Effect of Graphene Oxide-Modified CaAl-Layered Double Hydroxides on the Carbon Dioxide Permeation Properties of Fluoroelastomers.

This work aimed to investigate the CO₂ gas barrier and mechanical properties of fluorine rubber nanocomposites filled with Ca/Al layered hydroxide (graphene oxide [GO]/LDH-Ca₂Al) modified by GO. GO/LDH-Ca₂Al nanocomposite fillers were prepared by depositing Ca/Al layered hydroxide (LDH-Ca₂Al) into the surface of alkalized GO (Al-GO). The prepared GO/LDH-Ca₂Al nanocomposite fillers and complexes were characterized by Fourier infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) for structural and micromorphological characterization. The results showed that GO/LDH-Ca₂Al was successfully prepared with strong interactions between Al-GO and LDH, and the compatibility of GO/LDH-Ca₂Al nanocomposite fillers with the polymer was significantly improved compared with that of LDH-Ca₂Al. Consequently, both the fracture strength (σ_b) and strain (ε_b) of GO/LDH-Ca₂Al nanocomplexes remarkably increased, and they exhibited excellent mechanical properties. Differential scanning calorimetry and thermogravimetric analysis were used to characterize the thermal stability of GO/LDH-Ca₂Al nanocomposite fillers, and GO/LDH-Ca₂Al nanocomposite fillers have better thermal stability than LDH-Ca₂Al. The reaction products (S-LDH-Ca₂Al and S-GO-Ca₂Al) of LDH-Ca₂Al and GO/LDH-Ca₂Al with CO₂ were characterized using XRD and TGA, respectively, and the results show that LDH-Ca₂Al reacts readily and chemically with CO₂, resulting in a lower diffusion coefficient of CO₂ in the LDH-Ca₂Al nanocomplexes than that of the GO/LDH-Ca₂Al nanocomplexes and leading to the destruction of the laminar structure of LDH-Ca₂Al, while GO/LDH-Ca₂Al has better CO₂ resistance stability. GO/LDH-Ca₂Al nanocomplexes exhibited a reduced content of hydroxyl groups with pro-CO₂ nature exposed on the surface of LDH-Ca₂Al, improving the interfacial interaction between the nanofillers and the rubber matrix and enhancing the dispersion of GO/LDH-Ca₂Al in the polymers. Moreover, CO₂ in the soluble GO/LDH-Ca₂Al nanocomposites was significantly reduced, while the diffusion properties demonstrated weak temperature dependence on solubility. The mechanism of the CO₂ gas barrier of polymers filled with GO/LDH-Ca₂Al was proposed on the basis of the Arrhenius equation. [ABSTRACT FROM AUTHOR]