A new approach to sample preparation free micro ATR FTIR chemical imaging of polymer laminates

Importance of the Topic

Polymer laminates combine multiple polymer films with adhesive tie layers to achieve tailored mechanical and barrier properties. Detailed characterization of individual layers and interfaces at the micrometer scale is essential for quality control, troubleshooting and reverse engineering in industries such as food and pharmaceuticals. Conventional micro ATR FTIR imaging requires extensive sample preparation, including resin embedding and polishing, to maintain contact under high pressures, limiting throughput and risking contamination.

Study Aims and Overview

This work presents an ultralow pressure micro ATR FTIR imaging approach that eliminates the need for resin embedding and polishing by using Agilent’s Live ATR imaging mode with a focal plane array detector. The objective is to enable direct, non-destructive chemical imaging of polymer laminates in their native state.

Methodology

A streamlined five-step procedure was developed:

• Cut a small piece of the polymer laminate.
• Mount the sample in a micro-vice.
• Cross-section the sample with a razor blade.
• Place the micro-vice on the microscope stage.
• Raise the stage to achieve minimal contact and acquire the FTIR image.

Live ATR imaging enhances chemical contrast in real time, allowing visualization of the first point of contact and monitoring of contact quality under ultralow pressure. The method uses a germanium ATR crystal, yielding ~1.1 µm spatial resolution per pixel.

Used Instrumentation

• Agilent Cary 670 FTIR Spectrometer
• Agilent Cary 620 FTIR Microscope
• 64 × 64 MCT Focal Plane Array Detector
• Germanium ATR Crystal, Micro-vice and Razor blade

Main Results and Discussion

Analysis of a sausage wrapper (≈55 µm thick) revealed:

• Three polymer layers: polyethylene (11 µm and 20 µm) and nylon (16 µm).
• Two polyurethane adhesive layers with thicknesses of 2–3 µm and 5–6 µm.

Live ATR imaging captured the contact sequence and ensured complete, low-pressure contact without sample deformation. In contrast, standard ATR imaging could not detect the exact moment or quality of contact.

Benefits and Practical Use of the Method

• Eliminates resin embedding and lengthy polishing steps.
• Enables rapid, non-destructive analysis of ultrathin laminates (<50 µm).
• Delivers submicrometer spatial resolution for clear identification of micrometer-scale layers.
• Simplifies workflow, increases throughput and reduces contamination risk.

Future Trends and Possibilities

Potential developments include integration into inline quality control systems, application to other delicate or heterogeneous materials (e.g., biological tissues, nanocomposites) and coupling with complementary imaging modalities (e.g., Raman, AFM-IR) for comprehensive multimodal characterization.

Conclusion

Agilent’s Live ATR imaging technique represents a significant advance in micro ATR FTIR chemical imaging by enabling rapid, high-resolution analysis of polymer laminates without complex sample preparation. This approach improves analytical efficiency and expands the range of samples that can be characterized by FTIR microscopy.

References

• Application Note “A new approach to sample preparation-free micro ATR FTIR chemical imaging of polymer laminates”, Agilent Technologies, April 2011.