Multilayer packaging material analysis using Laser Direct Infrared (LDIR) Imaging

Significance of Topic

Multilayer polymer laminates are widely used in food and consumer product packaging due to their combined mechanical strength, barrier properties, and environmental resistance. Accurate layer identification and thickness measurement at the micrometer scale are essential for quality control, failure diagnosis, and material development. Traditional sample preparation and analysis methods can be time consuming and may lack the spatial resolution needed to detect defects or thin layers.

Objectives and Study Overview

This application brief describes the use of the Agilent 8700 Laser Direct Infrared (LDIR) Chemical Imaging System to map polymer layers in multilayer packaging materials. The goals include rapid sample preparation, high-resolution chemical imaging, precise thickness measurement, and straightforward identification of polymer layers for quality assurance, failure analysis, and reverse engineering.

Methodology and Instrumentation

The workflow combines the following elements:

• Sample Preparation: A dedicated Agilent laminate holder and Sample Planer microtome create a flat cross-section in under five minutes without resin embedding.
• Imaging System: The 8700 LDIR system integrates a visible-light microscope (up to 1 µm spatial resolution) and an ATR (attenuated total reflectance) module with an 80 × 80 µm field of view.
• Data Acquisition: Live imaging feedback automates ATR contact, ensuring optimal spectra. A high-brightness laser and fast-scanning optics capture infrared spectra in less than five seconds per point.
• Software: Agilent Clarity Software manages the entire workflow—from sample loading through spectral acquisition to chemical image generation—without extensive chemometric processing.

Main Results and Discussion

In a food packaging laminate of total thickness 117 µm, five polymer layers as thin as 2.6 µm were resolved and identified: polyethylene (PE), polyamide (PA), polypropylene (PP), polyurethane (PU), and ethylene vinyl alcohol (EVOH). Infrared multi-peak analysis enabled clear chemical contrast and precise thickness measurement. A second example with six layers in a 230 µm film demonstrated seamless ATR mosaicking across multiple contacts, preserving perfect alignment between visible and infrared images. The system revealed that visually indistinguishable layers could comprise different polymers or color variants of the same polymer.

Benefits and Practical Applications

Key advantages of the Agilent 8700 LDIR system include:

• Rapid, skill-free sample preparation in minutes versus hours for traditional resin embedding.
• High spatial resolution chemical imaging to detect sub-5 µm layers and defects.
• Automated ATR contact and seamless mosaicking for extended sample coverage.
• Real-time chemical layer mapping to accelerate QA/QC, failure analysis, and reverse engineering workflows.

Future Trends and Applications

Advancements may include integration with AI for automated layer classification, extensions to non-polymeric materials, and coupling with advanced chemometric models for complex mixtures. Industrial applications could expand into recycling quality control, regulatory compliance testing, and inline production monitoring of packaging films.

Conclusion

The Agilent 8700 LDIR Chemical Imaging System delivers rapid, high-resolution, and chemically specific analysis of multilayer packaging materials. Its user-friendly workflow, precise micrometer-scale mapping, and robust spectral quality enable detailed layer identification and thickness measurements, addressing critical needs in packaging development and quality assurance.

Reference

Agilent Technologies, Inc. Application Brief 5994-0312EN, September 2018.