Analysis of Antioxidants in Acrylonitrile Butadiene Rubber (NBR) Part 2 : Reproducibility in Quantitative Analysis

Importance of the Topic

The performance and durability of acrylonitrile butadiene rubber (NBR) depend heavily on the presence and stability of antioxidant additives. Accurate and reproducible quantification of these compounds is essential for quality control in the rubber industry and for ensuring long-term material resilience against oxidative degradation.

Aims and Study Overview

This study evaluates the reproducibility of quantitative analysis for two common NBR antioxidants, NOCRAC 810-NA and NOCRAC 6C, using a Double-Shot Pyrolyzer coupled with gas chromatography. The goal is to confirm that internal standard calibration yields consistent results for routine polymer testing.

Methodology and Instrumentation

Thermal desorption conditions followed a ramp from 100°C to 350°C at 10°C/min with a 5-minute hold. Volatile components were transferred to a GC system equipped with a flame ionization detector. Key instrumentation details include:

• Pyrolyzer: Double-Shot Pyrolyzer (PY-2020D)
• Carrier gas: Helium (column flow 1.2 ml/min, splitter flow 150 ml/min)
• Separation column: Ultra ALLOY+-1 dimethylpolysiloxane, 30 m × 0.25 mm id × 0.25 µm film
• GC oven program: 40°C to 320°C at 20°C/min (hold 1 min)
• Injection port: 320°C; sample size ~1 mg

Main Results and Discussion

Chromatographic separation of thermally desorbed components produced sharp, well-resolved peaks for both antioxidants. Quantitation via the internal standard method delivered average concentrations of approximately 3000 ppm for each additive. Reproducibility, expressed as relative standard deviation of area ratios, was:

• NOCRAC 810-NA: 1.98%
• NOCRAC 6C: 1.27%

These low RSD values highlight the method’s reliability for routine analysis.

Benefits and Practical Applications

This approach offers several advantages:

• Rapid sample preparation without solvent extraction
• High reproducibility suitable for quality assurance
• Minimal sample consumption (ca. 1 mg)
• Applicability to general polymer analysis and rubber industry QA/QC

Future Trends and Potential Applications

Advances may include coupling pyrolysis with high-resolution mass spectrometry for structural confirmation of degradation products, development of automated workflows for high-throughput testing, and miniaturization of pyrolyzer modules for on-site analysis.

Conclusion

The Double-Shot Pyrolyzer method demonstrated excellent reproducibility in quantifying NOCRAC 810-NA and NOCRAC 6C antioxidants in NBR. Its rapid, solvent-free workflow and reliable performance make it a valuable tool for polymer quality control and research.