Design of pressure-sensitive adhesives by free-radical emulsion copolymerization of methyl methacrylate and 2-ethylhexyl acrylate. 1. Kinetic study and tack properties

Pressure-sensitive adhesives must develop simultaneously two conflicting pr operties: adhesion and cohesion. To fulfill these requirements, it is imagi nable to synthesize suitable materials by free-radical emulsion copolymeriz ation of complementary monomers: methyl methacrylate (MMA) and 2-ethylhexyl acrylate (EHA). The copolymerization kinetics of various MMA/EHA mixtures is studied using a "batch" process. In all cases, the reaction proceeds at a steady-state rate and the copolymer composition (evaluated by H-1 NMR ana lysis) is quite proportional to the conversion degree. The tack properties of films obtained by coalescence of the latexes are evaluated using a "mech ano-optical tack tester", which allows one to determine the tack strength ( F-tack), the tack energy (G(tack)), and the actual contact area (A) as func tions of time. These tack properties are correlated with the copolymers and adhesive film structures.