Rapid characterization of plastics using laser-induced plasma spectroscopy (LIPS)

In the recycling of post-consumer plastic waste there is a pressing need for rapid, on-line or at-line measurement technologies for simple identification of the various commercial plastic materials. These include widely used household and industrial plastics such as polyethylene terephthalate (PET), high-density polyethylene (HDPE), polyvinyl chloride (PVC), low-density polyethylene (LDPE), polyethylene (PE), polypropylene (PP) and polystyrene (PS). To maintain the economics of recycling with extremely large volumes of waste materials, rapid, correct identification of these plastics is crucial. The goal of this work was instant identification of post-consumer plastics by laser-induced plasma spectrometry (LIPS). LIP spectra from plastics in a 200-800 nm spectral window were compared with reference spectral libraries stored in a computer. The libraries consisted of representative spectra from different groups of recycled plastic samples. The plasma emission spectra of PET, HDPE, PVC, LDPE, PP and PS were studied. Simple statistical correlation methods including linear and rank correlations were used. This technique is useful for application to the recycling of plastics.