Simulation of removal of HCI gas in a spray dry tower

A mathematical model of the absorption of HCI gas in a spray dry tower has been proposed. The proposed model describes the mechanism of HCI removal talking into account atomized droplet size distribution and the change in the droplet state from “slurry droplet” to “dry particle”. It is found that the removal efficiency can be simulated by using the model with the constant mean diameter of droplet from the simulation results. Simulation results of the removal of HCI gas are in good agreement with the experimental data in a spray dry tower.     

Observations macroscopiques et microscopiques des produits d'insertion du graphite avec le trichlorure d'or

The intercalation of gold trichloride has been studied in the classical manner by the action of the vapour on graphite in a sealed tube[12]. Tables 1 and 5 summarize the results obtained with various samples of natural and artificial graphite and with carbon materials graphitized at high temperatures. Under optimal reaction conditions (245°C), a blue, richest ($\text{Δm}\text{mo}\text{= 200\%}$) product is obtained, of formula C_12.6AuCl₃: gold trichloride intercalates in the pure state (Table 2). Comparison of the results obtained by thermogravimetry (Fig. 1), dialatométry (Fig. 2) and X-ray analysis (Fig. 3) indicates that this final product C_12.6AuCl₃ is of first stage with an interplanar distance of 6.80Å (Table 3). Study of the relative intensities[17] of the (001) reflections allows stating that the gold trichloride intercalates are in the form of planar molecules Au₂Cl₆ (Table 4). Macroscopic observation of the pyrographite samples shows that the insertion occurs in an “all or nothing” manner[18]: during the reaction the layers are gradually deformed in the neighbourhood of the “invasion front” (Fig. 4) and when the intercalation is terminated, a pleating of the layers appears very clearly at the surface (Figs. 5 and 6). These dislocations visible on the edges of the samples (Fig. 7) are a manifestation of the “separation work” necessary for the intercalation which practically excludes the possibility of reagent layers inserted with a lower ratio than in C_12.6AuCl₃.Graphite and its intercalation compounds lend themselves only with difficulty to a microstructural study by visualization of the lattice planes (instability of the products under an electron beam, basal carbon planes invariably parallel to the grid support).Carbon blacks (Sterling MTG 3000°C) are small circular rods (θ < 1μ) graphitized throughout their mass (Fig. 8) which give with gold trichloride, rich products ($\text{Δm}\text{mo}\text{= 140\%}$), almost of the second stage. With these carbons, it was not possible to intercalate ferric or chromic trichloride[21]. The lattice distances measured on micrographs of the intercalated products (Fig. 9) allowed to identify the most contrasted fringes as direct representations of gold trichloride layers inserted between those of the carbon (the finer fringes). The different types of layers observed along the segment AB (Fig. 9) indicate a succession of different stages from A to B (1st-1st-2nd-3rd-4th-3rd-5th) which indicates the inhomogeneity of the products studied[10]. These results seem to corroborate the “statistical definition” of stage identifiable in the combination of graphite with the halogenides[8,19,22].     

Barrier resistance of polyethylene,polyethylene/modified polyamide,and polyethylene/blends of modified polyamide and ethylene vinyl alcohol bottles against permeation of polar and nonpolar mixed solvents

The main objective of this study is to investigate the barrier properties and mechanisms of polyethylene (PE), PE/modified polyamide (MPA), and PE/blends of MPA and ethylene vinyl alcohol copolymer (MPAEVOH) bottles against permeation of polar/nonpolar (acetone/white spirit) mixed solvents. The mixed solvent permeation resistance improves dramatically after blending MPA and MPAEVOH barrier resins in PE matrices during blow molding. By using the proper MPAEVOH compositions, the white spirit permeation rate of PE/MPAEVOH bottles at 40°C can be about 145 times slower than that of the PE bottle specimen; however, it is still 2.5 times faster than that of the PE/MPA bottles. In contrast, the rate of polar acetone solvent permeation through the PE bottle is much slower than that of white spirit and only slightly faster than that through the PE/MPA and PE/MPAEVOH bottle specimens. In contrast, the permeation rates of acetone/white spirit mixed solvents into PE/MPA bottles are at least 20–60 times faster than the summation permeation rates calculated using the simple mixing rule when the acetone contents in the mixed solvents are between 10 and 70 wt %. It is somewhat interesting that, after blending the proper amounts of EVOH in MPA, the mixed solvent permeation rates of PE/MPAEVOH bottles are dramatically reduced and are very close to the summation permeation rates calculated using the simple mixing rule when the acetone contents are in the particular “window” range. These interesting barrier properties of PE/MPA and PE/MPAEVOH bottle specimens were investigated in terms of the free volumes, barrier properties, molecular interactions in the amorphous phases of the barrier resins, and their resulting morphological structures that present in their corresponding bottles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1333–1344, 2005     

Improvement of the Durability of Zinc-Coated Steel/Epoxy Bonded Joints

The durability properties of bonded lap shear joints made from an epoxy/dicyandiamide adhesive and hot-dipped galvanized (G2F) or electroplated-phosphated (EZ2) steel have been investigated. The degradation mechanisms have been studied after three accelerated ageing tests: the “cataplasme humide” (“C.H.T.”), immersion (“I.T.”), and salt spray (“S.S.T.”) tests. X-ray photoelectron spectroscopy (XPS) analysis of fracture surfaces after ageing have shown that anodic dissolution of the zinc-coating is responsible for debonding in all cases and that intergranular corrosion phenomena account for poorer performances of the hot-dipped galvanized substrate during “C.H.T.” and “I.T.” Silane coupling agents were successfully used as primers on both substrates to increase the hydrolytic stability of the metal/adhesive interface. XPS results indicate that both the interfacial dissolution of the phosphate coating of EZ2 and intergranular corrosion of G2F are delayed for silane-primed specimens. The observed improvements do not appear to depend on the nature of the silane coupling agents. Alkylsilanes have been found to perform as well as silanes having a group capable of reacting with the epoxy/dicyandiamide system.

Additional tests were carried out in view of the possible application of organosilane reagents as additives in corrosion-protective oils. Good durability properties have been obtained by priming the metal coupons with a standard oil/silane mixture prior to bonding.

When corrosion was the controlling degradation mechanism as is the case during the salt spray test, silane treated specimens did not generally perform better than control specimens.     

Intra-particle coating variability: Analysis and Monte-Carlo simulations

An analytical model is presented that describes the intra-particle coating variability of a single particle by a uniform spray. For uniformly random orientations, the film thickness coefficient of variation is proportional to the number of coating trials raised to the ?1/2 power, and thus the coefficient of variation asymptotes to zero as the number of coating trials increases. However, if the particle has a preferred orientation while in the spray zone, the limiting value of the coefficient of variation is non-zero. Monte-Carlo simulations of a single particle subject to a coating spray are also presented and verify the theoretical model. Finally, analysis of discrete element method (DEM) computer simulations of spheres in a rotating, circular drum without baffles show that a sphere passing through the “spray zone” has an orientation corresponding to a preferred rotation from the sphere's orientation during its last past through the spray zone. Although the intra-particle coefficient of variation for orientations exhibiting this effect still asymptote to zero over time, the rate at which this occurs is smaller than that for uniformly random orientations.     

Defensive Spiroketals from Asceles glaber (Phasmatodea): Absolute Configuration and Effects on Ants and Mosquitoes

Insects are the largest and most diverse group of organisms on earth, with over 1,000,000 species identified to date. Stick insects (“walkingsticks” or “phasmids”, Order Phasmatodea) are known for and name-derived from their camouflage that acts as a primary line of defense from predation. However, many species also possess a potent chemical defense spray. Recently we discovered that the spray of Asceles glaber contains spiroketals [a confirmed major component: (2S,6R)-(?)(E)-2-methyl-1,7-dioxaspiro[5.5]undecane, and a tentatively identified minor component: 2-ethyl-1,6-dioxaspiro[4.5]decane] and glucose. In this paper, we: 1) illustrate the identification of spiroketals and glucose in the defense spray of A. glaber by using Nuclear Magnetic Resonance (NMR), Gas Chromatography/Mass Spectrometry (GC/MS), and comparison with a synthetic reference sample; 2) provide the elucidation of the absolute configuration of the major spiroketal in that defense spray; and 3) demonstrate the effect of this compound and its enantiomer on both fire ants (Solenopsis invicta) and mosquitoes (Aedes aegypti).     

Composition of Polymerized Linseed Oil Bodied by a Molten Eutectic Salt Mixture

Quantities of alkali refined linseed oil, ARLO, were passed through molten eutectic mixtures of salts, KNO₃, NaNO₂ and NaNO₃ or KNO₃ and NaNO₃ in the temperature range of 280° C to 320° C at various flow rates. The oils increased in viscosity. Colour degradation was very slight and the acidity increased to as high as 5 mg KOH/g. The bodied oils were readily separated into two fractions on the basis of solubility in acetone. Acetone solubility decreased with the increase in bodying temperature in the eutectic salt mixture. Both fractions were analyzed for fatty acid composition and structure. Spectroscopic techniques, NMR and chromatographic studies indicated that there was an absence of nitrogen compounds, some degradation (to shorter than 18 carbon atom acids), formation of “oxy” groups and some cyclization in a single acid and in the formation of polymers which were di- and trimeric structures.     

The “cold‐solutioning” phenomenon in cellulose triacetate–acetone mixtures

Direct mixing of cellulose triacetate (CTA) in acetone at room temperature produces only an opaque swollen gel at all concentrations. However, cycling the mixture between room temperature and ?78 ± 3°C results in a stable solution at room temperature, if the concentration is less than 6% (w/w). This process has been called “cold‐solutioning.” Such a process also produces a clear solution at concentrations between 6% (w/w) and 10% (w/w); however, in time, the solution separates slowly into at least two phases, a clear liquid and an opaque gel phase. At concentrations above 10% (w/w) and below 20% (w/w), the system exhibits two phases. A completely opaque swollen gel forms at concentrations of 20% (w/w) and above. The above‐described cold‐solutioning phenomena are shown to be the coupled kinetic and thermodynamic consequences of (1) the large thermal stresses that would result from thawing a swollen mixture of CTA and acetone, arising from the large differences in their thermal expansion coefficients; and (2) the “bimodal” composition of the cellulose derivative. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1697–1707, 2003     

Solute–solvent interactions governing preferential solvation phenomena of acetaminophen in CO2-expanded organic solutions: A spectroscopic and theoretical study

The present work aims to characterize the nature and intensity of the specific and non-specific solute–solvent interactions responsible for the different solvating behaviour of “CO₂-expanded ethanol” and “CO₂-expanded acetone” towards acetaminophen, an analgesic drug commercially known as paracetamol. The intermolecular interactions between acetaminophen and solvent molecules involved in these expanded media and its sensitivity to solvent composition changes, have been analyzed by high-pressure IR spectroscopy, LSER analysis, and theoretical ab initio calculations performed with acetaminophen–(ethanol)_n and acetaminophen–(acetone)_n complexes. It comes out that the distinct perturbation experienced by the cybotactic region of acetaminophen in “CO₂-expanded ethanol” and “CO₂-expanded acetone” when CO₂ content increases is basically a consequence of the higher sensitivity to solvent composition changes of the dipole–dipole interactions, established between the acetaminophen carbonyl group and acetone solvent molecules, in relation to that of the hydrogen bond interactions existing between this group and ethanol solvent molecules.     

Evolution de diverses classes de carbones par irradiation neutronique

We investigated in previous studies the electronic properties of three graphites and one pyrocarbon damaged by neutrons [1,2]. We have now extended this work to various other carbons and we present in this paper a unified presentation of the results and a quantitative evaluation of the damage in terms of positive hole concentration in the valence band vs irradiation dose.The materials tested and the electronic properties which were measured are listed in Table 1. Irradiations were performed at 35°C in conditions identical to those of previous studies [1,2] at the “Melusine” reactor of the Grenoble Nuclear Center. Doses D ranging from 10¹⁷ to 4 × 10²⁰neutrons/cm² were recorded.The variation of the electrical resistivity at room temperature is shown in Figs. 1 and 2; of the Hall coefficient in Table 2 and of the magnetic mean susceptibility in Fig. 5. Figure 4 presents the relative transverse magnetoresistance (i irradiated sample; o non irradiated).The paramagnetic susceptibility χ_p was measured directly by EPR and its variation at 298°K with the neutron dose as shown in Fig. 6. Using the data on variation of χ_pwith temperature, the paramagnetic susceptibility is split[6] into contributions of the “localized paramagnetic centers” (Fig. 7) and of the conduction carriers (Fig. 8). The latter, χ_deloc (Fig. 8) increases more slowly than the dose, while χ,_loc (Fig. 7) increases first very rapidly, then much more slowly at high irradiation dose, when some recombination of point defects takes place.At higher doses when the Hall coefficient begins to decrease with increase of the dose, the data may be used to calculate the number N of positive holes created by irradiation: Figure 9 shows that approx. 4 holes/cm²are produced by 1 neutron/.cm². Figure 10 shows that χ_deloc of carriers is roughly proportional to √N, as expected for the band structure of graphite. It is clear from Fig. 11 that N_loc increases proportionally to N at low irradiation doses, but slower than N at high doses (recombination of vacancies).Although the radiation-induced changes in electronic properties differ widely for different carbons, it is possible to find some regularities in these results. We find that, in a given “class of carbons,” each unirradiated sample j may be characterized by an “equivalent neutron dose” Δ_j^p, Δ_j^p would be the dose needed to alter a property P of the most perfect material of the class from its value to the value equal to the unirradiated sample j. Then all the variations of P with (D + Δ_j^p) should be represented by a single curve for all the carbons of the same “class.” Such a parameter Δ_j^p can be useful only if Δ_j^p is independent from the nature of the property P: Δ_j^p = Δ_j.Figure 12 shows the variation of the diamagnetic mean susceptibility ?χ as a function of the “total dose” D + Δ_j^p (D = real dose). There is indeed a single curve and the values of Δ_j^p. (arbitrarily set at zero for pyrocarbon or for PGCCL) are listed in Table 3. In the same way Fig. 13 shows the “single curve” for the Hall coefficient A and Table 3 lists the corresponding values of Δ_j^A. It may be seen that Δ_j, is independent from the property P only for carbons belonging to the “class of graphites” or for those of the “class of pyrocarbons.” Papyex cannot be placed in any one of these classes, and there are not enough data for all the other carbons.For carbons in the same class, the value of Δ_j, can be interpreted in terms of defect concentration prior to irradiation.Finally, from the “single curves” of Figs. 12 and 13, an “irradiation path” for each class of carbons can be drawn by plotting ?χ vs A. Figure 14 shows that the irradiation and annealing paths of graphites are the same.     

Bulk polymerization and characterization of isocyanatoacrylate copolymers

The purpose of this investigation was to prepare by bulk polymerization six new isocyanatoacrylate copolymers and to characterize them. The isocyanatoacrylate copolymers, which were prepared by tri‐n‐butylborane oxide (TBBO)‐initiated free‐radical polymerization, were formed from 1 : 1 mol mixtures of 2‐isocyanatoethyl methacrylate (IEM) with 2‐hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate (HPMA), 2‐hydroxyethyl thiomethacrylate (HETMA), ethylthioethyl methacrylate (ETEMA), 2‐(acetoxyacetoxy)ethyl methacrylate (AAEMA), and tetrahydrofurfuryl methacrylate (THFMA). These six copolymers were compared to the homopolymer of IEM, which was polymerized in an identical fashion. The bulk polymers were fractionated into their acetone‐soluble and acetone‐insoluble components. Physical characterization via photoacoustic infrared (PASIR) spectroscopy showed vast differences in residual isocyanate content. Differential scanning calorimetry (DSC) thermal analysis was carried out on all polymers. Elemental analysis (nitrogen) determined the ratio of IEM to the comonomer and boron analysis showed whether the initiator stayed in the acetone‐insoluble fraction or was “extracted” into the acetone‐soluble fraction. In conclusion, we found that the composition of the copolymers correlated well with the predicted design. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1577–1583, 1999     

Resuspension of Dust Particles in a Chamber and Associated Environmental Factors

Experiments investigating particle resuspension from human activities were conducted in a full-scale experimental chamber. The experiments tested three types of flooring (vinyl tiles, new and old level-loop carpets) and two ventilation configurations (ceiling and side wall supply systems). The floorings were seeded with 0.1–10 μ m test particles. The airborne particle concentration was measured by an array of optical particle counters (OPCs) in the chamber. Resuspension rates were estimated in size ranges of 0.8–1, 1.0–2.0, 2.0–5.0, and 5.0–10 μm ranging from 10^?5–10^?2 hr^?1, with higher resuspension rates associated with larger particles. Resuspension via walking activity varied from experiment to experiment. “Heavy and fast” walking was associated with higher resuspension rates than less active walking, most likely due to a combination of increased pace, increased air swirl velocity, and electrostatic field effects established by the walking. The type of floorings also influenced the particle resuspension. Given the same size and mass distribution of test particles per unit floor area, resuspension rates for the seeded new level-loop carpet were significantly higher than those for the vinyl tile flooring for larger particles (1.0–10 μ m) under the ceiling air supply system.     

Absorption of oxygen by aqueous glycerol solutions and squalane

Highly viscous media are used in a number of process industries, such as the chemical, petrochemical, pharmaceutical, and food industries. Design of mass transfer equipment for such media is very difficult because of the rather limited experimental data. Therefore, the absorption of oxygen from air into glycerol—water solutions has been studied under different operating conditions and sieve tray geometries (namely, hole diameter and hole spacing). Furthermore, the results of supplementary absorption experiments of oxygen into squalane (C₃₀H₆₂) show that the results with the system oxygen—glycerol—water are transferable to other systems.

Abstract

Chemical, pharmaceutical, and petrochemical as well as food industries have to deal increasingly with processes where mass transfer in highly viscous media is involved. Design of mass transfer equipment for such media is very difficult because of the rather limited experimental data. Therefore, a study was started to partially fill this gap; in particular, it deals with evaporation of pure cyclohexanol into air [2] as well as absorption of oxygen from air into glycerol—water solutions on a sieve tray [3-6].In this paper the influence of the sieve tray geometry on mass transfer was studied.

1. (1) In the bubble and spray regime (υ_G < 1 m s⁻¹) for low viscosities there is no effect of the hole diameter on the efficiency.

2. (2) At higher viscosities and low gas velocities an increasing hole diameter results in a reduction of mass transfer.

3. (3) In the drop regime (υ_G > 1 m s⁻¹), i.e. for high gas velocities, an improvement in the efficiency is noticed for sieve trays with larger holes.

4. (4) In the bubble and spray regimes there is no effect of the hole spacing on mass transfer for low and high viscosities.

5. (5) In the drop regime a better efficiency is obtained with higher hole spacing.

The experimental results are explained well with the recently developed model based on high-speed photographs, which divides the two-phase fluid on a sieve tray into three distinct zones, as shown in Fig. 2. The droplet formation zone which represents break-up of the bubbles at the fluid surface into liquid laminae and droplets, as well as the mass transfer between the droplets formed and the surrounding gas, plays a dominant role with respect to the total mass transferred.Supplementary absorption experiments of oxygen into squalane have been carried out to indicate the transferability of the results to hydrocarbon systems. A comparison of these results with those of the absorption of oxygen into glycerol—water mixtures shows excellent agreement of the basic trends.     

The Relationship between Microstructure and Properties in PP/Rubber Powder/nano‐CaCO3 Ternary Blends

Summary: A new kind of rubber powder with “salami” structure (RPS) was prepared by spray drying the mixture of styrene‐butadiene rubber latex and nano‐CaCO₃ slurry. It was found that RPS is an effective toughener with synergistic toughening effect on poly(propylene) (PP). The Izod impact strength of PP/RPS blend is not only higher than that of PP/rubber powder or PP/nano‐CaCO₃ blends, but also higher than that of a PP/rubber powder/CaCO₃ blend. TEM images show that the microstructure of the PP/RPS blend is an “island‐sea” structure with “salami” structure in RPS, in which nano‐CaCO₃ particles are embedded in styrene‐butadiene rubber particles. The relationship between properties and microstructure has been studied by using TEM, SEM, DSC, etc.

     

Comparative study between vapor compression and multi effect boiling desalination systems

In the present study the following arrangements are considered:a- Multi effect vapor thermocompression (Fig. 1)b- Multi effect boiling (Fig. 2)c- A hybrid multi-effect boiling/vapor thermocompression.In arrangement “c” the effects operated at pressures higher than atmospheric pressure are of the vapor thermocompression type while these operated at sub atmospheric pressures are of the multi effect boiling type.Thermodynamics relations for the three systems under consideration are analysed. The numerical study includes the solution of these equations together with calculations of the heat transfer areas required for the units. The enter effect variations of the thermodynamics properties of water are accurately computed using special subroutines designed for this purpose.The present analysis starts by the arrangement “a” for which the thermodynamics representation of an effect is shown in Fig. 3. Sample of the results for the thermocompression process is presented in Fig. 4 which gives the entrainement ratio (the mass ratio of the secondary to priming steam) as a function of the temperature difference between the priming and secondary streams with the temperature difference across the evaporator condenser as a parameter.It should be realized that using an ejector to perform the compression of the entrained vapor is considered to be a low efficiency process due to irreversibilities encountered in the entrainment, mixing, and compression process. However, the advantages of using the ejector here is that it acts as a controlling device, influenced by the following parameters:1- total temperature difference between the hot and cold ends of the plant2- concentration ratio of the brine and its effect on the boiling point elevation3- number of effects4- temperature difference across the condenser evaporator unitscurves of Fig. 4 are used to calculate the performance ratio of the considered systems. The outcomes showed that using ejectors over the same total temperature difference would result in a reduction of the number of effects used in a conventional MEB without experiencing a proportional reduction in the plant productivity. That would lead to a reduction in the capital and running costs as far as the pumping power is concerned. For specific temperature difference, this arrangement could be benificial for small capacities since a smaller number of effects would require less maintaince and gives more stable characteristics.On the other hand, the hybrid arrangement would include the advantages of both MEB and VTC. That means less number of effects without loosing the plant's potential performance ratio. The deviding pressure line between the VTC and the MEB is chosen in such a way to avoid the interference of different ejectors, namely the driving and venting ejectors, in a subatmospheric effect.     

A modified “inside-out” algorithm for simulation of multistage multicomponent separation processes using the UNIFAC group-contribution method

A computational procedure using a modification of Boston and Sullivan's “inside-out” multistage multicomponent separation algorithm (1974) is developed. In order to improve convergence behavior for problems involving mixtures with highly nonideal liquid phases, a two-parameter model is used to describe liquid-phase compositional effects upon the K-factor. The quasi-Newton methods of Mehra et al. (1983) and Nghiem (1983) are applied to solving various sets of solution variables in the proposed algorithm. Activity coefficients are calculated using the UNIQUAC activity-coefficient model (1975) with parameters obtained from the UNIFAC group-contribution method (1975). The computational procedure is applicable to distillation, absorption and reboiled-absorption configurations. The proposed algorithm was implemented in a FORTRAN 77 program and tested on the Honeywell DPS 8/70M computer at the University of Calgary. Inclusion of the liquid-phase model resulted in improved convergence behavior for nonideal systems in which the original “inside-out” method failed to converge.     

Tissue-on-Tissue Testing of Dry Eye Formulations for Reduction of Bioadhesion

Glutaraldehyde-preserved, human umbilical cord vein graft (UCVG) was selected as a stable surrogate tissue source for testing of bioadhesion-reducing lubricants. Bioadhesion, as manifested in tissue-on-tissue friction coefficients of 0.2–0.4 for saline-lubricated UCVG, was quantitatively and persistently reduced after the instillation of a single aliquot of an ophthalmic “artificial tears” formulation containing active demulcents polyethylene glycol (PEG400) and propylene glycol (PG), as well as a gellable hydroxypropyl guar (HP Guar) in a borate-buffered solution between the “blinking” tissues. Reduced adhesion was maintained (was “substantive”), even after rinsing excess lubricant from the surfaces. Comparative tests with tissue-on-solid, and solid-on-solid, similarly lubricated couples point to a potentially unique mechanism that involves macromolecules modifying the tissue phases to provide rinse-resistant lubricity and surface protection in articulated tissue-to-tissue interfaces. Results for tissue-on-tissue couples were obtained in laboratory trials utilizing a reciprocating pin-on-disc type friction/wear test device articulating preserved human umbilical cord vein segments under increasing loads, and again after saline rinsing to determine persistence of the friction-reducing effects. A single confirmatory test using donated human cornea against vein graft tissue showed the lowest coefficient of friction, below 0.05, for the “artificial tears” formulation. Mechanistic studies employing the same test device and protocol for metal oxide (germanium)-on-metal oxide couples, as well as for metal oxide-on-tissue couples, indicated that simple increases in viscosity were not the likely sources of friction reduction, and revealed frictional values higher than measured for the similarly lubricated tissue-on-tissue couples. Thus, formulation development to minimize bioadhesion requires that appropriate simulations be used to obtain clinically predictive data for circumstances of liquid uptake into the tissues, resultant tissue swelling, and binding to impermeable adjacent materials.     

Gas absorption rates in a stirred cell with plane interface in the presence of fine particles

The rates of absorption of carbon dioxide into water and into 0.5 mol/L equimolar carbonate buffer solutions (containing varying amounts of arsenite) were measured in a stirred cell with plane interface in the presence of fine solids (activated carbon, kieselguhr and alumina). Experiments show that the absorption rate increases significantly when the activated carbon loading increases up to about 0.2 g/L and thereafter remains constant. No significant effects were observed for other solids. The results could be explained in terms of a “shuttle” mechanism where particles adsorb gas near the interface which is then followed by desorption (or reactions) in the bulk. At very high loadings (above 10 vol.%), the absorption rate decreased for all particles and this could be explained by the blockage of the interface and/or by the sharp increase in the suspension viscosity.     

Effect of shell phase composition on the dielectric property and energy density of core-shell structured BaTiO3 particles modified poly(vinylidene fluoride) nanocomposites

Dielectric nanocomposites have attracted much attention due to their wide applications in electronics and electrical industry. Recently, incorporating core-shell nanoparticles into polymer matrix to improve the dielectric properties of nanocomposites has been widely reported. Tailoring the interfacial region between the polymer and the nanoparticles plays a crucial role in achieving the desired dielectric and energy storage properties of nanocomposites. However, the effect of shell structure in the interface region on the dielectric and energy storage properties is rarely studied. Based on this, core-shell BaTiO₃ nanoparticles with two different shell polymers, a “hard-soft” copolymer of methyl methacrylate and butyl acrylate (P[MMA-BA]) and a “hard” homopolymer of methyl methacrylate (PMMA), were prepared in this paper. The effect of core-shell BaTiO₃ nanoparticles with different shell structures on the dielectric and energy storage properties of poly(vinylidene fluoride) (PVDF) was investigated in depth. Due to the formation of a tight interfacial region between P(MMA-BA)@BT and PVDF matrix, P(MMA-BA)@BT/PVDF nanocomposites not only have low dielectric loss but also higher energy efficiency than PMMA@BT/PVDF nanocomposites. This study suggests a potential strategy that fabricating a “hard-soft” copolymer shell on BaTiO₃ surface can obtain desirable energy storage efficiency than the single “hard” shell structure in dielectric nanocomposites.