Mechanical properties, molecular motions and density fluctuations in polymer-additive mixtures

Abstract

Two effects are of outstanding importance for the mechanical behaviour of polymer-additive mixtures, (a) the plasticizer effect and (b) an effect, which we shall refer to as the “β-suppression” effect: Additives can suppress the secondary (β-) relaxations of the polymer. The β-suppression effect is studied on a number of polymers and additives (dynamic mechanical and dielectric measurements), the molecular motions involved are characterized (2H-NMR spectroscopy) and the thermal density fluctuations are measured (SAXS experiments). A model to explain the effect in terms of the free volume fluctuations is presented.