Analysis of Artificially Weathered PET and a Separate PET Hydrolysis Evaluation Using the 4300 Handheld FTIR

Analysis of Artificially Weathered PET and Hydrolysis Evaluation Using the 4300 Handheld FTIR

Significance of the Topic

Polyethylene terephthalate (PET) is widely used in photovoltaic and industrial applications where long-term environmental stability is critical. Early chemical changes under weathering or hydrolysis can lead to surface cracking, loss of performance, and failure of polymer-based components. Rapid, nondestructive detection of these early-stage changes aids in the design of more durable materials, optimizes additive formulations, and supports on-site quality control of in-service products.

Objectives and Study Overview

This application study demonstrates how the Agilent 4300 Handheld FTIR spectrometer can monitor initial chemical alterations in PET films exposed to simulated sunlight in a xenon chamber and to accelerated hydrolysis in boiling water. The goals are to benchmark additive-free PET degradation, develop multivariate calibration models for oxidative and hydrolytic aging, and establish a field-ready method for real-time material assessment.

Methodology and Instrumentation

• Materials: 50 µm Mitsubishi Hostaphan RNK PET films without additives, aged for 0, 5, and 10 days.
• Weathering Protocol: Atlas XLS+ xenon arc chamber at 700 W/m2, filter set A, constant 40 °C irradiance, no cycling, to mimic equatorial sunlight.
• Hydrolysis Protocol: PET films fully submerged and refluxed in distilled water for up to 14 days.
• Spectral Acquisition: Agilent 4300 Handheld FTIR with interchangeable diamond ATR or external reflectance (ER) interfaces; 4 cm–1 resolution, 64 co-added scans, spectral range 4000–650 cm–1.
• Chemometric Modeling: Partial least squares (PLS) regression with derivative and scatter-correction preprocessing to correlate spectral changes to exposure duration; Mahalanobis distance used for sample validation.

Main Results and Discussion

ATR spectra of the irradiated PET surface revealed emerging oxidation bands at 1773 cm–1 and 1690 cm–1, indicating perester and aromatic acid formation respectively, along with broader OH/C–O features (1450–1150 cm–1). A five-factor PLS model achieved R2=0.987 for 0–10 day weathering predictions. ER data provided comparable calibration (R2=0.987) but require custom libraries. Hydrolyzed films showed subtler changes in aromatic ring vibrations; a two-factor PLS model yielded R2=0.913 for 0–14 day aging, categorizing low, medium, and high hydrolysis. Bottom side oxidation after 10 days confirmed radical diffusion. Color-coded warnings and exposure predictions were implemented in the 4300 MicroLab software.

Practical Benefits

• Nondestructive, on-site analysis eliminates sample removal for laboratory testing.
• Rapid screening accelerates additive formulation optimization and reduces testing costs.
• Surface-sensitive ATR measurements detect early-stage degradation before physical damage appears.
• Data models and warning thresholds support real-time decision making in field environments.

Future Trends and Potential Applications

Advances may include integrating handheld FTIR with automated weather stations for continuous monitoring of polymer performance, expanding chemometric models to diverse plastics and coatings, and coupling spectral data with machine-learning algorithms. Development of novel anti-degradation additives can be guided by real-time feedback from field sensors. Similar approaches could extend to marine paints, adhesives, and composite materials under complex environmental stressors.

Conclusion

The Agilent 4300 Handheld FTIR system effectively quantifies early oxidative and hydrolytic changes in PET films under accelerated stress conditions. High-quality PLS models enable precise exposure predictions, while software-based alerts simplify on-site evaluation. This methodology offers a powerful tool for ensuring the durability of polymeric components in photovoltaic modules and other industrial applications.

References

1. Higgins F. Non-Destructive Evaluation of Composite Thermal Damage with Agilent’s New Handheld 4300 FTIR. Agilent Technologies Application Note, 2014.
2. ISO 10640:2011(E). Plastics – Methodology for assessing polymer photoageing by FTIR and UV/Visible spectroscopy.
3. Junkichi S. Radical Migration as an elementary process in degradation. Pure & Appl. Chem. 1983;55(10):1595–1601.
4. Brennan WJ, Shepherd SJ. Developments in weatherable Polyester Films For Photovoltaic Applications. DuPont Teijin Films, 2011.