Styrene butadiene-based blends containing waste rubber powder: Physico-mechanical effects of mechanochemical devulcanization and gamma irradiation

Waste rubber (WR) powder was introduced in a two-roll mill in the presence of various ratios of curatives to develop sheets of devulcanized waste rubber (DWR). The selected product was investigated by FTIR, TGA and SEM. In a roll mill and hot press, styrene butadiene rubber (SBR) gum was differentially replaced by DWR feed ratios, and thereafter irradiated with gamma rays. The mechanical parameters of the developed blend were examined. Oil resistance and thermogravemetric behavior were discussed. Remarked improvement in the mechanical, thermal and physical parameters of SBR was generally determined by the incorporation of DWR and gamma irradiation.     

Effect of amino acids containing sulfur on the corrosion of mild steel in phosphoric acid solutions polluted with Cl−, F− and Fe3+ ions–behaviour near and at the corrosion potential

Research on non‐toxic inhibitors is of considerable interest in investigations into the replacement of hazardous classical molecules. This paper reports the action of four amino acids containing sulfur on the corrosion of mild steel in phosphoric acid solution with and without Cl^?, F^? and Fe³⁺ ions near and at the corrosion potential (E_corr) using both the polarization resistance method and electrochemical impedance spectroscopy (EIS). Both cysteine and N‐acetylcysteine (ACC) showed higher inhibition efficiency than methionine and cystine. Adsorption of methionine onto a mild steel surface obeys the Frumkin adsorption isotherm and has a free energy of adsorption value (ΔG °_ads) lower than those obtained in the presence of cystine, cysteine and ACC whose adsorption isotherms follow that of Langmuir. Both F^? and Fe³⁺ ions stimulate mild steel corrosion while Cl^? ions inhibit it. The binary mixtures of methionine, cysteine or ACC with Cl^? or F^? ions are effective inhibitors (synergism) while the combinations of the amino acid with Fe³⁺ or the ternary Cl^?/F^?/Fe³⁺ mixture have low inhibitive action (antagonism). EIS measurements revealed that the charge transfer process mainly controls the mechanism of mild steel corrosion in phosphoric acid solution in the absence and presence of the investigated additives. The mechanism of corrosion inhibition or acceleration is discussed. © 2002 Society of Chemical Industry     

New gasoline and gas barrier from plasticized carbon black reinforced butyl rubber/high‐density polyethylene blends

The effects of the high‐density polyethylene volume fraction on the curing characteristics and network structure of rubber blends have been studied in terms of the torque, scorch time, optimum curing time, Mooney viscosity, number of elastically effective chains, viscosity, interfacial tension, glass‐transition temperature, scanning electron microscopy, internal friction, sound velocity, acoustic attenuation, polymer–solvent interaction parameter, swelling index, and gel fraction. The applicability of the blends for gasoline barriers has been examined through the changes in the electrical resistance and volumetric swelling in gasoline versus time at room temperature. The transport mechanism of the solvent through the crosslinked butyl rubber/high‐density polyethylene blends is governed by Fickian diffusion law. The transport coefficients, namely, the diffusion coefficient, intrinsic diffusion, and permeation coefficient, have been computed. The experimental data for the permeation coefficient are in good agreement with the values calculated by Maxwell's model and far from those of Robeson's model. In addition, some thermodynamics parameters, namely, the standard entropy, standard enthalpy, and standard Gibbs free energy, have been estimated as functions of the high‐density polyethylene concentration of the butyl rubber blends. Furthermore, the applicability of butyl rubber/high‐density polyethylene composites for Freon gas barriers and antistatic charge dissipation has been examined. Finally, the mechanical properties, such as the tensile strength, hardness, stiffness, and elongation at break, of butyl rubber composites with different high‐density polyethylene concentrations have been evaluated. The increase in the mechanical properties is due to the increase in the crosslinking density and the interfacial adhesion of the blend. This proves that these new blends have important technological applications as gasoline and Freon barriers and for antistatic charge dissipation with good mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1237–1247, 2006     

The Influence of Halide Anions on the Anodic Behavior of Nickel in Borate Solutions

The anodic behavior of nickel in Na₂B₄O₇ solutions containing various concentrations of NaCl, NaBr, or NaI as pitting corrosion agents was studied using the potentiodynamic technique. In absence of the halide anions, the E/i curves exhibit active and passive regions prior to oxygen evolution. The passivity is due to the formation of nickel oxides on the electrode surface. The presence of low concentrations of the halide anions has no effect on the mechanism of nickel passivity. High aggressive anion concentrations stimulate the active region and tend to break down the passive film, leading to pitting corrosion. The susceptibility of the nickel anode to pitting corrosion is enhanced with increasing halide anion concentration and is decreased with increasing pH of solution. The aggressiveness of the halide anions towards the stability of the passive film decreases in the order: Cl^– > Br^– > I^–. The addition of increasing concentrations of tungstate, chromate, or molybdate anions causes a shift of the breakdown potential in the noble direction, indicating the inhibitive action of the added anions. The inhibiting tendency of these anions decreases in the order: WO₄^2– > CrO₄^2– > MoO₄^2–.     

Interfacial electrochemistry and electrodeposition from some ionic liquids: In situ scanning tunneling microscopy, plasma electrochemistry, selenium and macroporous materials

In this paper we report on recent results from our group, namely on the interface ionic liquid/electrode, plasma electrochemistry and electrodeposition of selenium and of macroporous structures. Ionic liquids show an interesting and liquid dependent surface chemistry: in some liquids the long range “herringbone” superstructure of Au(1 1 1) is visible, in others it is not. Glow discharge plasmas can be employed as a contact free electrode to make nanoparticles in solutions, e.g. nanoparticles of germanium. Selenium can be electrodeposited from ionic liquids under environmental conditions in an open cell and both the red and the grey phases of selenium are feasible. With the help of self organized opal structures of polystyrene spheres macroporous materials of Ag, Al and conducting polymers can be made. The prospects and limits of ionic liquids in surface electrochemistry and electrodeposition are shortly discussed.     

Ab initio characterization of Ti decorated SWCNT for hydrogen storage

Characterization has been performed on basis of several physicochemical parameters. The results indicate that the preferential adsorption is on Ti atom deposited on the top site of the (5,5) armchair SWCNT with energies (−0.44 and −0.71) eV for H₂ oriented parallel to the (x) and (y) axes respectively. The binding of H₂ is mostly dominated by the support-metal E (i)^S?Ti term. The role of the SWCNT is not restricted to support the metal. Significant reduction of the energy gap is observed when H₂ are anchored on the external surface of the SWCNT. The SWCNT?Ti?H₂(x) complex is the least reactive configuration with nucleophiles. The calculated parameters characterize H₂ that is oriented parallel to the (x)-[100] axis of the SWCNT to be the most suitable configuration for hydrogen storage based on the recommended adsorption energy range of DOE (−0.2 to −0.6) eV.     

New smart conducting elastomer blends of Bi‐based superconductor ceramics nanoparticles reinforced natural rubber/low‐density polyethylene for double thermistors,antistatic protectors,and electromagnetic interference shielding effectiveness applications

A new conducting blend from natural rubber (NR), low‐density polyethylene (PE), and Bi‐based superconductor (BSCCO) nanoparticles was successfully formulated. Blends were prepared by means of an open two‐roll mill for five ratios (100/0, 90/10, 80/20, 70/30, and 60/40 NR/LDPE). The microstructures of the blends were examined in terms of scanning electron microscopy (SEM), bound rubber (BR), cross‐linking density (CLD), and Mooney viscosity (M₁₀₀). The mechanical properties like hardness (H) shore A, tensile strength (TS), and elongation at break (EB) of the blends were studied. The applicability of the blends as double thermistors, i.e., positive and negative coefficient of resistivity (PTCR/NTCR), was examined. The applicability of the blend for antistatic charge dissipation was also tested. Finally, electromagnetic interference response of conducting NR/PE‐filled BSCCO in the frequency range 1–12 GHz has been studied. Shielding effectiveness of the conducting blends in the microwave range 8–12 GHz shows an attenuation of 44–60 dB for PE ≤10 wt%. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Electrodeposition of CoMoP thin film as diffusion barrier layer for ULSI applications

CoMoP thin films were fabricated by electrodeposition technique from citrate based bath onto Cu sheets for the application as diffusion barriers and metal capping layers in the copper interconnect technology. The study focused on the effect of (NH₄)₆Mo₇O₂₄·4H₂O concentrations in the plating solution on the plating rate and chemical composition of the deposited layer. It was found that the Mo wt.% in the deposited layer increased from 13 to 22 wt.% with increasing (NH₄)₆Mo₇O₂₄·4H₂O concentration. The influence of deposition current density, solution pH and deposition temperature at certain (NH₄)₆Mo₇O₂₄·4H₂O concentration in the plating bath on the plating rate and chemical composition was studied. Polarization behavior of induced co-deposition of CoMoP at various electrolyte pH values was studied using cyclic voltammetry and chronoamperometry to estimate the current efficiency (CE%) of the plating solutions and the optimum pH for the plating process. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques have been applied to characterize the morphology and chemical composition of the deposited layer. CoMoP alloys of high P wt.% as-deposited films showed irregular microcracks amorphous structure and of low P wt.% showed amorphous/nanocrystalline structure while, after annealing at 400 °C for 1 h, the films deposited with low and high P wt.% converted into polycrystalline structure. The results of oxidation property showed that, the Co-13.2 wt.% Mo-10.3 wt.% P alloy has highest stability against oxidation and lowest electrical resistance values (100-150 µΩ). The ferromagnetism nature of coated materials has been studied by hysteresis loop measurements. The electrochemical corrosion results were calculated from polarization studies for as-plated and annealed CoMoP coatings in 3.5% NaCl solution.