Shear-induced crystallization of isotactic polypropylene with different molecular weight distributions: In situ small- and wide-angle X-ray scattering studies

In situ synchrotron wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) were used to monitor the structural and morphological developments during crystallization of a series of isotactic polypropylene (iPP) blends with different molecular weight distributions (MWD). The experi...

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Autores: Nogales, Aurora, Hsiao, Benjamin S., Somani, Rajesh H., Srinivas, Srivatsan, Tsou, Andy H., Baltá Calleja, Francisco José, Ezquerra, Tiberio A.
Tipo de recurso: artículo
Fecha de publicación:2001
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/80944
Acceso en línea:http://hdl.handle.net/10261/80944
Access Level:acceso abierto
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spelling Shear-induced crystallization of isotactic polypropylene with different molecular weight distributions: In situ small- and wide-angle X-ray scattering studiesNogales, AuroraHsiao, Benjamin S.Somani, Rajesh H.Srinivas, SrivatsanTsou, Andy H.Baltá Calleja, Francisco JoséEzquerra, Tiberio A.In situ synchrotron wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) were used to monitor the structural and morphological developments during crystallization of a series of isotactic polypropylene (iPP) blends with different molecular weight distributions (MWD). The experiments were carried out in the undercooled melt at 150°C subjected to a high shear strain (1428%) at a fixed shear rate (57 s-1). The final WAXS patterns showed arcing of the main Bragg reflections, indicating the presence of oriented crystallites. These oriented crystallites, in the form of lamellae, were also revealed by two strong meridional reflections in the SAXS patterns. The crystallization kinetics exhibited a strong dependence on the molecular weight distribution, which were due to the production of primary nuclei induced by orientation. A method to deconvolute the total integrated scattered intensity (SAXS and WAXS) into the isotropic and anisotropic contributions from the crystallized polymer was used to analyze the data. The fraction of oriented morphology determined by SAXS and that of oriented crystallinity determined by WAXS showed good agreement with each other. However, it has been demonstrated that the oriented fraction from SAXS is more suitable for determining the 'critical orientation molecular weight' (M*) value. Only polymer chains above M* in the distribution can become oriented at a given shear rate. It is observed that, regardless of the MWD, a similar value for M* is obtained under our experimental conditions. © 2001 Elsevier Science Ltd.NSF DMR-9732653, US-Spain Science and Technology program 1999 and ExxonMobil. DGICYT, Spain, grant PB94-0049Peer ReviewedElsevier2013201320012013info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501http://hdl.handle.net/10261/80944reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)Inglésinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/809442026-05-22T06:33:51Z
dc.title.none.fl_str_mv Shear-induced crystallization of isotactic polypropylene with different molecular weight distributions: In situ small- and wide-angle X-ray scattering studies
title Shear-induced crystallization of isotactic polypropylene with different molecular weight distributions: In situ small- and wide-angle X-ray scattering studies
spellingShingle Shear-induced crystallization of isotactic polypropylene with different molecular weight distributions: In situ small- and wide-angle X-ray scattering studies
Nogales, Aurora
title_short Shear-induced crystallization of isotactic polypropylene with different molecular weight distributions: In situ small- and wide-angle X-ray scattering studies
title_full Shear-induced crystallization of isotactic polypropylene with different molecular weight distributions: In situ small- and wide-angle X-ray scattering studies
title_fullStr Shear-induced crystallization of isotactic polypropylene with different molecular weight distributions: In situ small- and wide-angle X-ray scattering studies
title_full_unstemmed Shear-induced crystallization of isotactic polypropylene with different molecular weight distributions: In situ small- and wide-angle X-ray scattering studies
title_sort Shear-induced crystallization of isotactic polypropylene with different molecular weight distributions: In situ small- and wide-angle X-ray scattering studies
dc.creator.none.fl_str_mv Nogales, Aurora
Hsiao, Benjamin S.
Somani, Rajesh H.
Srinivas, Srivatsan
Tsou, Andy H.
Baltá Calleja, Francisco José
Ezquerra, Tiberio A.
author Nogales, Aurora
author_facet Nogales, Aurora
Hsiao, Benjamin S.
Somani, Rajesh H.
Srinivas, Srivatsan
Tsou, Andy H.
Baltá Calleja, Francisco José
Ezquerra, Tiberio A.
author_role author
author2 Hsiao, Benjamin S.
Somani, Rajesh H.
Srinivas, Srivatsan
Tsou, Andy H.
Baltá Calleja, Francisco José
Ezquerra, Tiberio A.
author2_role author
author
author
author
author
author
description In situ synchrotron wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) were used to monitor the structural and morphological developments during crystallization of a series of isotactic polypropylene (iPP) blends with different molecular weight distributions (MWD). The experiments were carried out in the undercooled melt at 150°C subjected to a high shear strain (1428%) at a fixed shear rate (57 s-1). The final WAXS patterns showed arcing of the main Bragg reflections, indicating the presence of oriented crystallites. These oriented crystallites, in the form of lamellae, were also revealed by two strong meridional reflections in the SAXS patterns. The crystallization kinetics exhibited a strong dependence on the molecular weight distribution, which were due to the production of primary nuclei induced by orientation. A method to deconvolute the total integrated scattered intensity (SAXS and WAXS) into the isotropic and anisotropic contributions from the crystallized polymer was used to analyze the data. The fraction of oriented morphology determined by SAXS and that of oriented crystallinity determined by WAXS showed good agreement with each other. However, it has been demonstrated that the oriented fraction from SAXS is more suitable for determining the 'critical orientation molecular weight' (M*) value. Only polymer chains above M* in the distribution can become oriented at a given shear rate. It is observed that, regardless of the MWD, a similar value for M* is obtained under our experimental conditions. © 2001 Elsevier Science Ltd.
publishDate 2001
dc.date.none.fl_str_mv 2001
2013
2013
2013
dc.type.none.fl_str_mv info:eu-repo/semantics/article
http://purl.org/coar/resource_type/c_6501
format article
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/80944
url http://hdl.handle.net/10261/80944
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.publisher.none.fl_str_mv Elsevier
publisher.none.fl_str_mv Elsevier
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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score 15,811543

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