Effect of HBP modified γ-APS on the coating toughness and practical adhesion between galvanised steel and polyethylene

Epoxy-functionalised hyperbranched polymers (HBP) were combined with aminosilanes to form coatings and their effect on the practical adhesion between galvanised steel and polyethylene was investigated. It was shown that HBPs were initially soluble in silane, but phase-separated upon curing. Low modulus nodules formed and modified the crack propagation mechanisms in the coatings. The initial practical adhesion measured in three-point bending decreased with increasing HBP content in the coating. The loss after ageing was, however, not as significant as with pure silane coatings. Interface formation in the aminosilane-HBP/galvanised steel system was investigated to propose explanations for the role of HBP, by the formation of a new morphology.