Determination of Irganox 1010 in polypropylene by infrared spectroscopy

Importance of the Topic

The measurement of antioxidant additives such as Irganox 1010 in polypropylene is crucial for ensuring polymer stability and performance. Infrared spectroscopy offers a rapid, non-destructive approach to monitor additive levels during production and quality control.

Objectives and Study Overview

This study presents an infrared spectroscopic method to quantify Irganox 1010 and similar phenolic antioxidants in polypropylene when the additive package composition is fully known. The approach is designed primarily for process control of additive dosing in unfilled, unpigmented resins.

Methodology and Instrumentation Used

A representative polypropylene sample is compression molded into a 0.5–0.7 mm film at 200 °C under nitrogen conditions. The film is analyzed by FTIR at 4 cm⁻¹ resolution. Key steps include:

• Sample Preparation: Melt-stacking in chase molds with aluminum sheets and cooling on the benchtop.
• Spectral Acquisition: Using a 1000 µm path-length DialPath or TumblIR accessory on Agilent Cary 630, or equivalent mobile/portable 5500/4500 FTIR.
• Data Processing: Measurement of the additive ester carbonyl band at 1745 cm⁻¹ and reference PP band at 4062 cm⁻¹, followed by peak ratio analysis and linear regression calibration.

Main Results and Discussion

Calibration standards prepared by blending known wt% of Irganox 1010 with powder polypropylene yielded a linear relationship between Wt% and the absorbance ratio (1745/4062 cm⁻¹). Triplicate measurements demonstrated high reproducibility, with the software automatically applying slope and intercept values to report additive concentration.

Benefits and Practical Applications

• Rapid and non-destructive quantification of antioxidant levels in polymer films.
• Minimal sample preparation and straightforward sample mounting using DialPath/TumblIR cells.
• Real-time process control capability in polymer production and QA/QC laboratories.

Future Trends and Applications

• Extension to filled or pigmented resins with chemometric approaches to correct for spectral interferences.
• Integration of real-time inline FTIR monitoring for continuous production feedback.
• Application to a broader range of stabilizers and polymer matrices using multivariate calibration.
• Miniaturized portable FTIR systems for field inspections and on-site quality assurance.

Conclusion

The FTIR-based method using Agilent’s Cary 630 and specialized transmission accessories provides a robust, accurate, and efficient tool for quantifying Irganox 1010 in polypropylene. Its simplicity and automation make it well-suited for routine process control in polymer manufacturing.

Reference

Collins W., Seelenbinder J., Higgins F. (2012). Determination of Irganox 1010 in polypropylene by infrared spectroscopy. Agilent Technologies Publication 5991-0505EN.