Highly ductile glassy epoxy systems obtained by network topology modification using partially reacted substructures

Abstract A strategy for toughening epoxy thermosets via topological rearrangement of cross-linked networks is presented. Amine-cured epoxy systems were modified by mixing partially reacted substructures (mPRS), which were synthesized by partially curing tetraglycidyl ether of diaminodiphenylmethane (TGDDM) and polyether monoamine (Jeffamine M1000) to provide free unbound surfaces that enhance protovoid formation during deformation. The influence of mPRS conversion and weight ratio on the properties of diglycidyl ether of bisphenol A (DGEBA) and TGDDM systems cured with Jeffamine D230 was investigated. Adding mPRS resulted in high Tg systems capable of exceptional strain at failure in tension: 43% for the DGEBA (Tg = 75 °C) and 20% for the TGDDM (Tg = 135 °C). The addition of mPRS, however, decreases Tg relative to unmodified systems. SEM and SAXS characterization provide evidence of protovoid (18–34 nm) formation. Quasi-static compressive tests conducted at testing temperatures selected to maintain a constant (Tg - Ttest) reveal the protovoid opening mechanism plays a dominant role in enhanced ductility.