SynopsisGraft copolymerization of acrylamide (AM) onto silk fibers, using Mn(II1)-sulphate as initiator, has been investigated, in aqueous sulphuric acid in the temperature range of 30-55OC. Grafting reaction has been studied by varying the concentration of monomer, Mn(III), sulphuric acid, temperature, and also with the modified silk. The graft yield increases significantly with increase of monomer concentrations to the extent of 0.85M, after which the rate falls. With increase in Mn (II1) concentration and H+ ion concentration the graft yield increases, but after an optimum concentration a depression in the graft yield is noticed. The rate of the reaction is temperature-dependent; with increase of temperature the graft-on increases. Among the solvent composition studied a solvent/ water mixture containing 10% of the solvent seems to constitute the most favorable medium for grafting, and a further increase of solvent composition decreases the graft yield. The effect of various additives such as transition metal salts, aromatic and heterocyclic amines on grafting reaction has been studied. A suitable mechanism for grafting has been proposed. Finally physical characterization such as thermal analysis (TGA) of the grafted samples has been carried out in order to ensure grafting and to study the change in the properties of the fibers.
SynopsisGraft copolymerization of methyl methacrylate (MMA) onto cotton-cellulose has been carried out using hexavalent chromium Cr(V1) as initiator. Aqueous-methanolic solution of perchloric acid has been chosen as the reaction medium. The effect of monomer, initiator, acid, reaction medium, and temperature on the graft percentage has been found out. The reactions have also been carried out in the presence of polymerization, inhibitors, and retarders, such as hydroquinone and transition metal salts like CuSO4, FeCl3, etc. The giafted samples, after exhaustive separation of homopolymers and purification, were subjected to various chemical, mechanical, and thermal testings. The results of various analyses have been compared with the reference, and the improvement in the graft has been evaluated. A suitable mechanism for the grafting processes has been suggested, in accordance with the experimental results.
ABSTRACT:The catalytic influence of various Cu(II) salts and Cu(II)-chelate complexes of certain phenols and naphthols on potassium monopersulphate decomposition and vinyl polymerization of acrylonitrile has been investigated in aqueous medium. From the knowledge of the comparative rate data, the CuS04Ia-naphthol chelate complex was chosen for a detailed study of the kinetic aspects of acrylonitrile polymerization. The polymerization was studied at various concentrations of the reacting components and over a temperature range of 35-50°C. The rate of polymerization was found to beThe overall activation energy was computed to be 3.118 kcal mol-1 ' (13.03 kJ mol-1 ) and other thermodynamic parameters were evaluated. Fr.om the kinetic results and spectrophotometry studies on the interaction of KHS05 and a-naphthol with Cu(II), the mechanism of KHS0 5 decomposition and initiation of acrylonitrile polymerization are suggested.KEY WORDS Chelate Complex I a-Naphthol Effect I Copper Sulfate Effect I Monomer Effect I KHS05 Effect I Acid Effect I Solvent Effect I Complex Initiation IThe prominency of peroxygen compounds such as organic peroxides, hydroperoxides and inorganic peroxo salts is attributed to their ample applications as free-radical initiators and/or curing agents for polymers and resin industries. The choice of a peroxygen compound depends on its activity in regard to its decomposition reaction initiation. Apart from other reaction conditions, a trace of metal salt as an impurity causes a facile homolysis of the peroxobridge due to induced activity. 1 -? The catalytic effect of variable valency transition metal salts which are prominent in this regard, on the decomposition of peroxy compounds, is based on a known reaction scheme * To whom all correspondence is to be addressed. according to which the metal ion present both in the lower and higher oxidation states is catalytically effective.1.2 For this reason in the free radical polymerization of vinyl and diene monomer, these salts are widely used along with organic peroxides and hydroperoxides and peroxo salts as components of redox pairs. Sheldon et a/. 8 noticed that the participation of a given metal ion in a free radical process is strongly influenced by factors such as the kind of ligand bound to the metal ion and the presence of complexing agents in the reaction system. Barton and coworkers 9 -u noticed similar observations during their investigation on the effects of certain copper salts on cumene hydroperoxide (CHP) decomposition and vinyl polymerization. The rate of CHP de-453
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