Multilayer Film Analysis Using the AIRsight Infrared Raman Microscope

Significance of the Topic

The structural and chemical analysis of multilayer films used in food and pharmaceutical packaging is essential for ensuring barrier, mechanical and optical performance. Combined infrared and Raman microscopy allows comprehensive layer identification and thickness measurement without repositioning the sample.

Objectives and Overview of the Study

This application demonstrates the AIRsight infrared Raman microscope for mapping and compositional analysis of a hair conditioner packaging film. Key goals included:

• Determining layer composition and thickness
• Identifying ultra-thin (<10 µm) and inorganic layers
• Streamlining analysis by integrating IR and Raman measurements

Methodology and Used Instrumentation

Sample preparation involved cutting 15 µm cross-sections on a microtome and mounting on a barium fluoride window. Infrared mapping was performed with IRXross and AIRsight at 8 cm⁻¹ resolution, 15 scans, 10×30 µm aperture, 2 µm step size over a 30×410 µm area (T2SL detector). Raman mapping used a 50× objective (532 nm excitation), 5 s exposure, 2 cumulative measurements, 5 µm step size over 5×85 µm area (CCD detector). Layer thicknesses were measured via the AMsolution software length function.

Main Results and Discussion

Infrared mapping identified the outer layers as nylon and the central layer as polyethylene; boundary regions exhibited mixed spectra suggesting ultra-thin interlayers. Raman mapping of the interface between the second and third layers resolved additional components including polyethylene terephthalate and titanium dioxide, which infrared spectroscopy could not detect due to their low-wavenumber features. Infrared proved more effective for fluorescent polymers.

Benefits and Practical Applications

The AIRsight system combines IR and Raman in a single platform, reducing sample handling and improving workflow. Infrared analysis excels for layers thicker than 10 µm and fluorescent materials, while Raman is ideal for sub-10 µm layers and inorganic compounds. This dual capability supports film development, quality control and competitive benchmarking.

Future Trends and Potential Applications

Future directions include integration of advanced chemometric and AI-driven spectral analysis, in situ and inline monitoring of film production, and automated multilayer characterization workflows. Expanding to more complex film architectures and other multilayer materials can broaden industrial relevance.

Conclusion

The AIRsight infrared Raman microscope offers a unified solution for detailed compositional and thickness analysis of multilayer films, leveraging the complementary strengths of infrared and Raman spectroscopy within a single instrument.

References

• Shimadzu Corporation. AIRsight Infrared Raman Microscope Application Note, First Edition: March 2023.