Post-consumer polyolefins (PP-PE) recognition by combined spectroscopic sensing techniques

The efficient large-scale recycling of plastic waste is of increasing interest from an ecological and economic point of view, but it represents a goal that has yet to be achieved by the recycling industry. The possibility offered by different spectroscopic sensing techniques in order to identify different plastic particles to be recycled, with particular reference to polyolefins from complex wastes, has been investigated. Representative samples of polyolefins (polyethylene and polypropylene) have been collected and analyzed for laboratory set-up and testing by FT-IR spectroscopy, by Raman spectroscopy and by hyperspectral imaging in two different wavelength fields, 400-1000 and 1000-1700 nm, respectively. The spectral signature obtained by the different techniques of the two plastic typologies have been detected, analysed and compared. The main parameters that allow to perform the recognition of the polyethylene (PE) and polypropylene (PP) have been defined, with particular reference to the hyperspectral imaging innovative technique. The analytical strategies can be utilised to define sorting and/or control logics to be applied in “on-line” control architectures to directly act at industrial plant level