EGA thermogram of degraded high impact polystyrene <Correlation with Xe weather meter test>

Significance of Topic

High impact polystyrene (HIPS) is widely used in packaging and consumer products. Understanding its degradation under UV and weathering conditions is critical for predicting service life and performance. Rapid assessment methods can accelerate formulation screening and reduce development costs.

Study Overview

This study compares degradation profiles of HIPS exposed to a micro UV irradiator and a conventional Xenon weather meter. The goal is to determine if accelerated UV treatment can mimic long-term outdoor weathering in a fraction of the time.

Methodology

Samples of HIPS were prepared in solution and as solid plates. Two exposure protocols were used:

• Micro UV irradiator: 280–450 nm, 700 mW/cm2, 60°C furnace, irradiation durations of 30 minutes, 1 hour, and 12 hours.
• Xenon weather meter: 320–700 nm, 34 mW/cm2, solid plate exposure for 100 and 300 hours.

Post-irradiation samples underwent evolved gas analysis by pyrolysis-GC/MS to generate thermograms. Molecular weight changes were assessed by size-exclusion chromatography.

Used Instrumentation

• Double-Shot Pyrolyzer with micro UV irradiator and Xe weather meter attachments
• Pyrolyzer temperature program: 100–700°C at 20°C/min
• GC oven: 300°C, UADTM-2.5N column (2.5 m × 0.15 mm i.d.)
• Carrier gas: Helium at 1 mL/min, split ratio 1/50

Main Results and Discussion

Exposure to the micro UV source for 1 hour caused a 10°C decrease in peak apex and a reduction in pyrolysis onset from 360 to 300°C. After 12 hours, the thermogram peak broadened further. Xenon weathering for 300 hours yielded a 14°C drop in peak apex and onset temperature of 280°C. Both methods produced nearly identical thermograms, indicating comparable degradation pathways. Molecular weight dropped from 285,000 to 240,000 after 1 hour of micro UV, confirming main-chain scission.

Practical Benefits and Applications

Using a micro UV irradiator accelerates weathering assessment from hundreds of hours to minutes or hours. This enables rapid screening of polymer additives and formulations, reducing material costs and development timelines. The approach supports quality control and research in polymer degradation.

Future Trends and Potential Applications

Further refinement of UV exposure protocols could better simulate specific climates. Integration with automated sampling and high-throughput pyrolysis-GC/MS could enable large-scale formulation libraries. Advances in real-time analysis and machine learning correlation of thermogram data may improve predictive modeling of polymer longevity.

Conclusion

Micro UV irradiation coupled with evolved gas analysis provides an efficient surrogate for traditional weather meter testing of HIPS. Comparable thermogravimetric profiles and molecular weight reductions confirm its effectiveness. The accelerated method offers significant advantages in cost, time, and throughput for polymer degradation studies.

Reference

Related technical note PYA5-003E