Analysis of nylon-6,6 by reactive pyrolysis at high temperatures and high pressures using Online micro Reaction Sampler

Significance of the topic

Nylon polymers are common general-purpose plastics whose identification and characterization are critical in areas such as forensic analysis and quality control. Traditional pyrolysis-GC/MS methods can struggle with incomplete derivatization of polyamides due to inefficient reactive pyrolysis reactions. Chemolysis under high-temperature and high-pressure conditions offers a promising alternative for comprehensive polymer breakdown.

Objectives and study overview

This study evaluates an online chemolysis approach for nylon-6,6 analysis using a micro reaction sampler integrated into a multi-shot pyrolyzer. The goals were to achieve efficient monomer derivatization, improve reproducibility, and enable quantitative assessment of monomer ratios directly within the GC/MS system.

Methodology

Sample preparation:

• 50 µg of nylon-6,6 sample mixed with 10 µL of 25 wt% TMAH in methanol.
• Sealed in a glass tube (1.9 mm id, 2.4 mm od, 40 mm length) by torch heating.

Chemolysis conditions:

• Heating at 300 °C for 1 hour in a muffle furnace under sealed conditions.

Online transfer:

• Sealed tube fitted to the online micro reaction sampler PY1-1050.
• Tube crushed under helium to release products into the multi-shot pyrolyzer EGA/PY-3030D and injected into the GC/MS.

Instrumentation

• Online micro reaction sampler PY1-1050 (Frontier Labs).
• Multi-Shot Pyrolyzer EGA/PY-3030D (Frontier Labs).
• Gas chromatograph with quadrupole mass spectrometer detector.
• Ultra ALLOY+-5 capillary column (5% phenyl 95% dimethylpolysiloxane, 30 m × 0.25 mm × 0.25 µm).
• Muffle furnace for chemolysis.

Main results and discussion

Chemolysis of nine nylon samples consistently produced methylated monomer derivatives. Key observations:

• Tetramethyl hexamethylenediamine derivative (M1) and dimethyl adipic acid derivative (M2) were clearly detected.
• A mixed dimer methyl derivative (D1) was also observed.
• Reproducibility of M1 and M2 peak areas showed an RSD of approximately 2% (n=3), indicating high precision suitable for quantitative analysis.

Comparison with conventional reactive pyrolysis highlighted more efficient monomer generation and cleaner chromatographic profiles when using sealed-vessel chemolysis.

Benefits and practical applications

• Reliable identification and quantification of nylon monomers without offline workup.
• High reproducibility supports quantitative forensic and QA/QC applications.
• Integration into automated pyrolysis-GC/MS workflows reduces sample handling and analysis time.

Future trends and applications

Online high-pressure chemolysis can be extended to other condensation polymers beyond nylon, such as polyesters and polyurethanes. Advances may include miniaturized reactors, lower reagent volumes, and coupling with high-resolution MS for deeper structural elucidation. Further optimization could integrate inline derivatization agents and real-time data processing for rapid material identification.

Conclusion

The online chemolysis approach using a micro reaction sampler and multi-shot pyrolyzer offers an efficient, reproducible method for analyzing nylon-6,6 monomers. This technique overcomes limitations of conventional reactive pyrolysis and holds promise for routine forensic, industrial, and research applications in polymer analysis.

Reference

• A. Hosaka et al., Journal of Analytical and Applied Pyrolysis 106, 160–163 (2014).