Processing & permeability of polyimide-clay nanocomposite membranes

Different concentration of Organoclay and PANi-Clay reinforced Polyimide nanocomposite membranes were studied for the processing and permeation behavior of water and ethanol. Membranes were prepared by solution casting with 1-Methyl-2-Pyrrolidone (NMP) as the solvent. The Organoclay used is Cloisite 20 A montmorillonite containing an alkylated quaternary ammonium ion 2H2T. PANi-Clay was prepared by former group member Dr. Yanrong Zhu at year 2002.;The concentration of Organoclay is from 0.01% to 5.00% and 0.01% to 0.50% for PANi-Clay. The free standing films were of a thin thickness from 70 to 100 mum. The imidization temperature varied from 65 °C to 250°C, and related diffusion behaviors were studied. The permeation set up consisted of a U shaped diffusion cell with two vertical capillary cylindrical tubes anchored on each cylindrical chamber as a reservoir. One chamber was filled by pure water and the other was filled by ethanol/water mixture (5:95, V: V). Chambers were separated by Polyimide nanocomposite membranes.;The effect of concentration of Organoclay and PANi-Clay on permeation was studied in this study. The diffusion of water from water chamber took place in most membranes and continued for at least one week. Diffusion did not happen for fully imidized membranesat high temperature as 250 °C. Small amount of Organoclay will influence the stability and permeation property. The flux through Organoclay reinforced membranes increased with increased Organoclay weight percent up to 0.25% loading beyond which a drastic decrease in the flux occurred for any further increase in the weight percent of Organoclay. Accordingly, the diffusion coefficient of the Orgnoclay reinforced membranes increased with increased weight percent of Organoclay from 1.73 x 10 -10 cm2 s-1 for the neat PI membrane to 9.57 x 10-10 cm2 s-1 for 0.25 % Organoclay. The permeability shows the mass transferring in the composite membranes is highly dependent on the Organoclay loading level but exhibits a nonlinear dependency.;The incorporation of PANi-Clay showed similar behaviors of Organoclay with lower permeability. However, the dependency of PANi-Clay is more linear comparing to Organoclay, the diffusion coefficient increases as PANi-Clay load level increases. PANi-Clay reinforced membranes show longer life than Organoclay modified membranes. Both permeation results inspire us to separate ethanol from water with optimized polyimide nanocomposites with proper fillers. The mechanisms of permeation were attempted to be studied by FTIR and SEM. The different effects of Organoclay and PANi-Clay on rheological properties were also discussed.;KEYWORDS: Nanotechnology, Separation, Ethanol/Water, Polyimide, Organoclay, PANi-Clay...