Characterization of a Thin Film Composite Membrane: Fluorinated Copolymer in a Carbon Nanotube Matrix

IDEX Health and Science has created a thin-film composite membrane consisting of a carbon nanotube matrix impregnated with a fluorinated copolymer called Teflon® AF 2400. This membrane is being studied for use in degassing chambers of analytical instruments such as a High Pressure Liquid Chromatography (HPLC) degassing modules. The level of impregnation of the Teflon® in the carbon matrix affects the diffusion properties which are crucial for the performance of the membrane. Scanning Electron Microscopy (SEM) characterization techniques were used to measure the outer Teflon® and the inner carbon matrix layer thickness. The outer Teflon® and inner carbon matrix layer thicknesses ranged from 1.92 to 28.17 microns and 5.07 to 41.70 microns, respectively. Energy Dispersive X-ray Spectrometry (EDS) was used to measure the Teflon® fluorine concentration gradient across the composite membrane. Mechanical tensile testing was also performed on each sample to compare the mechanical properties of the membrane to the initial design parameters. Ultimate Tensile Strength (UTS), Young’s Modulus (E), and Percent Elongation were collected for each membrane. IDEX Health and Science used the following processing parameters to create each membrane: (a) Concentration, (b) Density, (c) Time, and (d) Recoat. Statistical analysis indicated that time and recoat had the largest effect on maximum stress at maximum load. The results from SEM imaging, EDS scans, and tensile testing helped determine how well the Teflon® infiltrated the carbon matrix. The interactions between the four processing parameters provided IDEX Health and Science with information to determine the optimal set of processing parameters for generating the ideal membrane