(A) Epoxy curing (B) Characterization of epoxy/SWNT nanocomposites & (C) MnO2 nanostructures for catalysis

Abstract

The main objective of this study is to prepare a better material, i.e. stronger, lighter, heat impact and gas permeable for aerospace application. In recent years, the development of filler/epoxy composites has shown large potential for new materials with improved properties. This work was focused on two aspects of epoxy composites: A) the study of cure behavior of sample epoxy amine systems B) the characterization of thermal and mechanical properties of the epoxy nanocomposites. The cure behavior of the sample epoxy amine systems at different concentrations of curing agents and ramp rates were studied by differential scanning calorimetry (DSC). Solvent-dispersed single-walled nanotubes (SWNTs) are incorporated into epoxy matrices, followed by evaporation of the solvent before curing. The effect of solvent choice in thermal and mechanical properties of the resulting nanocomposites is evaluated using N-methyl pyrrolidone and dimethyl formamide. In this study, fluorescence is used as the tool to monitor the dispersions of SWNTs in the solvent and epoxy matrix. This study also compares the thermal and mechanical properties of these epoxy nanocomposites with a nanotube loading ranging from 0.001-0.01 wt. %. Dynamic mechanical analysis results showed increase in the storage modulus of epoxy/SWNT nanocomposites compared to plain epoxy composite. The presence of residual solvent in the epoxy composites is determined by thermogravimetric analysis (TGA). Contact angle measurements showed an increase in the hydrophobicity of the epoxy/SWNT nanocomposites compared to plain epoxy composite.

alpha-, beta-, and gamma-MnO2 were synthesized by hydrothermal methods, and were characterized using x-ray diffraction, scanning electron microscopy, Brunauer Emmett and Teller (BET) surface area, and TGA. TGA analysis showed that alpha-MnO2 has greater water content compared to the beta- and gamma- forms of MnO2. BET measurements confirmed that the surface areas are in the order of beta > alpha > gamma-MnO2 samples. The catalytic activities of these samples against oxidation of arylmethylene compounds were studied, revealing that the primary factor controlling catalytic activity is the amount of adsorbed water. Additionally, novel structural features of the various forms of MnO2 will be reported.