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

Detalhes bibliográficos
Autor(a) principal: Teixeira, P. F.
Data de Publicação: 2015
Outros Autores: Fernandes, Susete N., Canejo, João, Godinho, Maria Helena, Covas, J. A., Leal, Catarina Rosa, Hilliou, L.
Tipo de documento: Artigo
Idioma: eng
Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
Texto Completo: http://hdl.handle.net/1822/36340
Resumo: The 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 g_ c is reached. For shear rates smaller than g_ c, the flowinduced texture consists of two set of bands aligned parallel and normal to the flow direction. At shear rates larger than g_ 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 g_ c, the stress relaxation is described by a stretched exponential. Above g_ 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.
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spelling Rheo-optical characterization of liquid crystalline acetoxypropylcellulose melt undergoing large shear flow and relaxation after flow cessationCellulose derivativeRheo-opticsExtrusionLiquid-crystalEngenharia e Tecnologia::Engenharia dos MateriaisCiências Naturais::Ciências FísicasCiências Naturais::Ciências QuímicasScience & TechnologyThe 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 g_ c is reached. For shear rates smaller than g_ c, the flowinduced texture consists of two set of bands aligned parallel and normal to the flow direction. At shear rates larger than g_ 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 g_ c, the stress relaxation is described by a stretched exponential. Above g_ 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.This work was partially supported by the Portuguese Science and Technology Foundation through projects, PTDC/CTM/099595/2008, PTDC/CTM/101776/2008, PTDC/CTM-POL/1484/2012 and UID/CTM/500025/2013. S.N. Fernandes and J.P. Canejo acknowledge FCT for grants SFRH/BPD/78430/2011 and SFRH/BPD/101041/2014, respectively. Funding for project "Matepro e Optimizing Materials and Processes", with reference NORTE-07-0124-FEDER-000037 FEDER COMPETE, is also acknowledged.ElsevierUniversidade do MinhoTeixeira, P. F.Fernandes, Susete N.Canejo, JoãoGodinho, Maria HelenaCovas, J. A.Leal, Catarina RosaHilliou, L.20152015-01-01T00:00:00Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articleapplication/pdfhttp://hdl.handle.net/1822/36340eng0032-386110.1016/j.polymer.2015.06.056info:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2024-05-11T04:17:53Zoai:repositorium.sdum.uminho.pt:1822/36340Portal AgregadorONGhttps://www.rcaap.pt/oai/openairemluisa.alvim@gmail.comopendoar:71602024-05-11T04:17:53Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse
dc.title.none.fl_str_mv Rheo-optical characterization of liquid crystalline acetoxypropylcellulose melt undergoing large shear flow and relaxation after flow cessation
title Rheo-optical characterization of liquid crystalline acetoxypropylcellulose melt undergoing large shear flow and relaxation after flow cessation
spellingShingle Rheo-optical characterization of liquid crystalline acetoxypropylcellulose melt undergoing large shear flow and relaxation after flow cessation
Teixeira, P. F.
Cellulose derivative
Rheo-optics
Extrusion
Liquid-crystal
Engenharia e Tecnologia::Engenharia dos Materiais
Ciências Naturais::Ciências Físicas
Ciências Naturais::Ciências Químicas
Science & Technology
title_short Rheo-optical characterization of liquid crystalline acetoxypropylcellulose melt undergoing large shear flow and relaxation after flow cessation
title_full Rheo-optical characterization of liquid crystalline acetoxypropylcellulose melt undergoing large shear flow and relaxation after flow cessation
title_fullStr Rheo-optical characterization of liquid crystalline acetoxypropylcellulose melt undergoing large shear flow and relaxation after flow cessation
title_full_unstemmed Rheo-optical characterization of liquid crystalline acetoxypropylcellulose melt undergoing large shear flow and relaxation after flow cessation
title_sort Rheo-optical characterization of liquid crystalline acetoxypropylcellulose melt undergoing large shear flow and relaxation after flow cessation
author Teixeira, P. F.
author_facet Teixeira, P. F.
Fernandes, Susete N.
Canejo, João
Godinho, Maria Helena
Covas, J. A.
Leal, Catarina Rosa
Hilliou, L.
author_role author
author2 Fernandes, Susete N.
Canejo, João
Godinho, Maria Helena
Covas, J. A.
Leal, Catarina Rosa
Hilliou, L.
author2_role author
author
author
author
author
author
dc.contributor.none.fl_str_mv Universidade do Minho
dc.contributor.author.fl_str_mv Teixeira, P. F.
Fernandes, Susete N.
Canejo, João
Godinho, Maria Helena
Covas, J. A.
Leal, Catarina Rosa
Hilliou, L.
dc.subject.por.fl_str_mv Cellulose derivative
Rheo-optics
Extrusion
Liquid-crystal
Engenharia e Tecnologia::Engenharia dos Materiais
Ciências Naturais::Ciências Físicas
Ciências Naturais::Ciências Químicas
Science & Technology
topic Cellulose derivative
Rheo-optics
Extrusion
Liquid-crystal
Engenharia e Tecnologia::Engenharia dos Materiais
Ciências Naturais::Ciências Físicas
Ciências Naturais::Ciências Químicas
Science & Technology
description The 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 g_ c is reached. For shear rates smaller than g_ c, the flowinduced texture consists of two set of bands aligned parallel and normal to the flow direction. At shear rates larger than g_ 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 g_ c, the stress relaxation is described by a stretched exponential. Above g_ 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.
publishDate 2015
dc.date.none.fl_str_mv 2015
2015-01-01T00:00:00Z
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
dc.type.driver.fl_str_mv info:eu-repo/semantics/article
format article
status_str publishedVersion
dc.identifier.uri.fl_str_mv http://hdl.handle.net/1822/36340
url http://hdl.handle.net/1822/36340
dc.language.iso.fl_str_mv eng
language eng
dc.relation.none.fl_str_mv 0032-3861
10.1016/j.polymer.2015.06.056
dc.rights.driver.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.publisher.none.fl_str_mv Elsevier
publisher.none.fl_str_mv Elsevier
dc.source.none.fl_str_mv reponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação
instacron:RCAAP
instname_str Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação
instacron_str RCAAP
institution RCAAP
reponame_str Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
collection Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
repository.name.fl_str_mv Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação
repository.mail.fl_str_mv mluisa.alvim@gmail.com
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