Photo, thermal and oxidative degradation of EPDM rubber using online UV irradiation PY-GC/MS

Significance of the Topic

Ethylene propylene diene rubber (EPDM) is extensively used in automotive and industrial applications for its excellent thermal stability and weather resistance. Characterizing its photo, thermal and oxidative degradation pathways is crucial to predict material lifetime, ensure product reliability and guide formulation improvements.

Objectives and Study Overview

This study demonstrates a rapid online UV/Pyrolyzer–GC/MS method to evaluate EPDM degradation. A commercial EPDM sample (JSR EP25, 5.1 wt% ethylidene norbornene) was exposed to controlled UV irradiation at 60 °C in air for one hour. The aim was to compare volatile and evolved gas profiles before and after UV exposure and establish degradation markers.

Methodology and Instrumentation

• Sample preparation: 200 µg EPDM placed in a sample cup attached to an optical fiber in a UV-1047Xe irradiator (280–450 nm, 700 mW/cm², xenon/Hg lamp).
• UV exposure: 60 °C in air atmosphere, duration 1 h.
• Cryo-trapping: Volatile products captured at the head of an Ultra ALLOY+-1 GC column using liquid nitrogen.
• GC/MS analysis: Dimethylpolysiloxane column (30 m × 0.25 mm i.d. × 0.5 µm), He flow 1 mL/min, split 1/50; oven ramp from 40 °C (2 min) to 280 °C at 20 °C/min.
• Evolved gas analysis (EGA)–MS: Pyrolyzer EGA/PY-3030D, temperature programmed 100–700 °C at 20 °C/min; GC oven held at 300 °C, same column flow and split ratio, sample weight 0.2 mg.

Main Results and Discussion

• Volatile degradation products: Key species detected after UV exposure include acetaldehyde, acetone, 2-butanone, 2,5-hexanedione and acetic acid originating from propylene units; nonanal and decanal derived from ethylene segments; propylene evolution was also observed.
• EGA thermogram changes: The post-irradiation sample exhibits a reduced peak intensity around 480 °C, an apex temperature shift to ~470 °C (–10 °C) and a broadening of the half-height width from 30 °C to 50 °C.
• Interpretation: The observed changes reflect chain scission, oxidation and reduced thermal stability induced by UV, which can be quantified via intensity, apex temperature and peak width metrics.

Benefits and Practical Applications

• Provides a fast (hours) alternative to conventional aging tests (days to weeks).
• Offers quantitative degradation markers for quality control and material screening.
• Facilitates formulation optimization and failure prediction in elastomeric components.

Future Trends and Applications

• Coupling online UV/Py-GC/MS with accelerated weathering chambers for in situ monitoring.
• Application to diverse polymers, composites and coatings to map environmental aging pathways.
• Integration with high-resolution MS or spectroscopic detectors for comprehensive chemical speciation.

Conclusion

The online UV/Pyrolyzer–GC/MS approach enables rapid, sensitive evaluation of EPDM photo, thermal and oxidative degradation. Key volatile and evolved gas signatures serve as reliable indicators of polymer breakdown, offering a powerful tool for materials research and industrial QA/QC.

Reference

• Technical Note PYA5-004E. Frontier Laboratories Ltd.