ELASTOMER-MODIFIED VINYL ESTERS AS STRUCTURAL ADHESIVES

Vinyl esters (epoxy-methacrylates) are preeminent chemical-and corrosion-resistant materials. Based primarily on addition-esterified epoxy resins with methacrylic acid and diluted with styrene monomer, several products are available based on diepoxide structure, molecular weight, modifier type (nitrile rubber, urethane, glycol, e.g.) and blends with styrenated polyester resins. A new class of vinyl ester urethanes has also become commercially available. Elastomer modification of both types has shown that the fracture energy of epoxy vinyl esters can be enhanced to have a four-fold improvement. Despite this, the elastomer-modified vinyl esters have not found use as a basis for free-radical curing structural adhesives. Addition of an epoxy-terminated rubber (ETBN) or a methacrylated-vinyl terminated rubber (VTBNX) to previously elastomer-modified vinyl ester resin significantly improves overlap shear, T-peel, and bulk fracture properties. This suggests potential application in structural adhesive development. The cured specimen morphology of the combined rubber system provides clues for toughness enhancement.