Plastic identification from end of life flat monitors by hyperspectral imaging methods

The amount of flat monitors from televisions, notebooks and tablets dramatically increased in the last years, thus originating a corresponding growth in Waste from Electrical and Electronic Equipment (WEEE). This fact is linked to the production of more and more high performance electronic devices. Some parts of spent flat panel screens are made of thermoplastic polymers such as polycarbonate (PC), that has flame retardant properties, and/or polymethyl methacrylate (PMMA) usually used for its optical clarity, high light transmission, toughness and high impact resistance. PC or PMMA constitute the light guide panel (LGP) that is often present in End of Life (EoL) monitor and liquid crystal displays (LCDs) screens. Identification of these plastic-based fragments is thus crucial for recycling purposes, in order to obtain polymers for many new applications. In this study, the analyzed samples are mainly constituted by particles of LGPs followed by metals, Printed Circuit Boards (PCBs) and a light fraction (i.e. other polymers and cellulose-based particles) resulting from milling process carried out after manual sorting. In order to identify LGP plastic (i.e. PC or PMMA) from the other particles for recovering purposes, HyperSpectral Imaging (HSI) procedures were explored. Spectral features of each analyzed particle were thus extracted and chemometric methods were applied for exploratory data purposes and to build classification models in order to recognize plastic from LGP fragments. Obtained results can be considered as a meaningful starting point for the implementation of a fast, non-invasive and reliable procedure that can be used as a core engine for separation and quality control logic of materials coming from spent flat monitor waste stream.