Thesis (M.S.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains ix, 129 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 114-120).

Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Rosario Gerhardt; Committee Member: Gleb Yushin; Committee Member: Hamid Garmestani. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Polymer nanocomposites represent a class of advanced, multifunctional materials, combining the attractive features of both nanomaterials and polymers. The level of dispersion of the nanoparticles directly controls the extent to which nanocomposites can maximize the unique attributes of their nano-scale fillers. However, as a consequence of the tendency of nanofillers to agglomerate, the anticipated superior properties of polymer nanocomposites are yet to be realised, and remain merely a theoretical prediction. As a result, the surface chemistry of nanofillers is often tailored to reduce the attractive interparticle interactions that promote agglomeration. This modification can also be used to enhance the interfacial interactions between the nanofiller and polymer matrices to achieve improved filler dispersion. Accordingly, this thesis addresses this challenge in nanocomposite technology by investigating the chemical surface functionalisation of various nanoparticles in order to produce polypropylene (PP) nanocomposites with superior electrical, mechanical and thermal properties. Part I describes covalent modification of nanosilica, microsilica, furnace Carbon Black (CB), acetylene black (ACB) and carbon nanotube (CNT) nanomaterials by carbene insertion and azo-coupling reactions, in a series of studies, in order to tailor their surfaces for application in polypropylene (PP) nanocomposites. The surface characterisation of the modified nanomaterials was assessed in detail using XPS, CHN, SSNMR, BET, ATR-IR and thermal analysis techniques. The surface grafting densities were estimated to be of the order of 10¹³ and 10¹⁴ molecules/cm² and additionally, SSNMR provided direct evidence of the diarylcarbene reaction to the silica surface. Following nanocomposite production with PP by solvent mixing methods, the macroscopic properties were studied demonstrating altered electrical, mechanical and thermal properties following assessment of the DC conductivity, dielectric properties, thermal analysis (TGA, DSC, DMA) and morphological measurements. In particular, the introduction to the CB surface of a diaryl complex with terminal dodecyl hydrocarbon chains demonstrated substantial improvements to the DC electrical and dielectric properties of the PP nanocomposites. Part II explores the non-covalent surface functionalisation of CB and ACB by the physisorption of the non-ionic surfactant Triton-X-100. Various protocols were developed in which an optimal surface loading for CB was determined by treatment at 0.024 mM(aq). In addition, the modification procedure was combined with the granulation protocol of ACB in an effort to evaluate the potential for industrial applications. The degree of surface functionalisation was extensively characterised by BET, XPS, thermal analysis, UV-Vis and ATR-IR analyses. PP nanocomposites produced by solvent and melt mixing methods demonstrated similar conductive properties following the nanoscale modification, however morphological, dielectric and thermal analysis indicated altered interfacial interactions demonstrating improved mechanical properties.

A solar simulator was used to test whether a carbon black additive could increase the solar absorption of a low temperature organic PCM (consisting of a eutectic mixture of palmitic acid and stearic acid). Various PCM and carbon black composites (0.01 % to 6 %) were tested, with the 0.06 % carbon black composites showing the fastest temperature increase, reaching 75 °C much quicker (350 % faster) than the pure PCM. All of the tested PCM composites reached 75 °C in less than half the time it took the pure PCM. It can therefore be seen that carbon black is very effective at increasing the solar absorption of the PCM. The carbon black did not have a negative impact on the melting/solidifying onset temperature or the latent heat of the PCM. This proves that at these low concentrations carbon black can help reduce the shortcomings of the PCM without adversely affecting its energy storage properties. The optimal carbon black concentration changes with the size of the PCM: a shallow PCM layer (2 cm) showed the fastest temperature increase at higher concentrations (between 0.06 % and 0.5 % carbon black), while the deep PCM layer (9 cm) showed the fastest temperature increase at lower concentrations (between 0.01 % and 0.08 % carbon black). The poor optical properties of the PCM were vastly improved by the carbon black, making the composite an effective direct solar absorber. The carbon black, however, does not provide meaningful thermal conductivity enhancements. Therefore additional heat transfer enhancements (like graphite) are needed if this novel PCM composite is to be used in a combined system (direct solar absorber, heat transfer fluid and energy storage system). / Dissertation (MEng)--University of Pretoria, 2016. / Chemical Engineering / MEng / Unrestricted

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