Quality control of Bromobutyl rubber

Importance of the topic

The quality control of Bromobutyl rubber (BIIR) is critical in industries relying on elastomers for sealing, automotive, and medical applications. Rapid, reliable analysis of key parameters—such as bromine content, viscosity, and additive levels—ensures product consistency and process efficiency while reducing reliance on time-consuming, reagent-based methods.

Objectives and study overview

This application note describes the development of a near-infrared spectroscopy (NIRS) method for simultaneous, multiparameter quantification in BIIR. The study aimed to build a calibration model capable of predicting Mooney viscosity, bromine content, volatile matter, calcium stearate, and functional bromide within one minute per sample.

Methodology and Instrumentation

A set of 68 BIIR samples were analyzed on a Metrohm NIRS DS2500 Liquid Analyzer (400–2500 nm) in transmission mode with an 8 mm pathlength. Samples were measured at 50 °C in disposable vials to ensure reproducibility and eliminate cleaning steps. Vision Air Complete software handled spectral acquisition and PLS model development.

Main results and discussion

Calibration models demonstrated strong correlations between NIR predictions and reference methods:

• Bromine content (titration): R² = 0.9629, SECV = 0.064%.
• Functional bromide (NMR): R² = 0.9580, SECV = 0.060%.
• Calcium stearate (XRF): R² = 0.9541, SECV = 0.153%.
• Volatile matter (oven method): R² = 0.7730, SECV = 0.056%.
• Mooney viscosity (viscometer): R² = 0.7257, SECV = 0.614%.

These figures of merit indicate that NIRS can deliver high precision and accuracy comparable to standard laboratory techniques.

Benefits and practical applications

NIR analysis provides a rapid, chemical-free alternative to traditional methods. Total analysis time is under one minute per sample, eliminating reagent costs and simplifying workflow. The approach is suitable for both laboratory and production-line quality control, enhancing throughput and reducing downtime.

Future trends and potential applications

Advances in NIR instrumentation and chemometric algorithms will further improve prediction accuracy and expand the range of detectable quality parameters. Integration with process analytical technology (PAT) systems may enable real-time rubber curing control and adaptive process optimization.

Conclusion

Near-infrared spectroscopy using the DS2500 Liquid Analyzer enables fast, simultaneous determination of multiple BIIR quality parameters with accuracy comparable to conventional methods. This approach streamlines QC workflows, reduces chemical usage, and supports in-line monitoring.

Reference

Internal reference AW NIR CN-0019-112022