{
  "abstract": "The study investigated the mechanism of colour change in coating formulations containing natural colorants—madder (Rubia tinctorum) and turmeric (Curcuma longa)—under UV irradiation using electron paramagnetic resonance (EPR) and Fourier-transform infrared spectroscopy (FTIR). Samples based on Epidian® 5 epoxy resin and Polimal® 109 unsaturated polyester resin containing radical and cationic photoinitiators were examined. EPR analysis revealed the involvement of transition metal ions (Fe3+, Cu2+) and organic radicals in the photo-oxidation processes. Characteristic signals at g ≈ 4.3, g = 2.2–2.3 and g = 2.001 were attributed to Fe3+, Cu2+ and aromatic radicals, respectively. UV irradiation caused the formation of oxygen- and phenoxyl-type radicals in turmeric-containing epoxy coatings and phenoxyl and semiquinone radicals in madder-containing coatings. The colour changes correlated with structural transformations identified by FTIR spectroscopy, while polyester coatings showed slower colour-change dynamics. The results confirm the usefulness of EPR and FTIR spectroscopy for analyzing UV-induced processes in polymer coating formulations containing plant-derived colorants and provide insight into the photochemical stability of bio-based components considered for more environmentally friendly coating materials.",
  "abstract_shown": true,
  "affiliations": [
    "Faculty of Exact and Technical Sciences, Institute of Materials Engineering, University of Rzeszow, Pigonia 1, 35-310 Rzeszow, Poland",
    "Department of Polymers and Biopolymers, Faculty of Chemistry, Rzeszów University of Technology, ul. Powstańców Warszawy 6, 35-959 Rzeszów, Poland"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 3,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Wojciech Żyłka",
      "orcid": "0000-0001-8896-3335"
    },
    {
      "affs": [
        1
      ],
      "name": "Barbara Pilch-Pitera",
      "orcid": "0000-0002-2412-2219"
    },
    {
      "affs": [
        0
      ],
      "name": "Ireneusz Stefaniuk",
      "orcid": "0000-0003-2616-9595"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/5z2gp03drdsyd.bib",
  "cited_by": 0,
  "doi": "10.3390/molecules31213930",
  "fulltext_url": null,
  "id": "5z2gp03drdsyd",
  "issns": [
    "1420-3049"
  ],
  "landing_url": "https://www.mdpi.com/1420-3049/31/21/3930",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [],
  "openalex": null,
  "pdf_url": null,
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-01",
  "publisher": "MDPI AG",
  "ris": "https://research.draconitic.com/paper/5z2gp03drdsyd.ris",
  "sources": [
    {
      "first_seen": "2026-11-04T00:24:01Z",
      "native_id": "10.3390/molecules31213930",
      "source": "crossref",
      "url": "https://www.mdpi.com/1420-3049/31/21/3930"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "issn:1420-3049",
      "subfield": "general"
    }
  ],
  "title": "UV-Induced Colour Changes in Bio-Based Coating Formulations Containing Turmeric and Madder Studied by EPR and FTIR",
  "title_text": "UV-Induced Colour Changes in Bio-Based Coating Formulations Containing Turmeric and Madder Studied by EPR and FTIR",
  "type": "peer-reviewed",
  "updated_at": "2026-11-05T00:20:53Z",
  "url": "https://research.draconitic.com/paper/5z2gp03drdsyd",
  "venue": "Molecules",
  "versions": []
}