PEEL ADHESION AND VISCOELASTICITY OF POLY(ETHYLENE-CO-VINYL ACETATE)-BASED HOT-MELT ADHESIVES .1. THE EFFECT OF TACKIFIER COMPATIBILITY

A series of poly(ethylene-co-vinyl acetate) (EVA)-based hot melt adhes ives containing either a rosin or a hydrocarbon (C5-C9) tackifier have been prepared to investigate viscoelastic properties and peel adhesio n. Fracture energies were determined by the use of a T-Peel geometry ( two polypropylene films bonded with model EVA adhesives). The rosin ha s only one glass transition temperature, but the C5-C9 resin has two g lass transition temperatures, indicating phase separation. The rosin h as better compatibility with EVA than does the C5-C9 resin. The bond s trength of tackified EVA to polypropylene depends not only on compatib ility, but also on viscoelastic properties. A higher storage modulus r esults in a higher T-Peel strength. Under certain test conditions, gla ssy C5-C9-rich domains act as reinforcing filler, resulting in a highe r storage modulus. Here, a C5-C9-tackified EVA adhesive has higher T-P eel strength than does one containing rosin. (C) 1997 John Wiley & Son s, Inc.