Nanocompósitos de óxido de grafeno e resina epóxi obtidos a partir de transferência de fase: estrutura e propriedades

Abstract

Epoxy-based polymers have a wide range of applications in industrial sectors such as oil and gas, automotive and aerospace, and the study of epoxy-based nanocomposites is a strategy to improve their properties. The processing methodology of nanocomposites is crucial to achieve both desirable good dispersion and strong interactions between the dispersed phase and the matrix, resulting in the expected enhancements in these properties. It is important that the production process of nanomaterials and nanocomposites are technologically and economically compatible with the industrial application of nanotechnology on a large scale. In this work, nanocomposites of graphene oxide (GO) and epoxy resin with strong interactions in the interphase and crosslinking occurring under aging were prepared. The GO was directly exfoliated in ethanol, and the spontaneous phase transfer of the suspension to epoxy resin was made to produce an epoxy/GO masterbach. The nanocomposites with 0.25, 0.50 and 0.75 wt.% GO were obtained by masterbach dilution. The samples were aged at ambient temperature and protected from light without the addition of a curing agent. Rheological characterization was performed over the first 90 days and showed significant increases in nanocomposites viscosity, while the neat resin was stable. After 190 days, the degree of crosslinking of the nanocomposites was measured, extending to 15 wt.%. The effects of partial crosslinking and interactions with the supramolecular epoxy chains on the nanocomposites were studied by rheological measurements and thermogravimetric analysis. The oscillatory shear rheology indicated an evolution to a solid-like behavior of the nanocomposite with 0.50 wt.% GO after 190 days of aging. The mechanism of oxidative decomposition of neat epoxy resin was significantly modified by GO addition. All results support the hypothesis that nanocomposites were structured in a first layer of GO-epoxy covalently bonded and a second layer of epoxy resin chemically interacting with the first layer, corresponding to ~10 wt.% and 40 wt.%, respectively, to the 0.50 wt.% nanocomposite after 190 days.