Analaysis Examples Using Carrier Gas Selector Part 3: Pyrolysis of Polycarbonate (PC) in Air

Significance of the Topic

The study of polycarbonate (PC) decomposition by pyrolysis in different atmospheres provides critical insights into polymer stability, degradation mechanisms, and environmental impact. Comparing inert and oxidative pyrolysis pathways aids material scientists, quality control laboratories, and environmental analysts in selecting appropriate analytical protocols for polymer characterization and fate assessment.

Objectives and Study Overview

This work aimed to evaluate the pyrolysis behavior of PC at 550 °C under helium and air atmospheres using the Frontier Double-Shot Pyrolyzer® system equipped with a Carrier Gas Selector. Flash pyrolysis products were captured and analyzed by gas chromatography–mass spectrometry (GC/MS) to identify differences in decomposition profiles.

Methodology

Flash pyrolysis of 30 µg PC samples was performed at 550 °C. Two carrier atmospheres were tested: helium (inert) and air (oxidative). The pyrolyzates were cryo-trapped and injected into a GC/MS system. Separation employed an Ultra ALLOY-5 column (30 m × 0.25 mm i.d., 0.25 µm film) with a temperature program from 40 °C (1 min hold) to 320 °C at 20 °C/min. The carrier gas flow was maintained at 60 mL/min total, with a column flow of 1 mL/min, and the injection port was held at 320 °C.

Instrumentation

• Double-Shot Pyrolyzer® with Carrier Gas Selector (CGS-1050E)
• Selective Sampler (SS-1010E)
• MicroJet Cryo Trap (MJT-1030E)
• Gas Chromatograph–Mass Spectrometer system
• Ultra ALLOY-5 capillary column

Main Results and Discussion

Pyrograms revealed that pyrolysis in helium produced high levels of bisphenol A (PC monomer), phenol, p-cresol, and p-isopropenylphenol. In contrast, air pyrolysis generated a dominant CO₂ peak with only trace amounts of phenolic compounds, indicating extensive oxidative degradation. This demonstrates that oxidative conditions convert PC largely to gaseous products, whereas inert pyrolysis preserves monomeric fragments.

Benefits and Practical Applications

• Rapid assessment of polymer composition and additive content
• Quality control in PC production by monitoring monomer recovery
• Environmental analysis of polymer oxidation products and emissions

Future Trends and Applications

Advancements may include coupling pyrolysis with high-resolution mass spectrometry for detailed degradation pathway elucidation, real-time online analysis for process monitoring, and integration with microscale reactors to study low-volume environmental samples. Expansion into biodegradation research could offer insights into PC breakdown under biological conditions.

Conclusion

The use of a Carrier Gas Selector in flash pyrolysis enables precise control of the atmospheric environment, revealing stark contrasts between inert and oxidative decomposition of polycarbonate. Helium pyrolysis preserves characteristic monomers, whereas air leads to extensive oxidation. This approach enhances polymer analysis capabilities across research, industrial QC, and environmental applications.

References

• Hosaka et al., 5th Polymer Analysis Symposium, II-4, p. 43–44 (2000).