Bonding process wetting

The cuprammonia process, the viscose process, and the acetate process have been employed for the production of rayon. Cuprammonia and viscose rayons have similar chemical and physical properties. Both are easily dyed and lose their strength when wet because of a disruption of hydrogen bonding this wet strength is improved through chemical treatment of the rayon fabrics. Acetate rayon is readily softened in the ironing process and loses its luster in boiling water. 

The process of wet-chemical etching of single-crystalline silicon was the first process suitable for the mass fabrication of micromechanical components [53]. Simple geometric structures like grooves, channels or membranes have been incorporated in microreactor components such as pumps, valves, static mixers and (most often) analytical devices. Bonding processes, either thermally or... 

Extrusion, lay flat tubing, calendering, casting, solvent or aqueous dispersion coating, etc. for single layer materials. Multilayer processes—wet or dry bonding (lamination), extrusion coating, coextrusion, etc. 

Because, in most cases, binder added for growth agglomeration is liquid, the discharge from equipment in which size enlargement occurs is moist (green) and only temporarily bonded by the effects of surface tension and capillary forces. With few exceptions (e.g., pan and some fluid bed agglomerators) a wide size distribution is obtained which, without removal of over- and under-sized material, is not acceptable as product. Since separation techniques that do not blind when processing wet solids. 

The physical dimensions of the interfacial discontinuities appear to be such that they cannot be detected by visible optics, nor have first attempts to show their existence by capacitance measurements been fruitful. Thus far it has been necessary to rely on data which support the proposition but do not provide unequivocal evidence that incomplete "wetting is primarily responsible for the observed performance. An example is the "activation energy" of the bonding process. This has... 

Adhesion, by its definition, depends on the ability of two unlike phases to hold themselves together across a common interface. Physical adhesion must first take place before any other bonding processes such as chemical reaction can occur, and such physical adhesion depends on the strength of intermolecular force interaction, on the area of contact and on the distance separating the atoms forming the top layer of each surface (see Dispersion forces, polar forces). When both phases are undeformable, such as with two solids that are not atomically smooth, poor adhesion results because an insufficient area of each surface is in atomic contact with the other. When one phase is deformable, such as with a liquid of low viscosity, physical adhesion takes place at all parts of the surface. Physical adhesion with a liquid in contact with a solid leads to spreading and wetting processes that now depend on the competition of adhesion forces with cohesion forces within the liquid. 

Depending on the curing conditions and material properties, atoms will diffuse across the interface to varying extents when two phases of coating and a substrate achieve molecular contact by wetting. The phenomenon is a two-stage process Wetting is followed by interdiffusion of an element across the interface to establish a chemical bond (Lee, 1991 Kendall, 2001). 

---