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Oxygen anomalous diffusion during photooxidation of polypropylene

Biochimica et Biophysica Acta (BBA) - Biomembranes 2025
José William de Lima Souza, Lucas Cordeiro de Oliveira, Taynah Pereira Galdino, Marcus Vinícius Lia Fook, Rômulo Feitosa Navarro

Summary

This study investigated how oxygen diffuses through polypropylene during photooxidation, finding that standard Fick's Law solutions become inoperative because structural changes in the polymer cause the diffusion coefficient to vary over time, and proposing a modified calculation method to accurately model the anomalous oxygen concentration profiles.

Polymers

Abstract This research paper is about the calculation of the diffusion coefficient and the oxygen concentration profile along polypropylene samples exposed to photooxidation in a dry environment. In this degradation process, oxygen diffusion is anomalous, as it is affected by structural modifications that occur over the exposure time. Thus, the diffusion coefficient starts to depend on time and the common solutions for Fick's 2nd Law for diffusion become inoperative for importante time intervals. In this work, a modification is proposed in the calculation of the diffusivity and, consequently, of the solution for the oxygen concentration profile in diffusion.

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