Decapsulating waste photovoltaic laminated modules by the combination treatment of thermal field and the solvent of the N-methyl-2-pyrrolidone.

Abstract

In order to achieve the goal of dual-carbon strategy, China has vigorously developed the photovoltaic industry. However, the life cycle of photovoltaic panels is limited, resulting in a large number of waste photovoltaic laminated modules. Waste photovoltaic laminated modules contain rich metallic and organic resources, and have high recycling value. In the process of recycling waste photovoltaic laminated modules, decapsulation is a key step. Pyrolysis was considered as the common decapsulation technology, but it would cause problems such as loss of organic resources, producing pyrolytic carbon black and toxic gases. This paper reported a wet decapsulation technology. It employed the combined treatment of thermal field and the solvent of N-methyl-2-pyrrolidone to swell ethylene vinyl acetate for liberating the materials of waste photovoltaic laminated modules. Under the conditions of 170 °C and 30 min, the 3 cm × 3 cm-sized waste photovoltaic laminated module was completely decapsulated. The analysis of Fourier transform infrared spectroscopy indicated that N-methyl-2-pyrrolidone was grafted to ethylene vinyl acetate structure, and some new groups were generated, such as N-H and C = O. Calculation results of density functional theory showed that N atom and methylene were active sites in N-methyl-2-pyrrolidone. They could react with the cross-linked bridge and side chain of ethylene vinyl acetate to form N-H and C = O groups, which made ethylene vinyl acetate lose its viscosity and produce decapsulation effect. This paper presents new scientific information for the eco-friendly wet decapsulation of waste photovoltaic laminated modules.