MIR measurements combined with photon-up-conversion technology to measure and identify black polymers

Identifying black polymers, which typically contain 0.5 to 3 mass percent of soot or black masterbatch, remains a considerable challenge in recycling sorting processes. Near-infrared spectroscopy (NIRS) is well-suited for the rapid and reliable identification of non-black polymers, making it a preferred choice for industrial sorting. However, due to the complete absorption of light in the NIR spectrum by black polymers, NIRS proves ineffective for such materials. Mid-infrared (MIR) spectroscopy offers a promising alternative for detecting black polymers. While conventional Fourier-transform infrared (FTIR) systems in the MIR range provide high accuracy, they lack the speed required for large-scale sorting operations. This paper introduces an innovative spectrometer system utilizing photon up-conversion, enabling the high-speed detection of black polymers and presenting a viable solution for industrial applications. Experimental results highlight the system's potential for efficient sorting of black polymers, addressing a critical gap in recycling technology.