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Handbook of Solvents - George Wypych - ChemTech - Ventech!

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966 Tilman Hahn, Konrad Botzenhart, Fritz Schweinsberg, Gerhard Volland<br />

Table 14.19.1.3. Wet coatings - coating materials for metals<br />

Natural<br />

substances<br />

Plastic<br />

materials<br />

Abbreviation Application State<br />

Curing<br />

method<br />

oil OEL<br />

oxidizing<br />

bitumen B<br />

binders for<br />

wet coating<br />

physical<br />

tar T physical<br />

alkyd resin AK<br />

oxidizing<br />

polyurethane<br />

epoxy resin<br />

PU<br />

EP<br />

liquid<br />

chemical<br />

chemical<br />

acrylic resin AY<br />

binders for<br />

wet coating<br />

physical<br />

vinyl resin PVC physical<br />

chlorinated<br />

rubber<br />

RUC physical<br />

The chemical properties <strong>of</strong> binders are not affected by the drying process if coatings<br />

are <strong>of</strong> physically drying type. After solvent has evaporated, the polymer molecules become<br />

intermeshed, thus producing the desired coating properties.<br />

In contrast to physical drying, binders based on reactive resins such as epoxy resins,<br />

polyurethanes or polyesters consist <strong>of</strong> two components (liquid resin and curing agent)<br />

which are either mixed shortly before the coat is applied, or, in the case <strong>of</strong> a one component<br />

system, one which is applied as slow reacting mixture. The setting reaction occurs at the<br />

surface <strong>of</strong> the coated material. The final products are normally more resistant and more<br />

compact than products based on physically drying binders. Pretreatment <strong>of</strong> substrate is<br />

more critical for applications where chemically hardening products are applied. Coatings<br />

can be more or less permeable to water vapor and oxygen. Damage to the metal substrate<br />

can occur if water and oxygen reach the reactive surface simultaneously. This is normally<br />

impossible if the coatings adhere well and the coated surface is continuous. The adhesion <strong>of</strong><br />

the coating also prevents the penetration by harmful substances via diffusion processes. Adhesion<br />

is enhanced by adsorption and chemical bonds.<br />

14.19.1.2.3 Other coating materials<br />

Other aspects <strong>of</strong> solvents contained in paint coatings and varnishes are given in Chapter<br />

18.3.<br />

The market <strong>of</strong>fers a wide spectrum <strong>of</strong> coating systems. Examples <strong>of</strong> common industrial<br />

coating materials are listed in Table 14.19.1.4 and relevant aspects concerning application<br />

and environmental or health risks are also included.

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