Quantitative analysis of copolymers using the Cary 630 FTIR spectrometer

Importance of the Topic

Quantitative determination of copolymer composition is critical in industrial settings where the mechanical and chemical properties of materials such as SBR and PEVA govern performance in tires, medical devices, and consumer goods. ATR-FTIR methods offer rapid, non-destructive analysis with minimal sample preparation, supporting robust QA/QC workflows.

Objectives and Overview

This study demonstrates how the Agilent Cary 630 FTIR spectrometer with a single-reflection diamond ATR accessory can be applied to determine styrene content in styrene–butadiene rubber (SBR) and the polyethylene to vinyl acetate ratio in polyethylene vinyl acetate (PEVA). Calibration strategies, method development, and validation procedures are outlined for both polymer systems.

Methodology and Instrumentation

• Instrument: Agilent Cary 630 FTIR spectrometer equipped with a single-reflection diamond ATR accessory.
• Software: MicroLab FTIR for real-time spectral acquisition and method editing.
• SBR analysis: Four calibration standards (0%, 5%, 23%, 45% polystyrene) measured at resolution 4 cm-1, triplicate measurements.
• PEVA analysis: Seven standards spanning 0–40 wt% vinyl acetate; spectra collected at 4 cm-1 resolution with 60 s for calibration and 5 s for validation.

Main Results and Discussion

• SBR quantification: Characteristic PS bands at 699, 759, and 1031 cm-1 increase linearly with concentration. The 699 cm-1 peak height vs. concentration yields R2=0.999. The method detects styrene down to 0.09% (3×StdDev of zero concentration).
• PEVA quantification: Use of the 1236 cm-1 vinyl acetate ester C–O band normalized to the 1467 cm-1 PE band produces a calibration curve with R2=0.999. Validation samples at 0.55% and 1.0% vinyl acetate show standard deviations near 0.01%. Limits of detection and quantitation are 0.03 wt% and 0.10 wt%, respectively.
• Fast analysis: Reducing scan times to 5 s facilitates rapid screening of raw materials with high repeatability, aided by color-coded in-spec/marginal/out-of-spec results in the software.

Benefits and Practical Applications

• Minimal sample handling and no sample destruction.
• High throughput analysis supporting incoming raw material inspection and product QA/QC.
• Direct ATR measurement streamlines workflow, suitable for routine lab and production environments.

Future Trends and Opportunities

• Integration of chemometric techniques to expand multicomponent analysis beyond binary copolymers.
• Automated and remote monitoring using IoT-enabled FTIR systems for in-line process control.
• Portable and handheld ATR-FTIR deployments for field analysis of polymer blends.
• Enhanced sensitivity through advanced detector technologies and optimized sampling accessories.

Conclusion

The Agilent Cary 630 FTIR with diamond ATR sampling provides a rapid, accurate, and reproducible platform for quantitative analysis of copolymers. Its ease of use, compact design, and powerful software make it a valuable tool for industrial quality assurance and research applications.