Rate of Bitumen Film Transfer from a Quartz Surface to an Air Bubble as Observed by Optical Microscopy

The rate of bitumen transfer from a bitumen‐coated quartz plate to a gas bubble surface in aqueous alkaline solutions was recorded photographically. During bitumen spreading, a bulk layer followed the formation of thin bitumen films (precursor films). The bulk layer spread at the bubble surface with a velocity of about one order of magnitude less than the velocity of the precursor film. The energy of activation for spreading of the bulk layer varied from about 66 to 123 kJ/mol depending on the stage of bitumen spreading but remained constant at about 105 kJ/mol for the precursor film. Results are discussed with respect to fundamental issues associated with flotation recovery of heavy oils.     

不同性质有机分散相对CO2吸收过程的影响

分别以环己烷、甲苯、正庚烷和正丁醇4种不同性质的有机溶剂作分散相,采用恒温槽反应器测定了CO2在水中的吸收速率. 结果表明,吸收速率与界面性质有关,未加表面活性剂时,甲苯、环己烷、正庚烷乳液中的传质速率与其在气液界面上的铺展状况相对应,甲苯>正庚烷>环己烷,铺展所产生的油膜造成了附加阻力,使低体积分率时CO2吸收速率反比纯水中低,最小时甲苯、环己烷、正庚烷所对应的体积分率分别为0.02, 0.08和0.04. 表面活性剂的加入促使乳液更趋稳定,但由于表面活性剂在气液界面及油水界面的吸附,传质阻力显著增加,吸收速率较无表面活性剂时更低,对此现象进行了理论分析. 与甲苯、环己烷等不同,正丁醇/水为部分互溶体系,在实验浓度范围内,吸收速率呈现先上升后逐渐下降的趋势,乳液与纯水中吸收速率比J/J0最高点与正丁醇在水中的溶解度相对应.     

Influence of precursor deficiency sites for borate incorporation on the structural and biological properties of boronated hydroxyapatite

The biological properties of hydroxyapatite (HA) are significantly influenced by its compositional characteristics especially doping elements and/or Ca/P ratio, which can be altered by precursor chemistry. In this study, a group of boronated (B-incorporated) hydroxyapatite (BHA) was synthesized using a precipitation method by setting the Ca/P ratio to the stoichiometric value of HA (1.67), while altering the precursor chemistry by adjusting either (Ca + B)/P (Ca-deficient precursor, BC) or Ca/(P + B) (P-deficient precursor, BP). After heat-treatment, the partial decomposition of the BC was observed, forming tricalcium phosphate as the byproduct, however, the BP showed phase stability at all temperatures. The B-ionic species in the form of (BO₂)^? and (BO₃)^3? were incorporated into the HA structure at the (PO₄)^3? and (OH)^? positions, respectively. The incorporation of the B species also facilitated the incorporation of (CO₃)^2? groups specifically in the BPs. This is the first finding on BHA reporting that preferential (CO₃)^2? incorporation depends on the precursor chemistry used. As a result, osteoblast adhesion was superior on the BPs compared to pure HA owing to the carbonated structure, increasing cell spreading area. As such, this in vitro study highlighted that the present P-deficient precursor approach for synthesizing BHA improved biocompatibility properties and should, thus, be further considered for the next-generation of improved orthopedic applications.     

Protein and lipid films at equilibrium at air-water interface

The surface activity of β-casein, caseinate, and a whey protein isolate in aqueous solutions has been investigated over a range of protein concentrations (1·10⁻⁵ to 5% w/w) at pH 5 and 7. The surface pressure data were determined by the Wilhelmy plate method. Surface pressure data at low protein concentration indicate a low surface activity that rises to a plateau as the monolayer is saturated at higher protein concentrations. The protein concentration and the surface pressure at the plateau depend on the pH and the type of protein in the aqueous phase. Protein-monoglyceride interactions were investigated by spreading an insoluble monoglyceride (monopalmitin, monoolein, or monolaurin) on a film of protein previously adsorbed on the interface at equilibrium. The existence of protein-monoglyceride interactions depends on the interfacial composition and on the protein/monoglyceride ratio. The surface activity of mixed protein-monopalmitin and protein-monoolein films is determined by the lipid as the surface pressure of the mixed film is the same as the monoglyceride equilibrium spreading pressure, and the monolayer is not saturated by the protein. However, the protein determines the surface activity of mixed protein-monopalmitin and protein-monoolein films as the protein saturates the monolayer. For protein and monolaurin mixed films, protein determines the surface activity over the range of protein-monolaurin compositions due to monolaurin dissolution in the bulk aqueous phase.     

Time scale analysis for fluidized bed melt granulation-II: Binder spreading rate

The spreading time of liquid binder droplet on the surface a primary particle is analyzed for Fluidized Bed Melt Granulation (FBMG). As discussed in the first paper of this series (Chua et al., in press) the droplet spreading rate has been identified as one of the important parameters affecting the probability of particles aggregation in FBMG. In this paper, the binder droplet spreading time has been estimated using Computational Fluid Dynamic modeling (CFD) based on Volume of Fluid approach (VOF). A simplified analytical solution has been developed and tested to explore its validity for predicting the spreading time. For the purpose of models validation, the droplet spreading evolution was recorded using a high speed video camera. Based on the validated model, a generalized correlative equation for binder spreading time is proposed. For the operating conditions considered here, the spreading time for Polyethylene Glycol (PEG1500) binder was found to fall within the range of 10⁻² to 10⁻⁵ s. The study also included a number of other common binders used in FBMG. The results obtained here will be further used in paper III, where the binder solidification rate is discussed.     

Liquid crystalline copolyester/polyethylene in situ composite film: Rheology,morphology, molecular orientation,and tensile properties

A thermotropic liquid crystalline copolyester (TLCP) was blended with low density polyethylene using a corotating twin screw extruder and then fabricated by extrusion through a miniextruder as cast film. Rheological behavior, morphology, and tensile properties of the blends were investigated. Melt viscosities of neat components and blends measured by using plate‐and‐plate and capillary rheometers at 240°C, in the shear rate range 1–10⁴ s^?1, showed similar shear thinning effect. The viscosity values measured by the two techniques in the overlapping range of shear rate are found to be identical, which is in accord with the Cox–Merz rule. Addition of TLCP slightly reduces the matrix melt viscosity. TLCP dispersed phase in the extruded strand appeared in the form of spherical droplets. These droplets were elongated into fibrils with high aspect ratio (length to width) at the film extrusion step. As a result, the Young's modulus in machine direction (MD) of the composite film was greatly enhanced. At 20 wt % of TLCP, the MD Young's modulus was found to be about 16‐fold increase compared to that of the neat polyethylene film. However, the elongation at break sharply dropped with the increase of TLCP content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 561–567, 2002; DOI 10.1002/app.10307     

Study of the partial wetting morphology in polylactide/poly[(butylene adipate)‐co‐terephthalate]/polyamide ternary blends: case of composite droplets

The prediction of the morphology of ternary polymer blends requires a good knowledge of the values of the three interfacial tensions. We selected three polymers, either biobased or biodegradable, polyamide (PA), poly[(butylene adipate)‐co‐terephthalate] (PBAT) and polylactide (PLA), and we accurately measured their interfacial tensions using the retraction method, varying the molar mass or inverting the phases. The following values of interfacial tension were obtained: γ_PBAT/PLA = 3.3 ± 0.7 mN m^?1, γ_PA/PLA = 5.6 ± 0.3 mN m^?1 and γ_PBAT/PA = 3.0 ± 0.4 mN m^?1. These values were used to calculate the spreading coefficients giving rise to two negative coefficients and one coefficient close to zero. Ternary blends with various compositions, two different levels of viscosity for PBAT and different processing conditions were prepared. There was a very good agreement between the predictions of the spreading theory, when using the values of interfacial tension of the right order of magnitude, and the observed morphologies, whatever the polymer serving as a matrix. When PLA or PBAT was chosen as the matrix, the ternary blend morphology was composed of composite droplets, presenting a partial wetting morphology, dispersed in the polymer matrix. This morphology was observed whatever the composition, the viscosity of the PBAT phase and the processing conditions. A further calculation of the free energy confirmed this morphology. The formation process of this semi‐encapsulated morphology was observed during blending. © 2018 Society of Chemical Industry     

New NLO-functionalized poly(1,4-phenylenevinylene) derivative containing dinitrobenzene moiety as electron acceptor

Summary New NLO-functionalized poly(1,4-phenylenevinylene) (PDNAPV) containing 2,4-dinitroanilino group, was synthesized through organic-soluble precursor pathway. The prepared polymer was characterized with NMR, FT-IR, UV-visible and other spectroscopic methods to identify its properties. The result from the thermal analyses and spectroscopic techniques showed that the precursor was converted into PDNAPV around at 200°C without any decomposition of 2,4-dinitroanilino group. The second-order NLO coefficient (χ⁽²⁾) of poled PDNAPV film was determined by second-harmonic generation technique. The resonant χ⁽²⁾ value was 26 pm/V and the resonance-corrected value (χ⁽²⁾(0)) was 12 pm/V, which was stable at room temperature for a month Received: 16 February 2001/Accepted: 13 March 2001     

A study of the mechanism of gas absorption into oil-water emulsions

The mechanism of oxygen and argon transfer into aqueous emulsions of n-alkans and of oleic acid was studied both theoretically and experimentally. An apparatus allowing to measure the coefficient of mass transfer from individual bubbles into the turbulent medium of either a single- or multi-phase liquid has been designed and constructed. The effect of the oil phase on the bubble-to-emulsion mass transfer coefficient was investigated. In o/w type emulsions (oil as the dispersed and water as the continuous phase) of n-alkans (the system with negative spreading coefficient) the mass transfer coefficient k_L^w is not affected by the content of the oil phase, and is equal to the coefficient of mass transfer into a pure aqueous phase. In the w/o type emulsion the k_L^w value increases proportionately to the volume fraction of n-alkans. In the oleic acid-in-water emulsion (the system with positive spreading coefficient) k_L^w initially decreases and then increases proportionately to the oil fraction. The initial decrease of k_L^w is attributed to surface activity effects of oleic acid. The data suggest that the mechanism of gas transfer to the emulsions is as follows: No direct contact between the oil and the gas phase exists in o/w type emulsions with negative spreading coefficient, and the transfer path is gas-water-oil. In w/o type emulsions (both with negative and positive spreading coefficient), however, there is a direct contact between the gas and both the continuous oil phase and the dispersed aqueous phase; there is a parallel transfer of gas to both the phases.     

Study on morphology of ternary polymer blends. I. Effects of melt viscosity and interfacial interaction

The morphology of some ternary blends was investigated. In all of the blends polypropylene, as the major phase, was blended with two different minor phases, ethylene–propylene–diene terpolymer (EPDM) or ethylene–propylene–rubber (EPR) as the first minor phase and high‐density polyethylene (HDPE) or polystyrene (PS) as the second minor phase. All the blends were investigated in a constant composition of 70/15/15 wt %. Theoretical models predict that the dispersed phase of a multiphase polymer blend will either form an encapsulation‐type phase morphology or phases will remain separately dispersed, depending on which morphology has the lower free energy or positive spreading coefficient. Interfacial interaction between phases was found to play a significant role in determining the type of morphology of these blend systems. A core–shell‐type morphology for HDPE encapsulated by rubber was obtained for PP/rubber/PE ternary blends, whereas PP/rubber/PS blends showed a separately dispersed type of morphology. These results were found to be in good agreement with the theoretical predictions. Steady‐state torque for each component was used to study the effect of melt viscosity ratio on the morphology of the blends. It was found that the torque ratios affect only the size of the dispersed phases and have no appreciable influence on the type of morphology. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1129–1137, 2001     

Photoinduced layer phenomenon caused by iodine formation in MoSe2: electrolyte (iodide) junctions

When iodide is photooxidized at a n-type MoSe₂ electrode at a high rate, a dim film is observed to spread over the metallic bright electrode and the reflected light intensity throughout the visible and near ir spectral region drops by 70–80%. The phenomenon can — in a reversible way — be controlled by small potential variations (0 ? +0.5 V) and beyond +1.0 V produces electrochemical oscillations, which are paralleled by an additional reflection change which can be seen to propagate across the electrode surface.The phenomenon could be reproduced in absence of light at semiconducting p-type MoSe₂, at metallic NbSe₂ and at Pt-electrodes which excluded the possibility that the pronounced optical changes are produced by a photoelectrochemical or electrochemical modification of layer-type electrode material in presence of iodide. The reflection anomalies can be explained by physical properties of an iodine layer, which is formed in the iodide-depleted diffusion region at the electrode surface.Evidence is given that the spreading of the dim film is actually a phase transition from dispersed to crystalline iodine with an asymmetrical size distribution within the I^? depleted diffusion layer. The resulting gradient of the refraction index works like an anti-reflecting coating. The described phenomenon will have to be considered in attempts to optimize solar cells based on the I^?/I₂ redox couple and it might be of some practical interest for antireflecting layer-technology and electro-optical applications.     

ON THE INTERLINE EVAPORATING REGION OF A WETTING THIN FILM

The extent interline of evaporating region is analyzed for polar liquid film, with the disjoining pressure expressed by P_d = B ln(t) + A. An average effective evaporation is defined for this region and expressed as a simple equation. The results of analysis show that the average effective evaporation rate varies with the relative vapor pressure and so does the length of the interline evaporating region. The increase in relative vapor pressure will make the evaporation from the wetting film more significant.     

Stabilized nanoparticles of metastable ZrO2 with Cr3+/Cr4+ cations: preparation from a polymer precursor and the study of the thermal and structural properties

Nanoparticles of stabilized ZrO₂ in a single cubic phase by 5–20 at.% (of total metal cations) Cr³⁺/Cr⁴⁺ addition are obtained through a chemical method using a polymer matrix made of sucrose and polyvinyl alcohol. On heating at 250–900 °C in air, the polymer network decomposes and burns out leaving behind a dispersed microstructure in 10–25 nm diameter particles of cubic ZrO₂ in spherical shape. A modified microstructure comprises of 10–14 nm crystallites of dispersed tetragonal phase, or both tetragonal and monoclinic phases, in cubic phase appear on a prolong (2 h or larger) heating of precursor at 900–950 °C. Particles in tetragonal ZrO₂ are in acicular shape, while the monoclinic phase is in the shape of platelets. The Cr³⁺/Cr⁴⁺ additive facilitates formation of cubic phase in small particles on a controlled decomposition and combustion of precursor. It stabilizes small particles by inhibiting their growth by forming a thin amorphous surface layer over them.     

High-performance polymer films. III. Preparation and characterization

A series of polyimide and copolyimide films were prepared by film casting, drying, and thermal imidization from the respective precursor poly(amic acid) (PAA) and copoly(amic acid) solutions derived from two dianhydrides, pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), and two diamines, 4,4′-oxydianiline (ODA) and a proprietary aromatic diamine (PD) as monomers. Depending on the solution's inherent viscosity value (molecular weight) and the nature of the polymer chains (derived from rigid or flexible monomers), precursor poly(amic acid) and copoly(amic acid) solution concentrations of 8–12% (w/w) were found to be suitable for the preparation of good quality polyimide/copolyimide films. The recovery of film toughness and creasability from the brittleness at the intermediate temperature of the cure cycle depended not only on the molecular weight of the precursor poly(amic acids)/copoly(amic acids) but also on their chain flexibility. The poly(amic acid) derived from both rigid dianhydride and diamine practically gave rise to a brittle film of polyimide even after curing to 360°C. The resulting polyimide and copolyimide films were compared with Du Pont's Kapton H film. The density of the films was in the range 1.39–1.42 g/cm³. The thickness of most of the films was in the range 20–30 μm. The HPF 3 film, based on PMDA–PD, appeared to be highly colored (reddish brown), and the HPF 2 film, based on BTDA–ODA, had the lightest yellow coloring among the films in this investigation, including Kapton H film. HPF 2, HPF 6, and HPF 8 films were more amorphous than the other films. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 976–988, 2001     

Spreading of emulsions on a solid substrate

The wettability of emulsions is a prominent factor with a broad impact on an extensive variety of industrial applications ranging from the petroleum to the cosmetic industries. Surprisingly, there is no comprehensive study of emulsion spreading to date. In this work, the spreading of water/silicone oil emulsions on glass substrates was investigated. The emulsions were prepared with varying volume fractions of water dispersed in silicone oil, with addition of small amounts of surfactant to stabilize the emulsion structure. The time-dependent variation of dynamic contact angle, base diameter, and the spreading rate of the emulsion droplets were studied. The effect of water/silicone oil weight percentage as well as the droplet size and dispersed phase bubble size were also investigated. The weight percentage of water/silicone oil emulsion and droplet size did not have a significant impact on the spreading dynamics; however, the dispersed phase bubble size affected the spreading dynamics substantially. The coarsening of the dispersed phase bubbles was the key factor in the distinct spreading behavior of emulsions compared to pure liquids.     

Numerical simulations of drop impact and spreading on horizontal and inclined surfaces

The phenomenon of drop spreading is important to several process engineering applications. In the present work, numerical simulations of the dynamics of drop impact and spreading on horizontal and inclined surfaces were carried out using the volume of fluid (VOF) method. For the horizontal surfaces, the dynamics of impact and spreading of glycerin drops on wax and glass surfaces was investigated for which the experimental measurements were available [Šikalo, Š., Tropea, C., Ganic, E.N., 2005a. Dynamic wetting angle of a spreading droplet. Experimental Thermal and Fluid Science 29, 795-802; Šikalo, Š., Tropea, C., Ganic, E.N., 2005b. Impact of droplets onto inclined surfaces. Journal of Colloid and Interface Science 286, 661-669]. The influence of surface wetting characteristics was investigated by using static contact angle (SCA) and dynamic contact angle (DCA) models. The dynamics of drop impact and spreading on inclined surfaces and the different regimes of drop impact and spreading process were also investigated. In particular, the effects of surface inclination, surface wetting characteristics, liquid properties and impact velocity on the dynamics of drop impact and spreading were investigated numerically and the results were verified experimentally. It was found that the SCA model can predict the drop impact and spreading behavior in quantitative agreement with the experiments for less wettable surfaces (SCA>90^°). However, for more wettable surfaces (SCA<90^°), the DCA observed at initial contact times were order of magnitude higher than SCA values and therefore the DCA model is needed for the accurate prediction of the spreading behavior.     

Surface tension of protein and insoluble lipids at the air-aqueous phase interface

The surface activity of bovine serum albumin (BSA) in water and aqueous solutions of ethanol (0.5, 1.0, and 2.0 M) and sucrose (0.5 and 1.0 M) has been investigated over a range of protein concentrations (5–1.10⁻⁵, % w/w). The surface tension data were determined by the Wilhelmy plate method. Surface data at low protein concentrations indicate a low surface activity, which rises to a plateau as the monolayer is saturated at higher protein concentrations. The protein concentration and surface tension at the plateau depend on the aqueous phase composition. The effect of aqueous phase composition on BSA-lipid interactions has been investigated by spreading an insoluble lipid (monostearin or monoolein) on a film of BSA previously adsorbed on the interface. The existence of protein-lipid interactions depends on the protein/lipid ratio. The surface activity of mixed BSA-lipid films is determined by the lipid because the surface pressure of the mixed film is the same as the lipid equilibrium spreading pressure, and the monolayer is not saturated by BSA. However, the surface activity of mixed BSA-lipid films is determined by BSA as the monolayer is saturated by the protein.     

Prediction of dispersed phase drop diameter in polymer blends: The effect of elasticity

This paper discusses the prediction of the dispersed phase drop diameter in polymer blends considering the viscoelastic properties of polymers. The prediction is based on a simple force proportionality. Polymers are viscoelastic, and thus the elasticity of the matrix and the elasticity of the dispersed phase affect the drop size. The forces that deform a polymer droplet in a polymer matrix are the shear forces, η_mγ, and the matrix first normal stress, T_11,m. This deformation is resisted by the interfacial forces, 2 Γ/D and the drop's first normal stress, T_11,d. As a first approximation, the forces were balanced to predict the particle size in polymer blends. The diameter of the dispersed phase was predicted reasonably well for several systems at different operating conditions. It was observed for some systems (PS/PP, PS/EPMA, PS/PA330) that, as the shear rate increased, the diameter of the dispersed phase initially decreased. At a critical shear rate, the diameter reached a minimum value, and beyond it, the diameter increased with shear. This critical value was found to be between 100 to 162.5 s⁻¹ for a PS/PP system. The force balance predicts this minimum drop diameter at a similar critical shear rate. The specific energy input (the amount of energy input into the blend) could not explain the phenomenon of a minimum drop diameter with increase in shear. This minimum is not observed for the high concentration systems, such as the 20% PP dispersed in PS, since the effects of coalescence become significant. In reactive blends, the predicted drop diameter was closer to the experimentally determined diameter, and there was less variation in diameter with changes in shear rate.     

Electrostatic Spray Deposition of Doped Ceria Films

Dense and thin electrolyte films are desirable for solid oxide fuel cells (SOFCs) because of their low gas leakage and low ohmic resistances. This work aims at the preparation of thin dense Gd‐doped ceria (CGO) electrolyte films using a cost‐effective deposition method in ambient atmosphere–electrostatic spray deposition (ESD). The deposition parameters such as deposition temperature, concentration and flow rate of precursor solution were changed systematically to examine their effects on film morphology and hence electrochemical performance. While the film morphology was examined by a scanning electron microscope, the electrochemical performance was revealed by measuring open circuit voltages (OCVs) of NiO‐CGO/CGO/Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3‐δ (BSCF) cells in 500–700 °C with humidified hydrogen as fuel and air as oxidant. The results show that a CGO film of 25 μm thick obtained at a deposition temperature of 400 °C, a precursor solution flow rate of 6 ml h^–1 and a precursor concentration of 0.3 M was dense with very few isolated pores and the OCV of the associated cell was 0.915 V at 500 °C. This implies that the CGO film has negligible gas leakage and ESD is a promising method for preparing thin dense electrolyte films for SOFCs.     

Desiccant films made of low-density polyethylene with dispersed calcium oxide: Water vapor absorption,permeation and mechanical properties

Polymers with dispersed desiccants are relevant for various packaging applications to protect packaged goods from water vapor. The intention of this study was to analyze and to describe a relevant system. Therefore, films with calcium oxide (CaO) were investigated, because such materials are hardly described in scientific literature. Monolayer films with 0.14 to 0.51 g dispersed CaO per 1 g film (PE-LD) were prepared and they absorbed up to 0.2 g water vapor per 1 g of film. The water vapor absorption was described by effective diffusion coefficients. By the use of effective diffusion coefficients and the absorption capacity, the absorption behavior of layers with various thicknesses can be estimated. The steady state (effective) water vapor permeation coefficients of the films with dispersed CaO were a factor of 2 to 24 (8.4 to 101.5 mg cm [cm² s Pa]^–1 × 10¹², at 23 °C) higher than for pure PE-LD films (4.26 mg cm [cm² s Pa]⁻¹ × 10¹², 23 °C). The tensile stress changed only slightly (pure PE-LD: 9.5 N mm⁻²; PE-LD with 0.14 g dispersed CaO per 1 g film: 8.1 N mm⁻²; PE-LD with 0.51 g dispersed CaO per 1 g film: 10.5 N mm⁻²), while the tensile strain at break was reduced with higher CaO concentration from 318% (pure PE-LD) to 10% (PE-LD with 0.51 g dispersed CaO per 1 g film). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47460.