Thermoreversible gelation of aromatic hydrocarbons

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dc.contributor.advisorWillson, C. G. (C. Grant), 1939-en
dc.contributor.advisorBarlow, Joel W.en
dc.creatorGoldmann, Edward Louisen
dc.date.accessioned2011-06-09T21:28:40Zen
dc.date.available2011-06-09T21:28:40Zen
dc.date.issued2002-12en
dc.descriptiontexten
dc.description.abstractFumed silica of nominal size 20 microns is used to fill many different polymer and prepolymer mixtures creating filled composite materials. Of interest in this work is silica combined with low-viscosity non-polar hydrocarbon liquids (aryl-vinyl monomers). Unless they are continuously mixed, unmodified binary mixtures that have flowable viscosity (<75 wt% solids) phase separate over time scales of several days to pure liquid and a close-packed cake of silica. It is desired that this phase separation not occur for at least several months with minimal required physical or chemical modification. This work investigates the thermodynamic and rheological (mainly elastic) properties of binary solutions of ethylbenzene, styrene, toluene, xylene, and tertbutyl styrene each with low concentrations of various molecular weight syndiotactic polystyrenes (SPS). These systems exhibit a distinct thermally reversible phase transformation when cooled, going from a low-viscosity polymer solution to a translucent waxy solid of varying physical properties. Various methods have been used to characterize both the polymers used in generating this behavior, as well as the resultant gels. Analyses include differential scanning calorimetry, nuclear magnetic resonance spectroscopy, gel permeation chromatography, and dynamic viscoelastic rheometry. For a given binary system gel formation temperatures and physical properties were found to be primarily a function of polymer loading and molecular weight. The molecular weight of polymer studied was between 4,300 and 42,000 Mn; concentrations used typically at or below 5 wt% polymer; observed modulii varied greatly and somewhat erratically but were in the 2 kPa to 20 kPa range. Nearly all mechanical property measurements were done in the elastic regime (0.1-0.2% strain; yield point 2-4%). Elastic networks were observed at extraordinarily low concentrations.
dc.description.departmentChemical Engineeringen
dc.format.mediumelectronicen
dc.identifier.urihttp://hdl.handle.net/2152/11609en
dc.language.isoengen
dc.rightsCopyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.en
dc.rights.restrictionRestricteden
dc.subjectAromatic compoundsen
dc.subjectPolymers--Synthesisen
dc.subjectElectronic packaging--Materials--Dynamic testingen
dc.titleThermoreversible gelation of aromatic hydrocarbonsen
thesis.degree.departmentChemical Engineeringen
thesis.degree.disciplineChemical Engineeringen
thesis.degree.grantorThe University of Texas at Austinen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen

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