Rheology of Hot-Melt PSAs: Influence of Polymer Structure
Résumé
At room temperature, the hot-melt pressure-sensitive adhesives (HMPSAs) satisfy the Dahlquist criterion, and consequently have permanent tack. It is well established that the tack properties of these adhesives are governed, to a large extent, by their rheological properties. We have studied the full formulations based on triblock and diblock copolymers, and also on new molecules, such as tetrablock or radial copolymers, designed to improve the end-user properties. We describe the dynamic mechanical properties in the linear domain, at room temperature, of the pure copolymer blends and the full HMPSA formulations. We propose a model, based on molecular dynamics concepts, which describes the rheological behavior in a very wide range of frequencies, for all the copolymers and full formulations in the study. The effect of the diblock copolymer content on the rheological behavior of the adhesive and the link with the morphology of the copolymers is discussed in detail. Finally, we conclude that, in using molecular dynamics concepts, it is possible to propose an efficient "virtual formulation" tool for the diblock-triblock systems studied. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.