Determination of Irganox 3114 in polypropylene by infrared spectroscopy

Significance of the topic

The measurement of antioxidant additives in polypropylene is critical for quality control in polymer processing. Irganox 3114 and similar stabilizers protect plastics against thermal and oxidative degradation. Rapid, accurate quantification ensures appropriate additive levels to maintain material performance and longevity.

Objectives and study overview

This study presents an infrared spectroscopic method for determining the concentration of Irganox 3114 in polypropylene when the full additive package is known. The aim is to offer a fast, non-destructive procedure suitable for process control rather than for heavily filled or pigmented resins.

Methodology

Sample preparation and measurement follow a defined protocol:

• Melt-press polypropylene into 0.5–0.7 mm films at ≤250 °C, ensuring a smooth surface.
• Trim and inspect films; discard those with defects or incorrect thickness.
• Collect FTIR spectra at 4 cm⁻¹ resolution for triplicate films, accumulating 74 scans per sample.

Instrumentation

Key instruments include:

• Agilent Cary 630 FTIR spectrometer with DialPath or TumblIR interface (1000 µm path length).
• Film micrometer for thickness verification.
• Hydraulic press (200 °C platen, 40 000 lb force).
• Chase mold, aluminum sheets (0.051–0.178 mm) and scissors.

Main results and discussion

A linear calibration between the absorbance ratio A₁₆₉₆/A₄₀₆₂ and known Irganox 3114 weight percentage yielded a strong correlation. The carbonyl band at 1696 cm⁻¹ and the polypropylene reference band at 4062 cm⁻¹ were integrated against defined baselines. Regression constants allow direct conversion of measured ratios into additive concentration, with triplicate replicates averaged for accuracy.

Benefits and practical applications

Advantages of this method include:

• Non-destructive analysis of thin films without chemical solvents.
• Rapid throughput with real-time sample positioning via DialPath/TumblIR.
• Automated software routines in Agilent MicroLab PC FTIR for peak integration, ratio calculation, and concentration reporting.

Future trends and possibilities

Advances could involve inline FTIR monitoring during extrusion, expanded calibration libraries for mixed additive systems, and integration with digital manufacturing platforms. Miniaturized, portable FTIR units may enable on-site quality checks across production lines.

Conclusion

This FTIR-based approach delivers reliable, high-throughput quantification of Irganox 3114 in polypropylene. The combination of robust sample handling, tailored instrumentation, and method-driven software ensures reproducible results for process control applications.

References

• Collins W, Seelenbinder J, Higgins F. Determination of Irganox 3114 in polypropylene by infrared spectroscopy. Agilent Technologies; 2012.