Wicking Action

Both aramid (Kevlar) and glass fibers absorb fluids. Consequently, the overall ingress of fluids is affected by the sorption within two disparate phases, namely the fibers and the polymeric resin. Typically, the combined effect may resemble the weight gain data representative of a two-stage diffusion. 

Capillary paths arise within fiber-reinforced composites due to mechanically or hygro-thermally induced micro cracks that are channeled parallel to the reinforcement directions. Such cracks can occur under both static and cyclic mechanical loads, and may also develop under sequential thermal spiking. Exposure to ambient environment will instigate the flow of fluid into those capillaries. Specific details will be given in Sect. 4.10. 

This process of fluid ingress occurs in fiber-reinforced composites along the fiber/ matrix interphase regions. These regions, which surround the fibers and are typically a fraction of micron in thickness, consist of a boundary layer of 

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Methods to control infiltration of water into low level waste disposal faciUties are being studied. Three techniques that may be employed separately, in sequence, or in conjunction are use of a resistive layer, eg, clay use of a conductive layer, involving wick action and bioengineering, using a special plant cover. 

In contrast, if the substrate were rather hydrophobic, the tendency would be to deposit less fluid by wicking action. This could also reduce the number of preprints because the deposited spots would smaller and more uniform at an earlier stage in the printing process. Less fluid deposited would also increase the number of spottings possible under these conditions. Printing is an empirical process, one in which the pin, buffer, and substrate properties must be matched to produce the desired microarray (see Figure 4.1). 

Microcrystalline cellulose Strong wicking action loses disintegrant action when highly compressed... 

Once the gel has been placed in the transfer apparatus, buffer in the pan is drawn through the gel by the wicking action of the filter paper. The transfer proceeds over 12 h. The upper filter papers are replaced when they are saturated with buffer. The nitrocellulose membrane is then removed, air-dried and heated to 80 °C for 2 h to ensure strong DNA binding. 

Hoy (27) has examined some factors that influence the efficiency of coalescing aids. An important factor is the distribution of solvent between aqueous and polymer phases at the critical time during film formation. Water-soluble solvents may be lost from the coating through wicking action into the substrate. 

Foam neoprene is similar to open-cell neoprene in that it is a compressible material with intercormecting cells. Its main area of application is for cushioning, for example, in mattresses, seating, and carpet underlay. Because of the good heat and oil resistance of neoprene, it has also found application as a railroad car lubricator. This absorbent open-cell structure provides a wicking action to deliver oil to the journal bearings. 

Wick action is the transport of water (and any species it may contain) through a concrete (porous material) element face in contact with water to a drying face with less than 100% relative humidity of air 129]. The mechanism involves capillary sorption and evaporation. 

During the process of wick action, if there is no evaporation, the solution level can increase through capillary rise in the concrete according to Eq. 5 ... 

Y. T. Puyate et al discussed the chloride transport due to wick action in the concrete in detail [31-34], One vital conclusion is that it was the vapour pressure of the solution and the relative humidity of air which control the position of the wet-dry interface PS). The position of dry-wet interface locates in the inner of the concrete faced to a low relative humidity situation (0%) (Pe l), and a sharp peak of chloride concentration exceeding the saturation value occurs [341. In contrast, in a high relative humidity condition (78%) (Pe l), the location of the interface is close to the concrete surface 32) Therefore, high evaporation can induce severe crystallization distress. 

Nuclear magnetic resonance (NMR) is used to study the crystallization of sodium chloride due to wick action. Measuring the moisture and ion profile in a fired-clay brick cylinder (0 20x45mm), an efflorescence pathway diagram is plotted [35.36] as shown in Fig. 3. 

In the previous tests, an opposite appearance to salt weathering was that the concrete was susceptive to be damaged under a higher relative humidity condition. Combining the role of relative humidity in wick action and chemical sulfate attack, it can be explained that a wider sulfate pore solution can be formed in the upper part of concrete in contact with moist air and chemical sulfate attack occurring in the pore solution zone resulted in concrete damage. 

The results confirm that a pore solution zone can be formed in the efflorescence zone in the concrete, and the sulfate concentration was much higher than the lower part under solution and even the exposure solution (10% by mass). The strong chemical reactions occurring in this high concentration pore solution cause severe concrete decay. This also confirms the wick action theory. 

Y.T. Puyate, C.J. Lawrence, Wick action at moderate Pedet number, Phys. Fluids. 1998,... 

Crucial components in attaching the copper sheets to the armature were the copper saddles, depicted in Fig. 5.12. These U-shaped components wrapped around the armature iron bars and were riveted to the copper skin. Some 1500 of these copper saddles were used. During construction in the United States, shellac-impregnated asbestos was placed between the armature and the skin, but this disintegrated with time and, through wicking action, acted as an undesirable trap... 

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