Capillary penetration technique

In many applications, powders come into contact with a liquid and we would like to quantify their wetting behavior. The usual way to do this is by the capillary rise method [233,234], In a capillary rise measurement the powder is pressed into a tube of typically 1 cm diameter (Fig. 7.7). This porous material is then treated as a bundle of thin capillaries with a certain effective radius [235-237], In order to measure this effective radius, first a completely wetting liquid is used. Either the speed of the liquid rise is measured (this technique is sometimes referred to as the capillary penetration technique [238]) or the pressure required to keep the liquid out of the porous material, is determined. This backpressure is equal to the... 

Desai TR, et al. Determination of surface free energy of interactive dry powder liposome formulations using capillary penetration technique. Colloids Surf B Biointerfaces 22(2) 107-113, 2001. 

Many different techniques have been developed for the measurement of contact angles 17.8). Of these, the three most useful methods are the Wilhelnty technique, the technique of capillary rise at a vertical plate, and the drop shape methods. These techniques require the solid surface to be flat and smooth. Direct measurement of contact angles on fibers (of uniform thickness) can also be performed using the Wilhelmy technique. For nonflat surfaces or particles, indirect methods such as capillary penetration into columns of powders, sedi-... 

II. 1.6b. Phenomena involving capillary penetration will be discussed in sec. 5.9 they are very relevant for a number of industrial processes. In fact, several techniques yield y cos a rather than / the trend is that / is more easily measured than cos a. 

Techniques for estimation of biofilm thickness were recently summarized by Charaklis et al. (1982). An ideal film thickness equal to the penetration depth of the limiting substrate or oxygen was stressed by Howell and Atkinson (1976). A capillary microelectrode technique has been developed by Bungay et al. (1969) for this purpose. The effect of growth rate on the biofilm buildup... 

B. Capillary-Penetration Method or Rising-Height-or Imbibition Technique... 

Techniques for phase identification are similar to those employed for thermotropic liquid crystals, although there are differences. Thus, optical microscopy is the most common technique used, but rather than prepare multiple samples at a range of concentrations it is more common to perform Lawrence Penetration Experiments [189]. In this experiment, some solid surfactant (maybe up to 50 mg) is placed on a microscope slide and a cover slip placed on the top. Water (or which ever solvent is to be used) is placed at the end of the cover slip and proceeds from one end to the other by capillary action, thus, setting up a concentration gradient across the sample. Now, at any given temperature, it is possible to have a snapshot of the whole phase diagram, and clear phase boundaries can often be seen. This experiment can be very... 

This is not a vaporization technique. The sample is deposited directly into the capillary column cold on-column or COC). A special micro-syringe, whose needle (steel or silica) is of 0.15 mm diameter, is necessary for penetrating the column which is cooled to 40 °C before being allowed to return to its normal operating temperature. This procedure, useful for thermally labile compounds or high boiling compounds, is difficult to master without the aid of an autosampler. It is known not to discriminate between compounds of different volatilities (Figure 2.5). 

The more hydrophobic neutral molecules tend to penetrate the micelle to the hydrophobic center and associate for an equilibrium amount of time. As a result, they are carried along for a short time with the micelle toward the anode. This large molecule lags further behind the main bulk of the system. Different neutral molecules penetrate and associate for various lengths of time. This means that neutral molecules can become separated. This technique has been called micellar electrokinetic capillary chromatography (MECC), Figure 31-8. 

The pendant drop experiments are a very new experimental technique to study penetration systems. The insoluble monolayer is spread onto the drop surface carefully by using a microsyringe [221]. The exchange of the drop bulk phase can be easily performed by using a coaxial double-capillary as shown in Fig. 4.20. 

Low viscosity materials offer a quick and simple way of sealing porous castings and hairline cracks. Anaerobic cure follows penetration by capillary action. Other porosity treatment techniques often involve long and complicated curing cycles. 

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