Autobond is a class of very high solids polymers that, when baked, yields a very tough, weatherable ink film which can be screen printed or roll coated. When pigmented, the mixture will contain smaller amounts of solvent in certain colors, thereby drastically reducing the VOC's (Volatile Organic Compounds). This blend of high-tech formulating combines with the best in available raw materials to yield "Autobond."
How Urethanes Form
There are several types of urethanes: single part bake, two-component air dry, one-component moisture cure, waterborne polyurethane, and radiation curable. For this document, we will only deal with the chemistry of the single part bake and the two-component air dry.
A coating film becomes a urethane when a polymer containing a hydroxyl or alcohol group is reacted with one of a family of isocyanates. These polymers are usually classified as polyesters, but there are other hydroxyl bearing polymers that will also act as coreactants with isocyanates.
The two major versions of isocyanates are free isocyanates and blocked isocyanates. Free isocyanates are used when a two-part system is required. Mixing the two parts creates a reaction between the two components. However, depending on the choice of reactants in the formula, the screen print must be applied within 10 minutes to several hours before the viscosity becomes too high and is then unprintable. The cure of a two-part system can be sped up by the use of a low temperature oven (120° F to 180° F).
Blocked isocyanates are used in one-part formulas where shelf stability is required. The reaction will not take place until the blocking element affixed to the isocyanate is severed from the isocyanate at an elevated temperature. The temperature range for the unblocking to occur is usually between 250° F and 450° F. Once the unblocking occurs, the isocyanate will then react with the other component carrying the hydroxyl group.
It is important to know what type of isocyanate is present in the urethane ink or coating that you intend to use. There are two major types of isocyanates: aromatic and aliphatic. Aromatic isocyanates contain cyclic configurations that are not weatherable and should be used for interior applications only. Aliphatic isocyanates are based on straight chain configurations and demonstrates excellent weatherability. Ask your ink supplier which one you need for your particular application. It is important to note, however, that the aromatic isocyanate version can yield physical properties, in some cases over and above that of the aliphatic version. This refers to interior applications.
How are urethanes useful to me?
Industries, such as automotive and appliance, rely on high-quality urethane inks and coatings to meet the demands of their customers. Physical properties such as weatherability, flexibility, abrasion resistance, chip resistance, chemical resistance, and gloss are characteristic of this high-quality urethane chemistry. Outdoor signage and nameplates can also benefit from the use of the aliphatic version of a urethane.
Available at Deco-Chem
AutoBond (ATB) is the urethane baking enamel of choice. It is available in many colors, including black and white. High performance primers and overprint clears are also available.
URE 2 is a two-part urethane that yields superior physical properties for interior applications. It is excellent for appliances and interior automotive. It is also available in many colors, including black and white. High performance primers and overprint clears are also available.
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