Coating, Adhesive and Printing
A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. Powder coatings. Paints and lacquers are coatings that mostly have dual uses of protecting the substrate and being decorative, although some artists paints are only for decoration, and the paint on large industrial pipes is for preventing corrosion and identification e.g. blue for process water, red for fire-fighting control etc.
Functional coatings for surface modifications may be applied to change the surface properties of the substrate, such as adhesion, wettability, corrosion resistance, or wear resistance. In other cases, e.g. semiconductor device microfabrication (where the substrate is a Si, Ge, or GaAs wafer), the coating adds a completely new property on the surface, such as a magnetic response or electrical conductivity, and forms an essential part of the finished product.
A major consideration for most coating processes is that the coating is to be applied at a controlled thickness, and a number of different processes are in use to achieve this control, ranging from a simple brush for painting a wall, to some very expensive machinery applying coatings in the electronics industry. A further consideration for ‘non-all-over’ pattern-specific coatings is that control is needed as to where the coating is to be applied. A number of these non-all-over coating processes are found in industrial printing processes. Many industrial coating processes involve the application of a thin film of functional material to a substrate, such as paper, fabric, film, foil, or sheet stock. If the substrate starts and ends the process wound up in a roll, the process may be termed “roll-to-roll” or “web-based” coating. A roll of substrate, when wound through the coating machine, is typically called a web.
The formulation of the coating depends primarily on the function of the coating and also on aesthetics required such as color and gloss. The selection of four primary ingredients are the resin (or binder), solvent which maybe water (or solventless), pigment(s) and additives is the key for researchers. The common printing methods used in the field are offset printing, rotogravure, flexography, letterpress printing, screen-printing, electrophotography, liquid electrophotography, inkjet printer, transfer-print, aerosol-jet printer, etc. They all need strong surface chemistry know-how to achieve their optimum efficacy.
Our devices which can help in coating and printing are: All types of contact angle meters used for solid surface, SITA SurfaSpector, A60, A100, A200, A300, RSD100, for liquid or solutions: SITA tensiometers Dynotetser, t15 Plus, t100, SITA ConSpector, SITA Cleanline ST and for surface cleanliness checking and validation: SITA CleanoSpector, SITA FluoScan 3D, SITA Cleanline CI, Viscometer, Rheometer, etc.