Polyethyleneimine as a surface activator for low surface energy substrates bonded with cyanoacrylate adhesives

Abstract The modification of surface properties of polypropylene (PP) substrates has attracted much attention in fundamental science and industrial applications. Primer treatment is one of the most simple and facile surface modification methods. This study used polyethyleneimine (PEI) as a surface activator for bonding polypropylene substrates with ethyl cyanoacrylate (ECA) adhesive. We have understood the effect of various factors such as the open time, solvent composition, optimum concentration and molecular weight of the primer. The bonding strength was maximum when the substrates were bonded immediately on priming. It was also observed that the solvent composition plays a minor role in the development of bond strength. The bond strength of substrates coated with a primer having a PEI concentration as low as 0.05% showed better results and was, in fact, three times better than the unprimed ones. It was also concluded that a low molecular weight PEI performs better than one having a higher molecular weight. DSC results confirmed that an improvement in strength is due to an increase in the molecular weight of the ECA polymer, which occurs in the presence of PEI molecules.