Bifunctionalization of Polypropylene via Melt Co‐Grafting Glycidyl Methacrylate and Ferulic Acid for Robust Aluminum Adhesion

The intrinsic low surface energy and weak polarity severely hinder the adhesion of polypropylene (PP) to metal substrates. Although grafting polar monomers onto the PP backbone improves interfacial adhesion, conventional reactive processing methods often suffer from low grafting efficiency, which limits adhesion performance. Herein, a bifunctionalization melt grafting strategy is proposed to simultaneously enhance grafting efficiency and interfacial adhesion by co-grafting glycidyl methacrylate (GMA) and ferulic acid (FA), a natural phenolic compound, onto the PP backbone via reactive processing. Specifically, FA dramatically increases the GMA grafting degree to 5.4% at 1.5 wt% loading, a value nearly sevenfold higher than that of the FA‑free counterpart. The FA-derived hydroxyl and carboxyl groups, together with the epoxy groups of GMA, establish strong physical and chemical interactions with aluminum (Al), as confirmed by x‑ray photoelectron spectroscopy. Consequently, the peel strength of the Al/PGF/Al laminated film reaches 2500 N/m, which is nearly 12 times higher than that of the FA‑free counterpart, with the interfacial failure shifted to a cohesive mode. This work demonstrates a sustainable and effective route to activate polyolefins for high‑performance metal adhesion through phenolic‑assisted interfacial design.