Experimental and density functional theory calculations on the pyrolysis characteristics and mechanism of polarizing film, the main organic component of waste liquid crystal display panels

Waste liquid crystal display (LCD) panels contain a significant amount of rare precious metal In, and In extraction is also the industry's driving force There are currently many reports on the recovery of In from waste LCD panels, but there are not many on the recovery of organic components from waste LCD panels, particularly polarizing film recovery. Pyrolysis is one of the most promising technologies for organic waste recycling. This work utilized TG, TG-FTIR, and Py-GC/MS to examine the pyrolysis properties and product distribution of the polarizing film. Additionally, a range of kinetic analysis methods and density functional theory calculation were utilized to examine the pyrolysis kinetics and mechanism of the polarizing film. Polarizing film are mainly composed of cellulose triacetate (CTA), triphenyl phosphate (TPHP), polyvinyl alcohol (PVA) and polyacrylate. The results showed that CTA first breaks the glycosidic bond through a synergistic reaction to form an active CTA with a low degree of polymerization, and then forms small molecule compounds such as glucan triacetate analog, methylglyoxal, and allyl benzoate, among others, through free radical reactions. PVA first forms long-chain olefins through a dehydration process, and then short-chain olefins by a free radical reaction. TPHP may merely undergo melting and evaporation rather than undergoing a chemical reaction. Polyacrylate generates esters and aldehydes mainly through free radical reactions. This study provides a theoretical foundation and comprehensive reference for the pyrolysis and recycling of waste LCD panels.