Urethanes
Like acrylic polymers, there are many forms and types of urethane resins; the basic types are aromatic and aliphatic urethanes. Aromatic urethane resins are less resistant to sunlight than aliphatics and are used on interior surfaces. Aliphatic urethanes are ultra violet (UV) resistant and provide excellent exterior durability, and are found in high performance coating applications such as automotive topcoats. The basic urethane classes are:
| ASTM Type |
Classification |
Cure Type |
| Type I |
One package, pre-reacted |
Oxidative air dry, assisted by metallic driers |
| Type II |
One package, moisture cured |
Cures by availability of atmospheric moisture |
| Type III |
One package, heat cured |
Thermoset cure |
| Type IV |
Two package, catalyst |
Requires the addition of a small amount of a catalyst sush as a monomeric polyol or polyamine |
| Type V |
Two package, polyol |
Requires the addition of a large amount of another resin containing active hydrogen groups, with or with out a catalyst |
| Type VI |
One package, non-reactive |
Thermoplastic cure by solvent evaporation |
Note:
Caution must be taken when handling or applying all urethane coatings (with the exception of the Type I urethane-modified alkyds and the Type VI urethane dispersions) as all urethanes use isocyanates that can cause long-term allergic reactions.
Vinyl
Vinyls are a versatile family of polymers that have found extensive use in many different industries. More polyvinyl chloride is used than any other plastic except polyethylene. Vinyl chloride (VC) - vinyl acetate (VA) co-polymers are the most widely used in the coatings industry as the VA improves solubility of the resin in organic solvents. Vinyl organosols and plastisols are commonly used for faux leather products (naugahyde) and flexible product finishing as well as marine coatings, furniture finishing (office), lawn furniture, and dishwasher interiors. Vinyl coatings are generally thermoplastic and remain soluble in the original solvent after curing, but hydroxyl modified vinyl resins can be co-polymerized with other functional materials such as alkyd, epoxy and acrylic to create cross linked products. Uses for vinyls include house siding, window frames, electrical insulation, eaves troughs, garden hose, pipe, floor tile, phonograph records, household goods, and water-resistant sheeting, such as raincoats and shower curtains. Vinyl polymers may be used to formulate both solvent-borne and waterborne coatings, but their largest use is as emulsions for water based systems. Poly vinyl acetate (PVA) co-polymer emulsions are found in most interior and exterior general purpose latex paints.
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