Volume 2 Issue 2
Authors: Juan F. Rodríguez; Manuel Carmona; Antonio de Lucas; Ángela Alcázar; Angel Perez
Abstract: Microcapsules from P(St-EGDMA) and P(St-DVB) containing di(2-ethylhexyl) phosphoric acid (DEHPA) as core material has been prepared by suspension-like polymerization technique by using two different recipes. These materials were synthesized by using percentage mass ratios of 0.1 wt.% and 18.6 wt.% for EGDMA/St and DVB/St, respectively. Toluene was required as diluent to produce microcapsules from P(St-DVB) due to the high reactivity of the crosslinking monomer (DVB) since polymerization reaction without toluene yielded to compacted block. Microcapsules containing DEHPA were obtained using the above shell materials having a smooth and spherical shape, a particle size in the range of those reported for commercial resins but the amount of encapsulated DEHPA was larger when P(St-DVB) was used, 34.86 wt.% respect to the 28.15 wt.% obtained for the P(St-EGDMA). Attending to this higher DEHPA content, P(St-DVB) was selected as shell material to develop microcapsules combining the advantages and capabilities of the ion exchange and the solvent extraction technologies. Once the extractant agent has been encapsulated, different sulfonation agents -chlorosulfonic and sulfuric acid- and the applicability of swelling agents to minimize the sulfonation treatment impact on the microcapsules were carried out to attribute them ion exchange properties. Swelling agents release the DEHPA from the microcapsules whereas the chorosulfonation treatment leads to a cracked material. Thus, the effect of the sulfonation by sulfuric acid on DEHPA and sulfur contents and swelling degree of microcapsules as function on the particle size was studied. Sulfonation results showed that sulfuric acid at 50ºC did not damage the microcapsules but it had big influence on the DEHPA content. Results showed that sulfur and swelling increased whereas the DEHPA decreased in a linear way with the sulfonation time. From the slopes of these curves, it was found that sulfonation process was dependent on the particle size and DEHPA was less released from particles having a particle size of 500 m and incorporating an enough amount of sulfonic groups in the shell material (-6.43 gDEHPA/gS). Besides, attending to the low sulfonation required for this material, a maximum time of 20 min is recommended to introduce a 30% of the sulfonic groups commonly found in commercial resins.
Keywords: Microcapsules; Extractant Agent; Sulfonation; Suspension-Like Polymerization; Heavy Metals
Authors: Farhad Fazllolahi; Mortaza Zivdar; Mohammad Mehdi Zarei; Majid Sarkari; Hossein Atashi; Larry L Baxter
Abstract: In this study, results of revamping of stabilizer unit of a refinery which includes a debutanizer, and a splitter column, are presented. The products of the unit are light straight run gasoline (LSRG) and Heavy straight run gasoline (HSRG). Revamping has been carried out by commercial software. Results of simulation illustrate that revamping by structured packings is an effective method for capacity increase while maintain product quality at the same time. Debutanizer and splitter units have been simulated with regard to inlet and outlet flow rates, flooding, operating pressure and temperature. The simulation results are in good agreement with the operating data and experimental analysis. By using MELLAPAK 250X, as a structured packing in revamping process, pressure drop was decreased from 196 to 23 mbar. In addition, Sichlmair model has predicted the pressure drop very accurately. The results also demonstrate 31% capacity increase in feed flow rate and higher quality product.
Keywords: Stabilizer; Distillation; Capacity; Revamp; Structured Packing
Authors: T. K. Chondhekar; Sunil G. Shankarwar; Sarika M. Jadhav; Vinod A. Shelke
Abstract: The solid complexes of La(III), Ce(III), Pr(III), Nd(III), Sm(III) and Gd(III) with asymmetrical tetradentate Schiff bases derived from 4-methyl-o-phenylenediamine, 3-Acetyl-6-methyl-pyran-2,4-dione and 2-hydroxy-1-naphthaldehyde have been synthesized and characterized by elemental analysis, conductometry, magnetic susceptibility, UV-visible, FTIR, 1H-NMR spectra, X-ray diffraction, thermal analysis and screened for antimicrobial activity. The IR spectral data suggest that the ligand behaves as a dibasic tetradentate ligand with ONNO donor atoms sequence towards central metal ion. From the microanalytical data, the stoichiometry of the complexes has been found to be 1:1 (metal: ligand). The X-ray differaction data suggest tetragonal crystal system for La(III) complex and orthomboic crystal system for Ce(III) complex. Thermal behaviour (DSC/TGA) of the complexes was studied and kintic parameters were determined by Horowitz-Metzger and Coats-Redfern method. The ligand and their metal complexes were screened for antibacterial activity against Staphylococcus aureus and Escherichia coli and fungicidal activity were tested against Aspergillus Niger and Trichoderma.
Keywords: Dehydroacetic Acid; Unsymmetrical Tetradentate Schiff Base; Rare Earth Metal Complexes; Thermal Analysis; Antimicrobial Activity
Authors: Kundan Singh Shekhawat; D K Sharma
Abstract: Calcium bis-(E)-3,5-dihydroxy-7-[4’-(4’’-flurophenyl)-2’-cyclopropyl-quinoline-3-yl]-hept-6-enoate 1 a HMG-CoA reductase inhibitor via novel acetonide intermediate 2, were synthesized. The operational simplicity, high purity, eco-friendly conditions and easily scalable process are major benefits of this process. The starting material 3 employed for the preparation were synthesized by known literature method[1].
Keywords: Acetonide; HMG-CoA Reductase; Pitavastatin Calcium; Deprotectio; Hydrolysis
Authors: Dennis N. Kevill; Jin Burm Kyong; Kyoung-Ho Park; Mi Hye Seong
Abstract: The specific rates of solvolysis of neopentyl fluoroformate (NeopOCOF, 1) have been measured at 45.0 oC in pure and binary solvent mixtures. These results correlated well with the extended Grunwald-Winstein equation in all of the solvents except the four TFE-ethanol binary solvents. Leaving group effects (kF/kCl values) and sensitivity (l and m values) to changes in solvent nucleophilicity and solvent ionizing power are appreciably similar to those observed previously for the solvolyses of primary and secondary alky haloformates. This is consistent with the addition-elimination pathway as rate-determining. The kinetic solvent isotope effects (KSIEs, kMeOH/kMeOD) and activation parameters for the solvolyses of 1 were also determined. The results are compared with those reported earlier for neopentyl chloroformate (NeopOCOCl, 2) and other alkyl haloroformate esters.
Keywords: Neopentyl Fluoroformate; Grunwald–Winstein Equation; Leaving Group Effect; Solvolytic Reaction; Addition-Elimination Pathway
Authors: Nonthaphong Phonphuak
Abstract: This research studies physical, mechanical and thermal properties of fired clay bricks due to the effects of charcoal addition. Thermal performance with the physical, mechanical and microstructures properties were also investigated. All samples were fired at 950 oC. The results indicated that the density of fired clay bricks was reduced by up to 10 wt%, depending on the percentage of charcoal incorporated into the raw materials. Compressive strength of fired clay bricks samples decreased according to the percentage of charcoal included in the mix. When the percentage of charcoal was up to 10 wt%, water absorption and apparent porosity was rapidly increased. It was apparent that as the percentage of charcoal increased in the body, the porosity was clearly observed. From the results, it can be reduced that thermal conductivity decreases with decrease in density and increase in fired clay bricks porosity.
Keywords: Brick; Porosity; Compressive Strength; Density; Charcoal
Authors: Yaroslav О. Shablovsky
Abstract: A thermodynamical approach to the analytical description of transitions “non-plastic phase – plastic phase” in organic crystals is proposed. An analytical expression for temperature dependence of heat capacity is obtained. It is shown that unlike “pre-transitional” anomalies commonly observed at structural (polymorphic) transformations, the influence of plasticization on elastic properties of organic crystals amounts to nothing more than abrupt changes of these properties in the plasticization point. Baric dependence of the plasticization temperature is found. Available thermodynamical data on adamantane, 1-aminoadamantane, and pentaerythrityl fluoride are analyzed.
Keywords: Organic Crystals; Crystal Mesomorphism; Plastic Crystal; Plastic Crystalline Phase; Thermodynamic Properties
Authors: Wei-qiang Pang; Xue-zhong Fan; Wei Zhang; Hui-xiang Xu; Ning Yan; Wu-xi Xie; Fang-li Liu; Shu-xin Wu
Abstract: Ammonium dinitramide (ADN), NH4N(NO2)2, can be used in the smokeless composite propellants by replacing AP. It is being considered as one of the most potential energetic oxidizers for propellants. The physical chemistry characteristics of ADN were investigated. The energetic performances, burning characteristics at various pressure ranges, mechanical sensitivity and SEM surfaces observation of HTPB-based propellant with ADN were determined and detected in details. The calculated results showed that the specific impulse and the adiabatic flame temperature are increasing with an increase in the content of ADN. The burning rate and pressure exponent of propellant with a change of pat content of ADN can be boosted higher than those of the AP formulations. The surface structures of composite propellants were little affected by the content of ADN.
Keywords: Composite Propellants; ADN; Thermal Decomposition; Energetic Property; Mechanical Sensitivity; Combustion Characteristics
Authors: Kunigal Shivakumar; Paul Akangah
Abstract: Polymer nanofiber interleaving is a novel technology to enhance toughness of composite laminates. This paper focuses on the comparison of low velocity impact damage resistance and tolerance of base (no interleaving) and polymer nanofiber interleaved composite laminates. A 24-ply aerospace grade AS4/3501-6 Carbon/Epoxy laminate was made in an autoclave. The interleaved laminate was made by placing a layer of Nylon-66 nanofiber between the adjacent plies and at the top and bottom of the laminate. The nanofabric was made by electrospinning 12% wt. of Nylon-66 solution made by dissolving Nylon-66 crystals in a mixture of 90% formic acid and chloroform in a weight ratio of 75/25, respectively. The average areal density of the fabric was 0.7 g/m2 and the AS4/3501-6 composite ply was 260 g/m2. Impacted panels were c-scanned and the measured damage of the two laminates was compared with each other. Compression was implemented to the specimens for impact test to measure the damage tolerance. Results showed that polymer nanofiber interleaving does have a potential to improve impact damage resistance and tolerance. Specifically, interleaving increased the threshold impact force by about 12% and the compression strength by about 10%.
Keywords: Nanofiber; Impact Damage; Impact Resistance; Interleaving