Studies of Cu(II)–IO4− initiated graft copolymerization of methyl methacrylate from defatted pineapple leaf fibres

A study of the graft copolymerization of methyl methacrylate (MMA) from defatted pineapple leaf fibre (PALF) was carried out in the temperature range 45–55 °C, using a copper sulphate (CuSO₄) and potassium periodate (KIO₄) combination as initiator in an aqueous medium. Effects of variation of time and temperature, concentration of Cu(II), KIO₄ and MMA, the amount of PALF, and also the effects of some inorganic salts and organic solvents on the percentage of graft yield have been investigated. On the basis of experimental findings, a reaction mechanism is proposed. FTIR spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy of the original defatted PALF and MMA grafted PALF have been carried out. The thermal stability of PALF is improved through grafting. © 1999 Society of Chemical Industry     

SPICE-compatible microwave model of an optically controlled high electron mobility transistor

The effect of optical illumination on the microwave characteristics of an optically gated AlGaAs/GaAs HEMT has been studied theoretically. This article describes an integral approach to the problem which includes the calculation of the capacitance and the sheet concentration of the two-dimensional (2D) electron gas in the illuminated condition. The changes in the various intrinsic parameters of the device under the illuminated condition have been utilized to calculate the Y-parameters of the device at microwave frequencies. The lumped circuit model of the device in the illuminated condition has been obtained with the various components determined from the Y-parameters. The attractive feature of the present model is that it is fully compatible with commonly used circuit simulation packages like SPICE. © 1996 John Wiley & Sons, Inc.     

Kinetics and mechanism of MnO2 dissolution in H2SO4 in the presence of pyrite

This paper describes a study of the kinetics and mechanism of MnO2 dissolution in H2SO4 in the presence of pyrite through leaching and electrochemical parameters. Manganese(iv) was found to dissolve mainly through reduction by the ferrous ion generated during oxidation of pyrite by the ferric ion. The oxidation which is slower and rate controlling may proceed through two different reactions, one producing S0 and the other SO42–. Manganese dissolution runs at the same rate as that of pyrite oxidation by maintaining ferrous ion concentration at a much lower level than that of ferric. Kinetic equations based on corrosion coupling principles are developed to explain the observed leaching behaviour.     

Methyl methacrylate–N-chlorophenyl maleimide copolymers: Effect of structure on properties

The article describes the preparation of cast acrylic sheets by copolymerizing methyl methacrylate (MMA) with varying mole fractions of N-o-chlorophenyl maleimide (OC), N-m-chlorophenyl maleimide (MC), and N-p-chlorophenyl maleimide (PC) using benzoyl peroxide as an initiator. The effect of incorporation of varying mole fraction of N-chlorophenyl maleimides in poly(methyl methacrylate) backbone on the optical, physicomechanical, and thermal properties of cast acrylic sheets were evaluated. Vicat softening temperature, glass transition temperature (T_g) and thermal stability of the copolymers increased with an increase in the maleimide content. The solar transmittance and percentage of transmittance of the copolymer sheets having low mole fractions of N-chlorophenyl maleimides (i.e., 0.025–0.085) were found to be comparable with that of PMMA. Further increase in the comonomer content resulted in a decrease in the percentage of transmittance. Copolymer sheets having low mole fractions of N-chlorophenyl maleimides (0.025–0.108) have tensile strength comparable to that of PMMA, whereas the percentage of elongation decreased. Tensile modulus increased with increasing mole fraction of N-chlorophenyl maleimides. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 527–534, 1998     

Hydrogen Plasma Smelting Reduction of Fe2O3

Metallurgical and Materials Transactions B - The paper reports successful smelting reduction of iron ore (hematite) in thermal hydrogen plasma. A specially designed reactor with water cooled copper...     

Nonisothermal Crystallization Modeling and Simulation of Polypropylene/Nano Ca3(PO4)2 Composites with Variation in Wt.% of Loading and Reduction in Nanosize

Nonisothermal crystallization kinetics of polypropylene (PP)/Ca₃(PO₄)₂ composites was studied using differential scanning calorimetry (DSC) for various nanosizes by employing Avrami and Ozawa's combined analysis. Parameters such as Avrami's exponent (n) and composite growth rate constant (Z_t) were determined, which characterize the system of different nanosize composites and virgin PP. The relative degree of crystallinity as a function of temperature for PP-nano Ca₃(PO₄)₂ composites at the same cooling rate and sigmoidal shape of curves indicates that there is a strong interaction between PP molecule and nanolayer, which leads to greater nucleation with reduction in nanosizes. A theoretical combination of kinetic equations is found to be suitable to describe the physical phenomena of a real system. The values of parameters n, Z_t, and predicted time t for crystallization at a single cooling rate were obtained from the mathematical model.     

Influence of stearic acid treated nano-CaCO3 on the properties of silicone nanocomposites

The aim of the work reported here was to study the influence of treated nano-CaCO₃ on the silicone:dicumyl peroxide system. Thermal degradation was studied using TGA of treated and untreated nano- and commercial CaCO₃:silicone rubber composites. Thermal stability as well as % char yield increased with increasing content of treated nano-CaCO₃ as compared to untreated and commercial CaCO₃. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were performed to study the degree of dispersion of treated and untreated nano-CaCO₃ and commercial CaCO₃ in silicone rubber composites. Moreover, the nanocomposites were subjected to various tests, such as those for tensile strength, % elongation at break, flammability and abrasion resistance. The tensile strength (8.5 kg/cm²) and elongation at break (780%) showed their greatest improvements at 10 wt% loading with treated nano-CaCO₃ in comparison to the untreated nano- and commercial CaCO₃:silicone rubber composites. The improvements in the properties of treated CaCO₃:silicone composites compared to the untreated nano- and commercial CaCO₃ silicone rubber composites were due to the uniform dispersion of nanoparticles in the treated composites and their good compatibility with the rubber chains, as shown by AFM and SEM studies.     

A novel electro‐organic synthesis of aniline‐based copolymers at platinum electrodes

A novel, efficient, and ecocompatible electro copolymerization of anilines at platinum electrode using acetonitrile as non‐aqueous solvent and lithiumperchlorate as supporting electrolyte was carried and described here. The progress and mechanistic study of copolymerization was done using cyclic voltammetry. The reaction proceeded smoothly and quantitatively at ambient temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012