Epoxy Polymer Networks with Improved Thermal and Mechanical Properties via Controlled Dispersion of Reactive Toughening Agents

Abstract

Highly cross-linked polymers are extensively used in the formulation of protective coatings, adhesives, and composite materials. The inherent densely cross-linked structure makes these materials strong but brittle limiting their use. This investigation reveals that rearranging the molecular structure of these polymers can significantly improve toughness without degrading and sometimes even enhancing other essential thermal and mechanical properties. Epoxy polymers are synthesized such that they have the same overall chemical composition but different molecular arrangements. These systems are referred to as polymer network isomers. The structural variations are introduced by using a processing technique termed “partially reacted substructures (PRS)”. The PRS were made from the stoichiometric reactions of poly(propylene oxide)diamine and diglycidyl ether of bisphenol A (DGEBA) up to specified extents of reaction (0, 60, 70, and 80%). The resulting still reactive PRS were mixed and cured with stoichiometric ...