SynopsisHydrophilic membranes were prepared by direct radiation grafting of methacrylic acid (MAA) onto poly (tetrafluoroethylene-perfluorovinylether) copolymer ( PFA) and poly (tetrafluoroethylene-hexafluoropropylene) copolymer (FEP) films followed by alkaline treatment to confer ionic character in the graft copolymer. Addition of 0.5 wt % FeC1, to the monomer solution effectively inhibited the homopolymerization process and higher grafting yield was obtained. The graft copolymerization of MAA was carried out in presence of methanol/water mixture (30/70 wt % ) in nitrogen atmosphere irradiation. The dependence of the grafting rate on MAA concentration was found to be 0.63 and 0.94 order for PFA and FEP films, respectively. This grafting system proceeds by the front mechanism in which the monomer diffuses through the already grafted layer formed initially. Some selected properties of the graft copolymers were investigated. It was found that the grafted membranes possess good mechanical, electrical, and hydrophilic properties which may make them promising in some practical applications.
SynopsisPreparation and some properties of the graft copolymers obtained by radiation-induced graft polymerization of methacrylic acid (MAA) and (acrylonitrile/MAA) comonomer onto polyethylene and polytetrafluoroethylene films, were investigated. The effect of reaction conditions, solvent, monomer, and inhibitor concentration, comonomer composition, and comonomer concentration, on the graft copolymerization process was studied. The grafting process was enhanced in the presence of comonomer (AN/MAA) as compared with individual grafting of MAA or acrylonitrile (AN). The optimum comonomer composition, at which the highest grafting yield was obtained, was found to be (80/20) wt ' % of (AN/MAA) comonomer. The graft copolymerization of (AN/MAA) comonomer was enhanced in presence of AN due to its higher polarity strength. The electrical and swelling properties of the graft copolymers were greatly affected by the contents of PAN and PMAA graft chains. Mechanical properties of the graft copolymers were significantly changed with the grafting yield.
The cathode current efficiency for the electrowinning of zinc was determined under different conditions of alkali concentration (2-8M), current density (10-40 mA. cm-2), and temperature (30-75~ Some remarkably high values of current efficiency were observed especially at 75~ A possible mechanism involving the discharge of monovalent complex ions is suggested. The effect of two tetra-alkyl ammonium salts TAS(a) and TAS(b) was investigated. The tetra-alkyl ammonium hydroxide, TAS(a) was found more suitable than the tetra-alkyl ammonium ethoxide, TAS (b). The morphology of zinc deposits was inspected by the scanning electronmicroscope; these were mainly spongy deposits. The cell voltage was measured and the energy consumption was calculated and was found to decrease with the increase of temperature. The total energy kWh/kg of deposited zinc from an additive-free solution at 75~ was 1.253 kWh/kg. In the presence of 0.37 rag/1 TAS(a), a further reduction was observed. The energy consumption amounted to 1.180 kWh/kg at the same temperature. The current density for maximum efficiency was 20 mA/cm 2. * Electrochemical Society Student Member.
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