Cellulose-based fibers from liquid crystalline solutions

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dc.contributor.authorDavé, Vipulen
dc.contributor.committeechairGlasser, Wolfgang G.en
dc.contributor.committeememberLoos, Alfred C.en
dc.contributor.committeememberMcGrath, James E.en
dc.contributor.committeememberWilkes, Garth L.en
dc.contributor.committeememberMarand, Hervé L.en
dc.contributor.departmentMaterials Engineering Scienceen
dc.date.accessioned2014-03-14T21:17:58Zen
dc.date.adate2007-08-23en
dc.date.available2014-03-14T21:17:58Zen
dc.date.issued1992-02-05en
dc.date.rdate2007-08-23en
dc.date.sdate2007-08-23en
dc.description.abstractSolutions of cellulose esters with different concentrations in dimethylacetamide (DMAc) and with different types of substituents were studied in relation to their liquid crystalline (LC) solution behavior. Classical LC behavior was revealed for all solutions. Critical polymer concentration (V<sub>p</sub><sup>c</sup>) is highest for cellulose acetate (CA) and lowest for cellulose acetate butyrate (CAB) with highest degree of butyration. This is opposite to the classical model by Flory which predicts an increase in V<sub>p</sub><sup>c</sup> with decreasing aspect ratio (L/d). Fibers were spun from isotropic and anisotropic DMAc solutions of cellulose esters by dry jet/wet spinning process. The mechanical properties, orientation, and crystallinity of the fibers increased as spinning progressed from the isotropic to the anisotropic solution state. High butyryl content enhances both overall solubility and the formation of LC solutions at lower concentration, but it results in lower fiber properties. Unmodified cellulose (C) and cellulose hexanoate (CH) also exhibited LC behavior. The V<sub>p</sub><sup>c</sup> value for CH was lower than that obtained for CAB with maximum degree of butyration. This indicates that bulky substituents may lower V<sub>p</sub><sup>c</sup> values. The formation of high modulus (152 g/d) cellulose fibers from LC solutions is attributed to the air-gap that exists in the dry jet/wet spinning process. Presence of lithium chloride (LiCl) in the LC solutions of CAB exhibited ionic interactions. Mechano-sorptive creep behavior of the fibers spun from these solutions decreases in the presence of residual LiCl salt. Fibers from blends of CAB and of C with lignin (L) were spun from Lc solution. Morphological investigations demonstrate that CAB and L formed intimately mixed blends whereas C and L were partially mixed. The mechanical properties of the fibers with L increased due to good phase mixing of CAB and L molecules in the fiber matrix.en
dc.description.degreePh. D.en
dc.format.extentxxii, 369 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-08232007-112345en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-08232007-112345/en
dc.identifier.urihttp://hdl.handle.net/10919/39205en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V856_1992.D383.pdfen
dc.relation.isformatofOCLC# 26064272en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V856 1992.D383en
dc.subject.lcshCellulose fibersen
dc.subject.lcshPolymer liquid crystalsen
dc.titleCellulose-based fibers from liquid crystalline solutionsen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineMaterials Engineering Scienceen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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