Adhesion and rheological properties of EVA-based hot-melt adhesives

Ethylene vinyl acetate (EVA) copolymers of various melt indexes were blended with aromatic hydrocarbon resin in the molten state, and the thermal and adhesion properties as hot-melt adhesives (HMAs) were investigated. The thermal properties for the EVA blends with aromatic hydrocarbon resin were studied using differential scanning calorimeter, Brookfield viscometer and dynamic mechanical thermal analyzer. Their adhesion strength was also obtained using single lap shear strength. The examination of thermal properties for the blend of EVA copolymers with aromatic hydrocarbon resin over a large temperature range showed that the glass transition temperature was independent of their melt index (MI), but that their heat of fusion decreased with increasing MI of EVA copolymers. Furthermore, the storage and loss moduli of the blends decreased with increasing temperature and MI of EVA copolymers, but the loss tangent (tan δ) of the blends increased. An increase in the MI of EVA copolymers decreased the adhesion strength of the blend at the same test condition.