37 research outputs found
Kinetics and mechanism of oxidation of methionine by chloramine-T in alkaline medium in presence of OsO4 catalyst
No full textKinetics and mechanism of oxidation of D-L methionine (Met) by sodium N-chlorotoluene-p-sulphanamide (CBT) in alkaline medium in presence of OsO4 catalyst have been investigated at 30 degrees C, and the results are compared to the reaction without Os(VIII) catalyst. The reaction rate shows a first order dependence each on CAT] and methionine] and inverse fractional order on OH-] and tractional order on OsO4]. Additions of halide ions and variation of ionic strength and dielectric constant of the medium do not have any significant effect on the reaction rate. Thermodynamic parameters have been evaluated
Kinetic studies on free radical polymerization of acrylonitrile, initiated by chloramine-T/hydrogen peroxide redox system
No full textAbstract The Kinetics of polymerization of Acrylonitrile initiated by chloramine-T/H2O2 Redox System was studied in aqueous medium in the temperature range of 35–50°C. The effects of variations such as Monomer, CAT, H2O2, temperature, and chloramine-T disappearance (−Rm) were measured. The effect of some water- miscible organic solvents and surfactants on the rate of polymerization was investigated. The polymerization process is initiated by the free radical arising from oxidation of H2O2 by chloramine-T and terminated by the mutual combination of the growing polymer radicals. Based on the kinetic results, a suitable reaction scheme is proposed and discussed for the various rates of polymerization and thermodynamic parameters were evaluated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5877–5883, 200
Polymerization of acrylonitrile initiated by cerium (IV)-oxalic acid redox system: A kinetic study
No full textAbstract The kinetics of aqueous polymerization of Acrylonitrile initiated by the Cerium (IV)-Oxalic acid redox system in Sulfuric acid medium has studied under nitrogen atmosphere in the temperature range of 25–50°C. The rate of polymerization (Rp) and the disappearance of Cerium (IV) have been measured. The water-miscible organic solvents and inorganic salts were depressed both the rate and the conversion. The effects of ionic strength, effects of surfactant have been investigated. The temperature dependence of the rate was studied and the activation parameters were computed using Arrhenius and Eyring plots. A mechanism consistent with the experimental data, involving Ce(IV)–Oxalic acid complexation that generates free radical was suggested. The chain termination step of the polymerization reaction was determined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 200
Polymerization kinetics of methylmethacrylate by oxidation: Reduction system using cerium(IV)/lactic acid in aqueous medium
No full textThe kinetics of polymerization of methylmethacrylate initiated by cerium(IV)–lactic acid redox system was studied in an aqueous medium in the temperature range of 25–50°C. The rate of polymerization (Rp) and the rate of cerium(IV) disappearance have been measured. The effects of some water-miscible organic solvents, cationic, anionic, nonionic surfactants, and complexing agents on the rate of polymerization were investigated. The temperature dependence of the rate was studied, and the activation parameters were computed using the Arrhenius and Eyring plots. The effects of inorganic and organic solvents on polymerization were also investigated. All of them depressed both the initial rate and limiting conversion. A mechanism consistent with the experimental data, involving cerium(IV)–lactic acid complex formation, which generates free radicals, is suggested. The chain termination step of the polymerization reaction is by mutual interaction of the growing macromolecules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3498–3505, 200
Thermal degradation kinetics, mechanical, and flame retardant properties of epoxy-HDPE fabric-clay composite laminates
No full textAddition of particulates into laminates has been found to influence thermal and mechanical properties. Composite laminates of epoxy-high density polyethylene (HDPE) fabric-clay were prepared by reinforcing clay in the range of 0.1-0.7 phr into epoxy-HDPE fabric laminates. These laminates are characterized for their mechanical, thermal, and flame retardant performances. With the addition of clay, an increase was found in impact resistance, tensile strength, flexural strength, and Young's modulus to an extent of 0.2 phr clay, after which there is a decrease in these properties. The thermal stability is found to decrease with the addition of clay. The improved mechanical properties are obtained at the slight expense of thermal stability. UL-94 tests indicate a reduction in the burning rate. Morphology of the broken samples indicate better dispersion at lower clay load and tactoid formation at higher clay loading. These materials have potential applications in agriculture, construction, and decorative purposes
Kinetics of oxidation of indole in high indole concentration range by bromamine-B in alkaline medium catalysed by Os(VIII)
No full textThe kinetics of oxidation of indole (In) in high indole concentration range by sodium N-bromobenzene sulphonamide (BAB) in alkaline medium in presence of OsO4 catalyst have been investigated at 30 degreesC The reaction rate shows a first order dependence of rate on BAB](0) and Indole], and inverse first order dependence of rate on OH-] and first order on OsO4]. Addition of halide ions and variation of ionic strength and dielectric constant of the medium do not have any signficant effect on the reaction rate. Thermodynamic parameters have been evaluated
Tailoring of ternary nanocomposite films of poly(vinyl alcohol)/ AgAlO2@reduced graphene oxide: An active material for flexible supercapacitors
No full textPoly(vinyl alcohol) (PVA)/silver aluminium oxide (AgAlO2)@reduced graphene oxide (rGO) nanocomposites (NCs) as flexible supercapacitor electrodes were fabricated via an eco-friendly and scalable solution casting approach. The crystallinity and morphological characteristics of the developed NCs were characterized by using X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The thermal properties were analysed by thermal gravimetric analysis (TGA). The electrochemical performance of PVA/AgAlO2@rGO NCs as a supercapacitor electrode material was investigated by cyclic voltammetry (CV) studies. PVA/AgAlO2@rGO NCs showed wide operating potential windows (1.2 V) which can greatly enhance their capacitive behaviour. The highest specific capacitance obtained was 273.4 F g-1 in the case of 2 wt % AgAlO2@rGO loaded PVA NC as compared to pristine PVA (6.04 F g-1). These NCs exhibited superior performance with the energy density (13.8 Whkg-1) and power density (150 W kg-1) at 0.5 A g-1 respectively. PVA/AgAlO2@rGO NCs exhibited the negligible equivalent series resistance and charge transfer resistance as an indication of excellent charge propagation at the interface between an electrolyte and an electrode. The NCs showed good capacity retention of 86.18% even after 1000 cycles. The NCs comprising of AgAlO2 NPs exhibited better specific capacitance than reduced graphene oxide incorporated PVA NCs, thus constituting a new approach for fabricating supercapacitors electrodes
Polymerization kinetics of acrylonitrile by oxidation: Reduction system using potassium persulfate/ascorbic acid in an aqueous medium
No full textThe kinetics of acrylonitrile polymerization initiated by free radicals formed in situ in a potassium persulfate/ascorbic acid redox system was investigated in an aqueous sulfuric acid medium in the temperature range of 40-70 degrees C. The rate of polymerization and the rate of the disappearance of potassium persulfate were measured. A kinetic scheme involving the production of initiating radicals from the oxidation of ascorbic acid by potassium persulfate ions and termination exclusively by the interaction of chain radicals with persulfate ions is proposed. The effects of some water-miscible organic solvents on the rate of polymerization were investigated. The temperature dependence of the rate was studied. A possible mechanism consistent with the experimental data is proposed. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 1299-1303, 201
Structural and ionic conductivity behavior in hydroxypropylmethylcellulose (HPMC) polymer films complexed with sodium iodide (NaI)
No full textSolid polymer electrolyte films based on Hydroxypropylmethylcellulose (HPMC) complexed with Sodium Iodide (NaI) were prepared using solution cast method. The dissolution of the salt into the polymer host and the micro structural properties of pure and NaI complexed HPMC polymer electrolyte films were confirmed by X-Ray diffraction (XRD) studies. The XRD results revealed that the amorphous domains of HPMC polymer matrix was increased with increase in the NaI salt concentration. The degree of crystallanity and crystallite size is high for pure HPMC samples. Direct current (dc) conductivity was measured in the temperature range of 313-383k. Temperature dependence of dc electrical conductivity and activation energy regions data indicated the dominance of ion type charge transport in these polymer electrolyte films
Polymerization of acrylonitrile initiated by Ce(IV)-sucrose redox system: A kinetic study
No full textAbstract The polymerization of acrylonitrile (M), initiated by the free radicals formed in situ in the Ce (IV)-sucrose redox system, was studied in aqueous sulfuric acid medium under nitrogen atmosphere in the temperature range of 30–60°C. The rate of polymerization is proportional to M1.0, R0.76, Ce(IV)0.8, and H+−0.46. The rate of Ceric ion disappearance and the rate of polymerization Rp have been measured. The effects of some water–miscible organic solvents, surfactants, ionic strength, and complexing agents on the rate of polymerization were investigated. The temperature-dependence of the rate was studied and the activation parameters were computed using the Arrhenius and Eyring plots. A mechanism consistent with the experimental data, involving Ce(IV)-sucrose complex formation, which generates free radicals, is suggested. The chain termination step of the polymerization reaction was determined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 200
