Moisture Cured Urethane (MCU) Coatings for Use on Antenna Towers: A feasibility Study

摘要

A feasibility study on the use of Moisture Cured Urethane (MCU) coatings for large antenna towers was conducted. Results are as follows: (1) MCU coating systems are performing well on Oregon's coastal bridges, (2) MCU coatings will produce a somewhat acceptable bond to either a damp or wet substrate, (3) MCU coatings form excellent bonds to both blasted steel and to MCU intercoats, (4) Aliphatic MCU topcoats exhibit a decrease in color retention and gloss when subjected to QUV Accelerated Weathering, (5) MCU application by either mitt or brush may producing unacceptable bubbling (pinholes), (6) Federal Highway Administration (FHA) research concludes that MCU coatings provide excellent barrier protection, however, all MCU coatings are not equivalent and require testing prior to use, (7) A Relative Humidity (RH) below 30% may produce unacceptable slow curing, whereas, a RH above 83% may produce too fast of a cure with unacceptable bubbling, (8) MCU coatings with xylene may cause film bubbling when DFTs exceed 3.0 mils, (9) MCU topcoats employing 100% aliphatic resins, when compared to two-component aliphatic urethanes, give rise to lower UV resistance. NFESC does not recommend MCU coating systems for use in painting erected antenna towers.