Pyrolysis-GC/MS of Clothing Fibers - Cotton and Polyester Poly(ethylene terephthalate)

Importance of the Topic

The differentiation of textile fibers such as cotton and polyester is essential for quality control, forensic analysis, recycling processes, and material authentication. Pyrolysis-GC/MS provides a rapid, reliable method to decompose large polymeric fibers into smaller diagnostic molecules for chromatographic separation and mass spectrometric detection.

Objectives and Overview

This study demonstrates the application of pyrolysis-GC/MS to analyze pure cotton and poly(ethylene terephthalate) (PET) fibers. The goal is to identify characteristic pyrolysis fragments, compare decomposition profiles of the two polymers, and illustrate how blends can be distinguished.

Methodology and Instrumentation

The analysis was conducted using a pyroprobe autosampler interfaced to a gas chromatograph with mass spectrometric detection. Key conditions included:

• Pyrolysis: 750°C for 15 seconds with valve oven held at 300°C
• GC column: 5% phenyl, 30 m × 0.25 mm i.d., 0.25 µm film thickness
• Carrier gas: helium with a split ratio of 75:1
• Injector temperature: 300°C
• Oven program: initial 40°C for 2 min; ramp at 8°C/min to 290°C; final hold 10 min

Main Results and Discussion

The pyrolysis-GC/MS analysis yielded distinct profiles for each fiber type:

• Cotton (cellulose) pyrolysis produced low molecular weight oxygenated compounds, including furan derivatives, aldehydes, ketones, water, and carbon dioxide.
• PET pyrolysis generated aromatic species such as benzene, benzoic acid (eluting at ~11 min), and various oligomeric fragments.
• Fiber blends exhibited a composite chromatogram containing peaks from both cotton and PET, enabling clear differentiation of each component.

Benefits and Practical Applications

The method offers several advantages:

• Rapid and unambiguous identification of textile polymers in quality control and forensic investigations.
• Ability to analyze fiber blends and estimate composition ratios.
• Minimal sample preparation and compatibility with micro-scale fiber samples.

Future Trends and Potential Applications

Emerging developments may include higher-throughput pyrolysis systems, expanded spectral libraries for automated identification, coupling with other detectors, quantitative pyrolysis methods, and integration of machine learning for spectral interpretation. Applications are anticipated in advanced recycling processes, environmental footprint analysis, and real-time manufacturing monitoring.

Conclusion

Pyrolysis-GC/MS is a robust technique for the rapid characterization of clothing fibers. By converting high-molecular-weight polymers into diagnostic fragments, it enables reliable differentiation of cotton, polyester, and their blends, supporting diverse applications from textile quality assurance to forensic science.

References

• H. Ohtani and S. Tsuge, Degradation Mechanisms of Condensation Polymers in Applied Pyrolysis Handbook, T. Wampler (Ed.), Marcel Dekker, New York.
• D. Radlein, J. Piskorz and D. Scott, Fast Pyrolysis of Natural Polysaccharides as a Potential Industrial Process, Journal of Analytical and Applied Pyrolysis, 19 (1991) 41.