Synthesis of poly(BA-co-MMA) dispersions having AA/MAA/AAm/MAAm comonomers and the comparison of their effect on adhesive performance

Pressure-sensitive adhesives (PSAs) bond to surfaces by applying a light pressure, and must be soft and tacky which requires the glass transition temperature (T_g) below −20 °C. Performance characterization is done via adhesion and cohesion. Achievement of high adhesion and high cohesion together is a challenge for PSA applications. In this study, a series of PSAs with different monomer compositions were prepared using emulsion polymerization to show the effect of polar comonomers on adhesive properties. The main monomer was butyl acrylate and methyl methacrylate, and the polar comonomer was chosen from acrylic acid (AA), methacrylic acid (MAA), acrylamide (AAm), and methacrylamide (MAAm). The adhesive performance was studied at 0.5, 1.25, and 2% of the polar comonomer content based on total monomer composition. Water-borne acrylic adhesive polymers obtained with constant thickness were coated onto a bi-oriented polypropylene and evaluated for the effect on performance by measuring their loop tack, peel, and shear strength on several surfaces, including stainless steel, glass, aluminum, and low-density polyethylene (LDPE). Results showed that MAAm increases cohesive forces compared to AAm due to dipole–dipole interactions. When the amount of polar comonomer with T_g above room temperature has been decreased, there have been a significant increase on the adhesion properties and tackiness of the polymers beside on LDPE due to its non-polar surface characteristics. When AA and MAA compared, there have been a significant increase on cohesive strength on all the surfaces. The highest adhesion has been obtained using AA in a lower amount. The adhesion and cohesion balances were better achieved with 0.5% s/m MAAm and 2.5% s/m AA, respectively. This study does not only show the effect of polar monomers on adhesion and cohesion properties, but also show the adhesive and cohesive effects of hydrogen bonding on different surfaces.