Time-gated Raman spectroscopy of recovered plastics

Abstract

Raman spectroscopy is a powerful non-destructive technique for the identification and characterization of plastics, but a major shortcoming of this technique is that environmental weathering, dyes, and additives in the material can generate a strong fluorescence background that overwhelms the Raman scattering. Here, we demonstrate that time-gated Raman spectroscopy can be used to successfully reduce the fluorescence signal and measure Raman spectra of recovered plastics. Time-gating removes a significant amount of background signal from the Raman spectra such that the polymers and color additives can be identified using similar measurement times compared to continuous-wave Raman spectroscopy. Examples of this are shown for a small subset of samples recovered from Hawaiian marine environments and a nonweathered commercial plastic. Time-gated Raman spectroscopy can also be used to characterize samples that are black in color due to carbon-based additives like graphite, which can be challenging to characterize via other common vibrational spectroscopic techniques.

Keywords: Characterization; Fluorescence rejection; Plastics; Polymers; Raman spectroscopy; Time-gating.