Improved adhesion of metal-polymer sandwich composites using a spontaneous polymer grafting process

Improving adhesion at the metal-polymer interface is a critical issue for metal-polymer sandwich composites. Herein, we report an efficient way to increase the adhesion via grafted organic layers. A redox activation process was used to graft organic layers to steel surfaces using 4-para-nitrobenezenediazonium (NBD) salt and L-ascorbic acid (LAA). Successful formation of a grafted organic layer was confirmed by microstructural analysis and its performance as an adhesion primer was evaluated by the single-lap shear test under various temperature and wet conditions. The introduction of NBD-induced layers grafted to various steel surfaces provided more than a 100% increase in adhesion between the polymer and the steel surface due to the interaction between the polymer chains of the substrate polymer and the organic layer covalently grafted to the metal surface. Finally, exposure of the steel and polymer composites to hot water demonstrated that the grafted adhesion primer enhanced the durability of the steel and polymer interface under harsh conditions.