This guide outlines urethane painting systems for structural steel surfaces. There are three types of urethane coatings covered by the guide. They are Types II@ IV@ and V@ as classifi ed by ASTM Standard D 16. COMMENT: One-Package Moisture-Cured Urethane Coating (Type II): This coating contains moisture curing isocyanate terminated prepolymers which cure by reaction with moisture from the atmosphere. Reduced cure rate will result from insuffi cient atmospheric moisture (low relative humidity). Two-Package Catalyzed Urethane Coating (Type IV): This coating contains isocyanate terminated prepolymers which cure by reaction with a low molecular weight reactive catalyst. One package contains a prepolymer similar to Type II; the second package contains a relatively small quantity of catalyst to accelerate the room temperature cure. This coating has limited pot life after mixing. Two-Package Polyisocyanate Polyol-Cured Urethane Coating (Type V): This coating contains isocyanate terminated prepolymers which cure by reaction with hydroxyl-bearing polyols. One package contains the isocyanate terminated prepolymers and the second package contains a large quantity of resinous material containing active hydrogen groups. This coating also has limited pot life after mixing. These painting systems are suitable for use on parts or structures exposed in varied types of environments ranging from severely corrosive environments to mild atmospheric conditions. These painting systems are intended principally for structural steel where excellent weathering@ color retention@ and chemical resistance is desired. The color of the fi nish must be specifi ed.
PS GUIDE 17.00-1982 history
1982PS GUIDE 17.00-1982 Guide for Selecting Urethane Painting Systems (Editorial Revisions November 1@ 2004)