Adhesion and viscoelastic property of poly(ethylene-co-vinyl acetate) based hot melt adhesives- effects of tackifier and wax

Abstract A series of hot-melt adhesives (HMAs) were made from poly(ethylene-co-vinyl acetate) (EVA) and a glycerol ester of partially hydrogenated rosin (Staybelite Ester 10, SE10) in various ratios. A content of 70 parts of SE10 per hundred parts (phr) of EVA showed a maximal peel strength. The effect of decreasing the rubbery plateau G′ value and increasing the glass transition temperature while increasing the SE10 content seems evident in the peel strength study. The trend also showed that the tackifier became less effective when the Tg's of the adhesive mixture were higher than a limit temperature (i.e., 15 °C). With 70 phr of SE10, the compatibility of the adhesive blend was further improved by adding 10 phr of wax, and the recipe displayed an even higher peel strength value. The presence of wax leads to ultrahigh cohesive strength, which is related to the rapid increase in crystallinity of the adhesive mixture. Formulating with a larger amount of wax worsens the peel strength, which may be explained by the formation of a weak boundary layer of the adhesive mixture on the surface of the adhesive blend.