Self-stratifying epoxy vitrimer/fluoropolymer coatings: Thermally induced detachment for substrate recovery

In this study, we propose an innovative approach to improve the sustainability of polyvinylidene fluoride (PVDF) coatings by incorporating an epoxy vitrimer primer. The dynamic nature of the vitrimer allows for controlled coating removal under specific conditions, facilitating end-of-life management and recyclability. The self-stratifying coating, developed through a one-step application and curing process, consists of an epoxy vitrimer bottom layer and a PVDF top layer. This system was designed to spontaneously form two distinct layers during curing. Two vitrimer resins containing disulfide dynamic bonds were evaluated as base layers: polysulfide epoxy (EPS35) and diglycidyl ether of vanillyl alcohol (DGEVA). The epoxy/fluorinated systems were applied on different substrates (carbon coated aluminum or copper foils) and at different thicknesses (from 25 µm to 230 µm) and then characterized. All systems present two distinct coating layers with the epoxy on the substrate and the PVDF on top. Cross hatch cutter test results confirmed the perfect adhesion of the coating at room temperature. The epoxy layers self-healing was proved, highlighting the achievement of a dynamic network. Finally, the coating films were removed easily from the substrate under thermal stimuli of at least 100 °C. Finally, the influence of key parameters on stratification, applied wet thickness, substrate and epoxy formulation was evaluated. In all cases, a well-defined stratification (type I), perfect adhesion at room temperature (type “0”) and a total removal at 100 °C was consistently observed. • Self-stratifying epoxy vitrimer/PVDF coatings achieved via one-step processing. • All systems show type I stratification and perfect room-temperature adhesion. • Thermal stimulus at 100 °C enables complete coating removal from substrates. • Vitrimer layers exhibit self-healing behavior under mild thermal conditions. • System thickness and substrate type do not affect stratification or removability.