Coatings application, methods

The most common coating application method is the knife over roll system (Fig. 2.16). The shape and angle of the coating blade, the gap between the blade and the fabric and the viscosity of the coating all affect the amount of coating applied and the penetration into the fabric. 

Surface preparation, coating application methods and coating materials chosen or specified can effectively help prevent potential damage to con-... 

TABLE 10.22 Theoretical Transfer Efficiencies TE of Coating Application Methods... 

The more automatic the method of coating application, the more economical and efficient it is, since automation lends itself more readily to more even coatings than do manual methods, e.g. large surface areas lend themselves more readily to spraying techniques, whereas open work structures are more suitable for dipping methods. The coating should also be applied to a specified minimum thickness which is adequate for the service conditions and life envisaged. 

Avoid cavities and recesses because this application process does not coat the inside surface of an article adequately. Where they are essential elements of the design consider using a different application method. 

It is wise to discuss methods jointly with the powder coating applicator. First, the materials used must withstand temperatures of circa 220°C. Second, some commonly used jointing materials are incompatible with all pretreatment systems. 

A matter of considerable importance in the selection of an application method is its efficiency. Spray techniques are usually inefficient, since many droplets drift past the target and are lost. Even electrostatic spraying can waste as much as 35% of the paint. There is some loss of paint in most methods, but roller coating, curtain coating and electrodeposition are very efficient. Electrodeposition is also a very useful technique where corrosion resistance is important, since it applies a uniform coating over nearly all surfaces of even the most complex-shaped article. 

Whatever application method is used, the maximum corrosion resistance can only be achieved if the metalwork is properly prepared. This preparation consists of dressing, blasting and conversion coating. 

Whatever application method is used, there is always a heating step. When p.v.c. plastisol is heated to over 100°C the p.v.c. resin which is suspended in plasticiser stabiliser etc. starts to dissolve in the plasticisers. When solution is complete the system is cooled to room temperature and a solid homogeneous coating results. 

Trimerization to isocyanurates (Scheme 4.14) is commonly used as a method for modifying the physical properties of both raw materials and polymeric products. For example, trimerization of aliphatic isocyanates is used to increase monomer functionality and reduce volatility (Section 4.2.2). This is especially important in raw materials for coatings applications where higher functionality is needed for crosslinking and decreased volatility is essential to reduce VOCs. Another application is rigid isocyanurate foams for insulation and structural support (Section 4.1.1) where trimerization is utilized to increase thermal stability and reduce combustibility and smoke formation. Effective trimer catalysts include potassium salts of carboxylic acids and quaternary ammonium salts for aliphatic isocyanates and Mannich bases for aromatic isocyanates. 

The second method of sample preparation for IMS is a matrix-coating method for MALDI imaging. In this chapter, we review the choices of matrix compound and solvent composition appropriate for IMS of tissue sections. Three kinds of matrix-application methods and examples of their use are illustrated. 

This test (ASTM D529) evaluates the relative weather resistance of asphalt used for protective-coating applications, especially for roofing. No direct measure of outdoor life or service can be obtained from this test. Methods for preparing test panels (ASTM D1669) and failure-endpoint testing (ASTM D1670) are available. 

Processing methods in the liquid state are also used casting, rotomoulding, dipping, coating... Applications... 

M. K. Debe. Novel catalysts, catalyst supports and catalyst coated membrane methods. In Handbook of fuel cells Fundamentals, technology and applications. Vol. 3 Fuel cell technology and applications, ed. W. Vielstich, H. A. Gasteiger, and A. Lamm, 576 (2003). New York John Wiley Sons. 

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