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Relative contributions of crystallinity and environmental factors to the degradation rate of poly(ε-caprolactone) (PCL) under coastal field conditions

Polymer Journal (2026)Cite this article

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Abstract

Evaluating the environmental fate of poly(ε-caprolactone) (PCL), a marine-biodegradable plastic, requires understanding its degradation behavior under realistic marine conditions. Previous studies have separately examined the effects of crystallinity and environmental conditions on PCL degradation, but in actual ocean environments where conditions vary spatiotemporally, the relative contributions of these factors remain insufficiently quantified. In this study, long-term coastal field tests in Japan were combined with machine learning analysis to construct a regression framework relating PCL degradation rates to crystallinity and environmental variables. PCL sheets with controlled crystallinity were exposed for 6–15 months at six coastal locations, and degradation rates were derived from mass loss. Among the regression models tested, CatBoost showed the best performance (test R² = 0.60). Within the present dataset and coastal seafloor deployment conditions, the SHapley Additive exPlanations (SHAP) analysis ranked water temperature highest in terms of mean absolute contribution, followed by depth and total nitrogen (TN), whereas crystallinity contributed moderately. Depth and TN may partly capture location-level background differences rather than isolated variable effects. These results suggest that environmental factors contributed substantially to the variation in observed degradation rates. These findings offer a basis for field-relevant environmental compatibility assessment and for interpreting the role of crystallinity in material design.

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Acknowledgements

This work was supported by the New Energy and Industrial Technology Development Organization (NEDO) under Project PNP18016. The authors thank Prof. Hirofumi Hinata, Prof. Hidetaka Takeoka, and Prof. Takahiro Matsubara (Ehime University) for their kind support and valuable assistance with the coastal field exposure experiments, including field logistics and sample deployment and retrieval.

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Authors and Affiliations

  1. Department of Automotive Science, Kyushu University, Fukuoka, Japan

    Hironori Taguchi & Keiji Tanaka

  2. Chemicals Evaluation and Research Institute, Japan (CERI), Sugimoto-machi, Saitama, Japan

    Hironori Taguchi & Takako Kikuchi

  3. Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwa-no-ha, Kashiwa City, Chiba, Japan

    Yoshifumi Amamoto

  4. Materials DX Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Central 2-1, 1-1-1 Umezono, Tsukuba, Ibaraki, Japan

    Hiroshi Morita

  5. Department of Applied Chemistry and Center for Polymer Interface and Molecular Adhesion Science, Kyushu University, Fukuoka, Japan

    Keiji Tanaka

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  1. Hironori Taguchi
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Contributions

Hironori Taguchi: Conceptualization, Methodology, Validation, Formal Analysis, Writing-Original Draft, Writing-Review & Editing, Visualization Takako Kikuchi: Conceptualization, Funding acquisition. Yoshifumi Amamoto: Conceptualization, Methodology Hiroshi Morita: Conceptualization, Methodology Keiji Tanaka: Conceptualization, Methodology, Writing-Review & Editing, Supervision, Project administration.

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Correspondence to Hironori Taguchi or Keiji Tanaka.

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Taguchi, H., Kikuchi, T., Amamoto, Y. et al. Relative contributions of crystallinity and environmental factors to the degradation rate of poly(ε-caprolactone) (PCL) under coastal field conditions. Polym J (2026). https://doi.org/10.1038/s41428-026-01153-w

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