Various Amounts Of Surfactant Research Articles

Fabrication of bioactive glass scaffolds by stereolithography: Influence of particle size and surfactant concentration

For decades, bioactive glass (BAG) has been utilized as a competent bone substitute owing to its intrinsic properties, such as outstanding biocompatibility and bioresorbability. Stereolithography (SL) is an additive manufacturing technology used to produce highly accurate three-dimensional BAG-based bone substitutes. However, the preparation of BAG-based SL resin is always a challenge, especially because of the inevitable sedimentation of BAG particles. In this study, BAG particles with different sizes were prepared by dry grinding (BAGdry, greater particle size) and wet grinding (BAGwet, finer particle size). Then, BAGdry or BAGwet SL resins with various amounts of surfactant were analyzed. The sedimentation rate for BAG powder increased with increasing particle size but decreased with increasing amounts of surfactant added to the resin. BAGwet SL resins had a longer shelf life, so printing could still be finished after 14 days, whereas BAGdry SL resins were no longer useable after 5 days. However, the BAG particle size did not affect the printing accuracy or scaffold strength. According to our results, BAG-based SL resin fabricated with BAGwet (particle size <1.6 μm) and 5 wt% surfactant exhibited better resistance to sedimentation.

Modification of mesoporous structure of silver-doped bioactive glass with antibacterial properties for bone tissue applications

Silver-containing mesoporous bioglasses powders with SiO2–CaO–P2O5–Ag2O composition have been successfully synthesized by sol-gel and evaporation-induced self-assembly (EISA) methods in presence of various amounts of surfactant (Pluronic-F127). The morphology and crystal structure of the powders were characterized by scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD). Also, the textural properties of samples have been evaluated by adsorption-desorption, Langmuir and BET methods. Accordingly, powders had a smooth surface morphology with cubic mesoporous structure and a desired surface area and pore volume. The in vitro bioactivity was assessed by SEM, XRD and Fourier transform infrared spectroscopy (FTIR) analyses. All samples enhance the formation of HA after soaking the material in simulated body fluid (SBF) solution. The antibacterial property of samples was evaluated to investigate the effect of silver content in chemical composition. The results showed an adequate antibacterial activity of the samples against Escherichia coli, Salmonella and Listeria monocytogenes.

Novel method suitable for decreasing the roofing tile failures generated during rapid drying

Only few papers in which principles for decreasing the failures generated during semi and rapid drying of porous shrinking materials, for example roofing tiles, are reported. One of the main differences between the traditional and rapid drying regimes is related with the fact that during the heating step products are heated to the much higher temperatures during rapid drying. If the humidity inside the industrial drying tunnels or chambers is not controlled all the time in the prescribed range of 90 - 95 %, especially during the heating step of the rapid drying regime, crack failures will be developed. In order to inhibit the cracks generation during intensive drying the non-ionic surfactant Igepal CO-630 was added in the raw material during forming process. Various amounts of surfactant around the critical micelle concentration (CMC) were used. Five isothermal experiments were recorded, on laboratory extruded roofing tiles, for each surfactant concentration. Calculated effective diffusivity and material strength -moisture ratio (Deff-MR & MS-MR) curves were used to monitor the development of the cracks during drying and to determine the most suitable concentration of the surfactant. The explanation, how the interaction of the surfactants with clay helps the water molecules to easily move up to the surface was also reported. The application of surfactant in a recommended amount has significantly reduced the drying induced fractures in roofing tiles during its intensive drying and consequently the industrial scarp-rate was accordingly lowered.

Influence of Cationic Cetyltrimethylammonium Bromide on Rate of Zn(II)-Histidine Complex and Ninhydrin.

Paper analyses the influence of cationic cetyltrimethylammonium bromide on rate of Zn(II)-histidine and ninhydrin. UV-visible spectroscopy was applied to note absorbance of Zn(II)-histidine complex with ninhydrin at the end of reaction in the two systems. Rate constant, kobs, (in aqueous) and rate constant, kψ, (in cetyltrimethylammonium bromide, CTAB) were determined by computer software. Reactions depict first-order in Zn(II)-histidine concentration and fractional-order in ninhydrin concentration in aqueous and micellar media. The results achieved indicate that the reactions take place principally by the same reaction mechanism in both the media. Critical micelle concentration of CTAB surfactant was calculated by recording the conductivity as a function of surfactant concentrations. Influence of various amounts of surfactant on Zn(II)-histidine complex and ninhydrin reaction was performed under different reaction conditions. Reaction was catalyzed and accelerated efficiently by surfactant medium compared to aqueous medium. The observed influence of surfactant on rate has been mentioned in details and their quantitative treatment of kinetic results have been deduced by the means of Menger and Portnoy model for micellar catalysis.

Preparation and optimization nanoemulsion of Tarragon (Artemisia dracunculus) essential oil as effective herbal larvicide against Anopheles stephensi

Continuous use of chemical larvicides causes resistance in many species around the world and also environmental pollution. Nanoemulsions of herbal larvicides (such as essential oil based larvicides) are suitable alternatives for this purpose. However, no work so far has investigated the stability of a nanoemulsion after 100–200 times dilution and its effect on larvae of Anopheles stephensi, a major vector spreading malaria. Tarragon is a common medicinal plants and its essential oil had effective larvicidal activity. Different nanoemulsions of Tarragon essential oil were prepared using various amounts of surfactants and co-surfactants. For the first time, a comparison of larvicidal activity between two optimized preparations (particle sizes of 15.6 & 14.5nm) with tarragon essential oil against Anopheles stephensi was performed. The components of Tarragon essential oil were identified by GC–MS analysis. Forty eight components were determined, with 5 major components including P-Ally anisole (67.623%), cis-Ocimene (8.691%), beta-Ocimene Y (7.577%), Limonene (4.338%) & 3-Methoxy cinnam aldehyde (1.49%). The bioassay of essential oil was performed, LC at 50 or 90% with values of 11.36 or 17.54ppm, were calculated using probit analysis. No larvicidal effect was observed from nanoemulsion inactive ingredients (i.e. Tween 20 and isopropyl alcohol). Larvicidal activity of the most stable formulation after dilution (particle size 14.5nm), showed significant increase compared to bulk of the oil and nanoemulsions with lesser stability profile after dilution. By designing and preparing a stable essential oil nanoformulation, against dilution, which takes the advantage of lesser volatile properties. And also, achieving to effective and environmentally friendly larvicides with low cost will be possible.

Effects of Silicone Surfactant on the Properties of Open‐Cell Flexible Polyurethane Foams

ABSTRACTIn this paper, the effects of silicone surfactant on the mechanical, thermal, and acoustical properties of flexible polyurethane foams are studied. At first, by introducing the reactions of the foam production and expressing the stoichiometric relationships, a method is provided to select the amounts of the basic compounds for getting the desirable properties. By knowing the OH number of polyol and the NCO content of isocyanate after selecting an amount of a blowing agent for the reaction, the quantity of each compound to produce the desirable foam can be found. Then different foams with various amounts of surfactant are produced. By preparing proper samples, the mechanical, thermal, nonacoustical, and acoustical properties of the foams are measured or calculated by using different instruments. The nonacoustical properties are obtained based on two distinct methods, i.e., a semiphenomenological method and an indirect method. The obtained properties are validated by comparing the calculated theoretical sound absorption coefficients with the measured ones. The results show that with a small increase of surfactant, the acoustical properties of foam samples improve by about 50% without any significant changes in other mechanical and thermal properties of the foams. This improvement results from the variations of reticulation rate and cell size. In addition, the initial desirable porosity and density considered in the stoichiometric relations are fairly achieved in produced samples. These results validate the accuracy of the stoichiometric relations.

Study on the thermal stability of ordered mesoporous SiO2 film for thermal insulating film

Ordered mesoporous SiO2 film has very low thermal conductivity compared to dense SiO2 film due to the presence of nanometer-sized pores. In order to apply this excellent material to thermal insulation fields, it is important to ensure the thermal stability of the pore structure at high temperature as well as thermal conductivity. In this study, ordered mesoporous SiO2 films were synthesized with various amounts of surfactant, and heat treatment at various temperatures was conducted with the synthesized films to confirm their thermal stabilities. Pore structure degradation of the mesoporous SiO2 film was observed with increasing temperature of the heat treatment as measured by grazing incidence small angle X-ray scattering. However, mesoporous SiO2 films with highly-ordered pore arrangements showed enhanced thermal stability and maintained their pore structures during additional heat treatment at higher temperatures. The mechanical properties and thermal conductivity of the ordered mesoporous SiO2 films with thermal stability at high temperature were analyzed.

Phase Separation in Polyelectrolyte Gels Interacting with Surfactants of Opposite Charge

Macroscopic phase separation in covalent sodium polyacrylate (PA) networks following the absorption of cetyltrimethylammonium bromide/chloride (CTAB/C) from aqueous solutions is studied experimentally and theoretically. The gels are shown to consist of a solvent-swollen polyelectrolyte network (core), surrounded by a dense surface phase (skin) of polyion/surfactant complexes. The effect of core swelling on network structure and polyion/surfactant interaction in skins is discussed. It is demonstrated that the skin limits the swelling of the core. A model of the equilibrium swelling of phase separated gels is developed, taking into account the osmotic swelling of the core due to the presence of mobile counterions, the work of deformation of the core network, and the work of deformation of the skin. The last contribution is described using the theory of rubber elasticity. The core network is described using an empirical equation of state. The model is used to calculate the volume of gels after the absorption of various amounts of surfactant. Comparison with experiments shows that the agreement is satisfactory. The skin microstructure is investigated by means of small-angle X-ray scattering, optical birefringence, and time-resolved fluorescence quenching. The size, shape, and spatial organization of surfactant micelles is found to depend on the composition of the skin. Stoichiometric polyion/surfactant complexes (free from simple ions) form an ordered cubic structure (space group: Pm3n). The incorporation of bromide or chloride ions leads to a transition to hexagonal structure. The transition is related to the corresponding transition in complexes between linear PA and CTAB. Skins with cubic structure are found to be elastic and can be deformed at constant volume. The structural basis for the rubber-like behavior is discussed. The appearance of hexagonal skin microstructure is found to correlate with an anomalous swelling/deswelling pattern leading to the formation of “balloon gels”.

Towards a general approach for the impurity profiling of drugs by micellar electrokinetic chromatography.

A general micellar electrokinetic chromatographic (MEKC) strategy for the impurity profiling of drugs was developed involving a sodium dodecyl sulfate (SDS) and a cetyltrimethylammonium bromide (CTAB) MEKC system. With this combination, in principle, each sample component passes the detector in at least one of the two MEKC systems provided that separation buffers of the same pH are used in both systems. In order to select the proper MEKC systems, the electroosmotic flow (EOF) and micelle migration time (t(mc)) were determined for separation buffers of several pH values, containing various amounts of surfactant and organic modifier. The selectivity of the MEKC systems was studied using a mixture of compounds with a wide range of physico-chemical properties. The final selection of two adequate MEKC systems for this approach was based on the requirements that the t(mc) (i.e., analysis time) of both systems was below 20 min and that the t(mc)/t(eof) ratio was above 3 or 2 for the SDS and CTAB system, respectively. Furthermore, the systems should provide high efficiency, exhibit differences in selectivity and use moderate concentrations of modifier and surfactant, so that, if needed, further optimization is possible. The selected MEKC systems contained 60 mM SDS or 10 mM CTAB, respectively, in a phosphate buffer (pH 7.5) with 10% acetonitrile. Some test compounds with extreme mobilities were used to demonstrate the suitability of the MEKC approach to detect each component of a sample. The potential of the proposed MEKC combination for impurity profiling was demonstrated by the analysis of fluvoxamine with several impurities at the 0.1% level.

An investigation into interactions between polyacrylic polymers and a non-ionic surfactant: an emulsion preformulation study

The aim of this study was to investigate possible interactions between a polymeric emulsifier and a non-ionic surfactant, with a view of achieving better understanding of emulsion stabilisation mechanisms. The polymeric emulsifier used was acrylates/C 10–30 alkyl acrylate crosspolymer (Pemulen TR-2®), while Polyoxyethylene 20 sorbitan mono-oleate (Polysorbate 80) has been chosen as a model surfactant. Both materials were used within the concentration range relevant for their practical application. A 0.2%w/w aqueous dispersion of polymeric emulsifier, containing various amounts of surfactant (from 0.01 to 1.0% w/w) was used throughout the study. Interfacial aspects of the proposed polymer/surfactant interactions were analysed by means of surface tension measurements. Changes in the network structure of the test dispersions were quantified by continuous shear rheometry, supported by the texture analysis. To analyse the influence of hydrophobic alkyl groups present on the Pemulen TR-2® chains, an unmodified, hydrophilic polyacrylic acid polymer, Carbopol 934P®, was assessed under the same conditions. The results obtained by both surface tension and rheological studies have revealed large differences in behaviour of the two polymers in the presence of the model surfactant. Pemulen TR-2® was shown to desorb the surfactant from the surface, within the whole concentration range studied. Furthermore, an increase in viscosity and texture profile parameters with increasing Polysorbate 80 concentration up to 0.3% w/w was evident in the case of Pemulen TR-2® dispersions. This was followed by a decrease in the gel network strength at higher surfactant concentrations. On the other hand, Carbopol 934P® has shown no signs of surfactant desorption and only small changes in the network structure with the increasing concentration of surfactant. It is shown in this study that an interaction between a polymeric emulsifier Pemulen TR-2® and a non-ionic surfactant Polysorbate 80 does occur in their aqueous dispersion, and that it is: (a) hydrophobic in nature; (b) concentration-dependent; and (c) has an impact on the rheological properties of dispersion.

Long-term cycling of surfactant films in Wilhelmy balance

Surface properties of porcine surfactant were observed during long-term cycling in Wilhelmy balance. Various amounts of surfactant were applied onto the surface as dry particles or droplets, or were suspended in the hypophase, and the films generated by this material were subjected to 50% cyclic compression at a rate of 1 cycle per min. Film spreading was faster from a droplet than from a particle of lyophilized surfactant, but the "stable period" during which minimum surface tension of the compressed film remained below 5 mN/m was significantly longer for the dry material. For surfactant suspensions the period of film "refinement", defined as the number of cycles required to reduce minimum surface tension to a level below 5 mN/m, was inversely correlated with the concentration of surfactant in the hypophase. Thirteen batches of porcine surfactant, used successfully in clinical trials for treatment of neonatal respiratory distress syndrome, were evaluated in the same system suspended in the hypophase at a concentration of 0.5 mg/ml. Films adsorbed from these batches had a median refinement period of 4 cycles, and a median stable period of 2160 cycles (36 h). In the same assay system, surfactant activity was inhibited in a dose-dependent manner by serum, fibrinogen, meconium, and bilirubin, but the specific inhibitory activity was significantly higher for bilirubin than for the other substances tested.

Some Comments on the Production of Medium Sized Spherical Particles by Anion and Water Extraction Variant of Sol-Gel Process

AbstractMedium sized spherical particles (with diameters below 100 μm) of ceramic materials (Al203 and Al203 +8%TiO2) were produced in the following steps: (1) preparation of concentrated hydroxide sols of cations by extraction of anions using Primene JMT, (2) formation of sol emulsion in 2-ethylhexanol-1 containing various amounts of surfactants (EH), (3) gelation of emulsion drops by extraction of water with partially dehydrated EH, (4) non-destructive thermal treatment. Principal properties of the sol depend on the temperature of the extraction process. For preparation of lowanionic sols a two step extraction process, separated by digestion of the aqueous phase at boiling point, was necessary. It was found that the parameters of emulsion formation as well as the properties of the sols significantly influence the particle size distribution. It was concluded that lowering of the sol- EH interracial tension by the surfactant does not influence the process. On the contrary the “anti-clustering” effect of surfactants is essential for preparation of perfect spherical powders. The thermal decomposition of gels to oxides is determinant for densities, specific surface area and carbon content. Medium sized spherical powders are free flowing. The compactibility and sinterability of those powders are poor. However drastic reduction of particle size by milling (connected with their transformation to irregular shape) significantly improves the sinterability.

Surface and Textural Heterogeneity of Fresh Hydrous Ferric Oxides in Water and in the Dry State

Fresh hydrous ferric oxides (HFO) are formed by precipitation of Fe3+ solution or ferric polycations initially formed at very acidic pH at different neutralization ratios n = 2 and 2.5. At pH 6.5 the precipitates are particles with a positive surface charge. The IEP and the surface charge measured in NaCl electrolyte vary with n. But in all cases IEP or ZPSE are lower than 8.3. The adsorption of sodium dodecane sulfonate molecules at 20°C allows us to compare the different samples formed by precipitation from n = 0, n = 2, and n = 2.5 solutions and named "n = 0," "n = 2," and "n 2.5." Using the two-dimensional adsorption on heterogeneous surfaces theory of Cases's group (Langmuir 8, 1251 (1992)), it is possible to compare the different solids relatively to the affinity of surfactants for the surfaces. The energetic heterogeneity decreases in the following order, "n = 2" > "n = 2.5" > "n = 0." The adsorption isotherms present several plateaus. The evolution of ζ vs Ce mimics the evolution of Qa vs Ce. This indicates that the adsorption sites are mainly located on external surfaces as adsorption within micro- or mesopores would correspond to a constant zeta potential. The available specific surface area at pH 6.5 can be derived from the adsorption isotherms. The plateaus of the isotherms corresponding to ζ = 0 mV. The available specific surface area S can then be calculated using the equation S=Qa · Na · A, where Qa is the adsorbed amount (mol/g), Na is Avogadro's number, and A is the molecular area in the hydrated crystal state (A = 20.8 Å2). The values of S are 163, 134, and 139 m2/g for "n = 0," "n = 2," and "n = 2.5," respectively. DRIFT spectroscopy carried out on precipitates covered by various amounts of surfactants show that they are adsorbed on positively charge sites which are the = Fe - OH(H) singly coordinated sites located on edges of the double chain of βFeOOH-like particles. Continuous Ar gas adsorption technique on "n = 0," "n = 2," and "n = 2.5" freeze-dry samples shows that pore sizes of 6 Å are intercrystal pores present in βFeOOH solids and also that dry samples are microporous with a specific surface area of 300 m2/g. The large discrepancies between textural properties of HFO in water and in a dry state are certainly due to the possibility of HFO swelling in water.

Coalescence mechanisms of polymer colloids: II. Coalescence with evaporation of water

Mechanisms of coalescence of model latices were studied under standard conditions, i.e., with simultaneous evaporation of water. The model latices had core—shell particles with the same diameters and the same bulk properties but different surface characteristics. Different surface compositions were achieved by varying the amount of methacrylic acid (MAA) in the shell, by neutralizing the MAA to different extents, or by adding various amounts of surfactant to the latices. The limit temperature/relative humidity diagrams for film formation were established for several latices. They were all identical, regardless of the surface characteristics of the particles. Total coalescence times of latices and dense packings of latex particles were measured and compared with the coalescence times of the same packings of particles in water. This led to the conclusion that particle—water interfacial tension has a negligible contribution to the coalescence mechanisms under standard conditions. The mechanisms and their relationship to evaporation of water for various thermal conditions of coalescence are discussed.

Filtration of a liquid in a fissured-porous coal seam when injected through long boreholes

Calculations performed with a computer revealed that a change in the contact angle theta over a wide range 30/sup 0/ < theta < 150/sup 0/, with a simultaneous change in the coefficient of surface tension ..cap alpha.. from 0.00004 to 0.00009 kg/cm, corresponding to various amounts of surfactant added to the water injected into the seam, has practically no effect on the pressure distribution in the coal seam; the pressures in the same cross section at various above-indicated values of ..cap alpha.. and theta differ by tenths of an atmosphere. This indicates that incorporation of a surfactant into the water has little effect on water injection into the seam.