No abstract available

[en] Direct radiation grafting of acrylic acid (AAc) onto polyethylene/polytetrafluoroethylene copolymer (ET) films was studied. In this grafting system ammonium ferrous sulphate (Mohr ∼ s salt ) and ferric chloride were used as inhibitors to minimize the homo polymerization of AAc and the suitable concentration of the inhibitor added to the reaction medium was found 1.0 and 1.5 Wt % for Mohr ∼ s salt and ferric chloride, respectively. Also the effect of the monomer concentration on the rate of grafting was investigated. The dependence of the grafting rate on the monomer concentration was found 1.4 order. This grafting system proceeded by a diffusion controlled process. Some selected properties of the grafted films such as swelling behaviour, dimensional change, mechanical and electrical properties were also investigated. 8 fig

[en] The proton formation and counter ion liberation in gamma-irradiated aqueous solutions of poly uracil were studied. Under steady-state irradiations conditions, G(H⁺) of poly U in N₂ o/o₂-saturated solutions around PH 5.5. Was found to be 2.2, dependent on temperature during irradiation but independent of the dose rate. The G(H⁺) values under steady-state conditions are in the order expected from a postulated mechanism suggested in the presence of oxygen. On the basis of PH and conductivity measurements, the G-values of counter ion liberation was calculated and found to be 27.5. The counter ion liberation reveals dependence on the dose rate as well as on the temperature during irradiation. The effect of heating after irradiation was also studied. The formation of protons due to post irradiation heating may be attributed to a process of hydrolysis as described by the postulated mechanism. However, it was found that G(H⁺) produced in poly U after heating is higher than that expected, 2.6 instead of 1.5. The increment of 1.1 is probably due to proton formation through other unknown mechanisms. The effect of heating was found to be dependent on the dose rate and temperature during irradiation

[en] In this study the model system polyinosinic acid(poly I) was investigated. A successful attempt was made to change the multi-stranded nature of this compound to single-stranded molecules. For this purpose the thermal treatment at 75 degree C for about ten minutes at PH between 7 and 8 was found to be the nest method for achieving this goal. Furthermore, it was possible to change to single-stranded molecules in absence of salt (KCl). The gamma-irradiation of poly I resulted in a non-significant change in the molecular weight, however,post-irradiation re denaturation gave rise to a marked change. The G-values were calculated for the single strand breaks of polyinosinic acid (G(ssb))

[en] The effect of gamma-irradiation on poly uridylic acid (poly U) under various reaction conditions has been investigated. The effect of PH on the measurements of average molecular weight of poly U was first studied to choose the optimum conditions for predicting the rate constant values of strand dissociation. The G-value for single strand break (G(ssb)) was calculated and found to be 2.3. The large G(ssb)-values obtained were explained not only as resulting from the reaction of OH radicals and H-atoms on the sugar moiety, but also on their reaction with the uracil moiety which leads to chain break formation in poly U via radical transfer to the sugar moiety. Two possible mechanisms for the strand break formation could be presented. Also, the G-values were determined in the presence of oxygen. Molecular weight determinations of poly U in the presence of salts such as KCl, NaCl and NaCl O₄ using the low-angle laser light scattering technique were carried out

[en] Electron spin resonance measurements were carried out to investigate the nature, amount, and decay of the free radicals produced by the gamma-irradiation of some cation exchange resins. Merck cation exchanger I, a strongly acidic exchanger based on styrene-divinylbenzene (DVB) copolymers, subjected to the same radiation dose generates about ten times as many free radicals in the H⁺-form of the cationite as in polystyrene cross-linked with divinylbenzene. This shows that, the introduction of sulfa-groups into the benzene rings diminishes the stability of this system towards radiation. The ESR spectra of the H⁺-from of the cationite (consisting of two lines) approaches that of the original copolymer, while the Na⁺-from consists of three clearly resolved linear of hyperfine structure. Merck cation exchanger IV, a weakly acidic cation exchanger gave 5 intense and 4 weak hyperfine structure lines. Also a nuclear magnetic resonance study of the nature of water in the resin showed its existence in both free and bound water forms by studying the variation of width at half-value ( )of the NMR signal with water content. Also, the chemical shifts it the NMR signal were measured which may be considered as the first of two terms due to the diamagnetic shielding of the resin frame work and to the bonding of water molecule to the exchanger surface

[en] The effect of repairing agents on polyuridylic acid model system has been investigated. Cysteamine and dithiothreitol (DTT) were used as radio-protectors. The effect of concentration, PH, ionic strength and counter ion on the G(ssb)-value in presence of cysteamine was studied. It was found 8% given off poly U strand break precursor radicals and the remainder 92% poly U strand break radicals were rationally repaired. A possible mechanism has been suggested. The least recorded G(ssb)-values were found at cysteamine concentration of 2 x 10^-5 M in presence of 0.01 M and 0.1 M Na Cl O₄. When DTT was used as a radio-protector, the rate constant K₄ was half the value obtained when cystamine was used. 12% of broken strands were determined and 88% of poly U strand break radicals were repairable. When oxygen was present in the system, 42% broken poly U strands were found and only 58% of poly U strand radicals were repairable

[en] Preparation of synthetic membranes using simultaneous radiation grafting of acrylic acid (AAc) and styrene (Sty) as individually and in binary monomer mixture onto low density polyethylene (LDPE) has been carried out. The effect of preparation conditions such as irradiation dose, monomer concentration, comonomer composition, and solvent on the grafting yield was investigated. Characterization and some properties of the prepared membranes using different analytical techniques are studied, accordingly the possibility of its practical use in industrial waste treatment is determined. The swelling behavior, electrical conductivity, thermal stability, and mechanical properties of the membranes were investigated as a function of the grafting degree. The prepared cation-exchange membranes possessed good electrical and mechanical properties, high thermal stability and possess good characteristics for separation processes. These membranes have also good affinity toward the adsorption or chelation with Fe³⁺ and Pb²⁺ ions either in mixture containing other metals or if exists alone in the waste solution

[en] Reverse osmosis membranes were prepared by the post radiation grafting of vinyl acetate onto low density polyethylene films. The factors affecting the grafting process such as radiation dose, monomer concentration and temperature on the grafting yield were studied. It was found that the dependence of the grafting rate on radiation intensity and monomer concentration was found to be of 0.64 and 1.4 order, respectively. The activation energy for this grafting system was calculated and found to be 4.45 kcal/mol above 30⁰C. Some properties of the grafted films such as specific electric resistance, water uptake, mechanical properties and thermal and chemical stability were investigated. An improvement in these properties was observed which makes possible the use of these membranes in some practical applications. The use of such membranes for reverse osmosis desalination of saline water was tested. The effect of operating time, degree of grafting and applied pressure on the water flux and salt rejection were determined. The results showed salt rejection percent over 90% and a reasonable water flux. A suitable degree of grafting of the membrane was determined as well as the optimum applied pressure. (author)

[en] The compound 1,3-di (2-aminoprimidinyl)-2,2,2,4,4,4-hexachlorocyclodi-phosphazane was prepared. The structure of this aminophosphorous compound was confirmed on the basis of microanalytical data, infrared, ultraviolet and proton NMR spectroscopic evidence. The compound was irradiated by gamma-rays and the ultraviolet measurements before and after irradiation were discussed. The influence of the dose rate on ultraviolet absorption was noticed at various concentrations of aqueous solutions. The PH values were also measured before and after heating as well as before and after irradiation at various dose rates and the correlation between the change in PH values with the ultraviolet absorption shifts were measured for the various concentrations. From the ultraviolet results, it may be suggested that the possible decomposition sites in the compound due to -irradiation are localized in the unsaturated bonds in the hetero aromatic ring. The thermal analysis of the compound and its bacteriological evaluation were also studied