Parallel Breakup of Polymer Drops under Simple Shear

The deformation and breakup of a single polycarbonate drop in a polyethylene matrix is studied at high temperatures under simple shear flow using a transparent Couette device. We observed “parallel breakup” where the drop breaks after being stretched into a thin sheet parallel to the flow. The breakup occurs at a viscosity ratio greater than 3.5. Deborah number and a stress ratio incorporating elastic moduli can characterize the “parallel breakup”.

Deformation and breakup of a polycarbonate drop in a polyethylene matrix.     

Headspace liquid-phase microextraction of methamphetamine and amphetamine in urine by an aqueous drop

This study developed a headspace liquid-phase microextraction (LPME) method by using a single aqueous drop in combination with high performance liquid chromatography (HPLC)-UV detection for the determination of methamphetamine (MAP) and amphetamine (AP) in urine samples. The analytes, volatile and basic, were released from sample matrix into the headspace first, and then protonated and dissolved in an aqueous H₃PO₄ drop hanging in the headspace by a HPLC syringe. After extraction, this drop was directly injected into HPLC. Parameters affecting extraction efficiency were investigated and optimized. This method showed good linearity in the investigated concentration range of 1.0-1500 μg L⁻¹, repeatability of the extraction (R.S.D. < 5%, n = 6), and low detection limits (0.3 μg L⁻¹ for both analytes). Enrichment factors of about 400-fold and 220-fold were achieved for MAP and AP, respectively, at optimum conditions. The feasibility of the method was demonstrated by analyzing human urine samples.     

The stability of hydrocarbon oil droplets at the surfactant/oil interface

Summary The effect of the nature of the oil on the coalescence of single oil droplets at the plane aqueous surfactant solution/oil interface has been investigated. The drop rest-times for the first stage coalescence of a range of hydrocarbon oils have been measured with constant drop volume. The apparatus was based on a design byNielsen et al. (13). Variables that affected drop lifetimes such as drop size, apparatus dimensions, saturation of the two phases with the other component, and surfactant concentration and chain length were investigated and a standard technique was developed. For saturated hydrocarbons the droplet stability falls progressively with increase in chain length. Unsaturation or aromatic character brings about a decrease in droplet stability. The results are discussed in terms of the balance between the cohesive forces between oil molecules and the adhesive forces, between the alkyl chain of the surfactant and oil molecules.The addition of small quantities of long chain alcohol brings about a marked increase in stability through the formation of a complex condensed film at the oil/water interface. Attempts to correlate droplet stability data and the stabilities of bulk emulsion systems and spreading coefficient were not successful.

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Zusammenfassung Die Koaleszenz von Öltropfen auf planen Oberflächen von Tensiden wurde untersucht, wozu eine Standardtechnik entwickelt wurde. Bei gesättigten Kohlenwasserstoffn nimmt die Stabilität der Tröpfchen mit zunehmender Kettenlänge ab. Auch ungesättigte Bindungen und aromatische Gruppen erniedrigen die Stabilität.Die Resultate werden diskutiert unter Berücksichtigung der kohäsiven Kräfte zwischen den Molekülen des Kohlenwasserstoffes und den adhäsiven Kräften zwischen den Alkylketten der Tenside und den Kohlenwasserstoffmolekülen.Die Stabilität wird stark erhöht, wenn geringe Mengen langkettigen Alkohols zugesetzt werden, infolge der Bildung eines komplexen kondensierten Films an der Öl/Wasser-Grenzfläche. Versuche, die gewonnenen Stabilitätsdaten mit der Stabilität der Bulkemulsionen und des Spreitungskoeffizienten in Beziehung zu setzen, waren nicht erfolgreich.

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Nomenclature A area per molecule of surfactant at the interface (nm²) - a activity - C concentration (mol dm^–3) - d drop diameter (cm or mm) - d ₀ mean droplet diameter on volume basis at initial storage - d _t mean droplet diameter on volume basis aftert days storage - h film thickness - K Boltzmann's constant - K ₁ coalescence constant - k first order rate constant for coalescence (s^-1) - k ₁ coalescence constant - k ₂ empirical constant - L distance from needle to interface (cm) - M geometric mean rest-time (s) - N number of droplets not coalesced - n exponent - R gas constant - S spreading coefficient (Nm^-1) - T absolute temperature - T1/2 first order half-life for coalescence (s) - t time (s) - t _d drainage time (s) - t1/2 time required for half of droplets to coalesce (s) - ^tmean mean rest-time (s) - V molar volume - v velocity of hole formation - Hv latent heat of vaporization - solubility parameter - interfacial tension (Nm^-1) - ⁰ interfacial tension between pure oil and water - _e viscosity of continuous phase - density - density difference - surface tension - ag geometric standard deviation - T surface excess - T ₀ saturation adsorption     

Extraction of Polonium from Aqueous α-Hydroxyisobutyric Acid Solutions Using Dioctyl Sulphide, Cyanex 272, Cyanex 301 or Cyanex 302 in Toluene

A study of the extraction of polonium from aqueous solutions containing -hydroxyisobutyric acid (-HIBA) was performed with four different extractants, di-n-octyl sulphide (DOS), Cyanex 272, Cyanex 301 and Cyanex 302, dissolved in toluene. The extracted complex for DOS at low -HIBA concentrations is most likely PoO(-HIB)₂·2DOS, while at higher -HIBA concentrations there seems to be a solvating effect implicating an extracted complex of the type PoO(-HIB)₂(-HIBA)₂·2DOS. For the extraction of polonium with Cyanex 272 the results are inconclusive. The extracted complex is either PoOA₂ or PoO(-HIB)₂·2HA. For extraction with Cyanex 301 or Cyanex 302 the major extracted species does not contain any -HIBA molecules. The neutral species in both cases is PoOA₂, extracted at low extractant concentrations, while at higher extractant concentrations a complex of the type PoOA₂·xHA is extracted. The extraction of polonium increases in the order Cyanex 272 < DOS < Cyanex 302 < Cyanex 301.     

Experimental observation of oscillatory effects on the relaxation of a sheared liquid drop

This work deals with the experimental observation of the shape oscillations followed by a viscous liquid drop immersed in another viscous fluid matrix when retracting from a deformed state into the spherical shape under the action of interfacial forces. The droplet is firstly deformed into an ellipsoidal shape by a shear flow and later allowed to recover the equilibrium shape after cessation of the flow. It is observed that such an oscillatory process occurs for a wide range of viscosity ratios and it may be described by a dampened oscillation. Viscous components dominate the drop retraction, just allowing few oscillations. The dampening factor, frequency and amplitude of the oscillations are affected by the drop viscosity. Frequencies and amplitudes are also influenced by the initial drop deformation.     

Enhanced headspace single drop microextraction method using deep eutectic solvent based magnetic bucky gels: Application to the determination of volatile aromatic hydrocarbons in water and urine samples

A facile headspace single drop microextraction method was developed using deep eutectic solvent‐based magnetic bucky gel as the extraction solvent for the first time. The hydrophobic magnetic bucky gel was formed by combining choline chloride/chlorophenol deep eutectic solvent and magnetic multiwalled carbon nanotube nanocomposite. Magnetic susceptibility, high viscosity, high sorbing ability, and tunable extractability of organic analytes are the desirable advantages of the prepared gel. Using a rod magnet as a suspensor in combination with the magnetic susceptibility of the prepared gel resulted in a highly stable droplet. This stable droplet eliminated the possibility of drop dislodgement. The prepared droplet made it possible to complete the extraction process in high temperatures and elevated agitation rates. Furthermore, using larger micro‐droplet volumes without any operational problems became possible. These facts resulted in shorter sample preparation time, higher sensitivity of the method, and lower detection limits. Under the optimized conditions, an enrichment factor of 520–587, limit of detection of 0.05–0.90 ng/mL, and linearity range of 0.2–2000 ng/mL (coefficient of determination = 0.9982–0.9995) were obtained. Relative standard deviations were < 10%. This method was successfully coupled with gas chromatography and used for the determination of benzene, toluene, ethylbenzene, and xylene isomers as harmful volatile organic compounds in water and urine samples.     

Generalized rheological characteristic of plastic disperse systems with polymeric and low-molecular dispersion media (matrices)

Analysis of literature data on the flow of polymeric and oligomeric compositions as well as on systems of low viscous dispersion media containing a high-disperse filler (carbon black, silica, high-disperse chalk) has been carried out. As the basic idea, a proposal is made that their viscosity anomaly is due not to the matrix viscosity anomaly, but to the gradual breakdown of the filler structural skeleton with increasing shear stress and shear rate . The viscosity anomaly of those compositions is determined by the zeroshear but not by the apparent matrix viscosity. A general relationship has been found to describe the flow of such systems depending on the zero-shear matrix viscosity values, ₀, their yield stress, _y , and filler volume concentration , whereK=4.9 andn=0.69 are constants.     

The effect of interfacial viscosity on the droplet dynamics under flow field

The effects of interfacial viscosity on the droplet dynamics in simple shear flow and planar hyperbolic flow are investigated by numerical simulation with diffuse interface model. The change of interfacial viscosity results in an apparent slip of interfacial velocity. Interfacial viscosity has been found to have different influence on droplet deformation and coalescence. Smaller interfacial viscosity can stabilize droplet shape in flow field, while larger interfacial viscosity will increase droplet deformation, or even make droplet breakup faster. Different behavior is found in droplet coalescence, where smaller interfacial viscosity speeds up film drainage and droplet coalescence, but larger interfacial viscosity postpones the film drainage process. This is due to the change of film shape from flat‐like for smaller interfacial viscosity to dimple‐like for larger interfacial viscosity. The film drainage time still scales as Ca⁰ at smaller capillary number (Ca), and Ca^1.5 at higher capillary number when the interfacial viscosity changes. The interfacial viscosity only affects the transition between these limiting scaling relationships. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1505–1514, 2008     

Melt flow behavior in capillary extrusion of nanometer calcium carbonate filled PCL bio-composites

Nanosized calcium carbonate (nano-CaCO₃) filled polycaprolactone (PCL) bio-composites were prepared by using a twin-screw extruder. The melt flow behavior of the composites, including the entry pressure drop, melt shear flow curves and melt shear viscosity, were measured through a capillary rheometer operated in a temperature range of 170∼200 °C and shear rates varying from 50 to 10³ s⁻¹. The entry pressure drop showed a non-linear increase with increasing shear stress when the filler weight fraction was less than 3%, while it decreased slightly with an increase of shear stress at a filler weight fraction of 4%. The melt shear flow roughly followed a power law, while the effect of temperature on the melt shear viscosity was estimated by using the Arrhenius equation. Moreover, the influence of the nano-CaCO₃ on the melt shear viscosity of the PCL composite was not significant at low filler levels.     

Rheology of heterophase polymer systems

This lecture attempts to elucidate rheological behavior of multiphase polymer systems through a comparison with our studies on much simpler systems such as suspensions of (a) non-aggregating and (b) aggregating monodisperse spheres in viscoelastic media, (c) polymer latex in the same polymer liquids, and (d) emulsions or blends of two polymers with or without an emulsifying block copolymer. For the system (a) not only the viscosity η but also the modulus obey the known simple dependence on volume fraction ϕ of hard-sphere suspensions, while for the system (b) the flow induced-aggregation and dissociation of the particles govern the rheology. In the system (c), relaxations of entanglements of the adsorbed chains as well as the spatial distribution of the latexes are essential. For the emulsion (d) of a biased composition range (e.g., ϕ₁ > ϕ₂) the matrix phase 1 dominates, unless η₁ << η₂. When η₁ ≥ η₂, deformation and/or bursting of the dispersed phase 2 take place. For those of an even composition, the viscosity is additive of those of the components and is enhanced by adding the emulsifying block copolymer component.     

Effect of POSS on morphology and properties of poly(2,6-dimethyl-1,4-phenylene oxide)/polyamide 6 blends

Poly(2,6-dimethyl-1,4-phenylene oxide)/polyamide 6 (PPO/PA6) (50/50 w) blends filled with epoxycyclohexyl polyhedral oligomeric silsesquioxane (POSS) were prepared via melt-mixing. The reactions between POSS and PPO/PA6 blends were studied by Fourier transform infrared spectroscopy, end group and gel content tests. The morphology of PPO/PA6/POSS composites was observed by field emission scanning electron microscope and transmission electron microscope. As a chain extender and a crosslinking agent for PA6, POSS largely affected the morphology of the composites, which was mainly dependent on the melt-viscosity ratio and interfacial tension between the components. With increasing POSS content from 2 to 4 phr, the morphology of the composites transformed from droplet/matrix to co-continuous morphology. The PPO/PA6/POSS composites with co-continuous morphology had the better mechanical properties than those with droplet/matrix morphology. Dynamic mechanical thermal analysis showed that the addition of POSS increased the T_g of PA6.     

Morphology and physical properties of polyethylene/silicate nanocomposite prepared by melt intercalation

Maleated polyethylene (PEMA)/silicate nanocomposites with a different aspect ratio of silicate and maleated PEMA/SiO₂ composite were prepared by melt intercalation. The nanocomposites with a high aspect ratio silicate (montmorillonite) showed a faster decrease in the terminal slope of the storage modulus and a steeper increase in complex viscosity than those with a low aspect ratio silicate (laponite) and SiO₂. The addition of montmorillonite increases the crystallization and the melting temperature of PEMA but decreases above 3 vol % of the silicate content because of the increased viscosity. The nanocomposite with montmorillonite showed the highest yield strength and secant modulus among the composites because of the highest aspect ratio of the filler. It also revealed strong interfacial adhesion with the matrix and orientation during tensile deformation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1454–1463, 2002     

Etude thermodynamique du systeme plomb—selenium par calorimetrie

The enthalpy of formation of PbSe liquid alloys was measured at nine temperatures by direct reaction calorimetry (drop method) for 0 < x_Se < 0.5 and 883 < T < 1365 K. The enthalpy of formation is strongly negative in the whole range investigated. It is not dependent on the temperature when x_Se < 0.3 but increases strongly with temperature when 0.3 < x_Se < 0.5 (ΔC_p,max ?90 J K^?1 mol^?1 at x_Se = 0.5).     

Bacterial biosorption and retention of thorium and uranyl cations by Mycobacterium smegmatis

Biosorption of Th⁴⁺ and UO ₂ ²⁺ ions, both separately and in mixed equimolar ratio, was carried out using nitrate-buffered solutions of the cations at pH 1 in the presence of 5%w/w non-proliferative cell suspensions of Mycobacterium smegmatis. At equilibrium following a 3 h treatment, specific adsorption for 2 mM Th and U was, respectively, 102 and 115 mol g^–1 dry biomass for individual solutions and 102 and 42 mol g^–1 for the mixed 2/2 mM solution. Desorption studies of the cation-loaded biomass preparations in aqueous media and in soilbacterial suspensions within the pH range <1 to 11 showed that leaching of throium was generally less than 1% at pH 1–11 after 7 d, whereas uranium was leached to the extent of 2% at pH 1 and up to 10% under the same conditions in Th–U mixtures.     

Controlled synthesis of palladium icosahedra nanocrystals by reducing H2PdCl4 with tetraethylene glycol

The controlled synthesis of Pd icosahedra in tetraethylene glycol with H₂PdCl₄ as a precursor and polyvinylpyrrolidone (PVP) as a stabilizer was demonstrated. Tetraethylene glycol served as both solvent and reducing agent, and uniform Pd icosahedra with a mean size of 45 ± 5 nm were successfully synthesized with a high yield of over 90% in oil-bath at 160 °C for 2.5 h. A certain affinity for the metal particles, a higher viscosity and a milder reducing power of tetraethylene glycol would be responsible for the formation of uniform and stable Pd icosahedra with a high yield. The optimum KOH/Pd(II) ratio, PVP/Pd(II) ratio, temperature, and heating time for the reaction system was 1.4/1, 1/1, 160 °C, and 2.5 h, respectively.     

Experimental study of the relative effect of pressure drop and flow rate on the droplet size downstream of a pipe restriction

An experimental setup consisting of a 100?mm inner diameter pipeline, a butterfly valve with inner diameter of 100?mm, and oil and water pumping capacities of up to 20?m³/h were used to study droplet breakup in two-phase oil–water flow. The tests were performed at atmospheric pressure and under ambient temperatures. A particle-sizing camera was used to quantify droplet sizes. Combinations of different flow rates, water cuts, and pressure drops were tested to determine the relative effects of flow rate and pressure drop over a valve on the droplet breakup process. The test matrix was designed so that it should be possible to determine if the droplet sizes produced were independent of the flow rate. The fluid system consisted of a water phase and a mineral oil with viscosity of 4?mPa?·?s. Two different droplet breakup models were compared against the measured droplet sizes. The two models considered turbulence and droplet acceleration through the restriction respectively as the main contributor for droplet breakup.     

Morphology and properties of biodegradable poly (lactic acid)/poly (butylene adipate-co-terephthalate) blends with different viscosity ratio

Phase morphology exerts a tremendous influence on the properties of polymer blends. The development of the blend morphology depends not only on the intrinsic structure of the component polymers but also on extrinsic factors such as viscosity ratio, shearing force and temperature in the melt processing. In this study, various poly (butylene adipate-co-terephthalate) (PBAT) materials with different melt viscosity were prepared, and then poly (lactic acid) (PLA)/PBAT blends with different viscosity ratio were prepared in a counter-rotating twin-screw extruder under constant processing conditions. The influence of viscosity ratio on the morphology, mechanical, thermal and rheological properties of PLA/PBAT (70/30 w/w) blends was investigated. The experimental results showed that the morphology and properties of PLA/PBAT blends strongly depended on the viscosity ratio. Finer size PBAT phase were observed for viscosity ratio less than 1 (λ < 1) compared to samples with λ > 1. It was found that the interfacial tensions of PLA and PBAT were significantly different when the viscosity ratio was changed, the lowest interfacial tensions (0.12 mN/m) was obtained when the viscosity was 0.77. Additionally, the maximal tensile strength in PLA/PBAT blends were obtained when the viscosity ratio was 0.44, while the maximal impact properties were obtained when the viscosity ratio was 1.95.     

Comparison of Dynamic Simulations with RBS Measurements of Low Energy Ion Implantation of Sb+ into SiO2/Si Substrates

Antimony ions were implanted into SiO₂/Si substrates at energies of 30 and 50keV at relatively low doses (max. 5×10¹⁵ionscm^–2). The behaviour of the implanted ions was simulated with a dynamic TRIM code, allowing treating alteration of the target in a dynamic mode, i.e. as a function of ion dose. For cases, where the projected range of the implant coincides with the interface, it has been observed that there is significant mixing between the SiO₂ layer and the Si substrate together with a constant value for the O/Si ratio except for a pronounced oxygen surface peak. Whereas in the cases, where the implant is far from the interface, the O/Si ratio shows characteristic oscillations together with the surface peak. For high doses, above about 10¹⁶ionscm^–2, a gradual increase of the sputtering yield of SiO₂ is observed due to Sb incorporation in the substrate. The balance between the sputtering and swelling of the target is shown to be negative up to a fluence of 9.5×10¹⁵ionscm^–2, although the total sputtering yield is more than 1. RBS (Rutherford Backscattering Spectrometry) measurements confirm the mixing at the interface in cases where the latter coincides with the projected range of the implanted ions.     

Selective extractions to assess the biogeochemically relevant fractionation of inorganic mercury in sediments and soils

Here we present a new method for sequential selective extractions (SSEs) for Hg in geological solids, validated with extensive quality assurance procedures. Mercury was separated into fractions which “make sense” biogeochemically, rather than being identified by specific compounds. Experiments elucidated the effects of extraction time, solids-to-liquid ratio, and alternate solvents in natural samples, reference materials, and pure compounds. Compounds tested included HgS (red and black), HgCl₂, Hg⁰, Hg₂Cl₂, HgSe, HgO, Hg(II) adsorbed on goethite, Hg-humate, and gold amalgamated Hg. Based on these findings, a five-step sequence of extractions was established to separate the compounds into biogeochemically distinct categories. The fractions and leaching media were as follows: F1 (deionized water), F2 (0.01 M HCl+0.1 M CH₃COOH), F3 (1 M KOH), F4 (12 M HNO₃), and F5 (aqua regia). Method blanks and method detection limits (MDLs) of 0.1-5 ng/g were obtained for the various analytical fractions, depending on the reagent concentrations used. Precision ranged from 2 to 8% for the major fractions in a sample, but increased to 2-40% for fractions making up <5% of the total. Recovery of total Hg by the sum of species in reference materials showed that the accuracy of the method ranges from 90 to 105%. Methylation potential, determined by anoxic incubation sample aliquots with biologically active sediments, showed that inorganic Hg extracted in the F3 fraction is most strongly correlated with methylation potential. In most natural and sediment incubation samples, the majority of Hg present was found either in the F3 or F5 fractions.     

Physicochemical Characterization of Poly(vinyl chloride). II. Molecular Weight Distributions

Abstract

Molecular weight distributions in poly(vinyl chloride) resins have been determined from simple viscosity measurements. Ratio of 11% solution viscosity to intrinsic viscosity yielded a figure which has been correlated with molecular weight distributions obtained (1) from the ratio of weight-average to number-average molecular weights and (2) from gel permeation chromatography. Ratio of viscosities is thus a useful short-cut technique for obtaining approximate molecular weight distributions in poly(vinyl chloride) resins which have 0. 77 < [η] < 1.15 and 1. 6 < ROM < 2. 8.