Vinyl esters are halfway between polyesters and epoxies as far as typical properties and toughness, and they are a step up on a cost basis. Their longer double bonded vinyl groups that link the ester groups together contribute a flexible nature to the resin. That flexible nature produces parts that withstand impacts and repeated flexing without developing cracks.
Vinyl esters provide excellent resistance to water, organic solvents and alkalis, but less resistance to acids than polyesters. Vinyl esters are stronger than polyesters and more resilient than epoxies. Molding conditions for vinyl esters are similar to those for polyesters.