Gas permeation, thermal, morphology and mechanical properties of polyimide/clay nanocomposites: Effect of organically modified montmorillonite

Abstract

Novel polyimide/clay nanocomposites were fabricated by incorporating organically modified clay at different loading percentage of 1–5 wt% within the polyimide (PI) matrix. A novel PI was synthesized through a direct polycondensation reaction between novel 5,5′-((4-methoxyphenyl)azanediyl)bis(isobenzofuran-1,3-dione)and 4,4′-(1,4-phenylenebis(oxy))bis(3-(trifluoromethyl)aniline). The organoclay was prepared from Sodium montmorillonite (Na-clay) and protonated form of diamine (modifier) via ion-exchange reaction. The structural characterization of nanocomposites were made using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the mechanical properties were obtained by tension tests. The results of XRD, TEM, and FE-SEM indicated that clay could well disperse in the PI matrix and were intercalated by diamine and PI macromolecules. The thermal stability and glass transition temperature of nanocomposite at lower clay loadings are similar to PI but gradually decrease with increase in clay content. The tensile properties of PI/Clay nanocomposites showed the highest values at the optimum clay content of 3 wt%. The gas permeation of PI/clay nanocomposites was increased with the increase in loading percentage of organoclay, whereas the gas selectivity was maintained at par to that of neat PI film until it diminished at 5 wt% percentage of organoclay causing mineral agglomeration. PI/clay 3 wt% MMMs exhibited 245% and 240% increase in CO2 and O2 gas permeability respectively, while showing minimal variation in the selectivity of O2/N2 and CO2/N2 compared to that of neat PI matrix.