Abstract
Traditional plants for plastic separation in homogeneous products employ material physical properties (for instance density). Due to the small intervals of variability of different polymer properties, the output quality may not be adequate. Sensing technologies based on hyperspectral imaging have been introduced in order to classify materials and to increase the quality of recycled products, which have to comply with specific standards determined by industrial applications. This paper presents the results of the characterization of two different plastic polymers—polyethylene terephthalate (PET) and polyvinyl chloride (PVC)—in different phases of their life cycle (primary raw materials, urban and urban-assimilated waste and secondary raw materials) to show the contribution of hyperspectral sensors in the field of material recycling. This is accomplished via near-infrared (900–1700 nm) reflectance spectra extracted from hyperspectral images acquired with a two-linear-spectrometer apparatus. Results have shown that a rapid and reliable identification of PET and PVC can be achieved by using a simple two near-infrared wavelength operator coupled to an analysis of reflectance spectra. This resulted in 100% classification accuracy. A sensor based on this identification method appears suitable and inexpensive to build and provides the necessary speed and performance required by the recycling industry.
Highlights
The annual production of plastic wastes in Europe in 2012 was 57 millions of tons; 62.2% of the total derives from household wastes
Plastic samples of polyethylene terephthalate (PET) and polyvinyl chloride (PVC) have been collected at different stages of their life cycle (Figure 1). presents the characteristics of the samples in terms of origin, color, density, mean particle size
From the hyperspectral cube of each plastic sample, Regions of Interest (ROI) have been created, and corresponding signatures have been extracted as spectral library
Summary
The annual production of plastic wastes in Europe in 2012 was 57 millions of tons; 62.2% of the total derives from household wastes (mainly container and packaging). Though a consistent decrease in delivery of plastic materials in landfill has been observed in the last years, improvements in plastic recovery are still needed to reduce the disposal rate down to the goal of zero plastic wastes in landfills by 2020 in Europe [1]. Due to their great chemical stability, degradation of plastics takes a long time and has a significant environmental impact. Recycling requires the separation of materials appearing in a mass of wastes of heterogeneous composition and characteristics, into single, almost pure, component/material flows [3]
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