Plasma polymer film as an interlayer to improve polymer-metal composites disassembly and recycling efficiency

Metal coatings on polymers are widely used in industries such as electronics, automotive, and packaging for their conductivity, barrier properties, and aesthetics. While strong adhesion between metal and polymer is typically beneficial, it poses a significant challenge for recycling. The separation of these layers is highly challenging (e.g., mechanical cleaning, burning, dissolving) and costly, often resulting in the disposal of such waste causing considerable environmental impact.
In this context, this study explores the use of plasma polymer films (PPF) as intermediate layers between metals and polymers to improve the recyclability. The PPF would ensure a strong adhesion with the metallic layer (i.e., Al) while weakening the interface with the polymer when exposed to a stimulus (e.g., heating).
The PPFs are synthesized from a gas mixture of C2H4 and CO2, known to generate PPF with a high content of carboxylic acid and alcohol functional groups1 ensuring a strong interaction with aluminum coatings2. The analysis of the XPS data reveals an increase in the OH and COOH concentration with the CO2 content in the gas mixture and the power. For extreme conditions, this also results in intense etching. Similarly, the cross-linking density also increases correlating the evolution of the glass transition temperature of the PPF. The latter property is crucial as it governs the behavior of the PPF when exposed to a thermal stimulus.