that both UF and MF successfully cross-linked acrylate chains. Thermal analysis corroborated that both MF and UF slightly increased the glass transition temperature of the resulting latexes. Morphological observations confirmed that with increasing UF, the particles size continuously decreased, while with increasing MF, the particles size first increased and then decreased. Gel content increased with increasing UF and MF contents, however, this increase was more significant for MF. The evaluation of the adhesion properties confirmed that tackiness of the PSAs decreased continuously with increasing UF, however, the adhesion first increased and then decreased with increasing MF content. Peel strength firstly showed an increasing trend but then with increasing UF and MF amounts it revealed a decreasing trend. Shear strength was raised with increasing UF and MF contents, however, the increase was more pronounced for MF. Taking all together, MF cross-linker at 1 wt% relative to the total weight of the core monomers produced a PSA with the best equilibrium among tack, peel, and shear strength.

Graphical abstract