Self-Passivation of Polymer-Layered Silicate Nanocomposites

Abstract

Nanoscale dispersion of only a few weight percentage of layered silicate (montmorillonite) in nylon 6 and epoxy results in the formation of a uniform passivating and self-healing inorganic surface region upon exposure to oxygen plasma. The enrichment of inorganic is compositionally graded with respect to the surface and is due to the preferential oxidation of the polymer from the nanocomposite and the corresponding enhancement of the nanoscale layered silicate on the surface. The structure of the inorganic region is turbostratic, with an average distance between layered silicates of 1−4 nm. This ceramic-like silicate layer provides an overcoat to the nanocomposite and can significantly retard the penetration of oxygen plasma. Thus, layered silicate containing nanocomposites may enhance the survivability of polymeric materials in aggressive oxidative environments, such as atomic oxygen in low earth orbit (LEO). The formed inorganic region was characterized chemically and morphologically by X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared (ATR), transmission electron microscopy (TEM), and X-ray scattering.