Solution coating technique

The solution coating technique involves preparing an excess of solution of known concentration of the stationary phase dissolved in appropriate solvent. A known weight of support is then added slowly to a known volume of solution while the solution is stirred until all of the support is in suspension. This slurry... 

The solution coating technique in most cases is preferred to the evaporative method because there is more uniform deposition of the phase and because there is less chance for damage of support particles. The evaporative procedure is more convenient for preparing high concentration packings (15-20%) of the viscous phases such as Carbowax, and for preparing packings with two or more stationary phases which are not soluble in a common solvent. 

Processing. In order to achieve the promise of cheap device fabrication it will be very beneficial to be able to use solution coating techniques and... 

The solution coating technique was used in the preparation of the cellulose triacetate membrane discussed above. A solution of cellulose triacetate in chloroform was deposited on the porous support and the solvent was then evaporated leaving a thin film on the porous support. Thin film polymerization was used to prepare a polyfuran membrane barrier layer on polysulfone. In this case, the monomer furfuryl alcohol is polymerized in situ by adjustment of pH and temperature. This membrane proved to be highly susceptible to oxidizing agents and is of limited value. By far the most valuable technique in the formation of membrane barrier layers is interfacial polycondensation. In this method, a polymer is formed on the porous support surface at the interface of organic and aqueous phases by reaction of specific molecules dissolved in each phase. It is by this method that a number of polyamides and polyurea membrane barrier layers have been formed on polysulfone. Elements containing these membranes are available commercially. 

Dip and Spin Coating. The dip coating technique described for webs can also be used to coat discrete surfaces such as toys and automotive parts. The surface to be coated is suspended on a conveyor and the part dipped into the coating solution. The surface is then removed, the coating drains, then levels to give the desired coverage. The object is then dried or cured in an oven. 

The rqjroducibility of polymer film formation is greatly improved by the spin coating technique where the polymer solution is applied by a microsyringe onto the center of a rapidly rotated disk electrode Rather thick films can be produced by repeated application of small volumes of stock solution. A thorough discussion and detailed experimental description of a reliable spin coating procedure was given recently... 

Falling-film crystallization utilizes progressive freezing principles to purify melts and solutions. The technique established to practice the process is inherently cyclic. Figure 20-15 depicts the basic working concept. First a crystalline layer is formed by subcooling a liquid film on a vertical surface inside a tube. This coating is then... 

The theory behind this coating technique involves the equilibrium between the centrifugal forces created by the rapid spinning and the viscous forces determined by the viscosity of the liquid.1,88 Die film thickness can be varied by controlling the spin speed and time, as well as the viscosity of the solution. 

Conformance of dry film to the copper surface is a concern, particularly with stiff films. One way to improve conformance is to coat a low viscosity photopolymer liquid direcdy on the substrate. Several coating techniques are available to deposit photoresists directly onto metal substrates. These techniques involve dissolving/dispersing the ingredients in a solvent, coating the solution on the substrate and removing the solvent. Some of the material is lost during the... 

The use of the dip-coating technique allows to obtain different overlay thicknesses by acting on the solution viscosity and extraction speed as stated by the Landau-Levich equation (see (3.14)). In particular, thicker overlays can be obtained by increasing the extraction speed and/or by increasing the solution viscosity. 

SMOLEDs contain small-molecule emissive materials that can be processed by either vacuum deposition (evaporative) techniques or solution coating. The emissive small molecule may be a fluorescent (singlet excited state) or a phosphorescent (triplet excited state) emitter. 

The spin coating technique of preparing PAMAM dendrimer samples for AFM is the best method to maintain undistorted dendrimer shape allows the visualization of isolated single dendrimer molecules. In spin coating, a dendrimer solution is rapidly spread across the sample surface and the majority of particles separate from one another. 

If suitable equipment for processing the polymer melt is not available, or if the polymer will not melt, or melts only with decomposition, the processing may be carried out from solution. This technique, however, is limited to the fabrication of films, membranes, fibers, coatings, and adhesives. 

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