Thermochemical Delamination of End-of-Life Photovoltaic Laminates: Kinetics, Thermodynamics, and Product Evolution of Next-Generation Encapsulants

Pyrolysis is a cornerstone for the circular economy of photovoltaics, yet the thermochemical mechanisms of next-generation polyolefin elastomer (POE)-based encapsulants remain elusive. Here, the pyrolysis behaviors, kinetic and thermodynamic characteristics, product evolution, and reaction pathways of POE, ethylene-vinyl acetate (EVA), and coextruded EVA/POE/EVA (EPE) films are systematically investigated. All three encapsulants completely decompose without detectable char formation between 280 and 510 °C. Crucially, kinetic and thermodynamic analyses reveal an overall antagonistic interaction between EVA and POE components within EPE structures, diverging from their individual behaviors. Product evolution analysis indicates that EPE initially releases acetic acid and other oxygenated compounds during the first mass-loss stage, whereas products formed in the second stage closely resemble those derived from POE. Radicals generated during EVA deacetylation promote POE cracking and hydrogen transfer, enhancing initial reactivity and increasing oxygenated and short-to-medium chain compound yields by 17% and 8%, respectively, at 600 °C. At later stages, random backbone scission limits gasification, yielding over 95% high-calorific oil, mainly composed of olefins, alkanes, and oxygenated compounds. EPE-derived products exhibit superior energy densities, with gaseous HHVs exceeding natural gas by ∼23% and oils surpassing anthracite coal by ∼23%. These findings provide mechanistic insights that advance the thermochemical delamination of end-of-life photovoltaic laminates employing POE-based encapsulants.