{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,11]],"date-time":"2026-09-11T05:05:57Z","timestamp":1789103157233,"version":"build-2803163510"},"reference-count":35,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T00:00:00Z","timestamp":1788912000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100016971","name":"Lomonosov Moscow State University","doi-asserted-by":"publisher","award":["AAAA-A21-121011590086-0"],"award-info":[{"award-number":["AAAA-A21-121011590086-0"]}],"id":[{"id":"10.13039\/501100016971","id-type":"DOI","asserted-by":"publisher"}]},{"award":["AAAA-A21-121011590086-0"],"award-info":[{"award-number":["AAAA-A21-121011590086-0"]}],"id":[{"id":"https:\/\/ror.org\/010pmpe69","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>Epoxy resins are widely used as binders in intumescent fire-retardant coatings; however, the effect of their molecular weight on the fire-retardant performance of coatings with different intumescent mechanisms remains insufficiently understood. In this study, five commercial bisphenol A-based epoxy resins with number-average molecular weights (Mn) ranging from 375 to 1520 g\/mol were characterized by HPLC, NMR, DSC, and TGA, and subsequently formulated into intumescent coatings of two types: classical ammonium polyphosphate\/pentaerythritol\/melamine (APP\/PER\/MEL) systems and expandable graphite (EG)-based systems. The fire-retardant efficacy and expansion factor were evaluated using a standard fire test and thermal shock exposure. In the APP\/PER\/MEL coatings, the optimal fire-retardant efficacy of 55 min was achieved at an intermediate Mn (645 g\/mol) and an optimal pore structure (mean equivalent pore diameter deq = 41 \u03bcm), whereas both low- and high-molecular-weight resins led to distinct structural defects\u2014macrocavities and through-thickness cracks, respectively, as revealed by SEM. In the EG-based coatings, a monotonic decrease in both the expansion factor (from ~2000% to ~1000%) and fire-retardant efficacy (from 65 to 52 min) was observed with increasing Mn, with the bisphenol A-based epoxy resin having a molecular weight of 375 g\/mol providing the best performance. The observed differences were attributed to the effect of melt viscosity on char expansion and structural integrity. These findings demonstrate that the molecular-weight range of the epoxy binder can be selected according to the expansion capacity of the intumescent system, providing a practical guideline for the formulation of high-performance epoxy-based fire-protective coatings.<\/jats:p>","DOI":"10.3390\/polym18182201","type":"journal-article","created":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T14:02:48Z","timestamp":1788962568000},"page":"2201","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Tailoring the Fire-Retardant Efficacy of Intumescent Coatings via Optimal Selection of Epoxy Binder Molecular Weight"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0009-0003-3366-6300","authenticated-orcid":false,"given":"Daria","family":"Kuznetsova","sequence":"first","affiliation":[{"name":"Faculty of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2232-8192","authenticated-orcid":false,"given":"Nikolay","family":"Yashin","sequence":"additional","affiliation":[{"name":"Faculty of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-1542-0620","authenticated-orcid":false,"given":"Vyacheslav","family":"Subbotin","sequence":"additional","affiliation":[{"name":"Faculty of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5573-2987","authenticated-orcid":false,"given":"Victor","family":"Avdeev","sequence":"additional","affiliation":[{"name":"Faculty of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Nazrun, T., Hassan, M.K., Hasnat, M.R., Hossain, M.D., Ahmed, B., and Saha, S. 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