Structure-Property Study of Rain Erosion Resistant Polyurethane Coatings

A study has been conducted on urethane elastomers in an attempt to define how chemical and structural features of the elastomer contribute to good rain erosion properties for aircraft radome coatings. Five correlations were developed between easily measured physical properties and rain erosion resistance as determined on a whirling arm rig. Thirty-three urethane elastomers were prepared in an experiment designed to study six chemical and structural properties. It was shown that the best performance would be expected from a polyester polyol such as polycaprolactone, with polyethers such as polytetramethylene glycol, and the poorest performance by hydrocarbon backbones such as polybutadiene. Rain erosion performance was seen to increase as the polyol molecular weight decreased. The urea to urethane ratio, TDI INDEX APPEARED TO GIVE BEST PERFORMANCE AT INDICES OF ABOUT 1.75 AND 1.25. The cross- link density appeared to have no effect on performance, and it was not possible to define the effect of molecular weight distribution of the polyol, nor of the urethane density. (Author, modified-PL)