1. Scope
1.1 This specification covers the requirements for a high performance two-component UV-stable polyurethane topcoat (ASTM D 16, Type V polyurethane). It is intended for a topcoat that provides excellent color and gloss retention, not for thick section elastomeric coatings.
1.2 Coatings meeting the requirements of this specification are generally suitable for exposures in environmental zones 1A (interior, normally dry), 1B (exterior, normally dry), 2A (frequently wet by fresh water, excluding immersion), 2B (frequently wet by salt water, excluding immersion), 3B (chemical exposure, neutral), and 3C (chemical exposure, alkaline).
1.3 The specified coating is intended for application by brush, spray, or roller. It is generally applied over a primer or intermediate coating.
2. Description
2.1 This coating is typically based on a hydroxyl-functional polyol resin and an aliphatic polyisocyanate co-reactant.
2.2 WEATHERING LEVELS: This specification contains three levels of accelerated and South Florida weathering performance. Table 1 specifies the amount of time the coating must perform before noticeable change in order to achieve the defined performance level. Polyurethane topcoats are available in a wide range of color and gloss. Procurement documents shall state the desired level of performance, exposure method, color and gloss. For example, a specifier may require Level 2 Florida exposure, initial gloss greater than 80, matched to a specific color. A certain level of accelerated weathering does not necessarily correspond to a particular level of atmospheric weathering and they need to be specified independently. These are two independent complementary tests for measuring coating performance. If no level is specified, Level 3 will be assumed.
