Plate coating: influence of concentrated surfactants on the film thickness

We present a large range of experimental data concerning the influence of surfactants on the well-known Landau-Levich-Derjaguin experiment where a liquid film is generated by pulling a plate out of a bath. The thickness h of the film was measured as a function of the pulling velocity V for different kinds of surfactants (C(12)E(6), which is a nonionic surfactant, and DeTAB and DTAB, which are ionic) and at various concentrations near and above the critical micellar concentration (cmc). We report the thickening factor α = h/h(LLD), where h(LLD) is the film thickness obtained without a surfactant effect, i.e., as for a pure fluid but with the same viscosity and surface tension as the surfactant solution, over a wide range of capillary numbers (Ca = ηV/γ, with η being the surfactant solution viscosity and γ its surface tension) and identify three regimes: (i) at small Ca α is large due to confinement and surface elasticity (or Marangoni) effects, (ii) for increasing Ca there is an intermediate regime where α decreases as Ca increases, and (iii) at larger (but still small) Ca α is slightly higher than unity due to surface viscosity effects. In the case of nonionic surfactants, the second regime begins at a fixed Ca, independent of the surfactant concentration, while for ionic surfactants the transition depends on the concentration, which we suggest is probably due to the existence of an electrostatic barrier to surface adsorption. Control of the physical chemistry at the interface allowed us to elucidate the nature of the three regimes in terms of surface rheological properties.     

甲壳胺药膜的控制释放研究

以阿司匹林为模型药物研究了小分子药物在甲壳腹膜中的释放行为，结果表明释放是扩散控制的，与膜厚、介质pH值，膜交联度及膜分散性密切相关。改变这些参数可达到比较恒定的延长释放和不同的给药途径。     

The effects of irradiation on controlled drug delivery/controlled drug release systems

The research of radiation effects on drugs over the past 60 years has mainly dealt with radiation sterilization of individual active pharmaceutical ingredients (APIs) in the form of pure substances or injectable solutions. However, the emergence of novel systems for drug administration and targeting via controlled drug delivery (CDD) and/or controlled drug release (CDR) has extended the use of irradiation with respect to pharmaceuticals: the capacity of radiation to act as an initiator of crosslinking has been used in the manufacturing and modification of a number of polymeric carriers with an added advantage of reducing the microbial load of products at the same time. The application of irradiation to these novel systems requires the understanding of radiation action not only on APIs alone but also on drug carriers and on the functioning of the integral CDD/CDR systems. In this paper, the significance of CDD/CDR systems is considered with a special emphasis on the role of irradiation for sterilization and crosslinking in the developments over the past 15 years. Radiation sterilization, crosslinking and degradation of the principal forms of drug carrier systems and the effects of irradiation on the release kinetics of APIs are discussed in light of radiation chemical principles. Regulatory aspects pertaining to radiation sterilization of drugs are also considered. Relevant results are summarized in tabular form.     

Effect of the thickness of the Pt film coated on a counter electrode on the performance of a dye-sensitized solar cell

The effects of the thickness and morphology of a Pt film coated on a counter electrode on the performance of a dye-sensitized solar cell (DSC) were investigated. Deposition of a Pt film ranging in thickness from 2 to 415 nm gradually decreases the sheet resistance of the counter electrode. No significant difference in the charge-transfer resistance at the electrolyte|counter electrode interface was observed for a Pt film thickness ranging from 25 to 415 nm. A high energy conversion efficiency of approximately 5% can be obtained for DSCs based on a counter electrode with a very thin Pt film of 2 nm, as well as with a 415-nm thick Pt film. These results are important for reducing production costs by reducing the required amount of expensive platinum.     

Research on permeability coefficient of a polyethylene controlled-release film coating for urea and relevant nutrient release pathways

The permeability coefficient is a key factor that reflects the nutrient release capability of polymer-coated fertilizers. To investigate the permeability coefficient of polyethylene (PE) controlled-release film and to determine the difference between the controlled-release film and a dense membrane, we designed a film permeation device to measure the permeability coefficient of a PE controlled-release film coating for urea, and a mathematical model was used to check the accuracy of these measurements. By measuring the permeation coefficient of a dense, PE membrane, the compactness of the PE controlled-release film was analyzed, and the nutrient release pathway of PE-coated fertilizer was discussed. Research indicated that urea was constantly released through PE controlled-release film and the permeability coefficient remained constant. The permeability coefficient for PE controlled-release film coating on urea with 1–4 months release time was in the range of 7.17–18.7E-15 m²/s with 2.6 times difference between the maximum and minimum. The permeability coefficient decreased as the release time increased, conforming to the inversely proportional relationship between permeation amount and time in the nutrient release model. It is investigated that the measured values are close to the theoretical values and can be used in model calculation. The urea permeability coefficient of PE dense membrane was 7.11E-18 m²/s, which is 1000–2600 times smaller than that of the PE controlled-release film. The contribution of permeability of polymer material itself is negligible. It can be concluded that PE controlled-release film is not a dense membrane but porous and that nutrient release is mainly determined by pore configuration of the film.     

The investigation of coating materials for the detection of nitrobenzene with coated quartz piezoelectric crystals

Powdered activated charcoal, quadrol tetrabase and polyethylene glycol (PEG)-400 and -750 are used as coatings on 15-MHz quartz piezoelectric crystals for the detection of nitrobenzene in air. The response to nitrobenzene over the range 2–10 ppm (2–10 × 10^?6 mol mol^?1)_was almost linear for all the coatings except charcoal which exhibited marked non-linearity, as well as greater sensitivity than the other coatings. The charcoal response was linear over the range 0.7–7.6 ppm nitrobenzene. For the other coatings, sensitivity increased in the order tetrabase < quadrol < PEG-400 < PEG-750.     

The importance of the film structure during self-powered ibuprofen salicylate drug release from polypyrrole electrodeposited on AZ31 Mg

Therapeutic drugs uploaded into conjugated conductive polymer matrices deposited on active magnesium alloys serve as controlled-dose, self-powered drug-delivery systems. Preferentially, drugs are added into polymer films in the largest amount possible, mostly to prevent long-term treatments. However, added drugs can interact with the polymer matrix affecting either the structure or the final mechanical properties of the polymer film. In this work, polypyrrole films (PPy) electrodeposited on an AZ31 Mg alloy in ibuprofen and salicylate-containing solutions are investigated in terms of their uploading capacity, surface morphology and mechanical properties. The techniques used to investigate the uploaded PPy films include cyclic voltammetry (CV), scanning electron microscopy (SEM), EDS, and depth-sensing indentation (DSI). A maximum ibuprofen concentration of 440 ± 40 μg cm^?2 was obtained in PPy films in the presence of sodium salicylate. The release fraction of ibuprofen as a function of time is fitted to Avrami’s equation. The hardness and reduced modulus decreased by 54 and 40 %, respectively, when the PPy films are prepared in the presence of sodium ibuprofen compared with those prepared in sodium salicylate only, indicating a more plastic film with ibuprofen.     

Electrooxidation of carbon monoxide and methanol on platinum-overlayer-coated gold nanoparticles: effects of film thickness

The electrooxidation of carbon monoxide and methanol on Pt-coated Au nanoparticles attached to 3-aminopropyl trimethoxysilane-modified indium tin oxide electrodes was examined as a function of Pt film thickness and Au particle coverage. For the electrodes with medium and high Au particle coverages, the CO stripping peak position shifts to more negative values with increasing Pt film thickness, from ca. 0.8 V (vs Ag/AgCl) at 1 ML to 0.45 V at 10 ML. Accompanying this peak potential shift is the sharpening of the peak width from more than 150 to 65 mV. For the electrode with low Au particle coverage, similar peak width narrowing was also observed, but the peak potential shift is much smaller, from 0.85 V at 1 ML of Pt to 0.65 V at 10 ML. These observations are compared with the CO oxidation on bulk Pt electrodes and on Pt films deposited on bulk Au electrodes. The film-thickness-dependent CO oxidation is explained by d band theory in terms of strain and ligand effects, the particle size effect, and the particle aggregation induced by Pt film growth. Corresponding to the increasing CO oxidation activity, the current density of methanol oxidation grows with the Pt film thickness. The peak potential and current density reach the same values as those obtained on a polycrystalline bulk Pt electrode when more than 4 ML of Pt is deposited on the Au particle electrodes with a particle coverage higher than 0.25. These results suggest that it is feasible to reduce Pt loading in methanol fuel cells by using Pt thin films as the anode catalyst.     

Analysis of the release process of phenylpropanolamine hydrochloride from ethylcellulose matrix granules II. effects of the binder solution on the release process

The release properties of phenylpropanolamine hydrochloride (PPA) from ethylcellulose (EC) matrix granules prepared by an extrusion granulation method were examined. The release process could be divided into two parts; the first and second stages were analyzed by applying square-root time law and cube-root law equations, respectively. The validity of the treatments was confirmed by the fitness of a simulation curve with the measured curve. In the first stage, PPA was released from the gel layer of swollen EC in the matrix granules. In the second stage, the drug existing below the gel layer dissolved and was released through the gel layer. The effect of the binder solution on the release from EC matrix granules was also examined. The binder solutions were prepared from various EC and ethanol (EtOH) concentrations. The media changed from a good solvent to a poor solvent with decreasing EtOH concentration. The matrix structure changed from loose to compact with increasing EC concentration. The preferable EtOH concentration region was observed when the release process was easily predictable. The time and release ratio at the connection point of the simulation curves were also examined to determine the validity of the analysis.     

The effects of film thickness and incorporated anions on pitting corrosion of aluminum with barrier-type oxide films formed in neutral borate and phosphate electrolytes

The pitting corrosion behavior of high-purity aluminum covered with barrier-type anodic films, which are formed in neutral borate and phosphate electrolytes, has been examined in 0.5 mol dm^?3 NaCl solution at an applied potential of ?0.6 V versus Ag/AgCl, which is slightly nobler than the pitting potential of ?0.64 V in the same solution. The pitting current density, i _p, increased with time after an incubation time, t _i. The double logarithmic plot of i _p and polarization time, t, reveal two straight lines, which are separated at the time, τ. The slope becomes larger after τ for the specimens anodized in the phosphate electrolyte, while it becomes smaller for those in the borate electrolyte. Both the t _i and τ increase with the thickness of the anodic films, and at the similar film thickness, they are much larger for the anodic films formed in the phosphate electrolyte than for those in the borate electrolyte. The corrosion process can be divided into three stages: the incubation period up to t _i, the pit nucleation period before τ, and the pit growth period after τ. We have discussed the different pitting corrosion behavior of the aluminum specimens covered with the anodic films formed in the borate and phosphate electrolytes in terms of ion selectivity of the anodic films.     

阳极氧化铅膜的光电流频谱曲线随膜增厚而位移的研究

铅在硫酸溶液中生长的阳极氧化铅膜的光电流频谱曲线随着膜增厚而红移。Dimitrov等认为长波对光电流的贡献随着膜的增厚而增大的程度要较短波的为大, 从而导致曲线的位移。我们的研究表明其主要原因为膜中的t-PbO和o-PbO的比例随膜增厚而发生的变化, 并非如上所述。本工作求出上述阳极膜中的t-PbO和o-PbO的禁带宽度分别为1.9和2.6eV。     

The effect of physical state on the drug dissolution rate

In this work, the enhancement of drug dissolution rate through the preparation of new formulations containing Nimodipine in molecular level dispersion or in nanodispersion into poly(vinyl pyrrolidone) (PVP) matrix, was investigated. Differential scanning calorimetry (DSC) and modulated-temperature differential scanning calorimetry (MTDSC) in combination with X-ray powder diffractometry (XRPD) and scanning electron microscopy (SEM) studies showed that Nimodipine was amorphous in solid dispersions of 10 or 20 mass%, and mainly dispersed on a molecular level. This behaviour is attributed to the strong interactions taking place between the amine group of Nimodipine and carbonyl group of PVP. At higher drug loadings, crystal reflections in XRPD patterns and melting peaks of Nimodipine in DSC traces, indicated presence of drug in crystalline form. Micro-Raman studies in combination with SEM micrographs showed that the mean particle size increases with drug content in the formulations, up to 10 μm. Moreover, both XRPD patterns and micro-Raman spectra seem to indicate that Nimodipine crystallized in a second, thermodynamically stable, crystal modification II. The physicochemical characteristics of Nimodipine and the particle size distribution directly affect the dissolution rate enhancement, which is higher in amorphous dispersions.     

Investigation of the detection limit for the determination,by pyrolysis-capillary GC,of the thickness of ultra thin PMMA layers coated on to PET film

The determination of nanometer thick layers of poly(methyl methacrylate) coated on to the surface of poly(ethylene terephthalate) film has been investigated by high resolution pyrolysis gas chromatography without sample pretreatment or modification of the instrumentation used. A good linear relationship was observed between the quantity of the characteristic pyrolysate and the thickness of the poly(methyl methacrylate) layer; the detection limit was sufficient to enable the quantitation of poly(methyl methacrylate)-to-poly(ethylene terephthalate) film thickness ratios of 1:20000 in composite materials.     

The effect of film thickness and sample history on the parameters describing transport in glassy polymers

The effect of a characteristic dimension of a glassy polymeric specimen on the kinetic mechanism controlling unidirectional absorption of organic vapors and liquids in glassy polymers is demonstrated by comparing n-alkane absorption experiments in microspheres, spheres, films, and sheets of polystyrene. Absorption in submicron microspheres is controlled by Fickian diffusion whereas, under otherwise identical boundary conditions, films (ca. 75μm thick) and spheres (ca. 184 μm in diameter) sorb according to Case II absorption kinetics. Thinner films (35 μm thick) sorb by Super Case II kinetics and relatively thick sheets (2000 μm thick) sorb initially by Case II kinetics but, at long times, diffusion through the outer swollen region contributes significantly to the overall resistance to mass transfer and the rate of absorption decreases progressively with time. p]The rather short experimental times, afforded by the exceedingly small mean diameter of the narrowly distributed microsphere powder sample, permitted convenient characterization of the effects of preswelling, sorption-desorption cycling, and annealing on the kinetics and apparent equilibria of sorption. History effects were quite dramatic and were related to glassy state relaxations initiated by the various thermal and swelling histories imposed upon the glassy microspheres. p]Prediction of sorption and permeation behavior in membranes, from kinetic and equilibrium parameters determined experimentally on film and powder samples, requires explicit recognition of these dimensional and history effects. These effects do not appear to be related to any special properties of this polymer-penetrant system.     

The impact of the layer thickness on the thermodynamic properties of pd hydride thin film electrodes

Recently, a lattice gas model was presented and successfully applied to simulate the absorption/desorption isotherms of various hydride-forming materials. The simulation results are expressed by parameters corresponding to several energy contributions, e.g., interaction energies. However, the use of a model system is indispensable in order to show the strength of the simulations. The palladium-hydrogen system is one of the most thoroughly described metal hydrides found in the literature and is therefore ideal for this purpose. The effects of decreasing the thickness of Pd thin films on the isotherms have been monitored experimentally and subsequently simulated. An excellent fit of the lattice gas model to the experimental data is found, and the corresponding parameters are used to describe several thermodynamic properties. It is analyzed that the contribution of H-H interaction energies to the total energy and the influence of the host lattice energy are significantly and systematically changing as a function of Pd thickness. Conclusively, it has been verified that the lattice gas model is a useful tool to analyze thermodynamic properties of hydrogen storage materials.     

Numerical analysis of the internal flow and the mixing chamber length effects on the liquid film thickness exiting from the effervescent atomizer

Journal of Thermal Analysis and Calorimetry - Two-phase flow was simulated within the effervescent atomizer by the volume of fluid interface tracing model. Different gas-to-liquid mass ratios...     

The dependence of the properties of liquid crystals on the film thickness and surface quality of capillary columns

Summary Glass capillary columns were prepared from non-deactivated and deactivated glass and coated with (2-methyl-4-[trans-4-n-propyl-cyclohexylcarbonyloxy]-benzoic acid-[4-n-heptyloxy-phenylester]) as the liqud phase, in different film thicknesses. The columns were tested using substances of different structures and polarities. It was verified that the capacity factors, retention indices and selectivity significantly depend on the thickness of the liquid crystalline stationary phase film and the quality of the tube, particularly in the case of columns with thin films. Trasition temperatures (melting and clearing point) of the liquid crystal are also dependent on these two factors.Dedicated to Professor J. F. K. Huber on the occasion of the his 60th birthday.