Surface tension, common solvents

CIJ inks need to work on numerous substrates and there is a relationship between drop spread on a substrate and print quality. The amount of drop spread depends upon a number of issues in a CIJ ink, including surface tension, viscosity, solvent evaporation rate, interaction with substrate, amount and type of polymer in the ink etc. You may wish to improve the print quahty of a certain ink-substrate combination by optimally adjusting the drop spread. A common method to do this is by adding a surfactant to the ink formulation. Depending upon the chemistry of the surfactant, it will either increase or decrease drop spread, and hence is a good mechanism for tuning print quality. There are many hundreds of surfactants available, and you can use all chemical types, including anionic, cationic, non-anionic forms. Specific examples include polyoxyethylene fatty ethers and diethylhexyl sodium sulphosuccinate. 

We present in this work all pubhshed data on density, refractive index, viscosity, electrical conductivity and surface tension for all systems IL + water and + ethanol covering a broad range of concentrations. For density, refractive index and viscosity the data for mixtures with water or ethanol are very similar, and also their behaviour with concentration is not really dependent of the IL mixed with any solvent (except for its value). Density and refractive index can be deduced one from another using Newton s model, which demonstrates the close relationship between both magnitudes. For electrical conductivity and surface tension, the solvent nature determines the data behaviour obtained. Thus, the electrical conductivity value of the pntre IL for aqueous systems increases up to 10 times, while that increase is halved for ethanol systems. In the case of surface tension the behaviour is completely different depending on the solvent and IL studied. For alkyl-methyl-imidazolium tetrafluoroborate the IL acts like a surfactant in water, and the surface tension value decreases sharply from that of water to that of the pure IL for small concentrations of this last, effect that does not appear for halogenated imidazohum ILs. If we change the water for ethanol, that surfactant like effect disappear, and the surface tension value of the only four ILs measured decreases linearly with the ethanol content down to a common value at about equimolar mixture, and then all data has the same value. 

Other effects. In addition to the compound formation and ionisation effects which have been considered, it is also necessary to take account of so-called matrix effects. These are predominantly physical factors which will influence the amount of sample reaching the flame, and are related in particular to factors such as the viscosity, the density, the surface tension and the volatility of the solvent used to prepare the test solution. If we wish to compare a series of solutions, e.g. a series of standards to be compared with a test solution, it is clearly essential that the same solvent be used for each, and the solutions should not differ too widely in their bulk composition. This procedure is commonly termed matrix matching. 

The physical constants (viscosity T], surface tension y, and dielectric constant e) [26] for some common solvents used in chromatography are given in Table 4.2. 

Enhanced-fluidity liquids (EELs) are mixtures that contain high proportions of liquefied gases, such as carbon dioxide [5]. Eluidity,/, is defined as the inverse of viscosity. EEL mixtures combine the positive attributes of commonly-used liquids, such as high solvent strength, with the positive attributes of supercritical fluids, such as low viscosity or high fluidity, low surface tension, high diffusivity. These attributes allow EELC to contribute to the quest for increased separation power. 

The most commonly used LC/MS interfaces in pharmaceutical analysis are ESI and APCI. An ESI interface on the majority of commercial mass spectrometers utilizes both heat and nebulization to achieve conditions in favor of solvent evaporation over analyte decomposition. While ionization in APCI occurs in the gas phase, ionization using ESI occurs in solution. Attributes of a mobile phase such as surface tension, conductivity, viscosity, dielectric constant, flow rate and pFi, all determine the ionization efficiency. They therefore need to be taken into consideration and controlled. 

The large differences in surface tension and dielectric constants between water and common organic solvents cause enzymes to unfold when they are exposed to the interface between the two solvents. This problem can... 

Colloidal potassium has recently been proved as a more active reducer than the metal that has been conventionally powdered by shaking it in hot octane (Luche et al. 1984, Chou and You 1987, Wang et al. 1994). To prepare colloidal potassium, a piece of this metal in dry toluene or xylene under an argon atmosphere is submitted to ultrasonic irradiation at ca. 10°C. A silvery blue color rapidly develops, and in a few minutes the metal disappears. A common cleaning bath (e.g., Sono-clean, 35 kHz) filled with water and crushed ice can be used. A very fine suspension of potassium is thus obtained, which settles very slowly on standing. The same method did not work in THF (Luche et al. 1984). Ultrasonic waves interact with the metal by their cavitational effects. These effects are closely related to the physical constants of the medium, such as vapor pressure, viscosity, and surface tension (Sehgal et al. 1982). All of these factors have to be taken into account when one chooses a metal to be ultrasonically dispersed in a given solvent. 

Dark reddish-brown liquid the only nonmetallic element that is a liquid at ambient temperatures strong disagreeable odor volatilizes density 3.12 g/mL at 20°C vapor density 7.59 g/L refractive index 1.6475 boils at 58.8°C solidifies at -7.2°C vapor pressure 64 torr at 0°C and 185 torr at 22°C critical temperature 315°C critical pressure 102 atm critical volume 127 cm /mol surface tension 39.8 dynes/cm at 25°C electrical resistivity 6.5 x 10i°ohm-cm at 25°C sparingly soluble in water (2.31 g/lOOg at 0°C and 3.35 g/lOOg at 25°C) soluble in common organic solvents. 

The transport phenomenon for any spray material released In the air Is foremost a function of the particle size and size distribution of the released spray. The particle density plays a minor role, the settling rate from Stokes law for example varies as the square root of the density. Further, the density differences between liquids commonly used for pesticides Is very little, varying only slightly from water at density of 1 gm/ml. Other formulation physical factors of surface tension, viscosity and viscoelasticity play significant roles In the atomization process. These are altered by the addition of petroleum and vegetable oil as solvents and carriers as well as a host of adjuvants In varying... 

TABLE 3.5 Surface Tension of Common Organic Solvents... 

Solvents can also be used to reduce the surface tension of the adhesive formulation. The surface tensions of common solvents are shown in Table 3.5. Of course, when using solvents, one needs to make sure that they evaporate from the bond line before cure. Solvent solutions do not change the equilibrium surface energetics of the system. They only provide lower viscosity so that wetting is established at a faster rate. 

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