Metering coating

The war itself also drove the development of improved and miniaturised electronic components for creating oscillators and amplifiers and, ultimately, semiconductors, which made practical the electronic systems needed in portable eddy current test instruments. The refinement of those systems continues to the present day and advances continue to be triggered by performance improvements of components and systems. In the same way that today s pocket calculator outperforms the large, hot room full of intercormected thermionic valves that I first saw in the 50 s, so it is with eddy current instrumentation. Today s handheld eddy current inspection instrument is a powerful tool which has the capability needed in a crack detector, corrosion detector, metal sorter, conductivity meter, coating thickness meter and so on. 

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). 

The dry thickness is directly related to the wet thickness and always depends on suspension properties such as volume fraction solids and colloidal stability. In this respect self-metered and pre-metered coating flows do not differ. The self-metered process is much more complex, because the wet thickness also depends on the suspension properties. 

Fig. 6.33. Pre-metered film-coating flows (a) and (b) and self-metered coating flows (after Rushak [58]).

Park. B. Han M. (2009). Photovoltaic characteristics of polymer solar cells fabricated by pre-metered coating process. Optics Express, vol. 17, no. 16,13830-13840. 

RUSCHAK, K.J. 1976. Limiting flow in a pre-metered coating device. Chem. Eng. Sci. 31, 1057-1060. 

Equipment for the Application of Adhesives and Sealants Mixing, Metering, Coating or Applying the Adhesives... 

Curtain coating utilizes gravity-fed slot orifice dies that meter coatings to the dimensions of the die, and that also control the thickness of the coating imparted as a falling curtain to typically a web-conveyed substrate (see Figure 9.6). 

Cognard P. Equipment for the application of adhesives and sealants mixing, metering, coating or applying the adhesives. In Handbook of adhesives and sealants, vol. 2. Amsterdam, the Netherlands Elsevier Publishing Co., 2006. pp. 51 — 195. 

Electromagnetic flow meters ate avadable with various liner and electrode materials. Liner and electrode selection is governed by the corrosion characteristics of the Hquid. Eor corrosive chemicals, fluoropolymer or ceramic liners and noble metal electrodes are commonly used polyurethane or mbber and stainless steel electrodes are often used for abrasive slurries. Some fluids tend to form an insulating coating on the electrodes introducing errors or loss of signal. To overcome this problem, specially shaped electrodes are avadable that extend into the flow stream and tend to self-clean. In another approach, the electrodes are periodically vibrated at ultrasonic frequencies. 

Principle appHcations of needle-punched nonwovens for the 1990s include automotive, apparel components, blankets, carpeting, carpet pa dding, coating substrates, filtration, furniture, geotextiles, insulation, roofing substrates, and wall coverings. In 1990, the production of needle-punched fabric was estimated to approach 91,000 t and 606 million square meters (15). 

In knife-over-roll or blade coating, the coating material is placed on the fabric surface behind a knife, or doctor blade, and metered according to the gap set between the blade and the fabric surface. This method is used to apply thick coatings of highly viscous materials such as pastes, plastisols, or foams. 

A number of laboratory procedures even more rapid than the accelerated Weather-o-meter have been described for the deterrnination of expected weatherabihty of coating asphalts. Research sponsored by the Asphalt Roofing Manufacturers Association describes a stepwise procedure to determine changes in the cmde asphalt source (see Asphalt). 

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