Composite nylon membranes

Scanning electron microscopy (SEM) combined with energy dispersive X-ray (EDX) analysis could be used to physico-chemical characterization of SILMs [26]. This technique allows the characterization of the membrane surface morphology and the examination of the global chemical composition of the membranes and the distribution of the ILs within pores. Figure 11.2 shows examples of SEM micrographs of a plain nylon membrane and supported liquid membranes based on [bmim ][PF ] prepared by using the pressure method [26]. 

Filtration is required to remove any particulate matter that could cause damage to the pump seals and could block the column and narrow tubing if they are not removed. The choice of filter will depend on the level of particulate contamination and the mobile phase composition. An example of this might be the use of a 0.45 pm nylon membrane filter, which is compatible with most mobile phases. Information in relation to filter compatibility for commonly used mobile phase components for RP-HPLC is given in Table 3.3. 

Although the hydrophobic surface of nylon membranes may be improved by hydrolysis or chemical modification, composite polyamide membranes are preferred in chromatographic applications. Klein et al. [42] prepared polyamide microporous membranes by modification of terminal amino groups. Covalent binding of a polyhydroxyl-containing material to the polyamide membrane increases the density... 

The incorporation of positive charges has decreased the fouling susceptibility of membranes even more effectively. This is the principle of the aromatic polyamide membrane series commercialized by Hydranautics as low fouling composite membranes (LFC). Cationic charge-modified nylon membranes are also commercially available from CUNO 3M, under the trademark Zeta Plus . Pall Corp. sells cationic charge-modified nylon membranes under the trademark Ngg Posidyne. There are different ways to make the membrane positively charged. A patent from Millipore [148] describes the surface modification of hydrophobic membranes by contacting them with a solution of polyamine epichlorohydrin... 

Improved organic rejections result from the chemical nature of the newer polymeric materials in the nylon and thin-film composite membranes. Data by Chian and Fang (6) represented in Figure 2 illustrate different membrane rejections for a variety of organic com-... 

Yoshikawa M, Shimada H, Tsubouchi K, and Kondo Y. Specialty polymeric membranes. 12. Pervaporation of benzene/cyclohexane mixtures through carbon graphite-nylone 6 composite membranes. J Membr Sci 2000 177 49-53. 

Jeong and co-workers (94) have electrospun nylon/MWNT nanofibers onto an ITO coated glass and measured the I-V clwacteristics of the CNT-containing nanofiber membrane supported by the conducting glass. The measured I-V characteristic showed a non-ohmic behavior over the MWNT contents from 0 to 20wt%, and the non-ohmic behavior was enhanced with increased MWNT contents. Similar electrical behavior was also reported for PVDF/SWNT (120) and PEO/MWNT (121) composite nanofibers. 

Novel membranes for PV were prepared from carbon graphite (CG) and nylon 6 (N6) by Yoshikawa s research group (Yoshikawa et al. 2000). Manbranes were prepared from a mixture of 2,2,2-trifluoroethanol (TFE) and CG. These composite membranes showed permselectivity toward benzene from benzene-CYH mixture. Benzene was permeated in preference to CYH from benzene-CYH mixtures and the separation factor of benzene reached 235 at the weight fraction of benzene in a feed of 0.1. Their work suggested that CG-nylon 6 composite manbrane has the potential for petroleum-refining process. 

The mechanical properties of the layered composites were tested on a custom-made thin film tensile strength tester (McAllister Inc.) recording the displacement and applied force by using pieces cut from ((PEI/PAA)(PEI/SWNT)5)6 and ((PEI/PAA)(PEI/SWNT)5)8 free-standing films. The tester was calibrated on similar pieces made from cellulose acetate membranes and Nylon threads. ((PEI/PAA)(PEI/SWNT)5)6 and ((PEI/PAA)(PEI/SWNT)5)8 samples had an average TEM thickness of 0.75 and 1.0 /um, respectively. Their typical stress (ct) vs strain (e) curves differed quite markedly from stretching curves seen previously... 

Quaternary ammonium (3) and phosphonium ions (61), crown ethers such as (62), cryptands such as (63) and poly(ethylene glycol) ethers (64) bound to PS are catalysts for reactions of water insoluble organic compounds with organic insoluble inorganic salts. " Silica gel, alumina, polystyrene-polypropylene composite fibers, nylon capsule membranes, and polyethylene (Mn 1000-3000) have also been used as supports. The reactions are called phase-transfer-catalyzed because one or both of the reactants are transported from the normal liquid or solid phase into a polymer phase, where the reaction proceeds. 

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