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Rheo-optical characterization of liquid crystalline acetoxypropylcellulose melt undergoing large shear flow and relaxation after flow cessation

2015-08-05Journal article Restricted access
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dc.contributor.authorTeixeira, Paulo F.
dc.contributor.authorFernandes, Susete N.
dc.contributor.authorCanejo, João
dc.contributor.authorGodinho, Maria Helena
dc.contributor.authorCovas, José A.
dc.contributor.authorR. Leal, Catarina
dc.contributor.authorHilliou, Loic
dc.date.accessioned2016-03-18T15:33:25Z
dc.date.available2016-03-18T15:33:25Z
dc.date.issued2015-08-05
dc.description.abstractThe rheological and structural characteristics of acetoxypropylcellulose (APC) nematic melt are studied at shear rates ranging from 10 s(-1) to 1000 s(-1) which are relevant to extrusion based processes. APC shows a monotonic shear thinning behavior over the range of shear rates tested. The negative extrudate-swell shows a minimum when a critical shear rate (gamma) over dot(c) is reached. For shear rates smaller than (gamma) over dot(c), the flow-induced texture consists of two set of bands aligned parallel and normal to the flow direction. At shear rates larger than (gamma) over dot(c), the flow induced texture is reminiscent of a 2 fluids structure. Close to the shearing walls, domains elongated along the flow direction and stacked along the vorticity are imaged with POM, whereas SALS patterns indicate that the bulk of the sheared APC is made of elliptical domains oriented along the vorticity. No full nematic alignment is achieved at the largest shear rate tested. Below (gamma) over dot(c), the stress relaxation is described by a stretched exponential. Above (gamma) over dot(c), the stress relaxation is described by a fast and a slow process. The latter coincides with the growth of normal bands thicknesses, as the APC texture after flow cessation consists of two types of bands with parallel and normal orientations relative to the flow direction. Both bands thicknesses do not depend on the applied shear rate, in contrast to their orientation. (C) 2015 Elsevier Ltd. All rights reserved.pt_PT
dc.identifier.citationTEIXEIRA, Paulo F.; [et al.] - Rheo-optical characterization of liquid crystalline acetoxypropylcellulose melt undergoing large shear flow and relaxation after flow cessation. Polymer. ISSN. 0032-3861. Vol. 71 (2015), pp. 102-112.pt_PT
dc.identifier.doi10.1016/j.polymer.2015.06.056pt_PT
dc.identifier.issn0032-3861
dc.identifier.issn1873-2291
dc.identifier.urihttp://hdl.handle.net/10400.21/5918
dc.language.isoengpt_PT
dc.peerreviewedyespt_PT
dc.publisherELSEVIER SCI LTDpt_PT
dc.relation.publisherversionhttp://www.sciencedirect.com/science/article/pii/S0032386115300768pt_PT
dc.subjectRheo-opticspt_PT
dc.subjectCellulose derivativept_PT
dc.subjectLiquid-crystalpt_PT
dc.subjectExtrusionpt_PT
dc.titleRheo-optical characterization of liquid crystalline acetoxypropylcellulose melt undergoing large shear flow and relaxation after flow cessationpt_PT
dc.typejournal article
dspace.entity.typePublication
oaire.citation.endPage112pt_PT
oaire.citation.startPage102pt_PT
oaire.citation.volume71pt_PT
person.familyNameMarques Mendes Almeida da Rosa Leal
person.givenNameCatarina
person.identifierA-2814-2009
person.identifier.ciencia-idAF15-486E-BB15
person.identifier.orcid0000-0001-5871-4936
person.identifier.scopus-author-id7005379280
rcaap.rightsclosedAccesspt_PT
rcaap.typearticlept_PT
relation.isAuthorOfPublication4db8990d-5eb1-4515-ae7a-68873cf776a5
relation.isAuthorOfPublication.latestForDiscovery4db8990d-5eb1-4515-ae7a-68873cf776a5

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