Characterization of plastics with hyperspectral methods

Plastic represents one of the larger categories among solid waste. This depends on the fact that this material is continuously replacing some other one in many types of applications. Plastic solid waste can be recycled to produce secondary raw materials. This solution is applied in order to decrease the use of raw material and to reduce the accumulation of material in landfill. For these reasons recycling represents an economic and social important issue. Technologies for plastic recycling have to guarantee high-quality secondary raw material, complying with specific standards, for use in industrial applications. The market value of recycled plastics is considerably affected by the purity, degree of decontamination and homogeneity of the plastics. To obtain that is possible to use mechanical recycling methods that usually involve the following steps: contaminant separation (plastics are separated from other types of materials such as paper or metal), separation of different types of plastic polymers (separated by flotation, density difference, aereodynamic or elettrostatic properties, etc), washing and drying, shredding, comminution, agglutination, extrusion. Mechanical recycling is complicated by the similarities in physical properties between several types of plastic. An alternative method to separate contaminants from plastic wastes and different types of plastic polymers can be developed by hyperspectral systems. It is an optimal, low cost, reliable and speedy method. Hyperspectral imaging system is based on the utilization of an integrated hardware and software architecture able to digitally capture and handle spectra, as an image sequence. Different materials are identified by their spectral signature, made by investigation of VIS (400-1000 nm) and NIR (900-1800 nm) range of wavelength.