A two-colour near-infrared sensor for sorting recycled plastic waste

This paper describes a simple device for automated sorting of post-consumer plastic waste. It is shown that rapid and reliable identification of certain polymers can be achieved by using a simple two-colour fixed filter near-infrared spectrometer in conjunction with a simple ratio circuit. The effectiveness of the proposed method is demonstrated in sorting of polyethylene terephthalate and polyvinyl chloride. A sensor based on this identification method is inexpensive to build and provides the necessary speed and performance required by the recycling industry.