{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,12]],"date-time":"2026-03-12T17:02:13Z","timestamp":1773334933001,"version":"3.50.1"},"reference-count":35,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2026,3,10]],"date-time":"2026-03-10T00:00:00Z","timestamp":1773100800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>Polyethylene glycols (PEGs) are emerging as superior and accessible phase change materials and heat transfer fluids, offering improved thermal properties over conventional thermal oils to meet the demand for innovative, sustainable energy solutions. While general research on PEG performance is still scarce, this paper contributes relevant experimental data. As part of a broad investigation into PEG and PEG-based nanocolloids, this experiment helps to clarify the true potential of these new fluids by outlining both their key advantages and their operational limitations. Consequently, PEG 200 and two PEG 200 + PEG 400 mixtures were considered as base fluids for manufacturing MWCNT nanocolloids, resulting in 15 samples that were thoroughly investigated in terms of density, viscosity and isobaric heat capacity variation with both nanoparticle concentration and temperature. Results revealed that nanocolloid density follows the basic rules for nanoparticle-enhanced fluids, with moderate increase with nanoparticle addition and temperature. Viscosity increased with MWCNT concentration and decreased with temperature, while isobaric heat capacity upsurges with nanoparticle addition. These findings are critical, as they can shed some light into the practical benefits, while clearly explaining the potential drawbacks, of employing these novel fluids in heat transfer applications.<\/jats:p>","DOI":"10.3390\/polym18060673","type":"journal-article","created":{"date-parts":[[2026,3,10]],"date-time":"2026-03-10T17:04:24Z","timestamp":1773162264000},"page":"673","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Polyethylene Glycol Nanocolloids as Advanced Phase Change Materials for Sustainable Energy: Experimental Data on Viscosity, Density, and Isobaric Heat Capacity"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-5878-3383","authenticated-orcid":false,"given":"C\u0103t\u0103lin Andrei","family":"\u0162ugui","sequence":"first","affiliation":[{"name":"Faculty of Materials Science and Engineering, Technical University \u201cGheorghe Asachi\u201d of Iasi, 700050 Iasi, Romania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-2673-1217","authenticated-orcid":false,"given":"Nicoleta","family":"Cojocariu","sequence":"additional","affiliation":[{"name":"Faculty of Materials Science and Engineering, Technical University \u201cGheorghe Asachi\u201d of Iasi, 700050 Iasi, Romania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5528-9177","authenticated-orcid":false,"given":"Bogdan","family":"Pricop","sequence":"additional","affiliation":[{"name":"Faculty of Materials Science and Engineering, Technical University \u201cGheorghe Asachi\u201d of Iasi, 700050 Iasi, Romania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2725-2326","authenticated-orcid":false,"given":"Dana","family":"Bejan","sequence":"additional","affiliation":[{"name":"\u201cPetru Poni\u201d Institute of Macromolecular Chemistry, 700487 Iasi, Romania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2473-184X","authenticated-orcid":false,"given":"Alina Adriana","family":"Minea","sequence":"additional","affiliation":[{"name":"Faculty of Materials Science and Engineering, Technical University \u201cGheorghe Asachi\u201d of Iasi, 700050 Iasi, Romania"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,10]]},"reference":[{"key":"ref_1","unstructured":"L\u00fcderitz, L.A.C. 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