Quantitative analysis of copolymers using the Cary 630 FTIR spectrometer

Significance of the Topic

ATR-FTIR with a diamond ATR sampling interface enables rapid, non-destructive quantification of copolymer compositions, addressing critical needs for material performance optimization and stringent quality control in industries such as automotive, medical devices, and consumer products.

Objectives and Study Overview

This study demonstrates the development of quantitative FTIR methods for two key copolymers: styrene content measurement in styrene-butadiene rubber (SBR) and polyethylene to vinyl acetate ratio in polyethylene vinyl acetate (PEVA), using the compact Agilent Cary 630 FTIR spectrometer.

Methodology

Calibration sets were prepared using commercial SBR standards with 0–45 wt% polystyrene and PEVA standards with 0–40 wt% vinyl acetate. Each SBR standard was measured in triplicate at 4 cm⁻¹ resolution with one-minute collection times. PEVA standards were likewise scanned, and validation samples at 0.55% and 1.00% VA were measured as thin films after dissolution and casting to assess method robustness with five-second scans.

Instrumentation Used

Agilent Cary 630 FTIR spectrometer equipped with a single-reflection diamond ATR accessory and MicroLab FTIR software for real-time spectral acquisition and quantitative method development.

Main Results and Discussion

For SBR, polystyrene absorbance peaks at 699 cm⁻¹, 759 cm⁻¹, and 1031 cm⁻¹ exhibited linear Beer’s Law behavior (R² = 0.999), with a detection limit of 0.09% PS. In PEVA, the vinyl acetate ester bands at 1737 cm⁻¹ and 1236 cm⁻¹ were ratioed to the PE band at 1467 cm⁻¹, yielding a calibration with R² = 0.999, LOD of 0.03 wt% VA, and LOQ of 0.10 wt% VA. Validation replicates at low VA levels showed standard deviations of approximately 0.01% VA.

Benefits and Practical Applications

The Cary 630’s compact design and intuitive software facilitate rapid QA/QC workflows, enabling five-second analyses of multiple sampling points with color-coded pass/fail indicators for real-time decision making in material inspection and incoming raw material verification.

Future Trends and Possibilities of Use

Integration of ATR-FTIR into automated sampling systems, inline process monitoring, and advanced data analytics or AI platforms offers potential for real-time polymer production control. The approach can be extended to diverse copolymer systems and complex formulations in pharmaceutical, environmental monitoring, and advanced materials research.

Conclusion

The Agilent Cary 630 FTIR with diamond ATR delivers fast, accurate, and reproducible quantitative analysis of copolymers, supporting robust quality assurance and control in polymer manufacturing environments.

References

• Higgins F, Rein A. Quantitative analysis of copolymers using the Cary 630 FTIR spectrometer. Agilent Technologies Application Note 5990-8676EN, September 1, 2011.