FTIR Analysis of Recycled Plastics Using the Spectrum Advisor Function

Importance of the topic

Recycling of plastic waste is becoming critical for environmental and regulatory goals worldwide. Fourier Transform Infrared Spectroscopy (FTIR) offers a robust method for qualitative polymer identification, including black and dark-colored plastics that challenge near‐infrared sorting systems.

Objectives and study overview

This study demonstrates how the IRSpirit-X FTIR spectrophotometer equipped with the built-in QATR-S ATR unit and its Spectrum Advisor function can streamline qualitative analysis of recycled plastic samples. Two representative specimens—a transparent bead and a black fragment—were analyzed under standard ATR conditions.

Methodology and instrumentation

• Instrument: Shimadzu IRSpirit-TX FTIR with QATR-S single-reflection ATR accessory.
• Measurement parameters: 4 cm-1 resolution, 45 co-added scans, SqrTriangle apodization, DLATGS detector.
• Spectrum Advisor function: automatic evaluation of spectrum quality with suggestions on sample placement, accessory selection, and data processing.

Key results and discussion

• Transparent bead: Initial spectrum was weak due to poor prism contact at a dented center area. Repositioning the bead flat side on the prism yielded a clear spectrum matching polypropylene.
• Black fragment: Initial spectrum displayed baseline drift and peak distortion from carbon black. Spectrum Advisor recommended switching to a germanium ATR crystal. The Ge prism produced a high-quality spectrum consistent with styrene-butadiene rubber containing calcium carbonate.

Benefits and practical applications

FTIR combined with Spectrum Advisor enables non-expert users to obtain reliable polymer identification across diverse sample shapes and colors. It enhances sorting accuracy in recycling workflows, supports quality control of recycled feedstocks, and detects contaminants post-molding.

Future trends and opportunities

• Integration of real-time guidance and automated optimization in FTIR instruments.
• Expansion of library models to cover complex polymer blends and additives.
• Potential coupling of FTIR with automated sorting lines for near-line or in-line quality assessment.

Conclusion

The IRSpirit-X with QATR-S and Spectrum Advisor delivers a user-friendly FTIR solution for qualitative analysis of recycled plastics, including challenging dark-colored samples. Its compact design and smart guidance support efficient, accurate polymer sorting and quality assessment in recycling operations.

Reference

• National Recycling Strategy, US Environmental Protection Agency, 2021.
• Proposal for amendment to Directive 94/62/EC on packaging and packaging waste, European Parliament, 2022.