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dc.contributor.authorBrondi, Cosimo
dc.contributor.authorSantiago Calvo, Mercerdes
dc.contributor.authorDi Maio, Ernesto
dc.contributor.authorRodríguez Pérez, Miguel Ángel 
dc.date.accessioned2023-11-17T12:49:18Z
dc.date.available2023-11-17T12:49:18Z
dc.date.issued2022
dc.identifier.citationMaterials, 2022, Vol. 15, Nº. 9, 3135es
dc.identifier.issn1996-1944es
dc.identifier.urihttps://uvadoc.uva.es/handle/10324/63070
dc.descriptionProducción Científicaes
dc.description.abstractIn this study, we investigated the influence of mixing conditions on the foaming process of water blown polyurethane (PU) foams obtained at different mixing speeds (50, 500, 1000 and 2000 rpm). In particular, the morphological evolution during the foaming process, in terms of the bubble size and bubble density, was studied via optical observations, while the effects on the reaction kinetics were monitored using in situ FTIR spectroscopy. At the slow mixing speed (50 rpm), no air bubbles were included and the early foaming process was characterized by the formation of new bubbles (CO2 nucleation), provided by the blowing reaction. Later on, it was observed that the coalescence affected the overall foaming process, caused by the gelling reaction, which was inhibited by the indigent mixing conditions and could not withstand the bubbles expansion. As a result, a PU foam with a coarse cellular structure and an average bubble size of 173 µm was obtained. In this case, the bubbles degeneration rate, dN/dt, was −3095 bubble·cm−3·s−1. On the contrary, at 500 rpm, air bubbles were included into the PU reaction system (aeration) and no formation of new bubbles was observed during the foaming process. After this, the air bubbles underwent growth caused by diffusion of the CO2 provided by the blowing reaction. As the gelling reaction was not strongly depleted as in the case at 50 rpm, the coalescence less affected the bubble growth (dN/dt = −2654 bubble·cm−3·s−1), leading to a PU foam with an average bubble size of 94 µm. For the foams obtained at 1000 and 2000 rpm, the bubble degeneration was first affected by coalescence and then by Ostwald ripening, and a finer cellular structure was observed (with average bubble sizes of 62 µm and 63 µm for 1000 rpm and 2000 rpm, respectively). During the first foaming stage, the coalescence was less predominant in the bubble growth (with dN/dt values of −1838 bubble·cm−3·s−1 and −1601 bubble·cm−3·s−1, respectively) compared to 50 rpm and 500 rpm. This occurrence was ascribed to the more balanced process between the bubble expansion and the PU polymerization caused by the more suitable mixing conditions. During the late foaming stage, the Ostwald ripening was only responsible for the further bubble degeneration (with dN/dt values of −89 bubble·cm−3·s−1 and −69 bubble·cm−3·s−1, respectively).es
dc.format.mimetypeapplication/pdfes
dc.language.isoenges
dc.publisherMDPIes
dc.rights.accessRightsinfo:eu-repo/semantics/openAccesses
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/*
dc.subjectPolimerses
dc.subjectPolyurethaneses
dc.subjectPlastic foamses
dc.subjectFoamed materialses
dc.subjectEspumas poliméricas de poliuretano - Propiedades mecánicases
dc.subjectNucleationes
dc.subjectAir bubblees
dc.subjectGelses
dc.subjectMaterials sciencees
dc.subjectCondensed Matter Physicses
dc.subjectFísica de la materia condensadaes
dc.titleRole of air bubble inclusion on polyurethane reaction kineticses
dc.typeinfo:eu-repo/semantics/articlees
dc.rights.holder© 2022 The Authorses
dc.identifier.doi10.3390/ma15093135es
dc.relation.publisherversionhttps://www.mdpi.com/1996-1944/15/9/3135es
dc.identifier.publicationfirstpage3135es
dc.identifier.publicationissue9es
dc.identifier.publicationtitleMaterialses
dc.identifier.publicationvolume15es
dc.peerreviewedSIes
dc.description.projectUniversidad de Nápoles Federico II y Fondo Europeo de Desarrollo Regional (FEDER) (POR CAMPANIA FESR 2014-2020) - (CUP B63D18000290007)es
dc.identifier.essn1996-1944es
dc.rightsAtribución 4.0 Internacional*
dc.type.hasVersioninfo:eu-repo/semantics/publishedVersiones
dc.subject.unesco2206.10 Polímeroses
dc.subject.unesco2304.21 Poliuretanoses
dc.subject.unesco3312 Tecnología de Materialeses


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