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dc.contributor.authorLaot, Christelle Marie IIIen_US
dc.description.abstractMechanical properties of (woven carbon fiber / vinyl ester matrix) composites can be greatly improved if the interphase between the reinforcing high-strength low-weight fiber and the thermoset resin is made more compliant. In order to improve the adhesion of the vinyl ester matrix to the carbon fiber, a thermoplastic coating such as poly(vinyl pyrrolidone) (PVP) can be used as an intermediate between the matrix and the fiber. The extent of mutual diffusion at the (sizing material / polymer matrix) interphase plays a critical role in determining the mechanical properties of the composite.

In this research, the molecular interdiffusion across a poly(vinyl pyrrolidone))/vinyl ester monomer (PVP/VE) interface is being investigated by Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR) spectroscopy. The ATR method which can be used to characterize the transport phenomena, offers several advantages, such as the ability to monitor the diffusion in situ or to observe chemical reactions. In order to separate the effects of the vinyl ester monomer diffusion and the crosslinking reaction, ATR experiments were carried out at temperatures below the normal curing temperature. Diffusion coefficients were determined by following variations in infrared bands as a function of time, and fitting this data to a Fickian model. The values of the diffusion coefficients calculated were consistent with values found in the literature for diffusion of small molecules in polymers. The dependence of diffusion coefficients on temperature followed the Arrhenius equation. Hydrogen bonding interactions were also characterized. The diffusion model used in this study, however, does not seem to be appropriate for the particular (PVP/VE) system. Because the glass transition temperature of the PVP changed as diffusion proceeded, one would expect that the mutual diffusion coefficient did not stay constant. In fact, it was shown that the Tg can drop by 140oC during the diffusion process. A more suitable model of the (PVP/VE) system should take into account plasticization, hydrogen bonding, and especially a concentration dependent diffusion coefficient. Further analysis is therefore needed.

dc.publisherVirginia Techen_US
dc.rightsI hereby grant to Virginia Tech or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University Libraries in all forms of media, now or hereafter known. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation.en_US
dc.subjectFTIR-ATR spectroscopyen_US
dc.subjectvinyl esteren_US
dc.subjectpoly(vinyl pyrrolidone)en_US
dc.titleSpectroscopic Characterization of Molecular Interdiffusion at a Poly(Vinyl Pyrrolidone) / Vinyl Ester Interfaceen_US
dc.contributor.departmentChemical Engineeringen_US
dc.description.degreeMaster of Scienceen_US of Scienceen_US Polytechnic Institute and State Universityen_US Engineeringen_US
dc.contributor.committeechairMarand, Evaen_US
dc.contributor.committeememberDavis, Richey M.en_US
dc.contributor.committeememberOyama, Hideko T.en_US
dc.contributor.committeememberWard, Thomas C.en_US

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