Univ Lyon, Université Claude Bernard Lyon 1, CPE Lyon, CNRS, UMR 5128, Chemistry, Polymerization, Processes and Materials (CP2M), 43 Bvd du 11 Novembre 1918, 69616 Villeurbanne, France
Abstract:
The activity of various additives promoting siloxane equilibration reactions is examined and quantified on model compounds. We found in particular that the “superbase” phosphazene derivative P4-tBu can promote very fast exchanges (a few seconds at 90 °C) even at low concentration (<0.1 wt %). We demonstrate that permanent silicone networks can be transformed into reprocessable and recyclable dynamic networks by mere introduction of such additives. Annealing at high temperature degrades the additives and deactivates the dynamic features of the silicone networks, reverting them back into permanent networks. A simple rheological experiment and the corresponding model allow to extract the critical kinetic parameters to predict and control such deactivations.