Crosslinking of epoxy-polysiloxane system by reactive blending

The epoxy-polysiloxane network was prepared by reactive blending of poly[(3-aminopropyl)methylsiloxane] (PAMS) containing pendant amino groups and diglycidyl ether of Bisphenol A (DGEBA). The initially immiscible blend is compatibilized during the reaction and crosslinked. Network formation, dynamics of the system and evolution of morphology were determined by dynamic mechanical analysis and light scattering techniques. The grafting epoxy-amine reaction involves a high extent of cyclization resulting in a high fraction of the sol in the networks. Dynamic light scattering data analysis reveals fast and slow relaxation modes of reacting species in the pregel and one single mode in the post-gel state. The network with a stoichiometric composition shows the most homogeneous morphology with a single glass transition temperature. On the contrary, the networks with excess of PAMS are strongly phase-separated exhibiting the unreacted PAMS-rich phase, PAMS phase partly grafted with epoxide and PAMS-DGEBA crosslinked phase.