UV-curable hyperbranched nanocomposite coatings

Nanoparticles have been used to reinforce polymer matrices since the late 1980s, with promising results. Hyperbranched polymers are densely branched molecules with a globular structure, leading to lower viscosity and many end-groups, creating property-designing opportunities. Here, the two research areas, nanocomposites and hyperbranched polymers, were combined to investigate the possibility of creating a nanocomposite resin, in order to prepare a UV-curable coating system. Nanocomposites were prepared from the hyperbranched polyester Boltorn® H30, acrylated to 30% and 70%, and the unmodified layered silicate Na+montmorillonite, added both before and after the acrylation of Boltorn® H30. Films prepared from 30% acrylated Boltorn® H30 with clay added after the acrylation, having a mainly exfoliated structure according to X-ray and TEM, exhibited the largest property improvement, compared with the unfilled film. These property improvements comprised a harder surface, better scratch resistance, better adhesion to metal substrates and a small improvement in flexibility.