Prins Cyclization of Styrenes or Acetophenone Catalyzed by DBSA in Water

Dodecylbenzenesulfonic acid (DBSA) was proved to be an efficient catalyst for Prins cyclization of styrenes and formaldehyde or acetaldehyde in water. A tandem dehydration/Prins cyclization reaction using a tertiary alcohol and formaldehyde as substrates proceeded very well by using DBSA as catalyst. Acetophenone, which is less reactive compared with styrene, can also react with formaldehyde when catalyzed by DBSA in water to afford 1,3-dioxan-5-ylphenylmethanone in good yield.     

Spectroscopic reflectometry as in‐operando method for thickness determination of anodic oxide films on titanium

The present work focuses on the development of an in‐operando technique based on the visible spectroscopic reflectometry (VSR) for simultaneous determination of the oxide film formation during anodizing. The establishment of the VSR as in‐operando technique requires an extensive validation by comparative in‐situ but non‐operando thickness measurements under aqueous conditions. The investigations were carried out on anodic oxide films on pure titanium. The authors demonstrate the VSR as a simple and robust method for measurement under electrolyte covering. Additionally, an empirical correction algorithm extends the limitation of the visible reflectometry in thin film thickness. Reliable film thickness values can be measured down to ≥5 nm. The in‐operando mode yields additional information about the film growth time resolved. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of ethylene-co-vinyl acetate-glycidylmethacrylate and cellulose microfibers on the thermal,rheological and biodegradation properties of poly(lactic acid) based systems

The properties and biodegradation behavior of blends of poly(lactic acid) (PLA) and ethylene-vinyl acetate-glycidylmethacrylate copolymer (EVA-GMA), and their composites with cellulose microfibers (CF) were investigated. The blends and composites were obtained by melt mixing and the morphology, phase behavior, thermal and rheological properties of PLA/EVA-GMA blends and PLA/EVA-GMA/CF composite films were investigated as a function of the composition. The disintegrability in composting conditions was examined by means of morphological, thermal and chemical analyses to gain insights into the post-use degradation processes. The results indicated a good compatibility of the two polymers in the blends with copolymer content up to 30 wt.%, while at higher EVA-GMA content a phase separation was observed. In the composites, the presence of EVA-GMA contributes to improve the interfacial adhesion between cellulose fibers and PLA, due to interactions of the epoxy groups of GMA with hydroxyls of CF. The addition of cellulose microfibers in PLA/EVA-GMA system modifies the rheological behavior, since complex viscosity increased in presence of fibers and decreased with an increase in frequency. Disintegration tests showed that the addition of EVA-GMA influence the PLA disintegration process, and after 21 days in composting conditions, blends and composites showed faster degradation rate in comparison with neat PLA due to the different morphologies induced by the presence of EVA-GMA and CF phases able to allow a faster water diffusion and an efficient PLA degradation process.     

Influence of oxygen flow rate on the surface chemistry and morphology of radio frequency (RF) magnetron sputtered zinc oxide thin films

Zinc oxide thin films were deposited, by radio frequency magnetron sputtering, on heated and unheated substrates. The oxygen flow rate was varied during deposition, and its effects on the structural and chemical properties of the films were investigated. The films had oriented c‐axis growth with nano‐crystallite size. Their surfaces manifested columnar microstructure, with a surface roughness that was suppressed by the introduction of oxygen. Chemical analysis showed that deposition under an oxygen atmosphere resulted in substantial reduction of oxygen vacancies, with a corresponding incorporation of chemisorbed species. Copyright © 2013 John Wiley & Sons, Ltd.     

A correlation between the variable melt flow index and the molecular mass distribution of virgin and recycled polypropylene used in the manufacturing of battery cases

This study looked at establishing a correlation between the variable melt flow index (VMFI) values of molten polypropylene (PP) with different piston-load masses using a standard MFI analyser. The study was done using virgin PP and recycled PP obtained from recycling Pb-acid batteries. The study showed that the results would fit a suitable power function equation where the size of the exponent reflects the increase in flow characteristics of the polymer with increased piston-load mass. The established correlation was then compared to the average molecular weight distribution of virgin PP determined by gel permeation chromatography (GPC). Good agreement was obtained for the range of grades of virgin PP samples that correlated well with the Mark-Houwink power law where the inverse of the MFI (1/MFI) would be proportional to the average molecular weight to the power of 3.4 (Mw^3.4). GPC analysis cannot be effectively used to study recycled PP, where a number of factors can influence the melt flow properties such as fillers, impurities and the presence of polyethylene in the polymer matrix. Instead, a comparative understanding of the flow behaviour of recycled PP to that of virgin PP was done by using the VMFI method to possibly show the dissimilar polymer melt flow behaviour of using virgin and recycled PP material in injection moulding of new battery cases and lids, or when attempting to seal the lid to the battery case during manufacturing.     

MICELLE FORMATION BY ANIONIC AND CATIONIC SURFACTANTS IN AQUEOUS 18-CROWN-6 ETHER,P-CYCLODEXTRIN,AND 1,10-PHENANTHROLINE SOLUTIONS AT DIFFERENT TEMPERATURES

The conductances of sodium perfluorooctanoate (SPFO), sodium dodecylsulphate (SDS), dodecyltrimethylammonium bromide (DTAB), and tetradecyltrimethylammonium bromide (TTAB) in 18-crown-6 ether + water (CR+W), p-cyclodextrin + water (CY+W), and 1,10-phenanthroIine + water (Phen+W) mixtures with fixed 4 mM of each additive were determined over the temperature range of 5-55 °C. The conductivity plots for all the surfactants showed single break from which the critical micellization concentration (cmc) and degree of micelle ionization (x) were computed. From the pre and the post micellar slopes of the conductivity curves, the equivalent conductivities of the monomeric (Aass) and the micellar states (Amjc), respectively, were calculated and discussed with respect to the surfactant-additive complexation. It was observed that the micelle formation of all the ionic surfactants irrespective of the nature of their head groups were delayed in CYC+W in comparison to that in CR+W and Phen+W systems over the temperature range studied. The micelle formation of SPFO and SDS in CR+W and Phen+W systems showed stabilization of the respective micelles due to the adsorption of Na⁺-CR and Na+-Phen complexes at the micelle solution interface in comparison to that of DTAB and TTAB.     

Pressure Drop and Performance Characteristics of Water-Based Al2O3 and CuO Nanofluids in a Triangular Duct

An experimental study is performed to determine the pressure drop and performance characteristics of Al₂O₃/water and CuO/water nanofluids in a triangular duct under constant heat flux where the flow is laminar. The effects of adding nanoparticles to the base fluid on the pressure drop and friction factor are investigated at different Reynolds numbers. The results show that at a specified Reynolds number, using the nanofluids can lead to an increase in the pressure drop by 35%. It is also found that with increases in the Reynolds number, the rate of increase in the friction factor with the volume fraction of nanoparticles is reduced. Finally, the performance characteristics of the two nanofluids are investigated using the data of pressure drop and convective heat transfer coefficient. The results show that the use of Al₂O₃/water nanofluid with volume fractions of 1.5% and 2% is not helpful in the triangular duct. It is also concluded that at the same volume fraction of nanoparticles, using Al₂O₃ nanoparticles is more beneficial than CuO nanoparticles based on the performance index.     

Relationship Between the Polymer Structures and Destabilization of Polymer‐Containing Water‐in‐Oil Emulsions

The viscous properties, scanning electronic microscopy (SEM), and water/oil interfacial tension (IFT) of partially hydrolyzed polyacryamide (HPAM) and hydrophobically associating hydrolyzed polyacryamides modified with N‐dodecylacrylamide were studied with the objective of investigating the influence on destabilization of emulsions. As expected, the copolymers exhibit significant viscosity enhancing capacity and three‐dimensional network structures due to intermolecular hydrophobic associations, and also present high interfacial activities as the IFT decrease with increasing polymer concentration. As a result, the existences of copolymers increased both the viscosity of emulsions and the intensity of interfacial film, in which case slow down the diffusion of demulsifier molecules and enhance the stability of emulsions, finally, the separation of water from oil becomes more difficult.     

Synthesis of Some Additives and Study Effect of Gas Oil Composition on Flow Properties

Nine additives were prepared by esterification of dibasic acid (succinic, adipic, sebacic acid) and polyethylene glycol (Mol.wt.=600, 1000, 4000). These additives were characterized by infrared spectral analysis, average molecular weight and polydispersity index. Their influence on the depression of pour point for two type of paraffin gas oils (G1 and G2) were investigated, blends of paraffin gas oils G1 and G2 by different ratio, when their untreated and treated by additives were evaluated as pour point depressant in comparison with the original paraffin gas oils G1 and G2.

The effect of additive type and gas oil composition on wax crystal modification were studied using the photo micrographic analysis. Diethoxylate (eo=182) sebacate with blend gas oil No. 3 has achieved the best performance as pour point depressant. The photo micrographic analysis showed that, the wax morphology was greatly modified to fine dispersed crystals of compact size. A correlation between the pour point depression and the extent of wax modification was detected.     

Determination of Drop Sizes in Annular Gas/Liquid Flows in Vertical and Horizontal Pipes

Measurement of drop sizes play vital role in applications dealing with gas/liquid flow mixtures. In the present work, drop sizes in vertical and horizontal pipe flows were determined using Malvern 2600HSD system that applies laser diffraction method. From the analysis of the experimental data obtained at two different pipe orientations, two separate expressions were developed to determine Sauter mean diameter, d ₃₂. Except for the 20 m/s superficial gas velocity in vertical flow case, a good agreement was found between the developed expressions and the experimental data.