Reaction induced phase separation in blends of epoxy and multifunctional polybutadiene

Thein Kyu, The University of Akron

Abstract

The phase behavior and separation dynamics have been investigated in blends of diglycidyl ether of bisphenol A (DGEBA), curing agent methylene dianiline (MDA), and a reactive liquid rubber (R45EPI) through application of differential scanning calorimetry (DSC), one- and two-dimensional light scattering, and optical microscopy. DSC analysis indicates that the system consists of three reactions: the self-condensations of DGEBA and R45EPI, as well as a cross-reaction between the two constituents. Observation of the dynamics of the 50/25.4/50 DGEBA/MDA/R45EPI system reveals that an initial phase separation is governed by the dominant self-curing reaction of DGEBA, followed by a phase dissolution characterized by a broadening of the interfacial regions catalyzed by a cross-reaction between the two species. A subsequent phase separation occurs at late stages since the copolymerization reaction does not proceed to completion. On the other hand, by changing the ratio of the beginning constituents to 70/25.4/30 DGEBA/MDA/R45EPI, the dissolution phenomena is not observed resulting from an even more dominant DGEBA/MDA condensation reaction. It is demonstrated that alterations in the initial compositional ratio greatly affect the phase separation dynamics of the system.