Interaction of sodium dodecyl sulfate with poly(ethyleneimine) in bulk solution and at the air-solution interface

Interaction of sodium dodecyl sulfate (SDS) with the cationic polyelectrolyte poly(ethyleneimine) (PEI) was investigated in this study. Turbidity measurements were performed in order to analyze the interaction and complex formation in bulk solution as a function of polymer concentration and pH. Surface tension measurements were made to investigate the properties of SDS/PEI/water mixtures at air/solution interface. Results revealed that SDS/PEI complexes form in solution depending on the surfactant and polymer concentration. A decrease was observed in surface tension values in the presence of SDS/PEI mixtures compared to the values of pure SDS solutions. Both solution and interfacial properties exhibited pH dependent behavior. A shift was seen in the critical micelle concentration of SDS solutions as a function of PEI concentration and solution pH. Monovalent and divalent salt additions showed some influence on the interfacial properties of SDS solutions in the presence of PEI. © Taylor & Francis Group, LLC

Alumina/water suspensions in the presence of PEO-PPO-PEO triblock copolymers

The aim of this study was to investigate the stability and dispersion behaviour of aqueous alumina suspensions in the presence of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) type triblock copolymers. For this purpose alumina suspensions at various solids loadings were prepared using four different methods. These are: Method I: powder and water were stirred only; Method II: powder and water were stirred and ultrasonic treatment was applied; Method III: powder and water were stirred in the presence of block copolymers; Method IV: powder and water were stirred and ultrasonic treatment was applied in the presence of block copolymers. These suspensions were characterized by means of rheological measurements. Sedimentation and turbidity measurements were also conducted to support these results and to investigate the stability of these systems for longer times. Surface tension measurements were performed to investigate the adsorption behaviour of block copolymers onto alumina surface. It was found that the use of PEO-PPO-PEO type triblock copolymers improved the dispersion behaviour of aqueous alumina suspensions in the presence of ultrasonic treatment at low solids loadings. However their effect was not significant at high solids loadings and without ultrasonic treatment

Influence of dispersing agents on the solubility of perovskites in water

In this study, solubility behavior of lead magnesium niobate (PMN) powders in water was investigated in the presence of pure polyacrylic acid and polyacrylic acid/polyethylene oxide comb polymers. Experiments were performed by measuring the solubility of PMN in terms of the concentration of Pb+2 and Mg+2 ions in supernatant as a function of pH and dispersing agent dosage. The concentrations of the metal ions in supernatant were found to be affected by the dispersant concentration, stirring time and the suspension pH. Results revealed that both dispersing agents enhance the cation dissolution from PMN surface at pH 9 due to weak (reversible) adsorption and complexation of Pb+2 and Mg+2 by carboxylate groups. On the other hand, under acidic conditions cation dissolution from PMN is inhibited and this was attributed to the strong adsorption of dispersing agents onto the powder surface and formation of a dense polymer layer

Synergistic effect of polymer-surfactant mixtures on the stability of aqueous silica suspensions

The aim of the present work was to investigate the effect of cationic/nonionic surfactant mixtures on the dispersion and flocculation behavior of aqueous silica suspensions. In the study dodecylamine (DDA) was used as the cationic surfactant and polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock copolymers were employed as the nonionic surfactant. The dispersion and flocculation behavior of aqueous silica suspensions were studied mainly by turbidity measurements at low solids loading (0.05 vol.%) to observe the stability of the system for a given time period. Rheological measurements were performed at higher solids loadings to determine the viscosity as a function of shear rate. Adsorption behavior of single and mixed surfactants onto silica surface was studied using a total organic carbon analyzer. Results of the study showed that dispersion and flocculation behavior of aqueous silica suspensions depends on the type and concentration of surfactant, cationic/nonionic surfactant ratio and surfactant addition sequence to the system

Investigation The Drying Behavior Of Ceramic Suspension Droplets

Drying is a major issue in wet processing ceramics. It has crucial effects on the final properties ceramics films especially produced by aqueous based tape casting. In this study structural evolution of ceramic suspension droplets were investigated during drying. Effect of binder concentration on the ring formation from droplets was tested. Results revealed that PMN:latex ratio have some influence on the particle migration and at high latex concentrations particle clusters were observed in the supersaturated region

Factors Affecting The Drying Behavior Of Ceramic Films

Drying behavior of PMN films were investigated using a cantilever deflection based device and scanning probe microscope. Drying stress of the films was measured as a function of suspension composition. Results showed that hydroxypropyl methycellulose (HPMC) has some influence on the stress formation due to its effect on the surface tension of the suspension. On the other hand roughness measurements showed that HPMC has insignificant effect on the roughness of the films and roughness is mainly depended on the binder content of the suspensions

Investigation The Drying Behavior Of Ceramic Suspension Droplets

Drying is a major issue in wet processing ceramics. It has crucial effects on the final properties ceramics films especially produced by aqueous based tape casting. In this study structural evolution of ceramic suspension droplets were investigated during drying. Effect of binder concentration on the ring formation from droplets was tested. Results revealed that PMN:latex ratio have some influence on the particle migration and at high latex concentrations particle clusters were observed in the supersaturated region

Near Net Shape Fabrication Of Pmn Scaffolds

Solid free form fabrication techniques are commonly employed in near net shaping of ceramics especially in the manufacture of microelectronics. Lead magnesium niobate (PMN) is an important relaxor ferroelectric material with perovksite structure used in the production of these multilayer ceramic devices. In this study two dimensional PMN arrays and three dimensional periodic structures were produced by robocasting which is a direct writing technique. Aqueous colloidal gels have been formulated for use as ink in solid freeform fabrication process. Results showed that complex PMN shapes having rod size down to 100 pm can be successfully produced by robocasting process to be used in microelectronic applications

Microhardness and fracture toughness of dental materials by indentation method

The main objective of this study was to measure the fracture toughness of the human teeth enamel using the microindentation technique and to compare the results calculated from the equations developed for Palmqvist and radial-median cracks. Vickers microhardness measurements of dental ceramic (alumina) and human teeth were performed using indentation fracture method. The fracture toughness of enamel was calculated using different equations reported in the literature. Vickers microhardness of the sintered alumina specimen (98.8% theoretical density) was measured to be 14.92 GPa under 9.8N indentation load. Three equations based on the radial-median cracks were found to be applicable for the fracture toughness determination of the enamel. Results show that indentation fracture method is adequate to measure microhardness and fracture toughness of dental materials. However the calculation of fracture toughness depended on the nature of the cracks and also on the location of the indentation. Therefore, it is necessary to identify the crack profile and to select the appropriate equation for accurate fracture toughness values

Effect of calcium hydroxide on slip casting behaviour

The effect of calcium hydroxide addition on the casting performance of ceramic slips for sanitary ware was studied. Powder composed of feldspar (24 wt.%), quartz (24 wt.%), kaolin (35 wt.%) and ball clay (17 wt.%) was mixed with water to contain 65 wt.% of solids (specific density 1800 g/l). Either Ca(OH)2 or Na2CO3 was added at concentrations ranging between 0.060 and 0.085 wt.% and the slurries were dispersed by the optimum addition of sodium silicate. Calcium hydroxide in presence of sodium silicate improved the casting behavior of the slips, lowering the viscosity, and water absorption, increasing bending strength and cake thickness, as compared to the addition of sodium carbonat