{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,14]],"date-time":"2026-02-14T04:28:16Z","timestamp":1771043296911,"version":"3.50.1"},"reference-count":21,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2018,6,19]],"date-time":"2018-06-19T00:00:00Z","timestamp":1529366400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100008530","name":"European Regional Development Fund","doi-asserted-by":"publisher","award":["POCI-01-0145-FEDER-006939"],"award-info":[{"award-number":["POCI-01-0145-FEDER-006939"]}],"id":[{"id":"10.13039\/501100008530","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Urea-formaldehyde (UF) resins are the most used resins in the wood industry due to high reactivity and low price. However, their reduced stability during storage is a drawback, imposing strict limits in terms of allowable shipping distances and storage times. This instability, manifested by viscosity increase that renders the resin unusable, occurs due to the progress of condensation reactions between the polymeric species present in the liquid medium. In order to achieve a stable resin formulation, dimethylurea (DMeU) was selected for being less reactive than urea. Dimethylurea is shown to co-polymerize with the UF polymer during the acidic synthesis condensation step. However, during storage it behaves like an end group blocker, due to its lower reactivity at basic pH. By adding 1.25% DMeU, it was possible to obtain a formulation that remained with stable viscosity during two-month storage at 40 \u00b0C. The reference UF resin remained stable only for eight days in these conditions. Wood particleboards produced with modified resins showed internal bond strengths of about 0.5 N\u00b7mm\u22122, similar to the fresh reference UF resin, even when the resins were used after the two-month storage period. Formaldehyde content values were below the limit for E1 class, \u22648 mg\/100 g oven dry board (EN 13986).<\/jats:p>","DOI":"10.3390\/ma11061032","type":"journal-article","created":{"date-parts":[[2018,6,19]],"date-time":"2018-06-19T11:20:36Z","timestamp":1529407236000},"page":"1032","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["Copolymerization of UF Resins with Dimethylurea for Improving Storage Stability without Impairing Adhesive Performance"],"prefix":"10.3390","volume":"11","author":[{"given":"Pedro","family":"Pereira","sequence":"first","affiliation":[{"name":"EuroResinas-Ind\u00fastrias Qu\u00edmicas, 7520 Sines, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jo\u00e3o","family":"Pereira","sequence":"additional","affiliation":[{"name":"ARCP\u2014Associa\u00e7\u00e3o Rede de Compet\u00eancia em Pol\u00edmeros, 4200 Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"N\u00e1dia. T.","family":"Paiva","sequence":"additional","affiliation":[{"name":"EuroResinas-Ind\u00fastrias Qu\u00edmicas, 7520 Sines, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jo\u00e3o. M.","family":"Ferra","sequence":"additional","affiliation":[{"name":"EuroResinas-Ind\u00fastrias Qu\u00edmicas, 7520 Sines, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jorge M.","family":"Martins","sequence":"additional","affiliation":[{"name":"DEMad\u2014Instituto Polit\u00e9cnico de Viseu, 3504 Viseu, Portugal"},{"name":"LEPABE\u2014Faculdade de Engenharia da Universidade do Porto, 4200 Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4557-7113","authenticated-orcid":false,"given":"Lu\u00edsa. H.","family":"Carvalho","sequence":"additional","affiliation":[{"name":"DEMad\u2014Instituto Polit\u00e9cnico de Viseu, 3504 Viseu, Portugal"},{"name":"LEPABE\u2014Faculdade de Engenharia da Universidade do Porto, 4200 Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4447-4473","authenticated-orcid":false,"given":"Fern\u00e3o. D.","family":"Magalh\u00e3es","sequence":"additional","affiliation":[{"name":"LEPABE\u2014Faculdade de Engenharia da Universidade do Porto, 4200 Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2018,6,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"95","DOI":"10.1016\/S0143-7496(97)00054-7","article-title":"Urea-Formaldehyde (UF) adhesive resins for wood","volume":"18","author":"Dunky","year":"1998","journal-title":"Int. J. Adhes. 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EN 13986+A1."}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/11\/6\/1032\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:09:14Z","timestamp":1760195354000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/11\/6\/1032"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,6,19]]},"references-count":21,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2018,6]]}},"alternative-id":["ma11061032"],"URL":"https:\/\/doi.org\/10.3390\/ma11061032","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,6,19]]}}}