Effect of Nickel Nitrate Concentration on the Size of Nickel Oxide Nanoparticles Bio-synthesized by Artemisia herba-alba Aqueous Leaves Extract and Improving Their Antioxidant Activities

Journal of Inorganic and Organometallic Polymers and Materials - This work aims to investigate the effect of nickel nitrate concentration on the size and antioxidant activity of nickel oxide...     

Controlled release PVC membranes: Influence of phthalate plasticizers on their tensile properties and performance

The design of controlled release polymer dispensers (CRPD) for effective release of the active ingredients at desired rates requires a careful study and generation of data on several properties of the polymer membranes. Presence of optimum tensile properties is one of the prerequisites for the CRPD in deciding their suitability for application in the fields. Polyvinylchloride (PVC) membranes containing di n-alkyl phthalate (alkyl= methyl, ethyl, butyl&octyl) with concentrations ranging from 10–30% with an increment of 2.5% were prepared. The tensile strength and percent elongation of these membranes as a function of concentration of the phthalate plasticizers, their size and aging period were performed. An increase in the tensile strength with increasing phthalate content was noticed up to 17.5% phthalate. Then followed a decrease with further increase of phthalate content. In contrast, the percent elongation was observed to increase constantly with increased concentration of the plasticizer. The ambiguous increase in the tensile strength up to 17.5% plasticized films is attributed to the antiplasticization effect of the plasticizer. The properties showed a linear behavior with respect to the size of the alkyl chain length and also the period of aging. The membranes with 17.5% and 20% were found to have optimum tensile properties and good property retention with aging for their application in controlled release of agrochemicals.     

Ionic liquids as novel surfactants for potential use in enhanced oil recovery

The screening and use of benign chemicals for enhanced oil recovery (EOR) applications is important because of their properties and relationship to the embedded fluids. We investigated a special type of ionic liquids (ILs) called “Ammoeng” for potential use in surfactant EOR to replace the currently used surfactants that have many disadvantages. The interfacial tension (IFT) between a representative oil sample from Saudi reservoirs and solutions of Ammoeng? ILs at different concentrations in 10 wt% NaCl aqueous solutions were measured as a function of temperature. It was found that the IFT values decreased with the increase of IL concentration. However, the effect of temperature on the IFT depended on the type of IL. Ammoeng? 102 gave the lowest IFT values among the screened ILs. The comparison of the results to those resulting from TritonX100, a commercially used surfactant, showed that the IFT values using Ammoeng? 102 were smaller than the corresponding values when TritonX100 was used at the same conditions. The possibility of having a synergetic effect when using a mixture of Ammoeng? 102 and Triton X 100 was also investigated. The results showed that the IFT values depended on the total concentration, the surfactant to IL mass ratio, and the temperature.     

Reverse Calculation of Pressure from Pseudopressure

Since the notation of pseudo pressure was introduced by Al-Hussainy and Ramey, the reverse calculation of pressure from its complementary pseudo pressure has become important. Up to the present time, the common way to do such a calculation has been to use a table of values. In this paper, a new technique is proposed for reverse calculation of pressure which employs the Newton-Raphson iterative method. In order to be practical, the iterative method is used in conjunction with an efficient method for pseudo pressure calculation. The proposed model is checked and its efficiency and practical applicability is evinced.     

Dielectric properties of copolymers based on cyano monomers and methyl α‐acetoxyacrylate

With the aim of developing dielectric polymers containing CN groups with strong dipole moment, alternating and statistical copolymers of the cyano monomers vinylidene cyanide (VCN), acrylonitrile and methacrylonitrile with methyl α‐acetoxyacrylate (MAA) were synthesized and characterized. The copolymer's composition and microstructure were analysed by NMR spectroscopy, SEC and elemental analysis. The reactivity ratios calculated from the Q–e Alfrey–Price parameters for these copolymers indicated the alternating and statistical structures confirmed by NMR analysis. The copolymers have glass transition temperatures T_g in the range 83–146 °C and are stable up to 230 °C. The thermal stability of the copolymers depends on the nature of the cyano monomers. Their molecular dynamics were investigated by dielectric relaxation spectroscopy. We revealed a weak relaxation β at sub‐T_g temperature for poly(VCN‐co‐MAA) usually originating from molecular motions that are restricted to the scale of a few bond lengths. Strong α‐relaxation processes occurred above T_g for these copolymers. This primary relaxation was associated with cooperative movements of the polar groups (CN) at the time of mobility of the principal chains. The activation energy of the α‐relaxation process was also calculated. The values of the dielectric increment Δε for these copolymers were determined by Cole–Cole plots and indicated that the copolymers exhibit interesting dielectric properties compared with similar cyano materials. The polarity–permittivity relationship was also established. © 2012 Society of Chemical Industry     

Morphological,electrical and electromagnetic interference shielding characterization of vapor grown carbon nanofiber/polystyrene nanocomposites

The influence of melt mixing conditions on the level of dispersion and the aspect ratio of vapor grown carbon nanofibers (VGCNFs) in a polystyrene (PS) matrix was studied. Final electrical and electromagnetic shielding capabilities in the 0.05–1.5 GHz frequency range are reported and discussed in the light of the composites' microstructure. The morphological study was based on analyzing scanning electron microscopy and optical microscopy micrographs and measuring the VGCNF length as a function of shear mixing conditions. The influence of mixing conditions on the microstructure was also indirectly studied by analyzing the dynamic mechanical behavior of the composites via rheology. Degradation of the VGCNF aspect ratio was found to be a function of the mixing energy. VGCNFs lost one‐third of their aspect ratio under gentle (low shear stress and mixing energy) mixing conditions. After VGCNFs had lost 40% of their aspect ratio, they had more resistance to breakage with increase in mixing energy. The dispersion of the VGCNFs was remarkably enhanced with increase in mixing energy. The percentage of area taken up by big agglomerates in the micrographs decreased from 14.1% to 5.5% when the mixing energy was increased from 100 J mL^?1 to 453 J mL^?1. The electrical and electromagnetic shielding properties of the 7.5 vol% VGCNF/PS composites were not affected by changing the processing energy because the enhancement of VGCNF dispersion with increasing mixing energy was accompanied by a loss in nanofiber aspect ratio. © 2012 Society of Chemical Industry     

Weibull statistics in electrical aging of polyesterimide under AC voltage

This article is aimed at the investigation of electrical aging of polyesterimide under AC voltage using Weibull statistical analysis. It's shown that the time to breakdown characteristic (V–t) of polyesterimide includes two zones (segments of straight line). The first zone characterizes a statistical dispersion of the intrinsic defects of material. The second zone expresses the real aging of polymer. The variation of the slope of lifetime curve is attributed to the change in the degradation mechanism. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Combustion synthesis of single-phase β-sialons (z = 2–4)

Single-phase β-sialon powders (z = 2–4) have been prepared with homogeneous compositions by the combustion synthesis. The raw materials (Si, Al and SiO₂) were combusted under N₂ pressure of 1 MPa. Without using a diluent, the reaction temperatures were very high (>2000 °C) and the combustion products contained Si and Al residues. With addition of commercial β-sialon (z = 1) as a diluent (up to 50 wt%), both the reaction temperatures and amount of residual Si and Al significantly decreased. The combustion reactions completed at 50 wt% dilution, and pure β-sialon phases were synthesized. When the combustion product itself is used instead of the commercial diluent, the phase content of desired z value increased with the repetition times until a single-phase powder is produced. The sinterability of the synthesized powders was then tested using 5 wt% Y₂O₃ as a sintering aid by the spark plasma sintering (SPS).