Analysis of Antioxidants in Acrylonitrile Butadiene Rubber (NBR) Part 1 : Study of Thermal Extraction by Evolved Gas Analysis (EGA)

Significance of the topic

The stabilization of acrylonitrile butadiene rubber (NBR) with antioxidants is crucial for preserving mechanical performance and extending service life under oxidative stress. Reliable analysis of these additives supports quality control, material development, and failure prevention in rubber applications.

Objectives and Study Overview

This study aimed to establish optimal thermal desorption conditions for quantitative analysis of two common NBR antioxidants, NOCRAC 810-NA and NOCRAC 6C, using evolved gas analysis (EGA) to minimize interference from polymer degradation.

Methodology and Instrumentation

Samples of NBR containing known concentrations of NOCRAC 810-NA and NOCRAC 6C were subjected to programmed heating from 50 °C to 600 °C at 10 °C/min. A pyrolysis unit coupled with gas chromatography–mass spectrometry (GC–MS) monitored the total ion chromatogram (TIC) and characteristic ions (m/z 226 and m/z 268). Carrier gas was helium at 50 kPa and 60 mL/min with a split ratio of approximately 1/50.
Instrument details:

• Pyrolyzer: Double-Shot Pyrolyzer
• GC column: UADTM-2.5N (0.15 mm i.d., 2.5 m)
• GC oven temperature: held at 300 °C
• Injection and interface temperature: 320 °C
• MS detector scan range: m/z 29–400 at 0.1 scans/s

Main Results and Discussion

EGA revealed two distinct regions: a broad peak from 120 °C to 320 °C attributable to additive volatilization, and a second peak from 320 °C to 520 °C corresponding to polymer backbone decomposition. Mass chromatograms confirmed that both NOCRAC 810-NA and NOCRAC 6C elute below 350 °C. Based on these data, the thermal desorption protocol was set to ramp from 100 °C to 350 °C at 10 °C/min with a 5 min hold.

Benefits and Practical Applications

The optimized thermal desorption method isolates antioxidant signals with minimal interference, enhancing accuracy and reproducibility in quantifying additives. This approach benefits rubber manufacturing QC, forensic polymer analysis, and R&D by providing a rapid, robust protocol for additive evaluation.

Future Trends and Potential Uses

• Integration of high-throughput automated GC–MS workflows for routine industrial testing
• Extension of the protocol to a wider range of polymer additives and stabilizers
• Coupling with advanced mass analyzers for improved sensitivity and structural elucidation

Conclusion

Evolved gas analysis effectively guides the development of thermal desorption conditions for antioxidant assessment in NBR. The established protocol ensures clean extraction, accurate quantitation, and reliable performance in analytical laboratories.

References

No external references provided.