Multilayer Film Analysis Using the AIMsight Infrared Microscope

Importance of Topic

Multilayer films are critical in food and pharmaceutical packaging for providing tailored barrier, mechanical and printing properties. Understanding the layer composition and thickness directly impacts product quality, material development and competitive benchmarking.

Objectives and Study Overview

This study demonstrates how the AIMsight™ infrared microscope can be used to characterize the number, thickness and chemical composition of individual layers in multilayer films sourced from three different manufacturers (Company A in Japan, Companies B and C overseas).

Methods and Instrumentation

Sample Preparation:

• Three potato-chip packaging films (Products A, B, C)
• Embedding in epoxy resin and microtome sectioning (20 µm) using HistoCore AUTOCUT R (Leica Microsystems)
• Sections mounted on barium fluoride (BaF₂) windows

Analytical Conditions:

• Infrared microscope: AIMsight with IRTracer™-100
• Resolution: 8 cm⁻¹; Scans: 45; Apodization: SqrTriangle
• Aperture: 10 µm × 30 µm; Step size: 2 µm; Mapping area: 30 µm × 120–154 µm
• Detector: T2SL

Instrument Features:

• Wide-field camera (10 × 13 mm field of view, up to 5× digital zoom, tiling for large composites)
• Microscope camera for high-magnification imaging
• Length measurement function for layer thickness on wide-field, microscope and stitched images
• Spectrum Advisor for interactive spectrum quality checking

Results and Discussion

Chemical mapping based on spectral similarity revealed:

• Company A: Four layers – outer PP, PP/PET blend, PET, inner PE (thickness 27 µm, 9 µm, 11 µm, 42 µm)
• Company B: Three layers – PP (20 µm), PET (14 µm), PE (65 µm)
• Company C: Five layers – PP (18 µm), PE (15 µm), PET (13 µm), PE (18 µm), PP (20 µm)

All films used polypropylene as the outer layer for printability (BOPP) and PET at the innermost interface for barrier properties, with variations in layer sequence and thickness reflecting different design priorities.

Benefits and Practical Applications

The AIMsight infrared microscope provides:

• Simultaneous visual and spectral analysis
• Accurate layer thickness measurements across micrographs
• High-resolution chemical imaging to map material distribution
• Tools suited for R&D, quality control, and competitive product comparison in the packaging industry

Future Trends and Possibilities

Advancements may include integration of multivariate data analysis for more nuanced material differentiation, automation of mapping workflows, enhanced spatial resolution for ultra-thin films, and application to emerging biopolymers and sustainable packaging materials.

Conclusion

The AIMsight infrared microscope, combined with the IRTracer-100, enables comprehensive multilayer film characterization by linking precise thickness measurements with high-resolution chemical mapping. This approach supports efficient material development and rigorous quality assurance in packaging applications.