Raman spectroscopy for identifying postconsumer packaging plastics for recycling

The identification of postconsumer plastic types is important for proper separation for recycling purposes. In this work, Raman spectroscopy was used as a tool to identify the type of postconsumer plastic and subsequent separation for applications in recycling stations and plants. The different postconsumer plastic samples were separated, and Raman spectra were obtained using a dispersive spectrometer (with an excitation wavelength of 830 nm, a laser power of up to 400 mW, an integration time of 3 s, and a spectral range between 400 and 1800 cm^-1). The peaks in the spectra of each type of plastic were correlated with the literature, and the spectra were separated into groups according to their symbology. The spectra were subjected to group classification using partial least squares regression. The types of plastics were identified, and the spectra of the PE-HD and PE-LD plastics were similar because they had the same chemical structure. Peaks of the dyes commonly used in packaging and labels were also observed. The classification model achieved 100% accuracy in separating plastics from 1 to 6. Plastics of type 7 were not modeled due to their mixed composition. Raman spectroscopy can be a useful tool in the identification and separation of postconsumer plastics for proper recycling.Implications: This study demonstrates the potential of Raman spectroscopy as an effective and accurate tool for identifying and classifying postconsumer plastics, achieving 100% accuracy for plastics classified from types 1 to 6 according to the recycling triangles. The ability to differentiate plastic types, including the detection of dyes commonly used in packaging and labels, can significantly enhance sorting efficiency in recycling facilities. By improving plastic separation, this method can contribute to more sustainable recycling practices, reducing contamination in recycled materials and supporting the development of a circular economy.