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Poly(methyl methacrylate)-silica nanocomposite (PSN) foams were formulated for the comparison of the effect of vinyl-modified silica (VMS) and raw silica (RS) particles on cell structure, insulation properties, and insulation properties. It was found that those thermoplastic foams containing VMS particles had improved dispersion capability than those containing RS particles. The incorporation of VMS particles was found to reduce the cell size and increase the cell density of the produced foams, thus enhancing the physical properties of the foams. The thermal transport capabilities of the foams containing VMS particles were significantly lower than those of the foams containing RS particles due to the presence of a relatively large quantity of air in the foams. The PSN foams containing VMS particles were found to be more thermally stable than those containing RS particles indicating that foams containing dispersed silica particles have a higher thermal stability than those containing aggregated particles.
Four electrically conductive polymers were tested for their thermal transport properties to better understand their degradation mechanism with temperature. The samples that were tested were polyaniline polymers doped with varying amounts of nickel and aluminum. It was found that the thermal conductivities increased as the aluminum:nickel ratio increased, and that the thermal conductivity and thermal diffusivity of the samples increased with temperature until they reached a maximum value, and then began to decrease. It was thought that the decrease was due to the presence of defects (dislocation of ions, ion vacancies in the lattice, etc.) in the composites at high temperature.
Three model polymer-bonded explosive compositions were prepared to determine the effects of damage on their mechanical and thermal properties. The composites were damaged in a controllable manner such that three different levels of damage could be produced, and the strain on the samples could be determined. The samples differed in the size of the particles that they contained, and the sample that showed the largest decrease in mechanical properties occurring in the sample with coarse particles; however, there was still a decrease in the samples containing fine particles, and thus it was determined that some damage had occurred in these samples as well. The fine particle samples showed no significant change in porosity or thermal conductivity over the three damage levels tested, indicating that the initially closed porosity of these samples was retained even after damage had occurred. This was not observed in the other samples.
Multi-walled carbon nanotube (MWCNT)/poly (methyl methacrylate) composites were prepared and their mechanical and physical properties were examined. An amphiphilic copolymer was used to aid in dispersing the MWCNTs throughout the composite. It was found that the use of this copolymer resulted in a good dispersal of the MWCNTs without drastically affecting the molecular weights of the composites, so it was concluded that the observed improvements in mechanical properties of the composites were due to the MWCNTs. Since the nanotubes that were used were short in length, the electrical and thermal conductivities were not as high as desired.
Sulfonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SPSPB) was used as a polymer matrix to create polymeric nanocomposites using graphite (G) and graphite-polyoxometalate (G-POM) as fillers. It was found that the nanocomposites had higher thermal and electrical conductivities than SPSPB alone, and that both the thermal and the electrical conductivity increased with increasing filler concentration. At all filler contents tested, the SPSPB/G-POM had both a higher thermal conductivity and a higher electrical conductivity than SPSPB/G. Increasing tensile strength was observed for the SPSPB/G-POM nanocomposite with increasing filler content which indicated that the nanoparticles significantly reinforced the polymer matrix.
