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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Reactive molding and self-assembly techniques for controlling the interface and dispersion of the particulate phase in nanocomposites.

Pranger, Lawrence A. 07 November 2008 (has links)
This research explored the processing and properties of PNCs using a polyfurfural alcohol (PFA) matrix. The precursor for PFA, furfuryl alcohol (FA) is sourced from feedstocks rich in hemicellulose, such as corn cobs, oat hulls and wood. To exploit FA as a polymerizable solvent, cellulose whiskers (CW) and montmorillonite clay (MMT) were used as the nanoparticle phase. Results from PNC processing show that CW and MMT can be dispersed in the PFA matrix by means of insitu polymerization, without the use of surfactants or dilution in solvents. Both CW and MMT nanoparticles catalyze the polymerization of furfuryl alcohol (FA). Moreover, the insitu intercalative polymerization of FA in the interlayer galleries of MMT leads to the complete exfoliation of the MMT in the PFA matrix. CW and MMT both function as effective matrix modifiers, increasing the thermal stability of PFA nanocomposites compared to pure PFA polymer. The increased thermal stability is seen as significant increases in the onset of degradation and in residual weight at high temperature. This research also explored the surface functionalization of Cu, Ni and Pt substrates by self-assembly of a range of difunctional linker molecules. Characterization by XPS and PM-IRRAS indicate that diisocyanides and dicarboxylic acids both form chemically "sticky" surfaces after self-assembly on Cu and Ni. Sticky surfaces may provide a means of increasing nanoparticle dispersion in metal nanocluster filled PNCs, by increasing their interaction with the matrix polymer. Another potential application for sticky surfaces on Cu is in the ongoing miniaturization of circuit boards. The functionalization of Cu bond pad substrates with linker molecules may provide an alternate means of bonding components to their bond pads, with higher placement accuracy compared to solder bumps.
2

Nanocomposites à matrice polymère : influence de silices nanostructurées sur la cristallisation, la transition vitreuse et les propriétés thermomécaniques / Nanocomposite polymers : influence of nanostructured silica on cristallization, glass transition and thermomechanical properties

Bosq, Nicolas 19 December 2013 (has links)
Le but de ce travail est de comprendre l'influence des nanoparticules de silice sur les transitions physiques de matrices polymères de nature différente : l'alcool polyfurfurylique (PFA), le polytétrafluoroéthylène (PTFE) et le polydiméthylsiloxane (PDMS). Pour cela, les techniques d'analyse thermique conventionnelles (ATG, DSC, DMA) ont été couplées à des techniques atypiques (DSC multifréquence, FSC, UFSC).Dans le cas du PFA, les nanoparticules de silice ont entrainé une augmentation de la Tg ainsi qu'une amélioration des propriétés thermomécaniques. En outre, il a été démontré que la seule présence de silice suffit à favoriser les mécanismes de polymérisation. La cristallisation du PTFE à partir de l'état fondu a été étudiée pour la première fois sur une gamme de vitesse de refroidissement très large (jusqu'à 800 000 K.s-1). L'effet nucléant des nanoparticules de silice a également été mis en avant à faibles vitesses de refroidissement lors de l'étude de la cristallisation du PTFE chargé. Cependant, il s'est avéré qu'elle ralentit également la diffusion des chaines dans le milieu pour certaines vitesses. L'influence des nanoparticules de silice sur la transition vitreuse et la cristallisation du PDMS a finalement été étudiée. Les résultats ont montré que la silice n'induit pas d'effet significatif sur la transition vitreuse. D'autre part, la silice influence fortement la cinétique de cristallisation. Cet effet a été directement lié au fait que la silice favorise la nucléation sans influencer la diffusion des chaines. / The aim of this work is to understand the influence of silica nanoparticles on the physical transitions of different polymer matrix : polyfurfuryl alcohol (PFA), polydimethylsiloxane (PDMS) and polytetrafluoroethylene (PTFE). Thus, the conventionnal thermal analysis techniques (TGA, DSC, DMTA) were employed in correlation with atypical techniques (multifrequency DSC, FSC, UFSC). In the case of PFA, the silica nanoparticles led to an increase of the Tg and of the thermomechanical properties. Besides, it was demonstrated that the presence of silica is enough to realise faster the polymerization process. The crystallization from the melt of PTFE was investigated for the first time on a very large range of cooling rates (untill 800 000 K.s-1). The enhancement of the nucleation process at slow cooling rates due to the silica nanoparticles has been put in relief with the study of filled PTFE crystallization. Yet, it has been shown that it slows down the diffusion of the chains through the medium for some of the cooling rates. The influence of silica nanoparticles on PDMS glass transition and crystallization was finally studied. The silica nanoparticles don't induce any significative effect on the glass transition. It appeared that the nanoparticles strongly influence the crystallization kinetics. This effect is linked to the enhancement of nucleation process by silica without any effect on chain diffusion.

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