Polyolefin copolymer PE-HEMA with increased metal adhesion properties

Abstract Polyethylene (PE) is a great material, but inherently is hard to functionalize. A neat way to introduce functionality is by including small quantities of a functional comonomer into the polymer. A suitable comonomer bearing hydroxyl functionality is 2-hydroxyethyl methacrylate (HEMA). PE-HEMA copolymers may combine the low cost of PE while allowing for addition of functional groups using the hydroxyl moiety. We analyze copolymers with varying amounts of HEMA by studying the influence of the increasing HEMA content on the mechanical properties, which are found to decrease due to a reduced crystallinity of higher HEMA containing samples. The varying degree of crystallinity between polymer samples was identified as the major influence on the β-transition shift of the PE-HEMA copolymers, which was not off-set by the additional hydrogen bonding in the polymers with, for instance, high HEMA content. At temperature above 220 °C, a permanent cross-linking of the HEMA groups through trans-esterification reaction, can be observed, which can be exploited in applications where cross-linking on demand is necessary. Finally, an improved adhesion of the copolymers to steel and aluminum was demonstrated in lap shear tests, owing to the increased hydrophilicity of the copolymers.