Stearic Acid Modified Stearyl Alcohol Oleogel: Analysis of the Thermal,Mechanical and Drug Release Properties

The present study delineates the effect of stearic acid on the properties of stearyl alcohol oleogel. Herein, a series of oleogels were prepared by mixing different proportions of fatty alcohol (Stearyl alcohol; gelator) and fatty acid (stearic acid; co‐gelator). The characterization of the oleogels was done by thermal, macro‐scale stress relaxation, drug release, and antimicrobial studies. The oleogels were formed by the self‐assembly of stearyl alcohol/stearic acid. Thermal studies indicated that the stearic acid alters the crystal morphology, polymorphic transition and rate of crystallization of stearyl alcohol. The firmness of the oleogels with higher stearic proportion was better, which was due to the formation of a rigid network structure of stearyl alcohol in the presence of stearic acid. The release of ciprofloxacin hydrochloride, model drug, from the oleogels was better from the oleogels with higher stearic acid content. The release of the drug from the oleogels was Fickian diffusion‐mediated; except the oleogel with the highest stearic acid proportion. The antimicrobial study showed that the drug loaded oleogels were able to resist the growth of Escherichia coli, model microbe.     

Sunflower Acid Oil-Based Production of Rhamnolipid Using Pseudomonas aeruginosa and Its Application in Liquid Detergents

Utilization of industrial waste as substrates for the rhamnolipid synthesis by Pseudomonas aeruginosa is a worthy alternative for conventionally used vegetable oils and fatty acids to reduce the production cost of rhamnolipid. Sunflower acid oil (SAO), a by-product of the oil industry, contains 70% 18:0 fatty acid, with oleic acid as a major component. In this scope, production and analysis of rhamnolipid was successfully demonstrated using SAO as a new substrate. Pseudomonas aeruginosa produced rhamnolipid (a glycolipid biosurfactant) at a maximum concentration of 4.9 g L⁻¹ with 60 g L⁻¹ of SAO in the medium. Structural properties of rhamnolipid biosurfactant are confirmed using thin layer chromatography (TLC), high performance liquid chromatography (HPLC), and fourier transformed infrared spectroscopy (FTIR) analysis. Further surface-active properties of the crude rhamnolipid were evaluated by measuring surface tension and emulsification properties. The synthesized rhamnolipid reduced the surface tension of water to 30.12 mN m⁻¹ and interfacial tension (against heptane) to 0.52 mN m⁻¹. Moreover, rhamnolipid shows the highest emulsification index (above 80%) for vegetable oils. This study confirms the use of SAO as a potential substrate for rhamnolipid production. The synthesized rhamnolipid was incorporated in liquid detergent formulation along with alpha olefin sulfonate (AOS) and sodium lauryl ether sulfate (SLES). The performance properties including foaming and cleaning efficiency of liquid detergent were compared.     

α-Alumina and spinel react into single-phase high-alumina spinel in <3 seconds during flash sintering

In situ X-ray diffraction measurements at the Advanced Photon Source show that α-Al₂O₃ and MgAl₂O₄ react nearly instantaneously and completely, and nearly completely to form single-phase high-alumina spinel during voltage-to-current type of flash sintering experiments. The initial sample was constituted from powders of α-Al₂O₃, MgAl₂O₄ spinel, and cubic 8 mol% Y₂O₃-stabilized ZrO₂ (8YSZ) mixed in equal volume fractions, the spinel to alumina molar ratio being 1:1.5. Specimen temperature was measured by thermal expansion of the platinum standard. These measurements correlated well with a black-body radiation model, using appropriate values for the emissivity of the constituents. Temperatures of 1600-1736°C were reached during the flash, which promoted the formation of alumina-rich spinel. In a second set of experiments, the flash was induced in a current-rate method where the current flowing through the specimen is controlled and increased at a constant rate. In these experiments, we observed the formation of two different compositions of spinel, MgO•3Al₂O₃ and MgO•1.5Al₂O₃, which evolved into a single composition of MgO•2.5Al₂O₃ as the current continued to increase. In summary, flash sintering is an expedient way to create single-phase, alumina-rich spinel.     

Reactive flash sintering: MgO and α-Al2O3 transform and sinter into single-phase polycrystals of MgAl2O4

We show that flash experiments with three phase mixed-powders of yttria-stabilized zirconia (8YSZ), MgO, and α-Al₂O₃ not only produce polycrystals of high density, but also the transformation of magnesia and alumina into single-phase spinel. The presence of zirconia facilitates the onset of the flash. The sintering experiments in the laboratory were extended to live experiments at the National Synchrotron Light Source II at Brookhaven National Laboratory in order to measure the time-dependent evolution of single-phase spinel. The phase transformation occurred in <3 seconds during Stage II. Later, during Stage III the cubic zirconia transformed partly into the monoclinic phase, which reverted back to the cubic phase when the flash was extinguished by turning off the current to the specimen. The results underpin a recent report on the synthesis of single-phase bismuth ferrite from constituent oxides in reactive flash experiments, raising the specter of flash as a method for synthesis as well as sintering of complex oxide ceramics. The role of zirconia in catalyzing the flash in the present study is discussed.     

Enhanced magnetoelectric properties in Bi0.95Ho0.05FeO3 polycrystalline ceramics

Polycrystalline samples of Ho doped BiFeO₃ were prepared by solid state reaction method and effect of partial substitution of Ho on dielectric, magnetic and ferroelectric properties was studied. High temperature dielectric results show two dielectric anomalies both in ? and tan δ, out of which, anomaly at higher temperature (∼400 °C) could be ascribed to antiferromagnetic Néel temperature which, is a signature of magnetoelectric coupling. The magnetic moment is greatly improved and the maximum magnetization was found to be 0.736 emu/g. Saturated ferroelectric hysteresis loops were observed for Bi_0.95Ho_0.05FeO₃ with remnant polarization (P_r) = 1.59 μC/cm², maximum polarization (P_max) = 2.56 μC/cm² and coercivity (E_c) = 5.45 kV/cm. We have conducted comprehensive magnetoelectric and magnetodielectric properties at room temperature. Magnetic field induced ferroelectric hysteresis loop observed in Bi_0.95Ho_0.05FeO₃ is of prime importance.     

Alkylation of hydroquinone with methyl-tert-butyl-ether and tert-butanol

The alkylation of hydroquinone yields industrially important compounds, amongst which tert-butylhydroquinone is a very important precursor for its use in pharmaceuticals and in developing photographic plates. Twenty per cent (w/w) dodecatungstophosphoric acid supported on K10 montmorillonite clay (DTP/K10) was found to be a very efficient and novel catalyst in comparison with several others for alkylation of hydroquinone with different alkylating agents such as methyl-tert-butyl-ether (MTBE) and tert-butanol at 150°C in an autoclave. A summary of characterisation of DTP/K10 is provided and related to the activity. Various reaction parameters were also investigated and a kinetic model was built. The rate of alkylation with MTBE was much faster than that with tert-butanol. The reaction follows a typical second order kinetics at a fixed catalyst loading with weak adsorption of both the species. The energy of activation was found to be 19.34 kcal/mol.     

Selectivity engineering in the O‐ versus C‐alkylation of p‐cresol with cyclohexene over sulfated zirconia

Solid acids are more widely used as heterogeneous catalysts, because they are eco‐friendly. This paper reports the results for the Friedel‐Crafts alkylation of p‐cresol with cyclohexene using solid acids sulfated zirconia, 20% w/w dodecatungstophosphoric acid (DTP) supported on K10 clay and ZnCl₂/K10 (Clayzic). This reaction gave substantial amount of 1‐cyclohexyloxy‐4‐methyl benzene (O‐alkylated product) and 4‐cyclo‐hexyl‐4‐methyl phenol (C‐alkylated product). Both products are of commercial importance as perfume and insecticide respectively. Sulfated zirconia catalyst was shown to be better than others studied in terms of activity and selectivity to the O‐alkylated product. The kinetics were studied with sulfated zirconia as catalyst where the rate determining step was the surface reaction between chemisorbed cyclohexene and p‐cresol from the liquid phase within pores according to the Eley‐Rideal mechanism. The production of O‐alkylated p‐cresol is favoured at lower temperatures and C‐alkylated product at higher temperatures. The best operating temperature is 353 K. The activation energies for O‐ and C‐alkylation are 72.68 and 118.28 kj/mol, respectively.     

Synergistic effect of some antiscalants as corrosion inhibitor for industrial cooling water system

In order to study synergistic effect, various combinations of antiscalants 1-hydroxyethane-1,1-diphosphonic acid (HEDP), sodium hexametaphosphate (SHMP), sodium tripolyphosphate (STPP), and trisodium phosphate (TSP), were investigated as corrosion inhibitors for carbon steel. Corrosion rate and percentage inhibition efficiency of various combinations of antiscalants as corrosion inhibitors (20/80, 40/60, 60/40, 50/50, 80/20, and 100 ppm of different combinations of HEDP, SHMP, STPP, and TSP) in synthetic cooling water VI (692 ppm of Cl⁻ ions) was determined by weight loss, electrochemical polarization technique, and metallurgical microscopy technique. It was observed that a 50/50 ppm combination of HEDP and SHMP gave 98% corrosion inhibition efficiency and maximum synergistic effect. The percentage inhibition efficiency of HEDP when mixed with other antiscalants as corrosion inhibitors at 50/50 ppm concentration was found in the following order HEDP/SHMP > HEDP/STPP > HEDP/TSP. The synergistic effect of HEDP/SHMP combination is due to intermolecular hydrogen bonding between the molecules of HEDP and SHMP, which results in the adsorption of uniform multilayered two-dimensional film of –HEDP–SHMP– molecules on carbon steel surface.     

Selectivity engineering in the nitration of chlorobenzene using eclectically engineered sulfated zirconia and carbon molecular sieve catalysts

Selective synthesis of the para‐nitro derivative from chlorobenzene by using nitric acid over an eclectically engineered sulfated zirconia carbon molecular sieve catalyst is reported. The p : o ratio in chlorobenzene nitration was found to be very high with eclectically engineered sulfated zirconia and carbon molecular sieve catalyst. This revised version was published online in July 2006 with corrections to the Cover Date.     

Newspaper-reinforced plastic composite laminates: Mechanical and water uptake characteristics

Several useful composite materials have been developed with natural fiber and plastic matrices, and their commercial viability has been established in terms of adding value to abundant and cheap natural resources. The Macromolecular Research Centre, Jabalpur, India, has recently developed composite from waste newspaper reinforced with plastic material using a prepreg technique wherein the matrix resin consists of resol type phenolic resin (PR) and bifunctional epoxy resin (EP) condensate. Laminates of newspaper and PR-EP condensate were prepared by hot press molding, and the newspaper weight fraction in these composites was varied from 0.30 to 0.65. The mechanical properties of five selected newspaper (PR-EP) condensate composites are reported for parameters such as ultimate tensile strength, elongation, tensile modulus, flexural strength and modulus, and heat deflection temperature (HDT). The water uptake behavior of these composites was examined by constructing water absorption isotherms, and the water diffusion coefficient and water absorption (24 h soak test) were determined. The specific tensile and flexural strengths and modulus properties of newspaper-(PR-EP) condensate composites are found comparable with one prepared elsewhere from recyclable newspaper-reinforced polypropylene thermoplastics.