Viscosity function of a fast reactive polymerization—Aqueous solution of acrylic acid in a rheometer

The focus of this research is a special technique to investigate the polymerization of the water soluble monomer acrylic acid in a rheometer. The rheokinetics is an approach to measure the viscosity of reactive solutions during polymerization and consequently monitor the reaction kinetics. Results are presented on the initial stage of acrylic acid polymerization in water at different temperatures, 50, 60, and 70°C with mass fractions between 12.5% and 35% and two different initiator ratios, 0.8 and 1.2 mmol/mol. An empirical viscosity model to describe the shear viscosity over time is available. With reaction kinetics from literature and the viscosity model, a determination of the exponents and of a rheokinetics model is undertaken; is 1.5 and is 1.9–2.8. Further investigations show that it is possible to analyze the monomer conversion at a certain time when quenching the reaction and measure the polymer concentration. With the use of a simple reaction model, the conversion is calculated like in a batch reactor, representing the gap in the rheometer. Differences with the stepwise measured conversions are not very high. A rheokinetics approach is consequently useful for optimizing processes, where fast reactions in a continuous flow are present. POLYM. ENG. SCI., 56:874–888, 2016. © 2016 Society of Plastics Engineers     

A natural frequency approach to study the blown film helicoidal stability of HDPE bimodal resins and its relation to their rheological behavior

A quantitative study of the helicoidal bubble stability (HBS) of five different HDPE bimodal resins processed under the same conditions was conducted to determine their natural frequencies and how these are related to molecular weight distribution features and typical viscoelastic data. The natural frequency , of each resin was obtained by representing the HBS phenomenon as an undamped system under the influence of a harmonic force, whose solution required force balance and Fourier series analyses of video‐recorded oscillations of the bubbles. It was found that was directly related to the stability grading on these bimodal resins established by experimental technicians running the blown film line. The same trends were observed when comparing with the entanglement index, Mw_B/Me, the characteristic retardation time t_67% obtained from recovery compliance data, and the cross‐over point frequency (COP). These trends were not linear, indicating perhaps the existence of a percolation threshold for with respect to the entanglement index and to the mentioned rheological parameters. POLYM. ENG. SCI., 55:2910–2921, 2015. © 2015 Society of Plastics Engineers     

The kinetics of isothermal nicotinamide release from poly(acrylic‐co‐methacrylic acid) loaded xerogel

The isothermal kinetics of in vitro nicotinamide release from poly(acrylic‐co‐methacrylic acid) loaded xerogel into water was evaluated. The isothermal kinetics curves of nicotinamide release from poly(acrylic‐co‐methacrylic acid) xerogel were measured at different temperatures ranging from 296 K to 315 K. It was proven that the kinetics of nicotinamide release from poly(acrylic‐co‐methacrylic acid) xerogel was a kinetically complex process which was neither controlled by the processes of drug diffusion nor with the relaxation of the xerogel. The kinetic of nicotinamide release from poly(acrylic‐co‐methacrylic acid) may be described by the kinetics model of reversible first order chemical reaction and the apparent activation energy have value of E_a,M = 14.1 kJ mol^?1 and preexponential factor ln(A_M min^?1) = 2.3. The rate constants of nicotinamide release ( ) and the rate constants of its reversible absorption reaction ( ) were calculated and found to fall within the range 0.019 min^?1?0.033 min^?1 for and 0.014 min^?1?0.016 min^?1 for . The value of activation energy for the nicotinamide releas, E_a.R =21.25 kJ mol^?1, is significantly higher than the value for the process of nicotinamide absorption (E_a,A = 2.6 kJ mol^?1). The rate of nicotinamide release was predetermined with the rate of nicotinamide molecules distribution between the hydrogel and surrounding solution. POLYM. ENG. SCI., 55:60–69, 2015. © 2014 Society of Plastics Engineers     

Nitrate permeability of semi‐permeable membranes prepared from binary blends of cellulose triacetate and chitosan

Semi‐permeable membranes of binary polymer blends of cellulose triacetate (CTA) and chitosan (CS) were produced to harvest microalgal biomass for biofuels. Relatively thick membranes of polymer blends containing more than 70% CTA were prepared via solution blending in formic acid. Various characterization methods revealed that both polymers are immiscible at the molecular level at room temperature. However, they were macroscopically compatible and exhibited uniform physical properties due to the molecular interactions between CTA and CS with the same cellulosic backbone containing two linear polysaccharides through a β‐1,4 glycosidic bond. Careful visual inspection revealed that these membranes are transparent and their light transmittance was greater than 90% at all blend compositions. All membranes showed excellent tensile strength at all compositions and the maximum tensile strength was 52.4 MP from the membrane with a CTA/CS weight ratio of 9:1. The permeability of these blend films increased with increasing CS content and the maximum value was 44.28 mg/m²/day. To improve the permeability or transfer rate of the CTA/CS membranes, the porous CTA/CS membranes were also prepared using various amounts of silica nanoparticles. POLYM. ENG. SCI., 58:192–197, 2018. © 2017 Society of Plastics Engineers     

Temperature‐ and strain rate‐dependent constitutive modeling of the large deformation behavior of a transparent polyurethane interlayer

The dynamic mechanical behavior of a polyurethane used as an interlayer in a laminated windshield construction is studied by dynamic mechanical analysis, compression testing at various strain rates (0.001/s to 7000/s), and various temperatures (?40°C to 25°C) by using the universal testing machine and split Hopkinson pressure bar (SHPB) equipped with temperature controllers. The obtained results show that the mechanical behavior of the polyurethane interlayer is sensitive to temperature and strain rate. Under dynamic loading condition, stress‐strain curves at ?40°C exhibit the transition from “rubbery” to “glassy”. On the basis of the constitutive theory and the experimental data, a one‐dimension thermal‐hyper‐viscoelastic constitutive equation is proposed to describe the large compressive deformation response of the polyurethane interlayer over wide ranges of strain rates and temperatures. The parameter of the function is significant to describe the trend of the stress–strain curve at larger strain. The stress–strain curves at low strain rate and low temperature can overlap the stress–strain curves at higher strain rate and higher temperature; there may be an equivalent relationship between temperature and strain rate. POLYM. ENG. SCI., 55:1864–1872, 2015. © 2014 Society of Plastics Engineers     

Synthesis and properties of silicon‐containing arylacetylene resins with polyhedral oligomeric silsesquioxane

A series of silicon‐containing arylacetylene resins containing polyhedral oligomeric silsesquioxane (PS resins) were synthesized by the hydrosilylation reaction between poly(dimethylsilyleneethynylenephenyleneethynylene) (PMSEPE) and octakis(dimethylsiloxy)octasilsesquoixane ( ) in the presence of a platinum catalyst (Pt‐dvs). The chemical structures and properties of PS resins were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, rheological analysis, differential scanning calorimetry, dielectric measurement, thermogravimetric analysis, and scanning electron microscopy. The results show that PS resins can be crosslinked to form thermosets at temperatures less than 260°C. With the increment of , the dielectric constants of the thermosets gradually decrease from 2.91 to 2.73. The thermooxidative stabilities of PMSEPE thermosets are obviously improved with the incorporation of . POLYM. ENG. SCI., 55:316–321, 2015. © 2014 Society of Plastics Engineers     

The role of wettability of nonideal nozzle plate: From drop‐on‐demand droplet jetting to impact on solid substrate

The dynamics of drop‐on‐demand (DoD) droplet formation and subsequently impact on the solid substrate are investigated using a three‐dimensional (3‐D) multirelaxation‐time (MRT) pseudopotential lattice Boltzmann (LB) model. The wettability of nonideal nozzle plate and solid substrate is modeled by a geometric scheme within the LB framework. The dynamics of droplet formation are explored in a range of the inverse of Ohnesorge number , , and , and the Reynolds number , , and . For , no satellite droplet is observed and the wettability of nozzle plate greatly influences the velocity and length of jetting fluids. For , the filament breakup and recombination are observed. The moment of filament breakup is delayed with advancing contact angle increasing. For with , the primary and satellite droplets could not be recombined with and which agree with the literature. Whereas with , the recombination occurs. The dynamics of subsequent oscillating droplet impact on the substrate are similar to that of equilibrium droplet which could obtain high‐resolution printed features. Consequently, considering with large and numbers, the printable range could be extended which could help increase the printing frequency and boost the production outputs of inkjet printing. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2837–2850, 2018     

Mass transfer coefficient of tubular ultrafiltration membranes under high‐flux conditions

The effect of suction flow on the mass transfer coefficient of tubular ultrafiltration membranes, in particular that under a high‐flux condition, was studied. We pointed out that is proportional to under turbulent conditions, and that the proportional constant, b, exceeds 0.023 when the effect of suction flow is not negligible. We conducted the velocity variation method using ultrafiltration membranes with MWCOs of 20k and 100k and dextrans having molecular weights of 40,000 and 70,000 at the conditions, where exceeded . We demonstrated that the effect of suction flow includes not only flux but also the diffusion coefficient of solute, and that the ratio of the flux to the diffusion coefficient, expressed as , is an important index. Finally, we concluded that , when is smaller than , giving the Deissler equation itself, and that , when exceeds . © 2017 American Institute of Chemical Engineers AIChE J, 64: 1778–1782, 2018     

Enhanced Energy Storage of Dielectric Nanocomposites at Elevated Temperatures

Enhancing the performance of dielectric capacitors toward higher energy density and higher operating temperatures has been drawing increased interest. Therefore, in this investigation, research efforts were dedicated to the fabrication and characterization of nanocomposites in order to enhance the energy density at both room temperature and elevated temperature. The dielectric capacitors are fabricated using nanocomposites composed of BaTiO nanoparticles with polyimide (PI) matrix aiming at combining the high relative dielectric permittivity of the ceramic filler and the high breakdown strength of the polymeric matrix. Dielectric energy storage performance is assessed for nanocomposites with volume fractions ranging from 0 to 20% under operating frequency from 20 Hz to 1 MHz and temperatures ranging from 20 to 120C. It is observed that with the increase of temperature, the capacitance increased while the energy density slightly decreased but significantly higher than pure polymer samples. The highest energy density was found for BaTiO/PI nanocomposites with 20% volume fraction, 9.63 J/cm at 20C and 6.79 J/cm at 120C. Overall, testing results indicate that using nanocomposites of BaTiO/PI as a dielectric component shows promise for implementation to preserve high energy density values up to temperatures of 120C.     

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.     

Counterion-Induced Cationic Flexible Nanoparticle Catalytic of Piperidinolysis of Phenyl Salicylate

The removal of PSa^? from bulk aqueous phase to the pseudo‐micellar phase by halobenzoate counterion X is responsible for the monotonic increase in k_obs (pseudo first‐order rate constants) with the increase in the values of [MX] where MX = sodium salts of 2‐, and 4‐halobenzoic acids. The values of ion exchange constants, or for X = 2‐ and 4‐halobenzoate ions in the presence of tetradecyltrimethylammonium bromide (TTABr) were calculated from the apparent catalytic rate constants, ^Xk_cat which represent the catalytic effect of CFN. Larger values of or were observed for X = 4‐halobenzoate ions than that for X = 2‐halobenzoate ions due to isomeric factors. The values of or determined in the presence of TTABr were compared with previously determined or values in the presence of cetyltrimethylammonium bromide (CTABr). The values of or are nearly 8 ~ 9‐fold larger for 4‐IBz^?, 4‐BrBz^? and 4‐ClBz^? compared to the respective values of X = 2‐IBz^?, 2‐BrBz^? and 2‐ClBz^?. The values of or for X = 4‐FBz^? is nearly 3‐fold larger than that for X = 2‐FBz^?. The values of or for X = 2‐ and 4‐halobenzoates are significantly smaller in the presence of TTABr than these in the presence of CTABr nanoparticles.     

NMR spectroscopic study of chemical equilibria in solutions of formaldehyde,water, and butynediol

Liquid mixtures of formaldehyde, water, and butynediol are complex reacting multicomponent systems in which formaldehyde forms oligomers both with water and butynediol. ‐ and ‐NMR spectra of these mixtures are elucidated. The species distribution of the oligomers is quantitatively determined by ‐NMR spectroscopy. The measurements cover temperatures from 293 to 366 K, overall formaldehyde mass fractions from to , and overall butynediol mass fractions from to . A mole fraction‐based and an activity‐based model of the chemical equilibrium in the studied system are developed and chemical equilibrium constants are reported. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4442–4450, 2017     

The Effect of Methanol on the Micellar Properties of Dodecyltrimethylammonium Bromide (DTAB) in Aqueous Medium at Different Temperatures

The micellar properties of dodecyltrimethylammonium bromide (DTAB) in water and methanol water mixtures at different temperatures have been studied by conductivity and surface tension measurements. The critical micelle concentrations (CMC), degree of ionization (α), standard Gibbs free energy of micellization (), standard enthalpy of micellization (), standard entropy of micellization () and free energy of transfer () were evaluated from conductivity data. The CMC, maximum excess surface concentration ( ), area occupied per surfactant molecule ( ), surface pressure at the CMC ( ), packing parameter (P) and standard free energy interfacial adsorption ) were estimated from surface tension measurements. The CMC of DTAB was found to increase with increasing volume fraction of methanol and increasing temperature. Thermodynamic parameters and surface properties revealed that the addition of methanol changes the relevant physicochemical properties which affect the process of micellization.     

Analysis of the thermal decomposition of munitions wastewater

The thermal decomposition of ammonium nitrate (AN) laden munitions wastewater and comparable control samples were studied under air and nitrogen environments at pressures from 0.1 MPa to 10 MPa. The decomposition enthalpies, measured using a Differential Scanning Calorimeter (DSC), and gaseous emissions, measured using a Fourier-Transform Infrared Spectrometer (FTIR), were used to evaluate the quality of decomposition. Experiments demonstrated that higher pressures improved the energy yield and reduced the quantities of harmful from the decomposition of all samples. At 10 MPa, experimentally measured decomposition enthalpy from the munitions wastewater was 1.8 MJ/kg, approximately 45 % of its standard enthalpy of decomposition, and NO and accounted for only 0.7 % and 0.08 % of the nitrogen in the sample, respectively. The emissions stream from the wastewater was found to primarily consist of , , and . An analysis of the heat releases and the emissions showed that higher pressures improved the extent and enthalpy of decomposition by preventing premature loss of gaseous intermediates and sensible heat through the pin-hole crucibles used in the experiments. Moreover, high pressures precluded the evaporation of water and promoted the decomposition of AN via a radical mechanism.     

Investigation and modelling of damping mechanisms of magnetorheological elastomers

Damping in MREs is considered to be ascribed to viscous flow of the rubber matrix, interfacial damping at the interface between the magnetic particles and the matrix and magnetism induced damping. In this study, individual components in MREs that contribute to material damping were investigated. A model was developed to include viscous flow of the rubber matrix, interfacial damping and magnetism induced damping to give the total damping capacity of MREs ( )It was found that depends on frequency, iron sand content, strain amplitude and is independent of the applied magnetic field over saturation magnetization. The proposed model was assessed experimentally using a series of isotropic and anisotropic MREs. Comparison between tan δ with showed that matched the experimental trends with average percentage difference of 8.1% and 21.8% for MREs with modified iron sand unmodified iron sand, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43247.     

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.     

Maldistribution susceptibility of monolith reactors: Case study of glucose hydrogenation performance

In this work an ultrafast electron beam X‐ray modality was applied for the first time to characterize the gas–liquid Taylor flow inside each channel of an opaque honeycomb monolith structure ( ) for and . Significant spatial and temporal deviations in the phase holdup as well as in the gas bubble and liquid slug lengths were found. To evaluate the impact of Taylor flow maldistribution on the reactor performance, the data of more than unit cells were used to simulate the reactor productivity in the hydrogenation of glucose. The results verify that a monolith reactor solely designed by using superficial velocities and empirical correlations for gas bubble and liquid slug lengths fails significantly in achieving high product selectivity and the desired conversion. The developed methods are a solid base to design and select proper distributors ensuring the favorable flow configurations for specific chemical processes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4346–4364, 2016     

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.     

Confirmation of the Dominant Defect Mechanism in Amorphous In–Zn–O Through the Application of In Situ Brouwer Analysis

The dominant point defect mechanism of amorphous (a‐) indium zinc oxide (IZO) was probed through in situ electrical characterization of sputtered a‐IZO thin films in response to changes in oxygen partial pressure (pO) at 300C. The results yielded a power law dependence of conductivity (σ) versus pO of ～?1/6. This experimental method, known as Brouwer analysis, confirms doubly‐charged oxygen vacancies as the dominant defect species in a‐IZO. The success of this study suggests that Brouwer analysis is a viable method for studying the defect mechanisms of amorphous oxides.     

Indirect effect of polyvinylpyrrolidone and cetyltrimethylammonium bromide on UV‐blocking efficiency of TiO2@PVP‐CTAB@SiO2 core‐shell nanohybrid particles

In this study, a novel and useful approach to fabricate @PVP‐CTAB@ (TPS) nanohybrid as an effective light stabilizer agent has been reported. Also, the indirect role of the Polyvinylpyrrolidone and cetyltrimethylammonium bromide on UV (ultraviolet) protection properties of nanohybrid particles was investigated. In addition, comparative studies were carried out to evaluate the photocatalytic and UV protection properties of @ (TS), commercial (US3490), synthesized nanparticles, and TPS nanoparticles. Furthermore, the UV protection property of 2‐(2H‐benzotriazol‐2‐yl)?4, 6‐bis (1‐methyl‐1‐phenylethyl) phenol, as an organic anti UV, was also compared with TPS nanoparticles. The as prepared nanohybrid was characterized by Fourier transform infrared spectroscopy, zeta potential, field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), and UV‐Vis spectroscopy. FESEM and TEM micrographs show monodispersity and nano‐metric size of TPS. Rhodamine B degradation study clearly shows that TPS present the lowest photocatalytic property. Also, UV‐Vis spectroscopy results show that the TPS nanoparticles illustrate higher UV blocking ability comparing to other presented anti UV materials. TPS with convenient and useful synthesis method, high UV blocking ability, and little effect on polymer matrix can be introduced as a novel UV‐blocking agent in polyurethane matrix. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44148.