Infrared Emission Spectroscopic Imaging of Microplastics Using Long-Wavelength Infrared Hyperspectral Camera with Imaging-Type Two-Dimensional Fourier Spectroscopy

We aim to realize a microplastic discrimination system, by using a hyperspectral camera that images in the longwave infrared (LWIR) band, which would be smaller, cheaper and faster than focal plane array-based Fourier-transform infrared spectroscopy (FPA-FTIR). We attempt to perform LWIR band (wavenumber range: 714–1250 cm−1) emission spectroscopic imaging of 35-μm-thick polyethylene (PE) and polypropylene (PP) heated on an aluminum plate (surface temperature of aluminum plate: 103.7 °C), in the hope for a consistent application to microplastics with a wide size range. It is confirmed that PE and PP exhibit a higher brightness than the aluminum plate. It is also confirmed that the infrared emission spectra of PE and PP produce characteristic peaks at the same positions as those in the reference absorption spectra, and the clustering results by the k-means++ method reveal the possibility for good discrimination among the aluminum plate, PE and PP.