MIR spectral characterization of plastic to enable discrimination in an industrial recycling context: II. Specific case of polyolefins. (October 2019)

• Record Type: Journal Article
• Authors: Signoret, Charles; Caro-Bretelle, Anne-Sophie; Lopez-Cuesta, José-Marie; Ienny, Patrick; Perrin, Didier
• Is Part Of: Waste management. Volume 98(2019)
• Page Start: 160
• Page End: 172
• Publication Date: 2019-10
• Subjects: Polymer recycling -- Sorting -- MIR -- WEEE -- Identification -- Polyolefins; ABS Acrylonitrile Butadiene Styrene -- ATR Attenuated Total Reflection -- CaCO3 calcium carbonate or calcite (chalk) -- DSC Differential Scanning Calorimetry -- ELV End-of-Life Vehicles -- EPDM Ethylene Propylene Diene Monomer -- EPR Ethylene Propylene Rubber -- EVA Ethylene Vinyl Acetate -- EoL End-of-Life -- FTIR Fourier Transform Infrared -- HDPE High Density Polyethylene -- HIPS High Impact Polystyrene -- HSI Hyperspectral Imagery -- LIBS or LIPS Laser Induced Breakdown/Plasma Spectroscopy -- LDPE Low Density Polyethylene -- LWIR Long Wavelength Infrared (7.4–14.0 µm or 1350–700 cm−1) -- MIR Mid-Infrared (4000–400 cm−1 or 2.5–25.0 µm) -- MWIR Middle Wavelength Infrared – 2 to 5 µm (5000 to 2000 cm−1) -- PC Polycarbonate (from bisphenol A) -- PE Polyethylene (HDPE or LDPE) -- PEG Polyethylene glycol (=POE) -- PET Polyethylene terephthalate -- PEX Cross-linked (X) Polyethylene -- POE Polyoxyethylene (=PEG) -- POM Polyoxymethylene -- PMMA Polymethylmethacrylate -- PP Polypropylene -- PPC or PP copo Polypropylene copolymer -- PPH or PP homo Polypropylene homopolymer -- PPE or PPO Polyphenylene ether or Polyphenylene oxide -- PVC Polyvinyl chloride -- PS Polystyrene -- THz Terahertz -- WEEE or W3E Waste of Electrical & Electronic Equipment -- XLPE Cross-linked LDPE -- XRF X Rays Fluorescence -- XRT X Rays Transmission; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2019.08.010
• Languages: English
• ISSNs: 0956-053X

Abstract

Graphical abstract: Highlights: 8 references of polyolefins and spectrally close polymers were considered. Pure polyethylene and polypropylene have very characteristic patterns. Polyolefins presents several intermediate cases between these two extrema. Styrenics and polyolefins display distinctive patterns in both LWIR and MWIR. Mid-infrared is theoretically adapted to these polymers for industrial sorting. Abstract: Sorting at industrial scale is required to perform mechanical recycling of plastics in order to obtain properties that could be competitive with virgin polymers. As a matter of fact, the most part of the various types of plastic waste are not miscible and even compatible. Mid-Infrared (MIR) HyperSpectral Imagery (HSI) is viewed as one of the solutions to the problem of black plastic sorting. Many Waste of Electrical and Electronic Equipment (WEEE) plastics are black. Nowadays, these materials are difficult to sort at an industrial scale because the main used pigment to produce this color, carbon black, masks the Near-Infrared (NIR) spectra of polymers, the currently most used technology for acute sorting in industrial conditions. In this study, laboratory Fourier-Transform Infrared (FTIR) in Attenuated Total Reflection mode (ATR) has been used as a theoretical toolbox based on physical chemistry to help building an automated HSI discrimination despite its limited conditions, especially shorter wavelengths ranges. Weaker resolution and very short acquisition times are other HSI limitations. Helping fast and exhaustive laboratory characterizations of polymeric waste stocks is the other goal of this study. This study focusses on polyolefins as they represent the second biggest fraction of WEEE plastics (WEEP) after styrenics and since little quantities mixed to styrenics during mechanical recycling can lead to important decrease in mechanical properties. Twelve references were thus evaluated and compared between each other and with real waste samples to highlight spectral elements, which can enable differentiation. Charts compiling the signals of discussed polymers were built aiming to the same objective.