New coating systems based on vinyl ether- and oxetane-modified hyperbranched polyesters

A series of hyperbranched aliphatic-aromatic polyesters has been synthesize d which contain vinyl ether or oxetane functionalities as curable groups. W e investigated the curing behavior of these multifunctional polymers in the presence of reactive diluents in order to analyze the possibility of their application in high solids coatings. The vinyl ether-modified hyperbranche d polyesters with a high degree of modification yield the best coatings. Fu rthermore, coating systems containing vinyl ether-modified hyperbranched po lyesters and triethyleneglycol divinyl ether (DVE-3) as reactive diluent sh owed a better performance compared to those containing 4-hydroxybutyl vinyl ether (HBVE). Real time FT-IR studies revealed a high conversion of functi onal groups (76%) for the cationic curing with DVE-3. On the other hand, th e curing reaction of the functional hyperbranched polymers without the pres ence of any reactive diluent stopped at 32% conversion of functional groups due to the reduced mobility of the polymer. The vinyl ether-modified hyper branched polyester could be cured also radically in the presence of diethyl maleate (DEM) as reactive diluent, whereas the curing of the oxetane-modif ied polyesters was very slow and incomplete in all attempts.