Abstract
Recent optical identification techniques for waste-plastic sorting are reviewed in this paper. The features of the optical sorting machines—high accuracy, non-contact, and high-speed—provide a single-component plastic recycle resource out of mixed waste plastics. The introduction presents the basic concepts of spectroscopy as it relates to optical sorting. One of the latest developments, hyperspectral imaging in near and mid-wavelength infrared absorption identifications, is then evaluated and specifications are given. There is also a summary of the original optical sorting technique known as Raman scattering identification with a discussion on its advantages and drawbacks. Attempts at identification of black-color plastic are introduced ; they show how mid-wavelength infrared absorption and Raman scattering optical sorting have been utilized. Lastly, the paper explains how x-ray transmission measurement is being applied to remove plastics containing brominated flame retardants in adaptation to RoHS restriction and detect talc contained a lot in plastics from end-of-life vehicles.
