A team of researchers from Spanish institutions has found that polystyrene used in healthcare packaging shows strong resistance to UVC sterilization, with minimal chemical degradation detected using FT-IR and Raman spectroscopy.
UVC Radiation Leaves Polystyrene Largely Unscathed, Study Finds
As ultraviolet C (UVC) radiation becomes an increasingly common method for sterilizing healthcare materials, researchers have turned their attention to its impact on the plastics that comprise much of modern medical packaging (1–3). A new study published in Polymer Degradation and Stability reveals that polystyrene (PS), a widely used polymer in pharmaceutical and medical packaging, remains chemically stable even after UVC exposure—an important finding for ensuring both safety and material integrity in sterilization protocols (1).
The work was conducted by C. Boronatb, V. Correcher, J. García-Guinea, and J.C. Bravo-Yagüe from several Spanish institutions: the National University of Distance Education (UNED), the Centre for Energy, Environment and Technology Research (CIEMAT), and the Spanish National Research Council (CSIC) (1).
A close-up view of ultraviolet light sterilization © Dounonji -chronicles-stock.adobe.com
Spectroscopic Tools Probe Polymer Integrity
To evaluate how UVC affects PS materials, the researchers used a combination of Fourier-transform infrared (FT-IR) spectroscopy, Raman spectroscopy, and thermoluminescence (TL) analysis. These techniques were key in detecting even subtle chemical changes (1).
Despite polystyrene’s known susceptibility to photo-oxidation, especially under UV exposure, the team found only minimal degradation in UVC-irradiated samples. FT-IR spectra showed nosignificant increase in carbonyl peaks—which would indicate chain scission or oxidation—suggesting the PS maintained its chemical structure. Similarly, Raman analysis detected only minor spectral variations, which the authors attributed more to inherent differences in the material than to radiation-induced damage (1–3).
These results support the notion that PS can withstand UVC exposure under controlled conditions, reinforcing its suitability for post-packaging sterilization applications in medicine and pharmaceuticals (1–3).
Thermoluminescence Confirms Radiation Exposure
While FT-IR and Raman methods assessed the integrity of the material, thermoluminescence (TL) analysis was employed to verify the presence and intensity of UVC exposure. The study examined several commercial TL dosimeters, evaluating their effectiveness in detecting non-ionizing UVC radiation (1).
The TLD-100 and TLD-200 dosimeters performed well, showing distinct luminescent emissions after UVC exposure, peaking at 310 °C and 150–250 °C, respectively. These findings suggest that such dosimeters can serve as reliable indicators of UVC treatment, ensuring quality control in sterilization processes. In contrast, TLD-400 and GR-200 dosimeters were deemed unsuitable due to inconsistent or diffuse emissions (1).
Material Thickness and UVC Penetration
The researchers also explored the effect of material thickness on UVC penetration. They noted that while UVC rays were able to pass through both 0.16 mm and 0.40 mm PS samples, penetration depth varied with thickness, highlighting the importance of customizing UVC treatment protocols based on packaging dimensions (1). Such findings are particularly relevant for the pharmaceutical and healthcare sectors, where consistent sterilization across different packaging forms is critical to ensure product safety.
Broader Implications for Healthcare Packaging
Given the global emphasis on sterilization in the wake of recent public health challenges, the study’s results offer reassurance for manufacturers relying on PS for packaging medical devices and pharmaceuticals. With growing interest in non-chemical, non-ionizing sterilization methods, UVC treatment offers a compelling option—and now, with evidence from advanced spectroscopic analysis, one that appears chemically safe for polystyrene under typical exposure conditions (1–3).
The authors conclude that more research is warranted, particularly to optimize dosimeter technologies and further refine treatment conditions based on material properties and environmental factors.
References
(1) Boronat, C. E. C. I. L. I. A.; Correcher, V. I. R. G. I. L. I. O.; García-Guinea, J.; Bravo-Yagüe, J. C. Effects of UVC Irradiation on Polystyrene for Healthcare Packaging: Study by FTIR and Raman Spectroscopy with Thermoluminescence. Polym. Degrad. Stab. 2024, 222, 110700. DOI: 10.1016/j.polymdegradstab.2024.110700
(2) de Castro Monsores, K. G.; da Silva, A. O.; Oliveira, S. D. S. A.; Weber, R. P.; Feliciano Filho, P.; Monteiro, S. N. Influence of Ultraviolet Radiation on Polystyrene. J. Mater. Res. Technol. 2021, 13, 359–365. DOI: 10.1016/j.jmrt.2021.04.035
(3) Yousif, E.; Haddad, R. Photodegradation and Photostabilization of Polymers, Especially Polystyrene: Review. SpringerPlus 2013, 2, 398. DOI: 10.1186/2193-1801-2-398
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