Multimaterial assemblies recycling such as photovoltaic (PV) panels is necessary to guarantee the circularity of materials. Today, PV panels recycling is mostly managed through pyrometallurgy which is limited in terms of materials recovery (polymers are incinerated and recovered silicium and silver yields are low) and emits noxious and greenhouse gases, such as HF generated by fluorinated polymer incineration.
Chemical delamination processes consist in the immersion of panels into a hot solvent to swell the polymeric tie-layers and separate the materials. These processes have the potential to largely improve recovery yields of all materials, but they are environmentally impacting due to the operating conditions and solvent use.
The solvent choice defines the impact of the process. In the current literature, this choice is mostly based on trial and error approaches that are tedious. Moreover, efficient solvents for PV delamination are generally toxic and flammable, which limits the environmental relevance of the processes.
Deep eutectic solvents (DES), which are the association of a hydrogen bond donor and acceptor (HBD and HBA), present interesting solvent properties for such processes. The use of organic hydrophobic molecules as HBA or HBD can impart the solvents with a dual hydrophobic and hydrophilic character that brings a capacity to interact with various molecules to the solvent, including polymers. As HBA/HBD combinations are numerous, it is important to develop a systematic methodology for their choice.
The present topic proposes a methodology based on a combination of theoretical modelling and experimental validation measurements to better understand the contributions of HBD/HBA structures on DES properties. The study will focus on the identification of the interactions between DES and EVA (ethylene vinyl acetate), a widely used polymer in PV panels, through the study of phenomenon of solubilization and solvolysis (covalent bond breakage) to identify the contributions to the delamination phenomenon. At the end of the thesis, the DES selection will be validated through the demonstration of the delamination of a PV panel and the analysis of the separated layers.