Rheological Properties of Hot-Melt Adhesives: A Model for Describing the Effects of Resin Content

Abstract

The complex shear modulus of a series of EVA/resin blends has been measured in a broad range of frequencies and temperatures. The variations of the viscoelastic parameters (plateau modulus, limiting compliance, zero-shear viscosity) have been studied as a function of resin content. The addition of small compatible molecules to the polymer has two effects: a topological effect due to the swelling of the entanglement network and a thermodynamic effect due to the increase of the glass transition temperature. It is possible to play on both effects to get the wanted elastic and viscous behavior, as far as process and adhesive properties are concerned. As a consequence, a viscoelastic model is given, allowing one to calculate in a wide range of frequencies (or times) the behavior of these bases of hot melt adhesives, given the composition of the blend and its temperature.