Carbon Black At-line Characterization Using a Portable Raman Spectrometer

Importance of the Topic

Carbon black is widely employed as a reinforcing filler in tire and rubber production and as a pigment in inks and paints. Its performance depends on molecular structure and crystallinity. Rapid and non-destructive analysis at-line or on-line is essential to ensure consistent quality and optimize manufacturing processes. Raman spectroscopy offers molecular fingerprints that can reveal structural order and disorder in carbon materials without sample preparation.

Objectives and Study Overview

This study demonstrates the use of a portable Raman spectrometer for at-line characterization of carbon black. The main goals are to show how Raman band analysis, especially the ratio of the disorder (D) band to the graphitic (G) band, correlates with carbon black microstructure and can be used for real-time process control.

Methodology and Instrumentation

The analysis was performed using the i-Raman Plus portable spectrometer with 532 nm laser excitation and 4.5 cm−1 resolution. A video microscope attachment ensured precise laser focusing. Spectra were recorded at room temperature with 40 mW laser power and 120 s integration. A back-thinned, TE-cooled CCD detector minimized dark noise, enabling detection of weak Raman signals. Baseline correction and peak fitting were conducted in BWSpec software using the adaptive iteratively reweighted penalized least squares algorithm (airPLS) to remove fluorescence and extract peak intensities.

Key Results and Discussion

The Raman spectra of three commercial carbon black samples revealed clear D-band (~1336 cm−1) and G-band (~1580 cm−1) features. Calculated intensity ratios (ID/IG) were:

• Sample C1: 0.81
• Sample C2: 0.98
• Sample C3: 1.23

The ID/IG ratio increased with structural disorder and inversely correlated with microcrystalline grain size. The D-band position shifted according to laser wavelength, consistent with literature reports.

Benefits and Practical Applications

Portable Raman spectroscopy enables rapid, non-destructive, in situ analysis of carbon black without sample preparation. Monitoring the D/G ratio supports:

• Real-time quality control and batch uniformity assessment
• Estimation of crystallite size and disorder level
• On-site process monitoring and troubleshooting

Future Trends and Opportunities

Advances in portable Raman instrumentation and data processing will facilitate integration into continuous production lines. Enhanced detectors and excitation options may extend applications to other carbon materials such as nanotubes and graphene. Coupling with machine learning can enable predictive maintenance and automated quality assessment.

Conclusion

This work demonstrates that portable Raman spectroscopy provides sensitive detection of carbon black structural features and enables at-line monitoring through the ID/IG metric. Adoption of this technology can improve process control and product performance in carbon black manufacturing.

References

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