Speed of coating

The practical aspects of dynamic contact angle phenomena, then, center around determining the maximum wetting rates that can be attained before entrainment or wetting failure occurs, and how a system can be modified to increase that maximum velocity, since in many, if not most, cases, speed is money. Liquid coating operations are obviously impacted by the dynamic restraints of a system. If one can increase the maximum speed of coating a substrate from, say, 200 to 400 m min productivity gains will be impressive. 

By the time a material is coated on a large production coater, it gas usually been coated many times on smaller, or pilot coaters. Here the speed of coating is anywhere from 5 to 50 feet/minute. As the drying conditions are likely to he different from those of the production coater, some uncertainty results. 

As the vessel is only about half filled with slurry, the disks become coated with the cake when immersed, the cake is dewatered when the disks emerge from the slurry, and scraped or blown off, by reverse blow, into the central conveyor which takes the cake to one end of the vessel. The planetary action and the slow movement of the disks through the feed slurry ensure exceptionally good homogeneity of the cake which is critically important for good dewatering characteristics the typical speed of rotation of the planetary system of shafts is from 0.8 to 1 rpm. 

Operation and Control. The amount of current appHed to the part determines the speed of which the anodic film is formed. Generally, a current density of 12.9—25.8 m A/cm (12—24 A/ft ) is appHed to produce a coating thickness of 10—20 p.m (0.4—0.8 mils) per 20 minutes. Most coatings range in thickness from 5—50 p.m (0.2—2.0 mils). 

Fig. 7. Schematic of a self-contained plasma processing unit designed to continuously plasma-treat and impregnate with resin, reinforcing fibers for enhanced composite strength. The unit can also be used to plasma-treat wires to be coated or treated for improved adhesion. Throughput speeds of over...

Modem furniture pohshes are designed for a wide variety of surfaces, eg, plastics, metals, and synthetic and natural resin coatings. Furniture pohshes impart shine and provide protection from abrasion, marring, and spills. The formulations clean weU in many cases. In common with most other pohshes, furniture pohshes are characterized by ease and speed of apphcation and of buffing, and by either the absence of objectionable odors or the addition of pleasing ones. 

AH the flow remains on the appHcator roU after the metering roU is transferred to the web thus it is important to know what this flow is. The thickness of the metered coating on the appHcator roU, /, is found to be a function of the gap, of the ratio of the speed of the metering roU to that of the appHcator roU, and of the capHlary number based on the roU speed (Fig. 10). 

Extmsion coating lines operate at speeds up to 1000 m /min and can apply 10—30 g/m of coating. Additionally, multiple layers can be extmded from one die. Multiple extmders feeding one die provide the unique capabiUty of producing layers of different resins to give superior functional properties. For example, an inexpensive resin can be used as the core of a three-ply extmdate, the outer pHes being more expensive but also much thinner than if extmded alone. 

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