Discrimination of Plastics Using a Portable near Infrared Spectrometer

Abstract

A portable near infrared (NIR) spectrometer was used to accomplish rapid identification of plastics. Thirteen kinds of plastics were collected and their NIR spectra were measured. Standardised normalisation treatment of the original spectra reveals the differences of the spectra more clearly. Absorbance spectra can be used to distinguish easily between polyethylene (PE) and polypropylene (PP) with the absorption band of the methylene group at 1410 nm. The result can be used to discriminate PE, PP and the copolymer. This suggestion is supported by a principal component analysis of the second-order derivatives spectrum.