Solution and diffusion properties of cyclohexane,cyclohexanol, and cyclohexanone in poly(ethylene glycol) by inverse gas chromatography

The solution and diffusion properties of cyclohexane, cyclohexanol, and cyclohexanone in poly(ethylene glycol) (PEG) and crosslinked PEG have been studied in the temperature range of 368.15 to 403.15 K using inverse gas chromatography (IGC) technique. The infinite dilute activity coefficient (Ω) and diffusion coefficient (D) have been determined for the above solvent/polymer systems. Accordingly, several thermodynamic functions, the diffusion pre‐exponential factor, and activation energy have been attained. The results showed a decrease in Ω and an increase in D with rising temperature. The order of the relative magnitude of Ω and D of the solvents were explained by comparing their interactions with the polymer and their collision diameters, respectively. Moreover, Ω and D in crosslinked PEG were smaller than those in PEG at various temperatures. The analysis of Ω, the infinite dilute selectivity and capacity showed the possibility of using crosslinked PEG as an appropriate membrane material for the separation of cyclohexane, cyclohexanol, and cyclohexanone mixture. A thermodynamic study also implied that the solvent sorptions in the polymers were all enthalpically driven in the experimental range. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Liquid–solid mass transfer for cocurrent gas–liquid upflow through solid foam packings

This article presents the liquid–solid mass transfer characteristics for cocurrent upflow operated gas–liquid solid foam packings. Aluminum foam was used with 10, 20, and 40 pores per linear inch (PPI), coated with 5 wt % Pd on γ‐alumina. The effects of gas velocity (u_g = 0.1?0.8 m m s^?1) and liquid velocity (u_l = 0.02 and 0.04 m m s^?1) are studied using the Pd/Bi catalyzed oxidation of glucose. The volumetric liquid–solid mass transfer coefficient, k_lsa_ls, is approximately the same for 10 PPI and 20 PPI solid foams, ranging from 2 × 10^?2 to 9 × 10^?2 m m s^?1. For 40 PPI solid foam, somewhat lower values for k_lsa_ls were found, ranging from 6 × 10^?3 to 4 × 10^?2 m m s^?1. The intrinsic liquid–solid mass transfer coefficient, k_ls, increases with increasing liquid velocity and was found to be proportional to u. Initially, k_ls decreases with increasing gas velocity and after reaching a minimum value increases with increasing gas velocity. The values for k_ls range from 5.5 × 10^?6 to 8 × 10^?4 m m s^?1, which is in the same range as found for random packings and corrugated sheet packings. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Effect of microstructure on crazing onset in polyethylene under tension

The influence of microstructure on dilatation onset is analyzed in polyethylene (PE) under tension. Tests are performed by means of a video‐controlled testing system that gives access to true stress σ₃₃—true strain ε₃₃ curve and records volume strain ε_v during stretching. The results indicate that the strain ε (and the corresponding stress σ) from which viscoplastic dilatation begins depends on microstructural properties of PE. At microscopic scale, materials having a low ε are characterized by inhomogeneous deformation mechanisms leading to pronounced crazing phenomena in amorphous layers. On the contrary, materials having a high ε involve homogeneous deformation mechanisms that limit crazing. These observations are discussed on the basis of crystallinity and tie molecules density. A simple model predicting ε is developed from these microstructural aspects. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Development of a mechanistic model for biological nutrient removal activated sludge systems and application to a full‐scale WWTP

In wastewater treatment plants (WWTPs) the production of nitrite as an intermediate in the biological nutrient removal (BNR) process has been widely observed, but not been taken into account by most of the conventional activated sludge models yet. This work aims to develop a mechanistic mathematical model to evaluate the BNR process after resolving such a problem. A mathematical model is developed based on the Activated Sludge Model No.3 (ASM3) and the EAWAG Bio‐P model with an incorporation of the two‐step nitrification–denitrification, the anoxic P uptake, and the associated two‐step denitrification by phosphorus accumulating organisms. The database used for simulations originates from a full‐scale BNR municipal wastewater treatment plant. The influent wastewater composition is characterized using batch tests. Model predictions are compared with the measured concentrations of chemical oxygen demand (COD), NH‐N, NO‐N, NO‐N, PO‐P, and mixed liquid volatile suspended solids. Simulation results indicate that the calibrated model is capable of predicting the microbial growth, COD removal, nitrification and denitrification, as well as aerobic and anoxic P removal. Thus, this model can be used to evaluate and simulate full‐scale BNR activated sludge WWTPs. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Determination of crystallinity ratio and some physicochemical properties of poly(4‐methyl‐1‐pentene)

It was determined that the thermal stability of poly(4‐methyl‐1‐pentene) (P4MP) was maintained up to 424°C in an inert atmosphere by thermogravimetric analysis. The retention diagrams of ethyl acetate, tert‐butyl acetate, and benzene on P4MP were plotted at temperatures between 30 and 280°C by inverse gas chromatography (IGC) technique. Melting temperature of the polymer was determined as 230 and 239.5°C by IGC and differential scanning calorimetry (DSC), respectively. The percent crystallinity of P4MP was obtained from the retention diagrams at temperatures below melting point. The percent crystallinity obtained by IGC is in good agreement with the ones obtained by DSC. Then, specific retention volume, V, weight fraction activity coefficient, Ω, Flory‐Huggins polymer‐solvent interaction parameter, χ, equation‐of‐state polymer‐solvent interaction parameter, χ, and effective exchange energy parameter, X_eff of octane, nonane, decane, undecane, dodecane, tridecane, n‐butyl acetate, isobutyl acetate, isoamyl acetate with P4MP, were determined between 240 and 280°C by IGC. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Riemannian formulation and comparison of color difference formulas

Study of various color difference formulas by the Riemannian approach is useful. By this approach, it is possible to evaluate the performance of various color difference formulas having different color spaces for measuring visual color difference. In this article, the authors present mathematical formulations of CIELAB (ΔE), CIELUV (ΔE), OSA‐UCS (ΔE_E) and infinitesimal approximation of CIEDE2000 (ΔE₀₀) as Riemannian metric tensors in a color space. It is shown how such metrics are transformed in other color spaces by means of Jacobian matrices. The coefficients of such metrics give equi‐distance ellipsoids in three dimensions and ellipses in two dimensions. A method is also proposed for comparing the similarity between a pair of ellipses. The technique works by calculating the ratio of the area of intersection and the area of union of a pair of ellipses. The performance of these four color difference formulas is evaluated by comparing computed ellipses with experimentally observed ellipses in the xy chromaticity diagram. The result shows that there is no significant difference between the Riemannized ΔE₀₀ and the ΔE_E at small color difference, but they are both notably better than ΔE and ΔE. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2011;     

Hybrid organic/inorganic dendritic triblock copolymers: Synthesis,nanostructure characterization,and micellar behavior

A new class of amphiphilic dendritic ABA triblock copolymers, which is based on organic linear polyethylene oxide (PEO) and inorganic dendritic carbosiloxane (CSO) was synthesized. The strategy used in synthesizing these materials is based on divergent method using hydrosilylation‐alcoholysis cycles. The reaction conditions and structural features of dendrimers were analyzed by different physicochemical techniques such as: GPC, NMR, UV spectroscopy, DSC, and viscometry. The generational limit of dendrimer after the first generation, OSC‐D‐PEO‐D‐CSO, forced us to employ HSiCl₂CH₃ as branching reagent. Also further hydrosilylation of the third generation yielded an irregular structure species. Self‐assembling and morphological studies of first, OSC‐D‐PEO‐D‐CSO, and second, OSC‐D‐PEO‐D‐CSO, generations in aqueous medium were monitored by using fluorescence, TEM and DLS techniques. However, the dendritic block copolymer with third generation, OSC‐D‐PEO‐D‐CSO, could not be dispersed in aqueous phase. The diameters of denderitic micelles had a narrow distribution in the ranges of 69 and 88 nm, respectively. Although the micelles were stable even in first generation, partition equilibrium constants of pyrene and critical micelle concentration in both of dendritic micelles imply that the micellar behaviors of the supramolecules strongly depend on the hydrophobic block's size in which increasing generation effectively promoted the micelle formation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The effect of poly(vinyl alcohol) hydrolysis on the properties of its blends with nylon 6

An investigation of the properties of the blends of nylon 6 (PA6) and poly(vinyl alcohol) (PVA) with varying degrees of hydrolysis was conducted. A near disappearance of the characteristics of the α‐form PVA crystals, crystallization exotherms, and hydrogen‐bonded hydroxyl groups and the tensile properties originally associated with the PVA molecules of PA6_xPVA PA6_xPVA, and PA6_xPVA specimens was observed as the PVA contents of the specimens became equal to or less than their corresponding ‘‘critical’’ values at 16.7 wt%, 33.3 wt%, and 50 wt%, respectively. These results support the idea that PVA molecules are miscible with PA6 molecules to some extent at the molecular level as the PVA contents of the blends become equal to or less than their corresponding critical PVA contents. In this article, we have proposed the possible reasons accounting for these properties of the PA6_xPVA_y series specimens with a varying degree of hydrolysis. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Tailoring the Degree of Polymerization of Low Molecular Weight Cellulose

The degradation of cellulose to lmw samples with $\overline {DP} _{{\rm w}} $ varying from 15 to 130 is investigated. Cellulose samples prepared from the hydrolysis of regenerated cellulose fibers in dilute HCl possess $\overline {DP} _{{\rm w}} $ = 50. Applying homogenous degradation of microcrystalline cellulose in H₃PO₄ at RT for 3 weeks, samples with $\overline {DP} _{{\rm w}} $ = 35 and a PDI of 1.58 are obtained. Decreasing the hydrolysis temperature to 8 °C results in lmw cellulose with $\overline {DP} _{{\rm w}} $ > 70. Fractionation in DMA/LiCl provides samples with $\overline {DP} _{{\rm w}} $ = 12 to 130, together with a narrow molecular weight distribution. Detailed structural analysis by 2D NMR spectroscopy reveals that the prepared lmw celluloses are suitable as mimics for cellulose.

     

Effect of Processing Variables on the Morphology of Electrospun Poly[(lactic acid)‐co‐(glycolic acid)] Nanofibers

A systematic study of the effects of , flow rate, voltage, and composition on the morphology of electrospun PLGA nanofibers is reported. It is shown that changes of voltage and flow rate do not appreciably affect the morphology. However, the of PLGA predominantly determines the formation of bead structures. Uniform electrospun PLGA nanofibers with controllable diameters can be formed through optimization. Further, multi‐walled carbon nanotubes can be incorporated into the PLGA nanofibers, significantly enhancing their tensile strength and elasticity without compromising the uniform morphology. The variable size, porosity, and composition of the nanofibers are essential for their applications in regenerative medicine.

     

Quiescent crystallization of natural fibers–polypropylene composites

The effect of natural fibers (vetiver grass and rossells) on quiescent crystallization of polypropylene (PP) composites was analyzed in this study. Also, equilibrium melting temperature (T) of the composites was elucidated. Natural fiber‐PP composites showed lower T when compared to neat PP. Thermal analysis was performed via differential scanning calorimeter to study the crystallization kinetics. Natural fiber‐PP composites exhibited higher rate of crystallization than that of neat PP. Furthermore, spherulitic growth rate and transcrystallinity of the composites were investigated under a polarized light optical microscope. It was found that the growth rates of the composites were lower than that of neat PP. The spherulitic growth rates combined with the crystallization rates were used to calculate number of effective nuclei. It was shown that the number of effective nuclei of the composites was higher than that of neat PP. This suggested that natural fibers could act as a nucleating agent in the composite. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Two‐dimensional electrolyte nature of exfoliated montmorillonite nanoplatelets fabricated by soap‐free emulsion polymerization and their affinity for cations

Montmorillonite (MMT) nanoplatelets, fabricated by the exfoliation of MMT during participating in the soap‐free emulsion polymerization of methyl methacrylate, were well‐dispersed in water and performed like a two‐dimensional electrolyte. Their ionic conductivity roughly follows the Manning's limiting law for the conduction of a polyelectrolyte. The dissociated MMT nanoplatelets that carry negative charges in water were able to rapidly adsorb cations, such as tris(2,2′‐bipyridyl)ruthenium(II) (Ru(bpy)) and methylene blue (MB⁺), and recover into a smectic configuration floating as a separating phase. By using the Langmuir equation, we were able to estimate the occupied surface areas of MMT nanoplatelets by each Ru(bpy) and MB⁺ cations as 4.708 and 1.806 nm²/ion, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

First‐Principles Study of Sc1−xTixF3 (x ≤ 0.375): Negative Thermal Expansion,Phase Transition,and Compressibility

We present the first‐principles investigation of (x ≤ 0.375). Controllable thermal expansion of is achieved by different Ti contents. The negative thermal expansion (NTE) behavior is weakened gradually with increasing Ti content, which is consistent with experimental measurements. The Jahn–Teller effect plays an important role in the cubic‐to‐rhombohedral phase transition, which stems from the enhanced energy stability when the 3d orbitals of cation split into triply degenerate and sets. The unusual thermal stiffening of is found, which is similar to that of and but contrary to other NTE materials.     

Equivalent lightness of elderlies investigated by cataract experiencing goggles

People get cataract in their eyes when they age. The color perceived by the senile cataract eyes desaturates because of the environment light that scatters in the eyes by the hazy crystalline lenses. We investigated the effect of the desaturation on brightness of objects in terms of the equivalent lightness , which is composed of the achromatic lightness and the chromatic lightness . If the color desaturates, becomes smaller and consequently becomes smaller in the cataract eyes. with and without cataract experiencing goggles at room illuminances to cover mesopic to photopic level was measured. Red, yellow, green, and blue patches of size 2° × 2° arc of the visual angle were investigated with the direct heterochromatic brightness matching between the color patches and a gray scale. Both took about the same value. with goggles was then transferred to the final where the matching gray scale was observed without goggles to express the equivalent lightness of cataract eyes by the gray scale perceived by normal eyes. with goggles was lower than without goggles by about 10 L* units in all the four colors. This reduction was almost equal to the reduction of L* by the reduced transmittance of the goggles showing that there was no effect of color desaturation. The color appearance in the color patches was measured by the elementary color naming method, and the results clearly showed the color desaturation with goggles implying decrease of . We concluded that the scattered environment light compensated the decrease of to keep the brightness of stimuli unchanged. © 2011 Wiley Periodicals, Inc. Col Res Appl, 38, 267–276, 2013     

Study on the surface properties of grafted polyethylene particles by inverse gas chromatography

Inverse gas chromatography (IGC) studies on the surface of polyethylene (PE) particles grafted with acrylic acid and acryl amide have been reported. Surface properties of the virgin and grafting‐modified PE were compared by IGC. The dispersive contributions of the surface free energy γ and the K_A and K_B parameters expressing the ability of the stationary phase to act as Lewis acid or Lewis base were calculated. The results showed that the γ value increased significantly after grafting. The PE samples grafted with acrylic acid and acrylamide showed a predominantly basic character while the virgin PE was acidic. All of these suggested that the surface of PE has been modified through the grafting reaction, and thus is expected to improve its adhesions with other polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis,Characterization and Aqueous Properties of a New Hybrid Fluorocarbon Cationic Surfmer

A novel hybrid fluorocarbon cationic surfmer has been synthesized and its aggregation and surface properties have been studied by surface tension, electrical conductivity, steady‐state fluorescence, Rayleigh light scattering, dynamic light scattering and transmission electron microscopy. Through surface tension, electrical conductivity, steady‐state fluorescence and Rayleigh light scattering measurements, the effectiveness of surface tension reduction, the maximum surface excess concentration, the minimum area occupied per surfactant molecule at the air/water interface, the micropolarity and aggregation number of micelles were investigated. The results shows that the surfmer has superior surface activity and lower micropolarity than other surfmers. The critical micelle concentration at different temperatures and a series of thermodynamic parameters (, , and , , , and ) of micellization were evaluated. The thermodynamic parameters showed that the micelle formation was entropy‐driven in the temperature range of 15–40 °C. The size and morphology of the aggregates were also confirmed by dynamic light scattering and transmission electron microscopy.     

Effect of Surface Concentration of Lu on Oxygen Permeation of Polycrystalline Alumina at High Temperatures

The effect of Lu surface concentration on oxygen permeation in polycrystalline α‐alumina wafers was determined at 1773 K under limited oxygen potential gradients (Δ), where the two surfaces of the wafer were deliberately subjected to different oxygen partial pressures [ (I) ?  (II)]. When oxygen permeation occurred mainly by oxygen GB diffusion under a Δ generated by a combination of low values, the Lu‐coating on the (I) [ (II)] surface decreased [increased] the oxygen permeability constants. When Δ was the result of a combination of high values, where oxygen permeation proceeded mainly by aluminum GB diffusion, the oxygen permeability constants were decreased only by the Lu‐coating on the (I) surface. The analysis of mass transfer parameters, such as the chemical potentials, GB diffusion coefficients, and fluxes of aluminum and oxygen in the wafers, suggested that ambient oxygen molecules were effectively attracted toward Lu‐coated surfaces exposed to low‐ environments, leading to a change in oxygen permeability.     

Experimental Correlation between Mechanical Non‐Linearity in LAOS Flow and Capillary Flow Instabilities for Linear and Branched Commercial Polyethylenes

An experimental correlation between the non‐linear behaviour of commercial polyethylene melts in LAOS flow, and the pressure fluctuations associated with melt flow instabilities developed in capillary rheometry are presented. Polyethylene melts with enhanced non‐linear behaviour under LAOS conditions present larger pressure fluctuations during capillary extrusion, and consequently, larger surface distortions on the extrudate. The combination of both methods can be a tool to predict the development of melt flow instabilities in the extrusion process of polyethylene melts, and can elucidate their correlation with material structural properties ( , MWD and topology).

     

Volumetric, Compressibility, and Surface Tension Studies on Micellization Behavior of SDS in Aqueous Medium: Effect of Sugars

The densities , velocities of sound , and surface tension , of anionic surfactant sodium dodecyl sulfate in presence of aqueous saccharides (fructose and maltose) with concentrations 0.01 and 0.10 mol kg^?1 have been reported over a wide temperature range (293.15–313.15 K) at an interval of 5 K. The apparent molar volume , isentropic compressibility , and apparent molar adiabatic compression values have been calculated using densities and velocities of sound data. Both, and vary non‐linearly at lower concentration of surfactant and tend to achieve linearity at higher concentration of surfactant in presence of saccharides. From the surface tension data, parameters like surface excess , minimum area occupied by the surfactant molecule at the saturated air/solution interface and surface film pressure have been computed. The effect of additives on these parameters has been discussed in terms of different types of the interactions pertaining in the micellar system. An attempt has also been made to draw an inference regarding the effect of these additives on the critical micelle concentration of the surfactant.     

Molecular dynamics simulation of desulfurization by ionic liquids

Ionic liquids (ILs) have shown an excellent performance for removing the sulfur compounds of fuel. In this work, molecular dynamic simulations were performed to screen suitable IL instead of the traditional method which is inefficient. DBT and DBTO₂ were used as model compounds to study the mechanism of desulphurization. An all‐atom force field was proposed for dibenzothiophene (DBT) and dibenzothiophene 5,5‐dioxide (DBTO₂). The calculated results are in good agreement with the experimental value. We investigated the interaction between the model compounds and a series of ILs composed of 1‐alkyl‐3‐methylimidazolium cations ([C_nmim]⁺, n = 4, 6, 8, 10) and BF, PF anions. We found that the interaction between hydrogen atoms in imidazolium ring and oxygen atoms in DBTO₂ is stronger than that of sulfur atoms in DBT, and it means that DBTO₂ is extracted by ILs more easily than DBT. In this work, we also compared and discussed the desulphurization mechanism as a function of different ILs, sulfur contents, temperatures, and inclusion of water or not. The above results may help us design extractant and improve the operating conditions. © 2010 American Institute of Chemical Engineers AIChE J, 56: 2983–2996, 2010