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 properties: adhesion and cohesion. To fulfill these requirements, it is imaginable to synthesize suitable materials by free-radical emulsion copolymerization 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 1H NMR analysis) is quite proportional to the conversion degree. The tack properties of films obtained by coalescence of the latexes are evaluated using a “mechano-optical tack tester”, which allows one to determine the tack strength (Ftack), the tack energy (Gtack), and the actual contact area (A) as functions of time. These tack properties are correlated with the copolymers and adhesive film structures.