Analysis of Food Wrap Films Using Double-Shot Pyrolyzer® Part 2: Analysis of Polypropylene (PP) + Nylon by EGA GC/MS Technique

Importance of the topic

Food wrap films composed of polypropylene and nylon are widely used in packaging to preserve food quality and safety. Understanding their thermal decomposition behavior and identifying additives is critical for ensuring regulatory compliance and product consistency.

Objectives and overview of the study

The study aims to characterize polypropylene (PP) and nylon blends in food wrap films using evolved gas analysis coupled with gas chromatography/mass spectrometry (EGA-GC/MS). Thermal zones are defined to segregate low-temperature volatiles and high-temperature pyrolysis fragments for comprehensive profiling.

Methodology and instrumentation used

This analysis employs a Double-Shot Pyrolyzer® with the following approach:

• Temperature program: 40–600 °C at 30 °C/min under helium carrier gas.
• Zone A trapping (100–320 °C) and Zone B trapping (320–600 °C) using MicroJet Cryo-Trap (MJT-1030E).
• GC separation on Ultra ALLOY-5 column (30 m × 0.25 mm, 0.25 µm), temperature ramp from 40 °C (1 min) to 320 °C at 20 °C/min.
• MS detection of separated fragments for structural elucidation.

Main results and discussion

Zone A analysis revealed low-temperature volatiles including acetic acid, fatty acids (lauric and myristic acids) and their ester derivatives, indicative of plasticizers and residual monomers. Zone B pyrolysis produced olefinic hydrocarbons (n-C6, n-C9, n-C12, n-C15) from polypropylene degradation and ε-caprolactam as the nylon-6 monomer. The distinct thermal profiles confirm the material composition and additive distribution.

Benefits and practical applications

• Rapid, simultaneous identification of polymer types and additives without extensive sample preparation.
• Quality control in film manufacturing by monitoring residual monomers and plasticizers.
• Evaluation of material degradation and safety assessment for food contact applications.

Future trends and potential applications

• Integration with high-resolution mass spectrometry for enhanced structural identification.
• Automation and high-throughput screening workflows for industrial quality control.
• Extension to multi-layer films and complex polymer composites.
• Real-time monitoring of packaging materials under service conditions.

Conclusion

EGA-GC/MS via double-shot pyrolysis provides a robust, detailed analytical platform for profiling polypropylene-nylon food wrap films. The method delivers clear separation of volatiles and high-temperature pyrolysis products, supporting material verification and additive analysis in QA/QC laboratories.

References

• Hosaka et al., 49th Japan Analytical Society Meeting, 2000.