Interface reaction‐induced separated phase structure in compatible epoxy thermosetting blending for unexpected mechanical properties and multi‐thermosensitive devices

Abstract Unlike the traditional reaction‐induced phase separation mechanism in incompatible polymer blending and the rigorous thermodynamic difference‐induced phase separation in compatible polymer blending, a new strategy for inducing separated phase in compatible thermosetting blending systems before cure was developed. Phase‐separated structure in the blending of thermosetting epoxy/glutaric anhydride (GA)/zinc (II) acetylacetonate (ZAA) system (EP1) and epoxy/polyether amine (D230)/butylglycidyl ether (BGE) system (EP2) was constructed by in situ interface reaction between EP1 and EP2. High concentration ZAA gave rise to high viscosity of EP1 that brought large EP2 droplets in EP1/EP2 systems. The phase‐separated structure was easily controlled by the formation of the polymer wall interface between EP1 and EP2. The synergistic effects of the barrier of wall interface and low diffusion behavior of high viscosity of EP1 could lead to the high conversion of epoxy groups in EP1/EP2, low levels of GA/D230 consumptions, and significant phase structure in EP1/EP2, which endowed the resulting EP1/EP2 with excellent mechanical property and good thermal property. The flexural strength, the impact strength and tensile strength of EP1/EP2 with large separated‐phase reached 119 MPa, 28 kJ/m², and 73 MPa, respectively, which were 34%, 12%, and 16% higher than that of high performance EP1 system. The resulting EP1/EP2 systems also showed good triple‐shape memory effect owing to the phase‐separated structure. It was significant for EP1/EP2 system to be used as multithermosensitive devices for fire early warning and monitoring detector, and high‐security anticounterfeiting application.