{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,7]],"date-time":"2026-10-07T20:23:29Z","timestamp":1791404609535,"version":"4.3.3"},"reference-count":30,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2023,3,27]],"date-time":"2023-03-27T00:00:00Z","timestamp":1679875200000},"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>Smart coatings and smart polymers have been garnering great interest in recent times due to their novel characteristics, such as being self-restoring, self-cleaning, and self-healing. However, most self-healing materials have a low glass transition temperature (Tg) and are inadequate for the repair of advanced composites. Because of their low Tg, the conventional self-healing materials plasticize and weaken the composites. In this study, moderate to high temperature self-healing microcapsules, capable of healing and thus stopping crack propagation, are prepared. The microcapsules were prepared using a two-step process involving the synthesis of poly(urea formaldehyde) (PUF) prepolymer, followed by the encapsulation of hexamethylene diisocyanate (HDI) in an oil-in-water emulsion to form a crosslinked PUF shell. Diisocyanates are of particular interest as self-healing encapsulants because of their diversity of structure and fast rate of hydrolysis. Successful encapsulation was verified by Fourier transform infrared spectroscopy (FTIR) and optical microscopy. Thermogravimetric analysis (TGA) was used to characterize the thermal properties of microcapsules. The onset temperature for microcapsule degradation varied from 155 \u00b0C to 195 \u00b0C. Dynamic mechanical analysis (DMA) was used to determine the thermomechanical response of microcapsule\/epoxy films. DMA showed that the glass transition temperature (Tg) of the epoxy\/microcapsule composite was greater than the Tg for neat epoxy and varied between 34 and 65 \u00b0C. The TGA analysis of the epoxy\/microcapsule composite shows that the thermal stability and char retention of the epoxy\/microcapsule composite increased and the low temperature decomposition peak at 150 \u00b0C, associated with the microcapsule, disappeared after the DMA test, indicating the occurrence of a reaction between HDI and the epoxy to form a crosslinked polyurea network structure.<\/jats:p>","DOI":"10.3390\/polym15071668","type":"journal-article","created":{"date-parts":[[2023,3,28]],"date-time":"2023-03-28T01:41:34Z","timestamp":1679967694000},"page":"1668","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":31,"title":["Self-Healing Poly(urea formaldehyde) Microcapsules: Synthesis and Characterization"],"prefix":"10.3390","volume":"15","author":[{"given":"Jehan","family":"Kothari","sequence":"first","affiliation":[{"name":"Mechanical and Materials Engineering Department, University of Cincinnati, Cincinnati, OH 45221, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0778-4023","authenticated-orcid":false,"given":"Jude O.","family":"Iroh","sequence":"additional","affiliation":[{"name":"Mechanical and Materials Engineering Department, University of Cincinnati, Cincinnati, OH 45221, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,3,27]]},"reference":[{"key":"ref_1","first-page":"509","article-title":"Microencapsulation: A review","volume":"3","author":"Jyothi","year":"2012","journal-title":"Int. J. Farma Bio Sci."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"372","DOI":"10.1007\/BF02412141","article-title":"Fracture testing of a self-healing polymer composite","volume":"42","author":"Brown","year":"2002","journal-title":"Exp. Mech."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"719","DOI":"10.3109\/02652040309178083","article-title":"In Situ poly(urea-formaldehyde) microencapsulation of dicyclopentadiene","volume":"20","author":"Brown","year":"2003","journal-title":"J. Microencapsul."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"5338","DOI":"10.1016\/j.polymer.2006.05.051","article-title":"Preparation and characterization of poly(urea-formaldehyde) microcapsules filled with epoxy resins","volume":"47","author":"Yuan","year":"2006","journal-title":"Polymer"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"2300","DOI":"10.1016\/j.polymdegradstab.2006.04.026","article-title":"Thermal stability of microencapsulated epoxy resins with poly(urea\u2013formaldehyde)","volume":"91","author":"Yuan","year":"2006","journal-title":"Polym. Degrad. Stab."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"417","DOI":"10.1016\/j.matchemphys.2008.02.035","article-title":"Preparation and properties of poly(urea\u2013formaldehyde) microcapsules filled with epoxy resins","volume":"110","author":"Yuan","year":"2008","journal-title":"Mater. Chem. Phys."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2531","DOI":"10.1016\/j.polymer.2008.03.044","article-title":"Preparation and characterization of microencapsulated polythiol","volume":"49","author":"Yuan","year":"2008","journal-title":"Polymer"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"11614","DOI":"10.1039\/C4TA01312C","article-title":"Robust microcapsules with polyurea\/silica hybrid shell for one-part self-healing anticorrosion coatings","volume":"2","author":"Wu","year":"2014","journal-title":"J. Mater. Chem. A"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"6751","DOI":"10.1002\/adfm.201401473","article-title":"A Versatile Approach towards Multifunctional Robust Microcapsules with Tunable, Restorable, and Sol-vent-Proof Superhydrophobicity for Self-Healing and Self-Cleaning Coatings","volume":"24","author":"Wu","year":"2014","journal-title":"Adv. Funct. Mater."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1195","DOI":"10.1021\/am100084k","article-title":"Robust, Double-Walled Microcapsules for Self-Healing Polymeric Materials","volume":"2","author":"Caruso","year":"2010","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1855","DOI":"10.1021\/ma902251n","article-title":"Microencapsulation of a Reactive Liquid-Phase Amine for Self-Healing Epoxy Composites","volume":"43","author":"McIlroy","year":"2010","journal-title":"Macromolecules"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"282","DOI":"10.1002\/adma.201303179","article-title":"Thermally stable autonomic healing in epoxy using a dual-microcapsule system","volume":"26","author":"Jin","year":"2014","journal-title":"Adv. Mater."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/BF02980037","article-title":"Control of encapsulation efficiency and initial burst in polymeric microparticle systems","volume":"27","author":"Yeo","year":"2004","journal-title":"Arch. Pharmacal Res."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"581","DOI":"10.1016\/j.polymer.2011.12.005","article-title":"Self-healing thermoset using encapsulated epoxy-amine healing chemistry","volume":"53","author":"Jin","year":"2012","journal-title":"Polymer"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2010","DOI":"10.1021\/ma402471c","article-title":"One-Pot Thermo-Remendable Shape Memory Polyurethanes","volume":"47","author":"Rivero","year":"2014","journal-title":"Macromolecules"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1782","DOI":"10.1016\/j.polymer.2014.02.033","article-title":"Self-healing polyurethane elastomer with thermalluy reversible alkoxyamines as crosslinkages","volume":"55","author":"Yuan","year":"2014","journal-title":"Polymer"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"4976","DOI":"10.1016\/j.surfcoat.2012.05.133","article-title":"Preparation of epoxy microcapsule based self-healing coatings and their behavior","volume":"206","author":"Lin","year":"2012","journal-title":"Surf. Coat. Technol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.apsusc.2013.09.182","article-title":"Corrosion re-sistance of siloxane\u2013poly(methyl methacrylate) hybrid films modified with acetic acid on tin plate substrates: Influence of tet-raethoxysilane addition","volume":"298","author":"Kunst","year":"2014","journal-title":"Appl. Surfaces Sci."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"590","DOI":"10.1016\/j.porgcoat.2013.11.023","article-title":"Corrosion resistance and lifetime of polyimide-b-polyurea novel copolymer coatings","volume":"77","author":"Feng","year":"2014","journal-title":"Prog. Org. Coat."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"109279","DOI":"10.1016\/j.eurpolymj.2019.109279","article-title":"Self-healing high temperature shape memory polymer","volume":"120","author":"Kong","year":"2019","journal-title":"Eur. Polym. J."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"56","DOI":"10.1016\/j.engfracmech.2014.12.009","article-title":"The effect of corrosion inhibitors on environmental fatigue crack growth in Al\u2013Zn\u2013Mg\u2013Cu","volume":"137","author":"Dorman","year":"2015","journal-title":"Eng. Fract. Mech."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1016\/j.porgcoat.2015.02.011","article-title":"Self-healing epoxy coatings loaded with inhibitor-containing polyelectrolyte nanocapsules","volume":"84","author":"Szczepanowicz","year":"2015","journal-title":"Prog. Org. Coat."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"613","DOI":"10.1016\/j.porgcoat.2019.06.015","article-title":"Preparation of Ce-MOF@TEOS to enhance the anti-corrosion properties of epoxy coatings","volume":"135","author":"Cao","year":"2019","journal-title":"Prog. Org. Coat."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"121","DOI":"10.1016\/j.surfcoat.2019.05.017","article-title":"Multifunctional self-healing polymeric nanocomposite coatings for corrosion inhibition of steel","volume":"372","author":"Ubaid","year":"2019","journal-title":"Surf. Coat. Technol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"978","DOI":"10.1016\/j.compscitech.2007.07.021","article-title":"Nanocapsules for self-healing materials","volume":"68","author":"Blaiszik","year":"2008","journal-title":"Compos. Sci. Technol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"11014","DOI":"10.1115\/1.4007140","article-title":"Cyclic viscoplastic-viscodamage analysis of shape memory polymers fibers with ap-plication to self-healing smart materials","volume":"80","author":"Shojaei","year":"2013","journal-title":"J. Appl. Mech. Trans. ASME"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"46778","DOI":"10.1039\/C7RA09017J","article-title":"Cooperative self-healing performance of shape memory polyurethane and Alodine-containing microcapsules","volume":"7","author":"Fan","year":"2017","journal-title":"RSC Adv."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"474","DOI":"10.1016\/j.compositesa.2019.04.012","article-title":"Self-healing composites: A state-of-the-art review","volume":"121","author":"Kanu","year":"2019","journal-title":"Compos. Part A Appl. Sci. Manuf."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"6637584","DOI":"10.1155\/2021\/5558457","article-title":"Shape Memory Corrosion-Resistant Polymeric Materials","volume":"2021","author":"Jacobson","year":"2021","journal-title":"Int. J. Polym. Sci."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1316","DOI":"10.1016\/j.porgcoat.2013.04.005","article-title":"Encapsulation of aliphatic amines into nanoparticles for self-healing corrosion protection of steel sheets","volume":"76","author":"Choi","year":"2013","journal-title":"Prog. Org. Coat."}],"container-title":["Polymers"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-4360\/15\/7\/1668\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T19:04:12Z","timestamp":1760123052000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-4360\/15\/7\/1668"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,3,27]]},"references-count":30,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2023,4]]}},"alternative-id":["polym15071668"],"URL":"https:\/\/doi.org\/10.3390\/polym15071668","relation":{},"ISSN":["2073-4360"],"issn-type":[{"value":"2073-4360","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,3,27]]}}}