CO2 absorption into a polymer within a multilayer structure: The case of poly(ethylene-co-vinyl acetate) in photovoltaic modules

The delamination of photovoltaic modules with supercritical CO2 is an interesting approach to integrate photovoltaics into a circular economy. This article describes the first phase of this process: the absorption of CO2 into poly(ethylene-co-vinyl acetate) (EVA-28), one of the layers in a photovoltaic module. The swelling of the polymer, determined by an on-line coupling between high pressure cell and an optical method using digital camera, under 60–200 bar at 60, 75 and 90 °C, was well reproduced by a modified Sanchez-Lacombe equation of state. The diffusion coefficient of CO2 into EVA-28 was determined using the same approach and was found to range, at 130 bar, from 1.1 × 10−9 m2·s−1 at 60 °C to 1.8 × 10−9 m2·s−1 at 90 °C. A preferential CO2 diffusion at the rear side of the cell, due to a high porosity, and at the “backsheet” interface was highlighted. [Display omitted] •Original methods are presented to study how EVA absorb supercritical CO2.•Swelling of EVA layers under CO2 was quantified by macroscopic image analysis.•CO2 solubility in EVA obtained by Sanchez-Lacombe modeling.•CO2 diffusion coefficient in EVA determined at 80–200 bar at 60, 75 and 90 °C.•CO2 diffusion is enhanced at layer interfaces in photovoltaic modules.