Intermediate coats

A single paint will rarely possess all the required properties and it therefore becomes necessary to formulate a system comprising a primer, a finish, and possibly one or more intermediate coats. 

In the majority of cases maximum durability will be produced by a multicoat system comprising priming and finishing paints only. Other considerations, however, such as uniformity of colour and smoothness of surface, may make it desirable to introduce intermediate coats, e.g. putty, filler and undercoat. The appearance of the final film or of the final painted structure is of some importance, and a final colour coat, which may contribute very little resistance to corrosion, may be necessary. 

The reactivity problem can be partially remedied with the use of intermediate coatings (see Sec. 2.5 below). 

Paint or coating systems consists of many layers which are known as coats. The first coat applied on a structure is the primer and the last is known as finish or top coat. The coats between the primer and finish coat are intermediate coats. 

Polyurethane 541-D-101 Valspar Moisture-cured urethane intermediate coat... 

What pore size and porosity should be aimed at For the particular application, the resistance of the layer 2 intermediate coating should be as low as possible which means large pore size, high porosity and low layer thickness. However, the pore size is largely restricted by the pore size of the tubular substrate (4 pm) and by the relevant coating mechanism. 

Ellipsometry was used in situ at all stages of the preparation of the substrates with their intermediate coatings as a monitor of surface concentration, and this study provides an excellent illustration of the power of the technique as a non-destructive and highly sensitive surface probe. 

A complete coating system, recommended for highly demanding situations, consists of several layers - the primer, the intermediate coats and the topcoat. The primer is an essential component for corrosion protection, because it is responsible for the adhesion of the coating to the substrate and also it provides most of the anticorrosive properties, through the use of inhibitors. Its requirements are a good adhesion to the substrate and to the intermediate coat, flexibility and cohesion and good chemical resistance. 

The intermediate coats are used mainly for increasing the final thickness, and consequently hinder the moisture permeation... 

Inorganic zinc silicate polymer, chemically curing epoxy or polyurethane intermediate coat, and aliphatic polyurethane top coat. 

Fillers and Putties for Wood Materials. Fillers are highly extended (resin/extender ratio, 1 2.5) compounds of high viscosity which are applied to cover any unevenness in a substrate such as chipboard. Putties contain less extender (1 1.5) and are normally used as an intermediate coat between the filler and the top coat. Fillers and putties are formulated using dissolvers, butterfly mixers or attrition mills. 

Large numbers of cars are manufactured on fast-running assembly lines. The paints must therefore be applied with highly efficient equipment, and must dry very quickly. The paint products are classified as primers, intermediate coats (also called fillers or surfacers), and topcoats (or finish). The primers and fillers are designated as the undercoating system. 

Car paints are cured with heat in special oven lines. Electrodeposition coatings (used as anticorrosive primers) contain only small amounts of volatile organic compounds (VOC), whereas intermediate and topcoats release considerable amounts of VOCs. Intermediate coats based on waterborne resins have been developed to decrease VOC emission and are already being used in some automotive plants. Basecoats, as part of base-clear topcoat systems, contain very high amounts of volatile organic solvents. Waterborne basecoats were developed more recently to lower this source of solvent emission. Some car manufacturers are operating pilot lines with the aim of introducing waterborne basecoats into their production processes. Many car producers in the United States and Europe have already switched their topcoat lines over to waterborne basecoats [11.3]. 

Paint systems for car repair comprise anticorrosive primers, putties, intermediate coats, and topcoats repair coatings applied to refinished cars have similar durabilities to those of the originally manufactured coating systems. 

Anticorrosive primers are followed by a 40- 50 pm intermediate coat, based on two-pack polyurethane resins. This coat is sanded to yield a smooth surface. 

Sometimes, the intermediate coat is overcoated with the topcoat in a wet-in-wet system. Normally, however, two-pack polyurethane topcoats are applied to the dried filler. These topcoats with aliphatic isocyanate hardeners have excellent gloss and color retention. The DFT of topcoats is 40 - 80 pm, depending on the hiding power of the topcoat. 

Although two-pack epoxy primers and polyurethane intermediate coats have high solids contents, they still contain significant amounts (20-30 wt%) of organic solvents. In polyurethane topcoats, the VOC is even higher. Anticorrosive, waterborne primers based on aqueous dispersions of two-pack epoxy resins and one-pack acrylic resins have been developed to decrease solvent emission. Waterborne, one-pack acrylic topcoats are also used. All of these waterborne paints contain 2 - 5 % organic cosolvents that are required for film formation. 

Field trials have shown that the expected durability of the new waterborne coating systems is equal to that of conventional solventborne paints. As a further advantage, the number of single coats can be reduced from three to two. Standard freight cars are painted with a three-coat alkyd system consisting of an anticorrosive primer, an intermediate coat, and a topcoat, total DFT is ca. 150 pm. Such systems are being replaced by single-coat systems of waterborne acrylic resins and acrylic copolymers to reduce solvent emission. 

There are two nonwelding methods in which the coating material is also in molten form. In homogeneous lead coating, lead is melted with burners and applied to the steel surface. Intermediate coatings (e.g., tin solder) are needed to improve adhesion. 

One favorable aspect of these layered compounds is their ability to form a layered structure from sol-gel precursors at temperatures as low as 600°C (1,112°F). This ability is critical, especially with complex chemistries, because a lower formation temperature can help avoid reactions between the fibers and intermediate coating phases. Additional work will be required to determine if these classes of compounds are stable with potential and commercially available fiber reinforcements. 

Cheiv. Descrip. Benzophenone CAS 119-61-9 EINECS/ELINCS 204-337-6 Uses Free radical initiator for UV curing used in adhesives, chem. intermediates, coatings (metal, paper, wood), electronics (conformal, encapsulants, photoresists, solder masks), inks (flexo and gravure, litho, offset, screen) intermediate for mfg. of antihistamines, hypnotics, insecticides... 

Uses Binder for one-pack stoving PU systems for highly flexible primers, intermediate coats, primer surfacers, and thin coil coating primers Properties Thinnable with esters, ketones, aromatic hydrocarbons dens. = 1.10 g/cm vise. 2000 01200 mPa-s-(23 C) flash pt. = 25 C 69 02% NV... 

Poly-G 300 Poly-G 400 Poly-G 600 intermediate, coating resins Methyltrimethoxysilane intermediate, coatings... 

Coatings may consist of one to three layers, depending on cost and quality. High quality coatings have a base or tie coat, an intermediate or filler coat, and finally a top coat. The base coat ensures adequate adhesion to the textile material. The intermediate coat is responsible for the system volume and the mechanical properties. The top coat determines the appearance and surface properties and also seals the surface. 

Coil coatings are used to create intermediate coated products which are then used in an end market sector. The largest single end use for coil-coated products (60% by area coated) is in the building industry. This market can be further subdivided according to substrate coated, mainly galvanised or zinc-coated steel and aluminium, but a more useful sub-split is by coating type ... 

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