Materials combined with a small amount of nanoparticles offer new possibilities in the synthesizing of multifunctional materials. Graphene nanoplatelets (GnP) are multifunctional nanoreinforcing agents consisting of stacks of graphene sheets with comparable properties to a single graphene layer at an overall lower cost in a more robust form. Such particles have been shown to have good thermal, mechanical and electrical properties. In addition, a low density multifunctional nanocomposite foam has the potential for multiple applications and potential use for the aerospace industry. This dissertation investigates two different microporous (foam) polymers that are modified by the addition of GnP to combat this density effect to improve the foam’s macroscopic properties Three sizes of GnP with varying aspect ratio were used to improve the polymeric foams’ dielectric, electrical and mechanical properties.GnP was added to a water-blown polyurethane/polyisocyanurate (PUR/PIR) foam with a neat density of 0.16 g/cm3. The largest aspect ratio GnP percolated to form a connected network to allow for the transfer of electrons, which resulted in a decrease of the electrical resistivity by 5 orders of magnitude. This same electrical contact improved the overall dielectric properties: increased the real permittivity by over double the amount of the neat foam, increased the electromagnetic interference (EMI) shielding effectiveness (SE) by about ten times by increase the nanocomposite’s absorbance and reflectance capabilities. However, these large particles suffer from agglomerations reducing the mechanical performance even though the cell size decreased and demonstrated little interaction of the particles with the matrix by the similar glass temperature between the solid and the foam.The edge groups on the GnP were successfully treated with either polymeric or molecular isocyanate to form urethane type groups as confirmed by x-ray photoelectron spectroscopy(XPS). Edge treatment of the GnP only showed significant advantages for the smallest size of GnP with the highest edge density, and resulted in improved mechanical strength, and some improvements in the dielectric and shielding properties. These particles were also found to have the least effect on the molecular structure. The effect of treating the edges with polymeric or molecular groups was most dependent on the size of the GnP. The shorter urethane molecules that formed when reacted with toluene diisocyanate (TDI) on the edges had little to no effect on the mechanical strength, but was able to lower the electrical resistivity by about an order of magnitude over the same particle size treated using the same method but with a polymeric isocyanate. The larger particles treated with isocyanate demonstrated no improvement in the compressive strength over the neat particles and in general increased the electrical resistivity as well causing the dielectric performance to decrease in conjunction.GnP was also added to a polydimethylsiloxane (PDMS) matrix, which is commonly used in aerospace applications due to its flexible properties at low temperatures and environmental resistance. The nanocomposite with the largest aspect ratio and highest loading of particles significantly improved the real permittivity and EMI shielding properties in the X-band over the neat PDMS including the reflectance and absorbance capabilities, but the GnP still showed significant agglomerations. A syntactic foam was used to improve the percolation of the GnP by first coating the hollow glass spheres (HGS) with smaller GnP prior to adding to the matrix. Although it is unclear from the SEM images if the GnP was able to stay adhered to the particles during processing, the dielectric and EMI shielding properties of the nanocomposite syntactic foam was similar to the neat while producing a foam that was 20% lighter.
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