Mixtures of ionic and nonionic surfactants have a wide range of industrial and household applications. The properties of the monolayer formed by such systems at the air-water interface depend on the interactions between the surfactants. The presence of salt influences the interactions between the surfactants in the monolayer as well as in the micelle. In this work, these interactions in the presence and absence of a 1:1 salt were studied using nonideal solution theory. An anionic surfactant, a cationic surfactant, and a nonionic surfactant were used. The stability of foams was significantly affected by the interactions between the surfactants. To study this effect, the coalescence of air bubbles in the mixed-surfactant systems was studied and compared with that in the corresponding single-surfactant systems. The effect of salt on the coalescence time was also studied. The results were analyzed using the film drainage and stochastic theories of coalescence. Seven film drainage models were employed to predict the coalescence time, and the values predicted by these models were compared with the experimental data. The parameters of the stochastic model were analyzed based on the properties of the systems.
SynopsisVinyl polymerization of acrylonitrile initiated by the Ce(IV)/thioacetamide redox system has been investigated in aqueous sulfuric acid in the temperature range of 10-2OoC. The rate of polymerization (R,) and the rate of Ce(1V) disappearance (-Rce) were measured. The effect of certain water-soluble organic solvents, added electrolytes, and aromatic and heterocyclic organic nitrogen compounds on the rate of polymerization has been investigated. Depending on the experimental results, we have suggested a suitable reaction scheme for the system which involves the production of initiating radicals from the oxidation of thioacetamide (TAm) by ceric ion and the termination of the polymer chain by metal ions.
SynopsisThe graft copolymerization of methyl methacrylate onto silk fibers was investigated in aqueous solution using Mn3+ acetyl acetonate [Mn(acac)a] as initiator. The rate of grafting was determined by varying monomer, acidity of medium, temperature, and reaction medium. The graft yield increases significantly with increase of [Mn(acac)a] concentration up to 0.01M, and with further increase of [Mn(acac)a] the graft yield decreases. The effect of the increase of monomer concentration brings about a significant enhancement in the graft yield, and with further increase the graft yield decreases. The rate of reaction is temperature dependent; with increasing temperature, the graft yield increases. Among the solvent composition studied, a watedsolvent mixture containing 10% of the solvent seems to constitute the most favorable medium for grafting; and, with further increase of solvent composition, the graft yield decreases. The effect of some inorganic salts, organic solvents, and complexing agents has been investigated.
SynopsisThe aqueous polymerization of acrylonitrile initiated by the bromate-ferrous redox system in aqueous sulfuric acid was studied under nitrogen atmosphere. The rate of polymerization increased with increasing concentration of ferrous in the range of 0.25-1 X 10-2M. The percentage of conversion increased with increasing concentration of the catalyst, but beyond 2.5 X 10-3M there was a decreasing trend in the rate of polymerization. The rate varied linearly with [monomer]. The initial rate of polymerization as well as the maximum conversion increased within the range of 1-2.5 X 10-3M KBr03, but beyond 2.5 X 10-3M the rate of polymerization decreased. The initial rate and limiting conversion increased with increasing polymerization temperature in the range 30-40OC; beyond 4OoC they decreased. The effect of certain neutral salts, water-miscible solvents, complexing agents, and copper sulfate concentration on the rate of polymerization was investigated. polymerization. It was therefore thought desirable to use the ferrous-bromate redox pair to examine its role in acrylonitrile polymerization.
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