Evolution of Viscosity Upon Crosslinking in Epoxy Resin: An Atomistic Investigation

Abstract

Adhesive materials such as epoxy resin (DGEBA/DETDA) are crucial in formation of any laminated and sandwich composites. Typically for these thermoset polymeric adhesives, crosslinking is an important step which eventually determines the thermomechanical response of the resultant composite. During this process of cross linking of epoxy resin, one observes changes in the viscosity of the resultant composite mixture of the resin and the hardener as well as change in temperature. This crosslinking of thermoset resins (DGEBA/DETDA at 2:1 ratio) is a complex chemical reaction process involving breaking of oxirane ring (C-O bond) in DGEBA, breaking of N-H bond in the amine (DETDA) and creation of N-C covalent bonds between the resin and the hardener. Apart from formation of new covalent bonds in the process, numerous non-covalent bonds such as hydrogen bonds and van der Waals interactions are also formed. This study is aimed at fundamental understanding of the correlation between viscosity changes in the composite upon crosslinking with the evolution of these non-covalent bonds. The study is primarily based upon molecular/atomistic investigations.