Abstract:

Polyisocyanate and dihydric alcohols with different fluorocarbon chain lengths were used as raw materialsto synthesize a series of fluorinated isocyanate prepolymers,and the prepolymers were then reacted with self- maderandom copolymerized polyester polyol to prepare transparent fluorinated polyurethane coatings.Afterwards,avariety of analytical methods were used to characterize the structure and properties of the coatings,and the effect offluorocarbon chains on the coating properties was finally discussed.The results indicate that (1) the introduction offluorocarbon chains increases the internal short- range ordered structure in polyurethanes,with an increase degreebeing inversely proportional to the length of fluorocarbon chains,which leads to a decline of coating transparency;(2) the mechanical properties of polyurethanes degrade with the introduction of fluorocarbon chains,and the degra-dation slows down in the presence of moderate micro- phase separation in fluorinated polyurethanes; (3) the intro-duction of fluorine improves the thermal resistance of polyurethanes,especially under the condition of shorter fluoro-carbon chains; (4) the fluorine in fluorinated polyurethanes may migrate to the surface and reduces the surface en-ergy,and the migration degree is related to the crystallization degree of fluorinated isocyanate; and (5) moderatecrosslinking and the migration of fluorine may lead to excellent water resistance of fluorinated polyurethanes.

Key words: polyurethane, fluorinated polyurethane, polyester ployol, fluorinated isocyanate prepolymer, transpa-rency, mechanical property, water resistance