{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,31]],"date-time":"2026-07-31T03:43:39Z","timestamp":1785469419310,"version":"3.56.0"},"reference-count":36,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2020,8,25]],"date-time":"2020-08-25T00:00:00Z","timestamp":1598313600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Research Foundation (NRF) of Korea and Korea Electric Power Corporation (KEPCO)","award":["NRF-2016R1D1A1B01012377; NRF-2017R1A5A1015596; NRF-2020R1A2C2004502; grant R17XH05"],"award-info":[{"award-number":["NRF-2016R1D1A1B01012377; NRF-2017R1A5A1015596; NRF-2020R1A2C2004502; grant R17XH05"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>The mechanically-enhanced urea-formaldehyde (UF) microcapsules are developed through a multi-step in situ polymerization method. Optical microscope (OM) and field emission scanning electron microscope (FE-SEM) prove that the microcapsules, 147.4 \u03bcm in diameter with a shell thickness of 600 nm, are well-formed. From 1H-nuclear magnetic resonance (1H-NMR) analysis, we found that dicyclopentadiene (DCPD), a self-healing agent encapsulated by the microcapsules, occupies ca. 40.3 %(v\/v) of the internal volume of a single capsule. These microcapsules are mixed with EPDM (ethylene-propylene-diene-monomer) and Grubbs\u2019 catalyst via a solution mixing method, and universal testing machine (UTM) tests show that the composites with mechanically-enhanced microcapsules has ca. 47% higher toughness than the composites with conventionally prepared UF microcapsules, which is attributed to the improved mechanical stability of the microcapsule. When the EPDM\/microcapsule rubber composites are notched, Fourier-transform infrared (FT-IR) spectroscopy shows that DCPD leaks from the broken microcapsule to the damaged site and flows to fill the notched valley, and self-heals as it is cured by Grubbs\u2019 catalyst. The self-healing efficiency depends on the capsule concentration in the EPDM matrix. However, the self-healed EPDM\/microcapsule rubber composite with over 15 wt% microcapsule shows an almost full recovery of the mechanical strength and 100% healing efficiency.<\/jats:p>","DOI":"10.3390\/polym12091918","type":"journal-article","created":{"date-parts":[[2020,8,25]],"date-time":"2020-08-25T09:30:07Z","timestamp":1598347807000},"page":"1918","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Self-Healing EPDM Rubbers with Highly Stable and Mechanically-Enhanced Urea-Formaldehyde (UF) Microcapsules Prepared by Multi-Step In Situ Polymerization"],"prefix":"10.3390","volume":"12","author":[{"given":"Hyeong-Jun","family":"Jeoung","sequence":"first","affiliation":[{"name":"Department of Organic Materials and Fiber Engineering, Soongsil University, 369 Sangdo-ro, Dongjak-gu, Seoul 156-743, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kun Won","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Organic Materials and Fiber Engineering, Soongsil University, 369 Sangdo-ro, Dongjak-gu, Seoul 156-743, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yong Jun","family":"Chang","sequence":"additional","affiliation":[{"name":"Department of Organic Materials and Fiber Engineering, Soongsil University, 369 Sangdo-ro, Dongjak-gu, Seoul 156-743, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8806-3070","authenticated-orcid":false,"given":"Yong Chae","family":"Jung","sequence":"additional","affiliation":[{"name":"Institute of Advanced Composite Materials, Korea Institute of Science and Technology (KIST), 92 Chudong-ro, Bongdong-eup, Wanju-gun, Jeonbuk 55324, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1961-5166","authenticated-orcid":false,"given":"Hyunchul","family":"Ku","sequence":"additional","affiliation":[{"name":"Department of Electronic and Communication Engineering, Konkuk University, Seoul 05029, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8602-2950","authenticated-orcid":false,"given":"Kyung Wha","family":"Oh","sequence":"additional","affiliation":[{"name":"Department of Fashion, Chung-Ang University, 4726 Seodongdae-ro, Daedeok-myeon, Anseong-si, Gyeonggi-do 17546, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hyung-Min","family":"Choi","sequence":"additional","affiliation":[{"name":"Department of Organic Materials and Fiber Engineering, Soongsil University, 369 Sangdo-ro, Dongjak-gu, Seoul 156-743, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jae Woo","family":"Chung","sequence":"additional","affiliation":[{"name":"Department of Organic Materials and Fiber Engineering, Soongsil University, 369 Sangdo-ro, Dongjak-gu, Seoul 156-743, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,8,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"10428","DOI":"10.1002\/anie.201500484","article-title":"Biomimetic self-healing","volume":"54","author":"Diesendruck","year":"2015","journal-title":"Angew. 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