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A Morphological Study of PFCB-Ionomer/ PVdF Copolymer Blend Membranes For Fuel Cell Application

A new material for use as a proton exchange membrane in fuel cells has been developed: a blend of a perfluorocyclobutane-based block ionomer (S-PFCB) and Poly (vinylidene-co-hexafluoropropylene) (Kynar Flex, KF). This thesis details the work done thus far to characterize the morphology of this material, using small angle x-ray scattering, differential scanning calorimetry, atomic force micrscopy, and some other techniques to a lesser extent.

Small angle x-ray scattering (SAXS) of pure S-PFCB showed a strong block copolymer- associated phase separation, on the order of 25 nm. Differential scanning Calorimetry (DSC) confirmed this finding. SAXS also revealed the presence of a peak representing individual ionic aggregates on the order of 3 nm. Finally, it was shown with DSC that no crystallinity develops in the S-PFCB block copolymer, while one of the blocks, known as 6F, crystallizes extensively.

SAXS of incremental blend compositions of KF and S-PFCB revealed a steady increase in size of the block copolymer phase separation peak in SAXS, demonstrative of the miscibility of KF and the non-sulfonated 6F block of S-PFCB. Furthermore, this incremental study determined the scattering vector range relevant for comparing amounts of KF crystallinity. DSC of incremental blend compositions revealed two phases of KF crystallinity develops upon cooling a membrane, independent of cooling rate.

Atomic force microscopy (AFM), small angle x-ray scattering (SAXS), and differential scanning calorimetry (DSC) corroborate to suggest a nonuniform morphology through the thickness of solution cast membranes. Also, the effect of different casting temperatures and after-casting anneals on morphology was assessed.

Future work on this project involves morphological studies at various relative humidities and temperatures, as well as following up on discoveries already made. Finally, transmission electron micrscopy (TEM) should be performed to provide a visual analog, which will greatly help in developing an accurate morphological model. / Master of Science

Identiferoai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/76853
Date22 September 2011
CreatorsMay, Nathanael Henderson
ContributorsMaterials Science and Engineering, Moore, Robert Bowen III, Dillard, David A., Hendricks, Robert W., Whittington, Abby R.
PublisherVirginia Tech
Source SetsVirginia Tech Theses and Dissertation
Languageen_US
Detected LanguageEnglish
TypeThesis, Text
Formatapplication/pdf
RightsIn Copyright, http://rightsstatements.org/vocab/InC/1.0/

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