Bulk and Interfacial Effects on Density in Polymer Nanocomposites Page: 2
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Sahu, Laxmi Kumari, Bulk and interfacial effects on density in polymer nanocomposites.
Doctor of Philosophy (Materials Science and Engineering), May 2007, 227 pp., 57 tables, 128
illustrations, chapter references.
The barrier properties of polymers are a significant factor in determining the shelf or
device lifetime in polymer packaging. Nanocomposites developed from the dispersion of
nanometer thick platelets into a host polymer matrix have shown much promise. The magnitude
of the benefit on permeability has been different depending on the polymer investigated or the
degree of dispersion of the platelet in the polymer. In this dissertation, the effect of density
changes in the bulk and at the polymer-platelet interface on permeability of polymer
nanocomposites is investigated. Nanocomposites of nylon, PET, and PEN were processed by
extrusion. Montmorillonite layered silicate (MLS) in a range of concentrations from 1 to 5% was
blended with all three resins. Dispersion of the MLS in the matrix was investigated by using one
or a combination of X-ray diffraction (XRD), scanning electron microscopy (SEM) and
transmission electron microscopy (TEM). Variation in bulk density via crystallization was
analyzed using differential scanning calorimetry (DSC) and polarized optical microscopy.
Interfacial densification was investigated using force modulation atomic force microscopy
(AFM) and ellipsometry. Mechanical properties are reported. Permeability of all films was
measured in an in-house built permeability measurement system. The effect of polymer
orientation and induced defects on permeability was investigated using biaxially stretched, small
and large cycle fatigue samples of PET and nylon nanocomposites. The effect of annealing in
nylon and nanocomposites was also investigated. The measured permeability was compared to
predicted permeability by considering the MLS as an ideal dispersion and the matrix as a system
with concentration dependent crystallinity.
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Sahu, Laxmi Kumari. Bulk and Interfacial Effects on Density in Polymer Nanocomposites, dissertation, May 2007; Denton, Texas. (digital.library.unt.edu/ark:/67531/metadc3619/m1/2/: accessed February 18, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .