Surface wettable

The capillary effect is apparent whenever two non-miscible fluids are in contact, and is a result of the interaction of attractive forces between molecules in the two liquids (surface tension effects), and between the fluids and the solid surface (wettability effects). 

Diamond behaves somewhat differently in that n is low in air, about 0.1. It is dependent, however, on which crystal face is involved, and rises severalfold in vacuum (after heating) [1,2,25]. The behavior of sapphire is similar [24]. Diamond surfaces, incidentally, can have an oxide layer. Naturally occurring ones may be hydrophilic or hydrophobic, depending on whether they are found in formations exposed to air and water. The relation between surface wettability and friction seems not to have been studied. 

Poljraer surfaces can be easily modified with microwave or radio-frequency-energized glow discharge techniques. The polymer surface cross-links or oxidizes, depending on the nature of the plasma atmosphere. Oxidizing (oxygen) and nonoxidizing (helium) plasmas can have a wide variety of effects on polymer surface wettability characteristics (92). 

Solids separation based on density loses its effectiveness as the particle size decreases. For particles below 100 microns, separation methods make use of differences in the magnetic susceptibility (magnetic separation), elec trical conductivity (electrostatic separation), and in the surface wettability (flotation and selec tive flocculation). Treatment of ultrafine solids, say smaller than 10 microns can also be achieved by utilizing differences in dielectric and electrophoretic properties of the particles. 

Adhesion of paints and adhesives to TPOs is especially problematical due to the aliphatic nature of the substrate material. In Europe, plasma and corona treatment is employed to render these surfaces wettable and obtain strong adhesion by adhesives and paints in automotive manufacture. In the United States, however, primers based on solvent-borne chlorinated polyolefin oligomers (CPOs) have become the treatment of choice for these substrate materials. The VOC emissions from these primers are considerable (as in all solvent-borne adhesives), but the less... 

The change in surface wettability (measured by the contact angle) with concentration for the three surfactants is plotted in Fig. 2.54 (Zhang and Manglik 2005). The contact angle reaches a lower plateau around the CMC where bilayers start to form on the surface. Wettability of non-ionic surfactants in aqueous solutions shows that the contact angle data attains a constant value much below CMC. Direct interactions of their polar chain are generally weak in non-ionics, and it is possible for them to build and rebuild adsorption layers below CMC. The reduced contact an-... 

Jarvis and Pethica [51] also investigated adhesion as a function of surface wettability but used a diamond tip for its known hydrophobic properties. They also used magnetic force-controlled AFM and applied forces to magnetic material behind the tip to bring the... 

Lewis, J. P, and D. E. Graesbeck, 1969, Tests of Sodium Boiling in a Single Tube-in-Shell Heat Exchanger over the Range 1720° to 1980°F, NASA TN D-5323, Lewis Res. Ctr., Cleveland, OH. (3) Liaw, S. P., and V. K. Dhir, 1986, Effect of Surface Wettability on Transition Boiling Heat Transfer from a Vertical Surface, Int. Heat Transfer Conf, San Francisco, CA, voL 4. (2)... 

Sigal GB, Mrksich M, Whitesides GM (1998) Effect of surface wettability on the adsorption of proteins and detergents. J Am Chem Soc 120 3464-3473... 

Ermilova EV, Zalutskaya ZM, Lapina TV, Nikitin MM (2003) Chemotactic behavior of Chlamydomonas reinhardtii is altered during gametogenesis. Curr Microbiol 46 261-264 Finlay JA, Callow ME, Ista LK, Lopez GP, Callow JA (2002) The influence of surface wettability on the adhesion strength of settled spores of the green alga Enteromorpha and the diatom Amphora. Integr Comp Biol 42 1116-1122... 

Control of fiber friction is essential to the processing of fibers, and it is sometimes desirable to modify fiber surfaces for particular end-uses. Most fiber friction modifications are accomplished by coating the fibers with lubricants or finishes. In most cases, these are temporary treatments that are removed in final processing steps before sale of the finished good. In some cases, a more permanent treatment is desired, and chemical reactions are performed to attach different species to the fiber surface, e.g. siliconized slick finishes or rubber adhesion promoters. Polyester s lack of chemical bonding sites can be modified by surface treatments that generate free radicals, such as with corrosive chemicals (e.g. acrylic acid) or by ionic bombardment with plasma treatments. The broken molecular bonds produce more polar sites, thus providing increased surface wettability and reactivity. 

The prototype of the present surface photografting is the surface photoreaction of maleic anhydride(MAH) onto poly(butadiene) film(15). Although fair improvement of surface wettability was achieved, photoaddition of MAH cannot be applied to other polymers having no ethylenic double bonds. The present process is applicable to almost all polymers except for poly(tetrafluoroethy-lene) and its analogues. 

As noted previously in Chapter 3, the improved dimensional stability of wood as a result of anhydride modification has been found to be a function of WPG only, irrespective of the anhydride used for modification (Stamm and Tarkow, 1947 Hill and Jones, 1996b Li etal., 2000b). This shows that improved dimensional stability arises due to a bulking phenomenon, caused by the volume occupied by the bonded acyl adducts in the cell wall. The dimensional stabilization of wood modified with crotonic anhydride has also been reported ( etin and Ozmen, 2001). Reductions in the EMC have also been attributed to a bulking phenomenon (Papadopoulos and Hill, 2003), and in at least one example of decay protection (Papadopoulos and Hill, 2002). Further research is needed to determine if this is the case for resistance to other decay organisms. Only with the phenomenon of surface wettability does the relationship between a physical property of chemically modified wood and WPG seem to be broken (Hill and Jones, 1996c) (Table 4.1). 

The surface wettability of heat-treated wood decreases due to a reduction in the hydroxyl content of the modified wood (Pdtrissans etal., 2003). There is a reduction in the water-sorption capacity, which is related to a reduction in the number of primary sorption sites (OH groups) within the wood cell wall, largely as a result of the removal/degradation of the hemicellulosic component. As remarked upon earlier, hygroscopic properties are strongly influenced by the treatment method employed. Podgorski etal. (2000) heated... 

In addition to the amount of filler content, the shape, size and size distribution, surface wettability, interface bonding, and compatibility with the matrix resin of the filler can all influence electrical conductivity, mechanical properties, and other performance characteristics of the composite plates. As mentioned previously, to achieve higher electrical conductivity, the conductive graphite or carbon fillers must form an interconnected or percolated network in the dielectrical matrix like that in GrafTech plates. The interface bonding and compatibility between... 

The total swelling time for a dried SPH in aqueous solution is determined by two factors q and t2- h is the time for water to reach all the surface of the pores in the SPHs. It is determined by the effectiveness of the capillary action in a SPH. 2 is the actual swelling time of the polymer matrix, which is determined by the thickness of the cell walls and struts. Because the cell walls and stints of SPHs are very thin, they have very short characteristic swelling times. For SPHs, t2 is comparable to that of a ultrathin hydrogel film. The capillary action is mainly determined by the availability of capillary channels and the wettability of the channels. Various approaches have been attempted to maintain good capillary action (i.e., to decrease q) by maintaining open intercellular channels and good surface wettability. 

Three properties of the current collector plate are particularly important for CFCD models. One is electric conductivity, the second is thermal conductivity, and the third is surface wettability. These properties for materials such as graphite and metals are well documented in standard textbooks. 

Sun RD, Akira N, Fujishima A, Watanahe T, Hashimoto K (2001) Photoinduced surface wettability conversion of ZnO and Ti02 thin film. J Phys Chem B 105 1984-1989... 

During the plasma surface reaction, the plasma and the solid are in physical contact, but electrically isolated. Surfaces in contact with the plasma are bombarded by free radicals, electrons, ions, and photons, as generated by the reactions listed above. The energy transferred to the solid is dissipated within the solid by a variety of chemical and physical processes, as illustrated in Figure 7.95. These processes can change surface wettability (cf. Sections 1.4.6 and 2.2.2.3), alter molecular weight of polymer surfaces or create reactive sites on polymers. These effects are summarized in Table 7.21. 

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